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STOCKHOLDERS’ EQUITY / DEFICIT (Tables)

12 Months Ended

Dec. 31, 2019

Assumptions used in black-scholes options pricing model

The following weighted average assumptions were used in the Black-Scholes options pricing model to estimate the fair value of stock options for the specified reporting periods:



	Twelve Months Ended December 31,
	2019		2018		2017
Risk free rate	2.30	%	2.80	%	2.10	%
Expected volatility	68	%	68	%	70	%
Expected life (in years)	6.2		6.2		6.1
Expected dividend yield	—		—		—

Share-based compensation, stock options, activity

The following table summarizes our stock option activity and related information for the year ended December 31, 2019:



			Weighted Average
	Shares Underlying Options		Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018	7,277,337		$	18.55	6.94	$	40,650
Granted	1,360,925		19.11		—	—
Forfeited and expired	(1,131,002	)	13.73		—	—
Exercised	(135,527	)	11.94		—
Outstanding at December 31, 2019	7,371,733		$	19.52	6.63	$	4,906

The following table summarizes our stock options exercisable at December 31, 2019, 2018 and 2017:



		Weighted Average
	Shares Underlying Options	Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
2018	4,834,781	$	16.81	5.98	$	35,387
2019	4,936,995	$	18.93	5.62	$	4,490

Schedule of unvested restricted shares

The following table summarizes our restricted stock unit activity for the year ended December 31, 2019:



	Number of RSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2018	400,426		$	24.95
Granted	559,815		17.15
Vested	(137,203	)	24.43
Forfeited/cancelled	(59,310	)	20.97
Unvested December 31, 2019	763,728		$	19.64

Share-based compensation, performance shares award nonvested activity

The following table summarizes our performance-based stock unit activity for the year ended December 31, 2019:



	Number of PSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2018	226,750		$	21.54
Granted	80,000		21.32
Vested	—		—
Forfeited/cancelled	(73,250	)	23.33
Unvested December 31, 2019	233,500		$	20.90

Schedule of share based compensation expenses

Total non-cash stock-based compensation expense consisted of the following for the years ended December 31, 2019, 2018 and 2017 (in thousands):



	Twelve Months Ended December 31,
	2019		2018		2017
Selling, general and administrative expenses	$	14,195	$	13,550	$	17,924
Research and development expenses	6,910		6,224		8,950
Total	$	21,105	$	19,774	$	26,874

Schedule of stock option activity

During the twelve months ended December 31, 2018 and 2017, the Company issued the following shares of common stock upon the exercise of warrants for cash received by the Company: (in thousands except share amounts)



	Shares Issued	Cash Received		Derivative Liability Reclassified as Equity		Change in Fair Value Expense
2017	607,481	$	3,645	$	11,221	$	3,033
2018	1,036,054	$	5,305	n/a		n/a
2019	n/a	n/a		n/a		n/a

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 62,436	$ 102,873
Marketable securities	336,088	368,668
Accounts receivable, net	18,048	12,662
Inventory, net	6,082	5,619
Prepaid expenses and other current assets	5,015	4,140
Prepaid taxes	1,395	1,716
Total current assets	429,064	495,678
Property and equipment, net	2,891	3,146
Other assets	14,709	7,709
Investment-equity	0	15,000
Intangible assets, net	157,200	186,691
Goodwill	936	936
Total assets	604,800	709,160
Current liabilities:
Accounts payable	26,614	6,954
Accrued expenses	51,745	49,695
Other current liabilities	8,590	6,165
Business combination-related contingent consideration	8,500	19,350
Convertible debt	0	22,457
Total current liabilities	95,449	104,621
Convertible debt	204,861	195,091
Other noncurrent liabilities	20,894	17,545
Business combination-related contingent consideration, less current portion	62,400	73,650
Total liabilities	383,604	390,907
Stockholders' Equity:
Preferred stock $0.0001 par value; 20,000,000 shares authorized; 0 issued and outstanding as of December 31, 2019 and 2018, respectively	0	0
Common stock $0.0001 par value; 100,000,000 shares authorized; 43,088,921 and 41,389,524 issued and outstanding as of December 31, 2019 and 2018, respectively	4	4
Additional paid-in capital	636,910	589,795
Accumulated deficit	(416,444)	(270,017)
Accumulated other comprehensive income (loss)	726	(1,529)
Total stockholders' equity	221,196	318,253
Total liabilities and stockholders' equity	$ 604,800	$ 709,160

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2016		37,906,669
Beginning balance at Dec. 31, 2016	$ 307,767	$ 4	$ 421,309	$ (490)	$ (113,056)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	26,645		26,645
Exercise of warrants and reclassification of derivative liability (in shares)		607,481
Exercise of warrants and reclassification of derivative liability	14,866		14,866
Unrealized gain/(loss) on marketable securities	(186)			(186)
Foreign currency translation adjustments	(339)			(339)
Issuance of common shares under the equity incentive plan and proceeds from exercise (in shares)		819,573
Issuance of common shares under the equity incentive plan and proceeds from exercise.	8,087		8,087
ESPP stock purchase and expense (in shares)		40,022
ESPP stock purchase and expense	893		893
Net loss	(59,731)				(59,731)
Ending balance (in shares) at Dec. 31, 2017		39,373,745
Ending balance at Dec. 31, 2017	293,134	$ 4	471,800	(1,015)	(177,655)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	19,494		19,494
Exercise of warrants and reclassification of derivative liability (in shares)		1,036,054
Exercise of warrants and reclassification of derivative liability	5,305		5,305
Unrealized gain/(loss) on marketable securities	(553)			(553)
Foreign currency translation adjustments	39			39
Issuance of common shares under the equity incentive plan and proceeds from exercise (in shares)		892,713
Issuance of common shares under the equity incentive plan and proceeds from exercise.	10,588		10,588
ESPP stock purchase and expense (in shares)		87,012
ESPP stock purchase and expense	2,269		2,269
Convertible debt issue	74,945		74,945
Net loss	(102,678)				(102,678)
Ending balance (in shares) at Dec. 31, 2018		41,389,524
Ending balance at Dec. 31, 2018	318,253	$ 4	589,795	(1,529)	(270,017)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	20,463		20,463
Unrealized gain/(loss) on marketable securities	2,163			2,163
Foreign currency translation adjustments	92			92
Issuance of common shares under the equity incentive plan and proceeds from exercise (in shares)		272,730
Issuance of common shares under the equity incentive plan and proceeds from exercise.	1,618		1,618
ESPP stock purchase and expense (in shares)		129,324
ESPP stock purchase and expense	2,444		2,444
Convertible debt issue	22,590		22,590
Convertible debt issue (in shares)		1,297,343
Net loss	(146,427)				(146,427)
Ending balance (in shares) at Dec. 31, 2019		43,088,921
Ending balance at Dec. 31, 2019	$ 221,196	$ 4	$ 636,910	$ 726	$ (416,444)

MARKETABLE SECURITIES (Details) - USD ($) $ in Thousands	12 Months Ended
MARKETABLE SECURITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	$ 208,906	$ 209,137
Debt securities available for sale, unrealized gain, current	598	0
Debt securities available for sale unrealized loss, current	(10)	(662)
Marketable securities	209,494	208,475
Debt securities, available-for-sale, amortized cost basis, noncurrent	126,300	160,810
Debt securities, available for sale unrealized gain, noncurrent	351	22
Debt securities available for sale unrealized loss, noncurrent	(57)	(639)
Debt securities, available-for-sale, noncurrent	126,594	160,193
Debt securities, available-for-sale, amortized cost	335,206	369,947
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	949	22
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(67)	(1,301)
Debt securities, available-for-sale	336,088	368,668
Proceeds from the sale/maturity of marketable securities	259,140	162,755	$ 114,526
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	17,136	59,313
Debt securities available for sale, unrealized gain, current	16	0
Debt securities available for sale unrealized loss, current	0	(58)
Marketable securities	17,152	59,255
Debt securities, available-for-sale	17,152	59,255
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	191,770	149,824
Debt securities available for sale, unrealized gain, current	582	0
Debt securities available for sale unrealized loss, current	(10)	(604)
Marketable securities	192,342	149,220
Debt securities, available-for-sale, amortized cost basis, noncurrent	113,799	150,813
Debt securities, available for sale unrealized gain, noncurrent	351	18
Debt securities available for sale unrealized loss, noncurrent	(56)	(638)
Debt securities, available-for-sale, noncurrent	114,094	150,193
Debt securities, available-for-sale	306,436	299,413
Securities of government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, noncurrent	12,501	9,997
Debt securities, available for sale unrealized gain, noncurrent	0	4
Debt securities available for sale unrealized loss, noncurrent	(1)	(1)
Debt securities, available-for-sale, noncurrent	12,500	10,000
Debt securities, available-for-sale	$ 12,500	$ 10,000

STOCKHOLDERS’ EQUITY / DEFICIT - Exercise of Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds exercise of warrants	$ 0	$ 5,305	$ 3,645
Class of warrant or right, title of security warrants or rights outstanding (in shares)	0	0
Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock called by warrants (in shares)		1,036,054	607,481
Proceeds exercise of warrants		$ 5,305	$ 3,645
Reclassification of derivative liability as equity			11,221
Change in fair value of warrants			$ 3,033

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

A summary of the significant accounting policies applied in the preparation of the accompanying consolidated financial statements follows:

Principles of Consolidation

The consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with accounting principles generally accepted in the United States ("U.S. GAAP"). All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

In preparing financial statements in conformity with U.S. GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of expenses during the reporting period. Due to inherent uncertainty involved in making estimates, actual results reported in future periods may be affected by changes in these estimates. On an ongoing basis, the Company evaluates its estimates and assumptions. These estimates and assumptions include revenue recognition, valuing equity securities in share-based payments, estimating expenses of contracted research organizations, estimating fair value of equity instruments recorded as derivative liabilities, estimating the useful lives of depreciable and amortizable assets, goodwill impairment, estimating the fair value of contingent consideration, estimating of valuation allowances and uncertain tax positions, and estimates associated with the assessment of impairment for long-lived assets.

Revenue Recognition

Effective January 1, 2018, the Company adopted Accounting Standards Codification ("ASC"), Topic 606, Revenue from Contracts with Customers, using the full retrospective transition method. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect substantially all the consideration it is entitled to in exchange for the goods or services it transfers to the customer.

Revenue from product sales is recorded at delivery, net of applicable provisions for rebates under government (including medicaid) programs, commercial rebates, prompt pay discounts, and other sales-related deductions. We review our estimates of rebates and other applicable provisions each period and record any necessary adjustments in the current period.

See Note 3 for further discussion.

Research and Development Costs

Research and development includes expenses related to sparsentan, fosmetpantotenate and our other pipeline programs. We expense all research and development costs as they are incurred. Our research and development costs are comprised of salaries and bonuses, benefits, non-cash share-based compensation, license fees, milestones under license agreements, costs paid to third-party contractors to perform research, conduct clinical trials, and develop drug materials and delivery devices, and associated overhead expenses and facilities costs. We charge direct internal and external program costs to the respective development programs. We also incur indirect costs that are not allocated to specific programs because such costs benefit multiple development programs and allow us to increase our pharmaceutical development capabilities. These consist of internal shared resources related to the development and maintenance of systems and processes applicable to all of our programs.

Clinical Trial Expenses

We record expenses in connection with our clinical trials under contracts with contract research organizations (CROs) that support conducting and managing clinical trials. The financial terms and activities of these agreements vary from contract to contract and may result in uneven expense levels. Generally, these agreements set forth activities that drive the recording of expenses such as start-up and initiation activities, enrollment and treatment of patients, or the completion of other clinical trial activities.

Expenses related to clinical trials are accrued based on our estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient studies and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. If the amounts we are obligated to pay under our clinical trial agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), we adjust our accruals accordingly on a prospective basis. Revisions to our contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain.

We currently have three Phase 3 clinical trials in process that are in varying stages of activity, with ongoing non-clinical support trials. As such, clinical trial expenses will vary depending on the all the factors set forth above and may fluctuate significantly from quarter to quarter.

Employee Stock-Based Compensation

The Company recognizes all employee share-based compensation as a cost in the financial statements. Equity-classified awards principally related to stock options, restricted stock units (“RSUs”) and performance stock units ("PSUs"), are measured at the grant date fair value of the award. The Company determines grant date fair value of stock option awards using the Black-Scholes option-pricing model. The fair value of RSUs and PSUs are determined using the closing price of the Company’s common stock on the grant date. For service based vesting grants, expense is recognized over the requisite service period based on the number of options or shares expected to ultimately vest. For PSUs, expense is recognized over the implicit service period, assuming vesting is probable. No expense is recognized for PSUs if it is not probable the vesting criteria will be satisfied. Forfeitures are accounted for as they occur.



	Vesting Term
Stock Options	3 to 4 years
Restricted Stock Units	1 to 4 years

Earnings (Loss) Per Share

We calculate our basic earnings per share by dividing net income by the weighted average number of shares outstanding during the period. The diluted earnings per share computation includes the effect, if any, of shares that would be issuable upon the exercise of outstanding stock options, derivative warrant liability, convertible debt and RSUs, reduced by the number of shares which are assumed to be purchased by the Company from the resulting proceeds at the average market price during the year, when such amounts are dilutive to the earnings per share calculation.

Cash and Cash Equivalents

We consider all highly liquid marketable securities with an original maturity of three months or less to be cash equivalents. Due to the short-term maturity of such investments, the carrying amounts are a reasonable estimate of fair value.

Marketable Securities

The Company accounts for marketable securities held as “available-for-sale” in accordance with ASC 320, “Investments Debt and Equity Securities” (“ASC 320”). The Company classifies these investments as current assets and carries them at fair value. Unrealized gains and losses on debt securities are recorded as a separate component of stockholders’ equity as accumulated other comprehensive loss. Realized gains or losses on marketable security transactions are reported in the Consolidated Statements of Operations and Comprehensive Loss. Marketable securities are maintained at one financial institution and are governed by the Company’s investment policy as approved by the Company's Board of Directors.

Trade Receivables, Net

Trade accounts receivable are recorded net of allowances for prompt payment and doubtful accounts. Estimates for allowances for doubtful accounts are determined based on existing contractual obligations, historical payment patterns and individual customer circumstances. The allowance for doubtful accounts was zero at both December 31, 2019 and 2018, respectively. For the years ended December 31, 2019, 2018 and 2017, bad debt expense recorded in the Statement of Operations and Comprehensive Loss was approximately $0.1 million, zero and $0.2 million, respectively.

Inventory, Related Reserves and Cost of Goods Sold

Inventory, which is recorded at the lower of cost or net realizable value, includes materials, labor, and other direct and indirect costs and is valued using the first-in, first-out method. The Company periodically analyzes its inventory levels to identify inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value, and writes down such inventory as appropriate. In addition, the Company's products are subject to strict quality control and monitoring which the Company’s manufacturers perform throughout their manufacturing process. The Company does not directly manufacture any product. The Company has single suppliers for products Chenodal and Thiola, and prospectively arranges for manufacture from contract service providers for its product Cholbam. The inventory reserve was $3.1 million and $1.8 million at December 31, 2019 and 2018, respectively.

Inventory, net of reserve, consisted of the following at December 31, 2019 and 2018 (in thousands):



	December 31, 2019		December 31, 2018
Raw material	$	2,713	$	2,883
Finished goods	3,369		2,736
Total inventory	$	6,082	$	5,619

Cost of goods sold includes the cost of inventory sold, third party manufacturing and supply chain costs, product shipping and handling costs, and provisions for excess and obsolete inventory.

Segment Information

The Company currently operates in one business segment focused on the development and commercialization of innovative therapies for people with serious and life-threatening rare diseases and medical conditions. The Company is not organized by market and is managed and operated as one business. A single management team reports to the chief operating decision maker who comprehensively manages the entire business. The Company does not operate any separate lines of business or separate business entities with respect to its products. Accordingly, the Company does not accumulate discrete financial information with respect to separate products, other than revenues, and does not have separately reportable segments.

Property and Equipment, net

Property and equipment are stated at cost, net of accumulated depreciation. Depreciation is computed using the straight-line method over the related estimated useful lives as presented in the table below. Significant additions and improvements are capitalized, while repairs and maintenance are charged to expense as incurred. Property and equipment purchased for specific research and development projects with no alternative use is expensed as incurred.

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Intangible Assets, Net

Our intangible assets consist of licenses and purchased technology. Intangible assets with definite lives are amortized on a straight-line basis over their estimated useful lives and are reviewed periodically for impairment.

Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. During the period the assets are considered indefinite-lived, they will not be amortized but will be tested for impairment. If and when development is complete, which generally occurs when regulatory approval to market a product is obtained, the associated assets are deemed finite-lived and are amortized over a period that best reflects the economic benefits provided by these assets.

Goodwill

Goodwill represents the excess of purchase price over fair value of net assets acquired in a business combination and is not amortized. Goodwill is subject to impairment testing at least annually or when a triggering event occurs that could indicate a potential impairment. The Company has one segment and one reporting unit and as such reviews goodwill for impairment at the consolidated level.

For the years ended December 31, 2019, 2018 and 2017 there were no impairments to goodwill.

Impairment of Long-Lived Assets

Our long-lived assets are primarily comprised of intangible assets and property and equipment. We evaluate our finite-lived intangible assets, other than goodwill and property and equipment, for impairment whenever events or changes in circumstances indicate the carrying value of an asset or group of assets may not be recoverable. If these circumstances exist, recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset group to future undiscounted net cash flows expected to be generated by the use and eventual disposition of the asset group. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets.

In addition, indefinite-lived intangible assets, comprised of IPR&D, are reviewed for impairment annually and whenever events or changes in circumstances indicate that it is more likely than not that the asset is impaired by comparing the fair value to the carrying value of the asset. To determine the fair value of the asset, the Company used the multi-period excess earnings method of the income approach. The more significant assumptions inherent in the application of this method include: the amount and timing of projected future cash flows (including revenue, cost of sales, research and development costs, and sales and marketing expenses), and the discount rate selected to measure the risks inherent in the future cash flows.

During the first quarter of 2019, the Company elected to discontinue development of the L-UDCA program, resulting in the write off of the IPR&D intangible asset, see Note 5 for further discussion.

There were no impairments related to intangible assets in the years ended December 31, 2018 and 2017.

Contingent Consideration

We record contingent consideration resulting from a business combination at its fair value on the acquisition date. On a quarterly basis, we revalue these obligations and record increases or decreases from their fair value as an adjustment to the consolidated statement of operations. Changes to contingent consideration obligations can result from changes to discount rates, accretion of the liability due to the passage of time, changes in revenue forecasts and changes in our estimates of the likelihood or timing of achieving commercial revenue milestones.

Income Taxes

The Company follows ASC 740, Income Taxes, which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax assets and liabilities are based on the differences between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance to the extent management concludes it is more likely than not that the asset will not be realized.

The standard addresses the determination of whether tax benefits claimed or expected to be claimed on a tax return should be recorded in the financial statements. Under ASC 740, the Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the tax authorities, based on the technical merits of the position. The tax benefits recognized in the financial statements from such a position should be measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. ASC 740 also provides guidance on de-recognition, classification, interest and penalties on income taxes, accounting in interim periods and requires increased disclosures. The Company’s policy is to record estimated interest and penalty related to the underpayment of income taxes or unrecognized tax benefits as a component of its income tax provision.

Reclassifications

Certain reclassifications have been made to the prior year financial statements in order to conform to the current year’s presentation.

Patents

The Company expenses external costs, such as filing fees and associated attorney fees, incurred to obtain issued patents and patent applications pending. The Company also expenses costs associated with maintaining and defending patents subsequent to their issuance in the period incurred.

Derivative Financial Instruments, Warrants

The Company does not use derivative instruments to hedge exposures to cash flow, market or foreign currency risks. However, since 2013, the Company has issued five tranches of common stock purchase warrants to secure financing, remediate covenant violations and provide consideration for amendments with respect to a credit facility extinguished in 2015.

Historically, the Company accounted for these instruments, which did not have fixed settlement provisions, as derivative instruments in accordance with FASB ASC 815-40, Derivative and Hedging - Contracts in Entity’s Own Equity. This was due to an anti-dilution provision for the warrants that provided for a reduction to the exercise price if the Company issued equity or equity linked instruments in the future at an effective price per share less than the exercise price then in effect for the warrant ("down round provision"). As such, the warrants were re-measured at each balance sheet date based on estimated fair value. Changes in estimated fair value were recorded as non-cash adjustments within other income (expenses), net, in the Company’s Consolidated Statements of Operations and Comprehensive Income (Loss).

As of January 1, 2018, the Company early adopted ASU 2017-11, which revised the guidance for instruments with down round provisions. As such the Company treats outstanding warrants as free-standing equity linked instruments that will be recorded to equity in the Consolidated Balance Sheet.

The fair value of the derivative liability balance as of December 31, 2017 of $15.7 million was reclassified by means of a cumulative-effect adjustment to equity as of January 1, 2018.

Restructuring

On March 7, 2017, the Company initiated a plan to consolidate its operations to its corporate headquarters in San Diego, California. The Company adjusted employee related separation charges by $0.2 million and $3.6 million in 2018 and 2017 as a result of this consolidation.

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases. The new standard establishes a right-of-use ("ROU") model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. See Note 18 for further discussion.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. Under the new standard, revenue is recognized at the time a good or service is transferred to a customer for the amount of consideration for which the entity expects to be entitled for that specific good or service. Entities may use a full retrospective approach or report the cumulative effect as of the date of adoption. The Company adopted the new standard on January 1, 2018 using the full retrospective approach and there was no impact on timing or recognition of revenue. See Note 3 for further discussion.

In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. The new guidance changes the accounting for income tax effects of intra-entity transfers of assets other than inventory. Under the new guidance, the selling (transferring) entity is required to recognize a current tax expense or benefit upon transfer of the asset. Similarly, the purchasing (receiving) entity is required to recognize a deferred tax asset or deferred tax liability, as well as the related deferred tax benefit or expense, upon receipt of the asset. As of January 1, 2017, the Company reversed the balance of $4.9 million in its prepaid tax asset account as a charge to retained earnings.

In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features. These amendments simplify the accounting for certain financial instruments with down round features. The amendments require companies to disregard the down round feature when assessing whether the instrument is indexed to its own stock, for purposes of determining liability or equity classification. See Note 15 for further discussion.

In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The new guidance dictates that, when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, it should be treated as an acquisition or disposal of an asset. The guidance was adopted as of January 1, 2018.

Recently Issued Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its consolidated financial position or results of operations upon adoption.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Topic 326 amends guidance on reporting credit losses for assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, Topic 326 eliminates the probable initial recognition threshold in current GAAP and, instead, requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. For available for sale debt securities, credit losses should be measured in a manner similar to current GAAP, however Topic 326 will require that credit losses be presented as an allowance rather than as a write-down. This ASU update affects entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. The amendments affect loans, debt securities, trade receivables, net investments in leases, off balance sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. This

update is effective for the company for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The Company evaluated the adoption of the new standard and it will not have a material effect on its consolidated financial statements and related disclosures.

STOCKHOLDERS’ EQUITY / DEFICIT - 2017 Employee Stock Purchase Plan (Details) - 2017 ESPP - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for issuance under the plan (in shares)	980,000	380,000
Potential increase in shares available for issuance, as a percent of total outstanding common stock	1.00%
Maximum number of additional shares authorized for issuance (in shares)	300,000
Purchase price of common stock, percent of fair market value	85.00%
Stock purchase offering period	6 months
Employee stock purchase plan, maximum compensation	15.00%
Employee stock purchase plan annual limit	$ 25,000
Shares reserved for future issuance (in shares)	$ 723,642

INCOME TAXES - Reconciliation of Federal Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory rate - federal	(21.00%)	(21.00%)	(35.00%)
State taxes, net of federal benefit	(4.35%)	(4.44%)	(3.30%)
Change in FV of derivative liability (warrants)	0.00%	0.00%	2.82%
Change in federal tax rate	0.00%	0.00%	23.29%
Convertible Debt	0.00%	21.77%	0.00%
Loss on extinguishment of debt	0.00%	4.09%	0.00%
Other permanent differences	0.24%	0.10%	1.04%
Tax credits	(15.17%)	(11.86%)	(5.79%)
Return to provision adjustments and other true-ups	0.44%	1.42%	(3.48%)
Other	2.32%	1.06%	1.25%
Change in valuation allowance	37.50%	9.79%	21.62%
Income tax provision (benefit)	(0.02%)	0.93%	2.45%

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
Business Acquisition [Line Items]
Business combination-related contingent consideration			$ 70,900	$ 93,000
Investment	$ 15,000
Impairment of long-term investment		$ 15,000	$ 15,000	$ 0	$ 0
Business combination, option agreement, purchase price	$ 65,000
Business combination, option agreement, purchase price, percent transferred in cash	20.00%
Business combination, option agreement, purchase price, percent transferred by issuance of equity	80.00%
Business combination, option agreement, share price (in dollars per share)	$ 21.40
Business combination, option agreement, percent of consideration paid in cash if share price falls below share price threshold	100.00%
Business combination, option agreement, contingent consideration	$ 25,000
Censa Pharmaceuticals Inc.
Business Acquisition [Line Items]
Payments for the option to acquire business	10,000
Business combination-related contingent consideration	$ 19,900
Business combination, development funding						$ 2,800
Business combination, option agreement, weighted average ten day share price, which requires all cash payment (in dollars per share)	$ 19.26
Censa Pharmaceuticals, Inc, Equity Holders
Business Acquisition [Line Items]
Additional required payments for the option to acquire business, successful development milestones	$ 5,000

INTANGIBLE ASSETS

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLE ASSETS

Ligand License Agreement

In 2013, the Company entered into a $2.5 million agreement with Ligand for a worldwide sublicense to develop, manufacture and commercialize a drug technology compound including sparsentan (the “Ligand License Agreement”). The cost of the Ligand License Agreement, which is presented net of amortization in the accompanying Consolidated Balance Sheet in intangible assets, net, is being amortized to research and development on a straight-line basis through September 30, 2023. As consideration for the license, we are required to make substantial payments upon the achievement of certain milestones, totaling up to $114.1 million. Through 2019, we have made milestone payments to Ligand of $7.2 million under the terms of the Ligand License Agreement. Should we commercialize sparsentan or any products containing related compounds, we will be obligated to pay to Ligand an escalating annual royalty between 15% and 17% of net sales of all such products.

In September 2015, the Ligand License Agreement was amended to facilitate sub-licensing in Asia-Pacific. As consideration for the amendment the Company paid $1.0 million.

In March 2018, the Ligand License Agreement was amended to update certain development milestones set forth in the Sublicense Agreement to comport with the current development timeline for sparsentan. As consideration, the Company paid Ligand $4.6 million, which replaced the amount that would have been due upon initiation of the first Phase 3 trial for sparsentan.

Manchester Pharmaceuticals LLC

In 2014, the Company acquired intangible assets with finite lives related to the Chenodal product rights, trade names, and customer relationships with the values of $67.8 million, $0.2 million, and $0.4 million, respectively. The useful lives related to the acquired product rights, trade names, and customer relationships are expected to be approximately 16, 1 and, 10 years, respectively. Amortization of product rights, trade names and customer relationships are being recorded in selling, general and administrative expense over their respective lives.

Thiola License Agreement

The Company entered into a license agreement with Mission Pharmacal in 2014, in which the Company obtained an exclusive, royalty-bearing license to market, sell and commercialize Thiola (tiopronin) in the United States and Canada, and a non-exclusive license to use know-how relating to Thiola to the extent necessary to market Thiola. The initial term of the license is 10 years and will automatically renew thereafter for periods of one year.

The Company paid Mission an up-front license fee of $3 million and will pay guaranteed minimum royalties during each calendar year the greater of $2 million or twenty percent (20%) of the Company’s net sales of Thiola through May 28, 2024.

In November 2017, the Company amended its agreement with Mission to extend the term of the current exclusive U.S. and Canada licensing agreement by an additional five years, to 2029. The royalty rate and guaranteed minimum payment were also extended through the new agreement term. Upon execution of the amendment, the Company capitalized an additional $5.9 million in intangible assets and recorded a guaranteed minimum liability for the same amount.

In November 2018, the Company amended its agreement with Mission to remove all territorial restrictions on our license. As consideration for the expanded territory the Company paid an up-front fee of $0.3 million and will pay guaranteed minimum royalties equaling the greater of $0.1 million or 20% of our Thiola net sales generated outside of the United States during each calendar year. Upon execution of the amendment, the Company capitalized an additional $1.0 million in intangible assets and recorded a guaranteed minimum liability of $0.7 million related to this amendment.

The present value of guaranteed minimum royalties payable using a discount rate of ranging from approximately 7% to 11% based on the Company’s then borrowing rate is $14.3 million and $15.2 million as of December 31, 2019 and 2018, respectively. As of December 31, 2019, the guaranteed minimum royalty current and long-term liability was approximately $2.1 million and $12.2 million, respectively, and is recorded as Other Liability in the Consolidated Balance Sheet. As of December 31, 2018, the guaranteed minimum royalty current and long-term liability was approximately $2.1 million and $13.1 million, respectively, and is recorded as Other Liability in the Consolidated Balance Sheet. The Company has capitalized $85.8 million related to the Thiola intangible asset which consists of the up-front license fee, professional fees, present value of the guaranteed minimum royalties and any additional payments through 2019 in excess of minimum royalties. In 2019 the Company added $15.8 million to the intangible asset related to the royalties in excess of the minimum.

There are 9.4 years remaining in the term of the license agreement.

Cholbam (Kolbam) Asset Purchase

On March 31, 2015, the Company completed its acquisition from Asklepion of all worldwide rights, titles and ownership of Cholbam, including all related contracts, data assets, intellectual property, regulatory assets and the PRV. The Company capitalized $75.9 million and $7.3 million for the U.S. and international economic interest, respectively.

L-UDCA

On June 20, 2016, the Company signed a definitive agreement to purchase the rights, titles, and ownership of L-UDCA from Asklepion. The purchase included $25.5 million for an intangible asset with a definite life related to product rights for the U.S. The useful life related to the acquired product rights is expected to be approximately 17 years once the NDA is approved by the FDA. During the first quarter of 2019, the Company elected to discontinue development of the L-UDCA program, resulting in the write off of the intangible asset of $25.5 million. See Note 5 for further discussion.

Amortizable intangible assets as of December 31, 2019 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(24,451	)	$	43,398
Thiola License	15	85,824		(20,417		)	65,407
Economic Interest - U.S. revenue Cholbam	10	75,900		(36,071		)	39,829
Economic Interest - International revenue Cholbam	10	7,544		(3,585		)	3,959
Ligand License	11	7,900		(3,555		)	4,345
Manchester Customer Relationships	10	403		(232		)	171
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(116		)	91
Total		$	245,802	$	(88,602	)	$	157,200

Amortizable intangible assets as of December 31, 2018 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(20,213	)	$	47,636
Thiola License	15	70,009		(14,523		)	55,486
Economic Interest - U.S. revenue Cholbam	10	75,900		(28,487		)	47,413
Economic Interest - International revenue Cholbam	10	7,700		(2,890		)	4,810
Economic Interest - L-UDCA (acquired IPR&D)	Indefinite	25,500		—			25,500
Ligand License	11	7,900		(2,397		)	5,503
Manchester Customer Relationships	10	403		(192		)	211
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(75		)	132
Total		$	255,643	$	(68,952	)	$	186,691

The following table summarizes amortization expense for the twelve months ended December 31, 2019, 2018 and 2017 (in thousands):



	2019		2018		2017
Research and development	$	1,158	$	976	$	327
Selling, general and administrative	18,549		17,052		17,004
Total amortization expense	$	19,707	$	18,028	$	17,331

As of December 31, 2019, amortization expense for the next five years is expected to be as follows (in thousands):



2020	$	20,773
2021	20,773
2022	20,739
2023	20,449
2024	19,543
Thereafter	54,923
Total	$	157,200

STOCKHOLDERS’ EQUITY / DEFICIT - 2015 Equity Incentive Plan (Details)	May 18, 2016 shares	Dec. 31, 2019 shares	Dec. 31, 2018 shares	May 17, 2017 shares	Jun. 08, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)		100,000,000	100,000,000
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)					1,400,000
Shares remaining available for issuance under the plan (in shares)					600,000
2015 Equity Incentive Plan Amended
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	1,600,000			1,800,000
Shares remaining available for issuance under the plan (in shares)	700,000
Options \| 2015 Equity Incentive Plan Amended
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, reduction in number of shares available for grant	1
Restricted Stock \| 2015 Equity Incentive Plan Amended
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, reduction in number of shares available for grant	2.0

RETIREMENT PLAN (Details) - USD ($) $ in Millions	12 Months Ended
RETIREMENT PLAN (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined contribution plan, employer contributions	$ 1.0	$ 0.9	$ 0.6

LEASES - Supplemental Cash Flow Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating cash flow for operating leases	$ 1,710
Right-of-use assets obtained in exchange for lease obligations: operating leases	$ 11,717

INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 0	$ 0
Increase in current period positions	235	0
Decrease in prior period positions	0	0
Increase in prior period positions	0	0
Ending balance	$ 235	$ 0

CONVERTIBLE SENIOR NOTES - Narrative (Details) $ / shares in Units, shares in Millions		1 Months Ended		12 Months Ended
	Sep. 10, 2018 USD ($)	May 31, 2019 USD ($) shares	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) day	Dec. 31, 2017 USD ($)	Sep. 30, 2019	May 29, 2014 USD ($) $ / shares
Debt Instrument [Line Items]
Debt instrument, repurchase amount	$ 23,400,000		$ 23,400,000
Debt instrument, convertible, threshold percentage of stock price trigger				130.00%
Debt instrument, convertible note, market price, per $1,000				$ 775
Debt conversion, liability				198,600,000
Debt conversion, equity				77,400,000
Debt issuance costs, net				$ 8,800,000
Debt instrument, interest rate, effective percentage				7.70%
Loss on extinguishment of debt				$ 0	$ 17,042,000	$ 0
Convertible debt				0	22,457,000
Interest expense				$ 18,828,000	9,810,000	$ 4,422,000
Convertible debt issue (in shares) \| shares		1.3
Convertible Notes Due 2019
Debt Instrument [Line Items]
Aggregate carrying value					22,600,000
Unamortized debt discount					100,000
Convertible debt					22,500,000
Senior Notes \| Senior Notes Due 2025
Debt Instrument [Line Items]
Long-term debt, excluding current maturities	$ 276,000,000
Interest rate percentage	2.50%
Proceeds from issuance of debt	$ 267,200,000
Debt instrument, convertible, conversion price (in USD per share) \| $ / shares				$ 38.80
Credit agreement amount				$ 213,900,000
Long-term debt, excluding current maturities, repaid if converted				$ 276,000,000.0
Debt instrument, convertible, conversion ratio				0.02577
Long-term debt, term				7 years
Debt issuance costs, net				$ 5,176,000	6,073,000
Debt redeemable by holders							100.00%
Aggregate carrying value				276,000,000	276,000,000
Unamortized debt discount				$ 65,963,000	$ 74,836,000
Senior Notes \| Convertible Notes Due 2019
Debt Instrument [Line Items]
Interest rate percentage	4.50%
Debt instrument, repurchase amount			40,200,000
Debt instrument, convertible, threshold trading days \| day					20
Debt instrument, convertible, threshold consecutive trading days \| day					30
Debt instrument, convertible, threshold percentage of stock price trigger					130.00%
Debt instrument, convertible, threshold consecutive days measuring period \| day					10
Trading price per principal, percentage					98.00%
Loss on extinguishment of debt			$ 17,000,000.0
Outstanding principal		$ 22,600,000
Note Purchase Agreement \| Convertible Debt
Debt Instrument [Line Items]
Interest rate percentage								4.50%
Debt instrument, convertible, conversion price (in USD per share) \| $ / shares								$ 17.41
Credit agreement amount								$ 46,000,000
Aggregate carrying value								43,000,000
Unamortized debt discount								$ 3,000,000

STOCKHOLDERS’ EQUITY / DEFICIT - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares underlying options (in shares)	4,936,995	4,834,781
Exercise Price (in USD per share)	$ 18.93	$ 16.81
Remaining contractual term, exercisable (in years)	5 years 7 months 13 days	5 years 11 months 23 days
Exercisable, aggregate intrinsic value	$ 4,490	$ 35,387
Closing stock price of stock options outstanding and exercisable (in USD per share)	$ 14.20	$ 22.63	$ 21.07
Stock Options
Shares
Outstanding, beginning balance (in shares)	7,277,337
Granted (in shares)	1,360,925
Forfeited and expired (in shares)	(1,131,002)
Exercised (in shares)	(135,527)
Outstanding, ending balance (in shares)	7,371,733	7,277,337
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 18.55
Granted (in USD per share)	19.11
Forfeited and expired (in dollars per share)	13.73
Exercised (in USD per share)	11.94
Outstanding, ending balance (in USD per share)	$ 19.52	$ 18.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Remaining contractual term, outstanding (in years)	6 years 7 months 17 days	6 years 11 months 8 days
Outstanding, aggregate intrinsic value	$ 4,906	$ 40,650
Weighted average grant date fair value of options (in USD per share)	$ 12.11	$ 16.21	$ 11.77
Compensation expense not yet recognized, stock options	$ 26,900
Weighted average period for unrecognized costs (in years)	2 years 7 months 6 days

LEASES

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

LEASES

As of January 1, 2019, the Company adopted ASU No. 2016-02, Leases, using a modified retrospective basis method under which prior comparative periods are not restated.

The new standard establishes an ROU model that requires a lessee to record an ROU asset and a lease liability on its balance sheet for all leases with terms longer than 12 months. Leases will be classified as either financing or operating, with classification affecting the pattern of expense recognition in the income statement. In addition, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, ASU No. 2018-11, Targeted Improvements, and ASU No. 2018-20, Narrow-Scope Improvements for Lessors, to clarify and amend the guidance in ASU No. 2016-02. The Company has elected the following as practical expedients from within these ASUs: 1) an entity need not reassess whether any expired or existing contracts are or contain leases; 2) an entity need not reassess the lease classification for any expired or existing leases; and 3) an entity need not reassess initial direct costs for any existing leases.

As of January 1, 2019, the Company had a single operating lease for its office located in San Diego, California. The lease was originally signed in July 2016, and was amended in July 2017 to add office space in adjacent buildings. The term of the original lease is 7 years, 7 months, and is coterminous for all space occurring in July 2024. Under the terms of the lease, the Company will pay base annual rent (subject to an annual fixed percentage increase), plus property taxes and other normal and necessary expenses, such as utilities, repairs, security and maintenance. Certain incentives were included in the lease, including rent abatement and approximately $2.3 million in tenant improvement allowances. The Company has the right to extend the lease for five years.

As of January 1, 2019, the Company's remaining minimum lease payments and unamortized lease incentives were approximately $14.0 million and $1.8 million, respectively. Using a discount rate equal to our borrowing rate of 7.7% and a remaining term of 5 years, 7 months, the Company determined the ROU asset and lease liability as of adoption were $7.9 million and $11.3 million, respectively. There was no cumulative adjustment to our beginning accumulated deficit balance.

In March 2019, the Company amended the existing office lease to add office space in adjacent buildings. The total additional space is expected to be utilized through August 2020 and has future minimum lease payments of approximately $1.0 million. The Company determined the ROU asset and lease liability were each $0.4 million for the lease space that has commenced and was occupied as of September 30, 2019.

On April 23, 2019, the Company entered into an office lease with an effective date of April 12, 2019 with Kilroy Realty, L.P. (the "Landlord"). The Company expects to use the premises as its new principal corporate offices and plans to consolidate its corporate headquarters into the premises from the current location of multiple suites. Under the terms of the lease, the Company will have the one-time right of first offer on the suites it currently occupies and a general right of first offer to lease additional space from the Landlord in the development. The commencement date of the lease is expected to be October 1, 2020. The initial term of the lease is 7 years, 7 months, and the Landlord has granted the Company an option to extend the term of the lease by a period of 5 years. The aggregate base rent due over the initial term of the lease is approximately $36.5 million. The Company is conducting a tenant build improvement project to ensure that space requirements are met.

Following is a schedule of the future minimum rental commitments for our commenced operating lease reconciled to the lease liability and ROU assets as of December 31, 2019 (in thousands):



	December 31, 2019
2020	$	2,613
2021	2,486
2022	2,561
2023	2,637
2024	1,584
Thereafter	—
Total undiscounted future minimum payments	11,881
Present value discount	(1,874		)
Total lease liability	10,007
Lease incentives	(1,463		)
Straight line lease expense in excess of cash payments	(1,549		)
Total ROU asset	$	6,995

As of December 31, 2019, the ROU asset of $7.0 million was recorded to the Consolidated Balance Sheets as non-current Other Assets.

The current and non-current portions of the lease liability were recorded to the Consolidated Balance Sheets as follows (in thousands):



	December 31, 2019
Other current liabilities	$	2,613
Other non-current liabilities	7,394
Total lease liabilities	$	10,007

For the twelve months ended December 31, 2019, the Company recorded $2.7 million in expense related to operating leases.

Supplemental cash flow information related to leases is as follows (in thousands):



	December 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flow for operating leases	$	1,710
Right-of-use assets obtained in exchange for lease obligations:
Operating leases¹	$	11,717

¹Includes leases that commenced during the year ended December 31, 2019, as well as balances related to leases in existence as of the date of the adoption of Topic 842.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Vesting Awards (Details)	12 Months Ended
	Dec. 31, 2019
Stock Options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Stock Options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Restricted Stock Units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Restricted Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years

STOCKHOLDERS’ EQUITY / DEFICIT - 2018 Equity Incentive Plan (Details) - shares	12 Months Ended
	Dec. 31, 2019	May 09, 2019	Dec. 31, 2018	May 08, 2018
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	100,000,000		100,000,000
2018 Equity Incentive Plan
Class of Stock [Line Items]
Common stock, shares authorized (in shares)				1,800,000
Shares remaining available for issuance under the plan (in shares)				1,600,000
Award expiration period	10 years
Increase in authorized shares issuable (in shares)		2,000,000.0
Award vesting period	4 years

PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

Property, plant and equipment, net consisted of the following (in thousands):



	December 31,
	2019			2018
Computers and equipment	$	577		$	506
Furniture and fixtures	1,251			1,150
Leasehold improvements	2,654			2,628
Construction-in-progress	249			—
	4,731			4,284
Less: Accumulated depreciation	(1,840		)	(1,138		)
Total property and equipment, net	$	2,891		$	3,146

The construction-in-process balance consists of costs related to the Company’s leasehold improvements at its facilities in San Diego, California.

Depreciation expense for the years ended December 31, 2019, 2018 and 2017 was $0.7 million, $0.6 million and $0.5 million, respectively.

The Company has not capitalized interest related to the property and equipment purchases.

ACQUISITIONS AND DISPOSITIONS - Amendment to Trademark License and Supply Agreement (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense			$ 19,707	$ 18,028	$ 17,331
Thiola License
Acquired Finite-Lived Intangible Assets [Line Items]
Licensing agreement, extension term		5 years
Payments for the option to acquire business	$ 300
Payment of guaranteed minimum royalty	$ (100)
Minimum royalty, percentage	20.00%
Amortization expense	$ 1,000
Guaranteed minimum liability	$ 700

CONVERTIBLE SENIOR NOTES - Convertible Notes Payable (Details) - Senior Notes Due 2025 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest expense, debt	$ 16,670	$ 4,963
Senior Notes
Debt Instrument [Line Items]
Interest expense, debt	6,900	2,108
Amortization of debt discount	8,874	2,582
Amortization of debt issuance costs	$ 896	$ 273

FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Asset:
Cash and Cash Equivalents	$ 62,436	$ 102,873
Marketable securities, available-for-sale	336,088	368,668
Total	398,524	471,541
Liabilities:
Business combination-related contingent consideration	70,900	93,000
Total	70,900	93,000
Quoted prices in active markets (Level 1)
Asset:
Cash and Cash Equivalents	62,436	62,978
Marketable securities, available-for-sale	0	0
Total	62,436	62,978
Liabilities:
Business combination-related contingent consideration	0	0
Total	0	0
Significant other observable inputs (Level 2)
Asset:
Cash and Cash Equivalents	0	39,895
Marketable securities, available-for-sale	336,088	368,668
Total	336,088	408,563
Liabilities:
Business combination-related contingent consideration	0	0
Total	0	0
Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	0	0
Marketable securities, available-for-sale	0	0
Total	0	0
Liabilities:
Business combination-related contingent consideration	70,900	93,000	$ 90,000
Total	$ 70,900	$ 93,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
Computers and equipment
Property, Plant and Equipment [Line Items]
Use life (in years)	3 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Use life (in years)	7 years

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Compensation related costs	$ 14,045	$ 10,446
Research and development	16,067	16,515
Government rebate reserves	6,584	8,464
Selling, general and administrative	3,552	2,990
Royalty/contingent consideration	7,272	6,805
Miscellaneous accrued expenses	4,225	4,475
Total accrued expenses	$ 51,745	$ 49,695

STOCKHOLDERS’ EQUITY / DEFICIT - Share Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 21,105	$ 19,774	$ 26,874
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	14,195	13,550	17,924
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 6,910	$ 6,224	$ 8,950

STOCKHOLDERS’ EQUITY / DEFICIT

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

STOCKHOLDERS’ EQUITY / DEFICIT

Common Stock

The Company is currently authorized to issue up to 100,000,000 shares of $0.0001 par value common stock. All issued shares of common stock are entitled to vote on a 1 share/1 vote basis.

Preferred Stock

The Company is currently authorized to issue up to 20,000,000 shares of $0.0001 par value preferred stock, of which 1,000 shares are designated Class "A" Preferred shares. Class A Preferred Shares are not entitled to interest, have certain liquidation preferences, special voting rights and other provisions. No preferred stock has been issued to date.

2015 Equity Incentive Plan

On June 8, 2015, the Company's stockholders approved the 2015 Equity Incentive Plan (the "2015 Plan"). The 2015 Plan is intended as the successor to and continuation of the Company’s 2014 Incentive Compensation Plan. Stockholders approved 1.4 million new shares to be issued under the 2015 Plan, in addition to 0.6 million unallocated shares remaining available for issuance under the 2014 Incentive Compensation Plan that were added to the 2015 Plan.

On May 18, 2016, the Company's stockholders approved an amendment to the 2015 Plan (the "Amended 2015 Plan"). The amendment provides for an additional 1.6 million new shares to be issued under the Amended 2015 Plan, in addition to 0.7 million unallocated shares remaining available for issuance. The amendment also includes a provision that on or after March 21, 2016, the number of shares available for issuance under the Amended 2015 Plan will be reduced by one share for each share subject to a stock option or stock appreciation right and by 2.0 shares for each share subject to any other type of stock award issued pursuant to the Amended 2015 Plan, and any such shares will return to the share reserve at the same rates upon cancellation or other forfeiture of such awards or shares.

On May 17, 2017, the Company's stockholders approved an amendment to the Amended 2015 Plan. The amendment provides for an additional 1.8 million new shares to be issued under the Amended 2015 Plan.

2018 Equity Incentive Plan

On May 9, 2018, the Company's stockholders approved the 2018 Equity Incentive Plan (the "2018 Plan"). The 2018 Plan is intended as the successor to and continuation of the Amended 2015 Plan. Stockholders approved 1.8 million new shares to be issued under the 2018 Plan, in addition to 1.6 million unallocated shares remaining available for issuance under the Amended 2015 Plan that were added to the 2018 Plan. Options issued under the 2018 Plan will generally expire ten years from the date of grant and vest over a four-year period. On May 9, 2019, the Company’s stockholders approved an amendment to the 2018 Plan that increased the number of authorized shares issuable under the 2018 Plan by 2.0 million shares.

2017 Employee Stock Purchase Plan

The 2017 Employee Stock Purchase Plan ("2017 ESPP") originated with 380,000 shares of common stock available for issuance. Beginning on January 1, 2018, and ending on (and including) January 1, 2026, the number of shares of common stock available for issuance under the 2017

ESPP shall increase by an amount equal to the lesser of (i) one percent (1%) of the total number of shares of common stock outstanding on December 31st of the preceding calendar year and (ii) 300,000 shares of common stock.

Substantially all employees are eligible to participate and, through payroll deductions, can purchase shares on established dates semi-annually. The purchase price per share sold pursuant to the 2017 ESPP will be the lower of (i) 85% of the fair market value of common stock on the first day of the offering period or (ii) 85% of the fair market value on the purchase date. Each offering period will span up to six months. Purchases may be up to 15% of qualified compensation, with an annual limit of $25,000. The 2017 ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code.

As of December 31, 2019, there were approximately 980,000 shares authorized and 723,642 shares reserved for future issuance under the 2017 ESPP.

Stock Options

The fair values of stock option grants during the years ended December 31, 2019, 2018 and 2017 were calculated on the date of grant using the Black-Scholes option pricing model. Compensation expense is recognized over the period of service, generally the vesting period. During the year ended December 31, 2019, 1,360,925 stock options were granted by the Company. The following weighted average assumptions were used in the Black-Scholes options pricing model to estimate the fair value of stock options for the specified reporting periods:



	Twelve Months Ended December 31,
	2019		2018		2017
Risk free rate	2.30	%	2.80	%	2.10	%
Expected volatility	68	%	68	%	70	%
Expected life (in years)	6.2		6.2		6.1
Expected dividend yield	—		—		—

The risk-free interest rate was based on rates established by the Federal Reserve. The Company’s expected volatility was based on analysis of the Company’s volatility, as well as the volatilities of guideline companies. The expected life of the Company’s options was determined using the simplified method as a result of limited historical data regarding the Company’s exercise activity. The dividend yield is based upon the fact that the Company has not historically paid dividends, and does not expect to pay dividends in the foreseeable future.

The following table summarizes our stock option activity and related information for the year ended December 31, 2019:



			Weighted Average
	Shares Underlying Options		Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018	7,277,337		$	18.55	6.94	$	40,650
Granted	1,360,925		19.11		—	—
Forfeited and expired	(1,131,002	)	13.73		—	—
Exercised	(135,527	)	11.94		—
Outstanding at December 31, 2019	7,371,733		$	19.52	6.63	$	4,906

The following table summarizes our stock options exercisable at December 31, 2019, 2018 and 2017:



		Weighted Average
	Shares Underlying Options	Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
2018	4,834,781	$	16.81	5.98	$	35,387
2019	4,936,995	$	18.93	5.62	$	4,490

The weighted average grant date fair value of options granted was $12.11, $16.21, and $11.77 during the years ended December 31, 2019, 2018 and 2017, respectively. The aggregate intrinsic value for outstanding options is calculated as the difference between the exercise price of the underlying awards and the closing price of the Company’s common stock of $14.20, $22.63 and $21.07 as of December 31, 2019, 2018 and 2017, respectively. Unrecognized compensation cost associated with unvested stock options amounts to $26.9 million as of December 31, 2019, which will be expensed over a weighted average remaining vesting period of 2.6 years.

Restricted Stock Units

As of December 31, 2019, there was approximately $11.9 million of unrecognized compensation cost related to restricted stock units ("RSUs") granted. This amount is expected to be recognized over a weighted average period of 2.6 years.

The following table summarizes our restricted stock unit activity for the year ended December 31, 2019:



	Number of RSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2018	400,426		$	24.95
Granted	559,815		17.15
Vested	(137,203	)	24.43
Forfeited/cancelled	(59,310	)	20.97
Unvested December 31, 2019	763,728		$	19.64

Performance-based Stock Units

As of December 31, 2019, there was approximately $0.5 million of unrecognized compensation cost related to performance-based stock units ("PSUs") granted. This amount is expected to be recognized over a weighted average period of 1.0 years.

The following table summarizes our performance-based stock unit activity for the year ended December 31, 2019:



	Number of PSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2018	226,750		$	21.54
Granted	80,000		21.32
Vested	—		—
Forfeited/cancelled	(73,250	)	23.33
Unvested December 31, 2019	233,500		$	20.90

Share Based Compensation

Total non-cash stock-based compensation expense consisted of the following for the years ended December 31, 2019, 2018 and 2017 (in thousands):



	Twelve Months Ended December 31,
	2019		2018		2017
Selling, general and administrative expenses	$	14,195	$	13,550	$	17,924
Research and development expenses	6,910		6,224		8,950
Total	$	21,105	$	19,774	$	26,874

Exercise of Warrants



	Shares Issued	Cash Received		Derivative Liability Reclassified as Equity		Change in Fair Value Expense
2017	607,481	$	3,645	$	11,221	$	3,033
2018	1,036,054	$	5,305	n/a		n/a
2019	n/a	n/a		n/a		n/a

As of December 31, 2019, there are no warrants for common shares outstanding. See Note 15 for further discussion.

DERIVATIVE FINANCIAL INSTRUMENTS - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Business combination-related contingent consideration			$ 15.7
Class of warrant or right, title of security warrants or rights outstanding (in shares)	0	0

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (4,868,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	10,316,000
Additional Paid-in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 5,394,000

REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Net product sales	$ 46,688	$ 44,373	$ 44,707	$ 39,570	$ 43,771	$ 40,706	$ 41,337	$ 38,432	$ 175,338	$ 164,246	$ 154,937
Thiola License
Disaggregation of Revenue [Line Items]
Net product sales									95,638	89,176	82,311
Bile acid products
Disaggregation of Revenue [Line Items]
Net product sales									$ 79,700	$ 75,070	$ 72,626
Geographic Concentration Risk \| Revenue from Contract with Customer \| United States
Disaggregation of Revenue [Line Items]
Concentration risk, percentage									95.00%

LEASES - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Apr. 23, 2019	Jan. 01, 2019	Jul. 31, 2016
Lessee, Lease, Description [Line Items]
Operating lease term					7 years 7 months
Lease incentives	$ 1,463			$ 1,800	$ 2,300
Operating lease extension term					5 years
Future minimum lease payments	11,881			$ 14,000
Operating lease discount rate				7.70%
Remaining lease term				5 years 7 months
Operating lease right-of-use asset	6,995			$ 7,900
Operating lease liability	10,007			$ 11,300
Operating lease expense	$ 2,700
March 2019 Operating Lease Amendment
Lessee, Lease, Description [Line Items]
Future minimum lease payments		$ 1,000
Operating lease right-of-use asset		400
Operating lease liability		$ 400
3611 Valley Centre Drive, San Diego, California
Lessee, Lease, Description [Line Items]
Operating lease extension term			5 years
Future minimum lease payments			$ 36,500
Remaining lease term			7 years 7 months

CONVERTIBLE SENIOR NOTES

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

CONVERTIBLE SENIOR NOTES

Convertible Senior Notes Due 2025

On September 10, 2018, the Company completed its registered underwritten public offering of $276 million aggregate principal amount of 2.50% Convertible Senior Notes due 2025 ("2025 Notes") and entered into a base indenture and supplemental indenture agreement ("2025 Indenture") with respect to the 2025 Notes. The 2025 Notes will mature on September 15, 2025 ("Maturity Date”), unless earlier repurchased, redeemed, or converted. The 2025 Notes are senior unsecured obligations of the Company and bear interest at an annual rate of 2.50%, payable semi-annually in arrears on March 15 and September 15 of each year, beginning on March 15, 2019.

The composition of the Company’s 2025 Notes are as follows (in thousands):



	December 31, 2019			December 31, 2018
2.50% convertible senior notes due 2025	$	276,000		$	276,000
Unamortized debt discount	(65,963		)	(74,836		)
Unamortized debt issuance costs	(5,176		)	(6,073		)
Total 2025 Notes, net of unamortized debt discount and debt issuance costs	$	204,861		$	195,091

The net proceeds from the issuance of the 2025 Notes were approximately $267.2 million, after deducting commissions and the offering expenses payable by the Company. A portion of the net proceeds from the 2025 Notes were used by the Company to repurchase $23.4 million aggregate principal amount of its 4.5% senior convertible notes due in 2019 in privately-negotiated transactions.

Holders may convert their 2025 Notes at their option only in the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2018 (and only during such calendar quarter), if the last reported sale price per share of the Company’s common stock for each of at least 20 trading days, whether or not consecutive, during the period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter exceeds 130% of the conversion price on the applicable trading day; (2) during the five consecutive business days immediately after any 10 consecutive trading day period (“measurement period”) if the trading price per $1,000 principal amount of 2025 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company’s common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company’s common stock; (4) if the Company calls the 2025 Notes for redemption; and (5) at any time from, and including, May 15, 2025 until the close of business on the scheduled trading day immediately before the Maturity Date. The Company will settle conversions by paying or delivering, as applicable, cash, shares of the Company’s common stock, or a combination of cash and shares of the Company’s common stock, at the Company’s election, based on the applicable conversion rate.

The initial conversion rate for the 2025 Notes is 25.7739 shares of the Company’s common stock per $1,000 principal amount of 2025 Notes, which represents an initial conversion price of approximately $38.80 per share. If a “make-whole fundamental change” (as defined in the 2025 Indenture) occurs, then the company will, in certain circumstances, increase the conversion rate for a specified period of time.

The 2025 Notes will be redeemable, in whole or in part, at the Company’s option at any time, and from time to time, on or after September 15, 2022 and, in the case of any partial redemption, on or before the 40th scheduled trading day before the Maturity Date, at a cash redemption price equal to the principal amount of the 2025 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date, but only if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price on each of at least 20 trading days during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice. If a fundamental change (as defined in the 2025 Indenture) occurs, then, subject to certain exceptions, holders may require the

Company to repurchase their 2025 Notes at a cash repurchase price equal to the principal amount of the 2025 Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date.

As of December 31, 2019, the 2025 Notes had a market price of $775 per $1,000 or $213.9 million principal amount. In the event of conversion, holders would forgo all future interest payments, any unpaid accrued interest and the possibility of further stock price appreciation. Upon the receipt of conversion requests, the settlement of the 2025 Notes will be paid pursuant to the terms of the 2025 Indenture. In the event that all of the 2025 Notes are converted, the Company would be required to repay the $276.0 million in principal value and any conversion premium in any combination of cash and shares of its common stock at the Company’s option. In addition, calling the 2025 Notes for redemption will constitute a “make whole fundamental change.”

The 2025 Notes are the Company’s general unsecured obligations that rank senior in right of payment to all of its indebtedness that is expressly subordinated in right of payment to the 2025 Notes, and equal in right of payment to the Company’s unsecured indebtedness.

The 2025 Notes are currently classified on the Company’s consolidated balance sheet at December 31, 2019 as long-term debt.

Under ASC 470-20, Debt with Conversion and Other Options, an entity must separately account for the liability and equity components of convertible debt instruments (such as the 2025 Notes) that may be settled entirely or partially in cash upon conversion, in a manner that reflects the issuer’s economic interest cost. The liability component of the instrument is valued in a manner that reflects the market interest rate for a similar nonconvertible instrument at the date of issuance. The initial carrying value of the liability component was $198.6 million. The equity component of $77.4 million, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the 2025 Notes and is recorded in additional paid-in capital on the consolidated balance sheet at the issuance date. That equity component is treated as a discount on the liability component of the 2025 Notes, which is amortized over the seven-year term of the 2025 Notes using the effective interest rate method. The equity component is not re-measured as long as it continues to meet the conditions for equity classification. The Company allocated the total transaction costs of approximately $8.8 million related to the issuance of the 2025 Notes to the liability and equity components of the 2025 Notes based on their relative values. Transaction costs attributable to the liability component are amortized to interest expense over the seven-year term of the 2025 Notes, and transaction costs attributable to the equity component are netted with the equity component in stockholders’ equity.

The effective interest rate on the liability components of the 2025 Notes for the period from the date of issuance through December 31, 2019 was 7.7%. The following table sets forth total interest expense recognized related to the 2025 Notes (in thousands):



	Twelve Months Ended December 31,
	2019		2018
Contractual interest expense	$	6,900	$	2,108
Amortization of debt discount	8,874		2,582
Amortization of debt issuance costs	896		273
Total interest expense for the 2025 Notes	$	16,670	$	4,963

The 2025 Notes do not contain any financial or operating covenants or any restrictions on the payment of dividends, the issuance of other indebtedness or the issuance or repurchase of securities by the Company. The 2025 Indenture contains customary events of default with respect to the 2025 Notes, including that upon certain events of default, 100% of the principal and accrued and unpaid interest on the 2025 Notes will automatically become due and payable.

Convertible Senior Notes Due 2019

On May 29, 2014, the Company entered into a Note Purchase Agreement relating to a private placement by the Company of $46 million aggregate principal senior convertible notes due 2019 (the “2019 Notes”) which were convertible into shares of the Company’s common stock at an initial conversion price of $17.41 per share. The conversion price was subject to customary anti-dilution protection. The 2019 Notes bore interest at a rate of 4.5% per annum, payable semiannually in arrears on May 15 and November 15 of each year, beginning on November 15, 2014. The 2019 Notes had a maturity date of May 30, 2019. The aggregate carrying value of the 2019 Notes on their issuance was $43 million, which was net of the $3 million debt discount.

In September 2018, the Company used part of the net proceeds from the issuance of the 2025 Notes discussed above to repurchase $23.4 million aggregate principal value of the 2019 Notes in privately-negotiated transactions for approximately $40.2 million in cash. The partial repurchase of the 2019 Notes resulted in a $17.0 million loss on early extinguishment of debt.

As of December 31, 2018, the total 2019 Notes, net of unamortized debt discount and debt issuance costs was $22.5 million, consisting of $22.6 million of aggregate principle and $0.1 million of unamortized debt discount and debt issuance costs.

In May 2019, the remaining $22.6 million outstanding principal amount of 2019 Notes was converted by the holders thereof into approximately 1.3 million shares of common stock.

Interest Expense

Total interest expense recognized for the years ended December 31, 2019, 2018 and 2017 was $18.8 million, $9.8 million and $4.4 million, respectively.

LEASES - Future Minimum Rent Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Jul. 31, 2016
Leases [Abstract]
2020	$ 2,613
2021	2,486
2022	2,561
2023	2,637
2024	1,584
Thereafter	0
Total undiscounted future minimum payments	11,881	$ 14,000
Present value discount	(1,874)
Total lease liability	10,007	11,300
Lease incentives	(1,463)	(1,800)	$ (2,300)
Straight line lease expense in excess of cash payments	(1,549)
Total ROU asset	$ 6,995	$ 7,900

INCOME TAXES - Narrative (Details) - USD ($)	12 Months Ended
INCOME TAXES - Narrative (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ (84,745,000)	$ (36,194,000)
Increase in valuation allowance primarily attributable to Tax and Jobs Act of 2017	48,600,000
Unrecognized tax benefits	235,000	0	$ 0
Income tax examination, penalties and interest expense	0	0	0
Income tax examination, penalties and interest accrued	0	$ 0	$ 0
U.S. federal
Operating Loss Carryforwards [Line Items]
Available unused NOL carryforwards	113,600,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Available unused NOL carryforwards	65,800,000
Federal Orphan Drug Tax Credit
Operating Loss Carryforwards [Line Items]
Research and development tax credits	28,500,000
Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credits	3,300,000
Tax Competes Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credits	$ 2,000,000.0

DERIVATIVE FINANCIAL INSTRUMENTS

12 Months Ended

Dec. 31, 2019

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVE FINANCIAL INSTRUMENTS

Since 2013, the Company has issued 5 tranches of common stock purchase warrants to secure financing, remediate covenant violations related to a credit facility and provide consideration for credit facility amendments.

Historically, the Company accounted for these instruments, which do not have fixed settlement provisions, as derivative instruments in accordance with FASB ASC 815-40, Derivative and Hedging - Contracts in Entity’s Own Equity. This was due to an anti-dilution provision for the warrants that provides for a reduction to the exercise price if the Company issues equity or equity linked instruments in the future at an effective price per share less than the exercise price then in effect for the warrant ("down round provision"). As such, the warrants were re-measured at each balance sheet date based on estimated fair value. Changes in estimated fair value were recorded as non-cash adjustments within other income (expenses), net, in the Company’s Consolidated Statements of Operations and Comprehensive Income (Loss).

The fair value of the derivative liability balance as of December 31, 2017 of $15.7 million was reclassified by means of a cumulative-effect adjustment to equity as of January 1, 2018.

The following table presents the Company’s derivative warrant issuances and balances outstanding during the year ended December 31, 2018:



		Weighted Average
	Warrants	Exercise Price		Grant Date Fair Value
Outstanding at December 31, 2017	1,159,424	$	7.86	$	4.15
Issued	—	—		—
Canceled	554	5.99		3.33
Exercised	1,158,870	7.88		4.15
Outstanding at December 31, 2018	—	—		—

As of December 31, 2019 and 2018, there were no outstanding warrants.

SUBSEQUENT EVENTS (Details)	Feb. 24, 2020 USD ($)
Subsequent Event
Subsequent Event [Line Items]
Aggregate offering price (up to)	$ 100,000,000.0

FAIR VALUE MEASUREMENTS

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

The Company accounts for financial instruments in accordance with ASC 820, “Fair Value Measurements and Disclosures” (“ASC 820”). ASC 820 establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under ASC 820 are described below:

Level 1 – Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 2 – Quoted prices in markets that are not active or financial instruments for which all significant inputs are observable, either directly or indirectly; and

Level 3 – Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

The Company acquired two businesses, related to the Cholbam and Chenodal products, whose purchase price included potential future payments that are contingent on the achievement of certain milestones and percentages of future net sales derived from the products acquired. The Company recorded contingent consideration liabilities at their fair value on the acquisition date and revalues them at the end of each reporting period. In estimating the fair value of the Company’s contingent consideration, the Company uses a Monte Carlo Simulation. The determination of the contingent consideration liabilities requires significant judgments including the appropriateness of the valuation model and reasonableness of estimates and assumptions included in the forecasts of future net sales and the discount rates applied to such sales. Changes in these estimates and assumptions could have a significant impact on the fair value of the contingent consideration liabilities. Based on the fair value hierarchy, the Company classified contingent consideration within Level 3 because valuation inputs are based on projected revenues discounted to a present value

Financial instruments with carrying values approximating fair value include cash and cash equivalents, accounts receivable, notes receivable, deposits on lease agreements, and accounts payable, due to their short-term nature.

The following table presents the Company’s asset and liabilities that are measured and recognized at fair value on a recurring basis, classified under the appropriate level of the fair value hierarchy as of December 31, 2019 (in thousands):



	As of December, 2019		Fair Value Hierarchy at December 31, 2019
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	62,436	$	62,436	$	—	$	—
Marketable securities, available-for-sale	336,088		—		336,088		—
Total	$	398,524	$	62,436	$	336,088	$	—
Liabilities:
Business combination-related contingent consideration	$	70,900	$	—	$	—	$	70,900
Total	$	70,900	$	—	$	—	$	70,900

The following table presents the Company’s assets and liabilities that are measured and recognized at fair value on a recurring basis, classified under the appropriate level of the fair value hierarchy as of December 31, 2018 (in thousands):



	As of December, 2018		Fair Value Hierarchy at December 31, 2018
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	102,873	$	62,978	$	39,895	$	—
Marketable securities, available-for-sale	368,668		—		368,668		—
Total	$	471,541	$	62,978	$	408,563	$	—
Liabilities:
Business combination-related contingent consideration	93,000		—		—		93,000
Total	$	93,000	$	—	$	—	$	93,000

The following table sets forth a summary of changes in the estimated fair value of the Company's Level 3 business combination-related contingent consideration for the years ended December 31, 2019 and 2018 (in thousands):



	Contingent Consideration (Level 3)
	2019			2018
Balance at January 1,	$	93,000		$	90,000
L-UDCA write-off	(18,000		)	—
Increase from revaluation of contingent consideration	15,051			11,590
Contractual Payments	(6,696		)	(6,373		)
Contractual Payments accrued at December 31	(12,253		)	(2,171		)
Foreign currency impact	(202		)	(46		)
Balance at December 31,	$	70,900		$	93,000

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

INCOME TAXES - Components of Net Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Loss before provision for income taxes	$ (30,227)	$ (37,013)	$ (38,632)	$ (40,576)	$ (7,455)	$ (54,101)	$ (22,162)	$ (18,149)	$ (146,448)	$ (101,867)	$ (58,363)
United States
Operating Loss Carryforwards [Line Items]
Loss before provision for income taxes									(129,452)	(87,573)	(55,611)
Foreign
Operating Loss Carryforwards [Line Items]
Loss before provision for income taxes									$ (16,996)	$ (14,294)	$ (2,752)

CONVERTIBLE SENIOR NOTES - Schedule of Carrying Amount of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Sep. 10, 2018
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (8,800)
Senior Notes Due 2025 \| Senior Notes
Debt Instrument [Line Items]
Interest rate percentage			2.50%
2.50% convertible senior notes due 2025	276,000	$ 276,000
Unamortized debt discount	(65,963)	(74,836)
Unamortized debt issuance costs	(5,176)	(6,073)
Net carrying amount	$ 204,861	$ 195,091

PROPERTY AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Summary of Property, Plant, and Equipment

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Property, plant and equipment, net consisted of the following (in thousands):



	December 31,
	2019			2018
Computers and equipment	$	577		$	506
Furniture and fixtures	1,251			1,150
Leasehold improvements	2,654			2,628
Construction-in-progress	249			—
	4,731			4,284
Less: Accumulated depreciation	(1,840		)	(1,138		)
Total property and equipment, net	$	2,891		$	3,146

ACCRUED EXPENSES (Tables)

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Schedule of accrued expenses

Accrued expenses consist of the following at December 31, 2019 and 2018 (in thousands):



	2019		2018
Compensation related costs	$	14,045	$	10,446
Research and development	16,067		16,515
Government rebate reserves	6,584		8,464
Selling, general and administrative	3,552		2,990
Royalty/contingent consideration	7,272		6,805
Miscellaneous accrued expenses	4,225		4,475
Total accrued expenses	$	51,745	$	49,695

DERIVATIVE FINANCIAL INSTRUMENTS - Derivative Warrant Issuances (Details) - Derivative - Warrants	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Shares
Outstanding, beginning balance (in shares) \| shares	1,159,424
Issued (in shares) \| shares	0
Canceled (in shares) \| shares	554
Exercised (in shares) \| shares	1,158,870
Outstanding, ending balance (in shares) \| shares	0
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 7.86
Issued (in USD per share)	0
Cancelled (in USD per share)	5.99
Exercised (in USD per share)	7.88
Outstanding, ending balance (in USD per share)	0
Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance (in USD per share)	4.15
Issued (in USD per share)	0
Cancelled (in USD per share)	3.33
Exercised (in USD per share)	4.15
Outstanding, Ending Balance (in USD per share)	$ 0

QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Consolidated Statements of Operations data for each quarter

The following table presents selected consolidated statements of operations data for each quarter for the fiscal years ended December 31, 2019 and 2018 (unaudited, in thousands, except for per share data):



	Fourth Quarter			Third Quarter				Second Quarter			First Quarter

For the year ended December 31, 2019:
Net product sales	$	46,688		$	44,373			$	44,707		$	39,570
Total operating expenses	74,855			78,810			¹	81,236			77,798			²
Operating loss	(28,167		)	(34,437		)		(36,529		)	(38,228		)
Total other expense, net	(2,060		)	(2,576		)		(2,103		)	(2,348		)
Loss before provision for income taxes	(30,227		)	(37,013		)		(38,632		)	(40,576		)
Income tax benefit (provision)	(32		)	523				(69		)	(401		)
Net income (loss)	$	(30,259	)	$	(36,490	)		$	(38,701	)	$	(40,977	)
Net Loss per common share
Basic and diluted	$	(0.70	)	$	(0.85	)		$	(0.92	)	$	(0.99	)
For the year ended December 31, 2018:
Net product sales	$	43,771		$	40,706			$	41,337		$	38,432
Total operating expenses	48,756			76,289			³	62,897			56,344
Operating loss	(4,985		)	(35,583		)		(21,560		)	(17,912		)
Total other income (expense), net	(2,470		)	(18,518		)	⁴	(602		)	(237		)
Income (loss) before provision for income taxes	(7,455		)	(54,101		)		(22,162		)	(18,149		)
Income tax benefit (provision)	—			(415		)		(167		)	(229		)
Net income (loss)	$	(7,455	)	$	(54,516	)		$	(22,329	)	$	(18,378	)
Net loss per common share
Basic and diluted	$	(0.18	)	$	(1.34	)		$	(0.56	)	$	(0.46	)

¹ In August 2019, following a strategic review of the CNSA-001 program in patients with PKU, the Company made the decision to decline to exercise its option to acquire Censa Pharmaceuticals and accordingly discontinue its joint development program for CNSA-001. The Company impaired the $15 million long-term investment during the third quarter of 2019.

² During the first quarter of 2019, the Company elected to discontinue development of the L-UDCA program, resulting in the removal of the intangible asset of $25.5 million which was originally recorded in 2016, and the reversal of associated contingent consideration of $18.0 million. This resulted in a net $7.5 million non-cash charge to first quarter operations.

³During the third quarter of 2018, the Company's operating expenses increased due to the ramp up in on-going Phase 3 clinical trials for fosmetpantotenate in PKAN and sparsentan in FSGS, and changes in fair value of contingent consideration.

⁴In September 2018, the Company executed a partial repurchase of the 2019 Notes that resulted in a $17.0 million loss on early extinguishment of debt. See Note 7 for further discussion.

Cover Page - USD ($)	12 Months Ended
Cover Page - USD ($)	Dec. 31, 2019	Feb. 20, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-36257
Entity Registrant Name	RETROPHIN, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-4842691
Entity Address, Address Line One	3721 Valley Centre Drive
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92130
City Area Code	888
Local Phone Number	969-7879
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	RTRX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 853,241,144
Entity Common Stock, Shares Outstanding		43,115,508
Documents Incorporated by Reference	Portions of the Proxy Statement for the registrant’s Annual Meeting of Stockholders to be held May 13, 2020, to be filed within 120 days after the conclusion of the registrant's fiscal year ended December 31, 2019, are incorporated by reference into Part III of this Annual Report on Form 10-K.
Entity Central Index Key	0001438533
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY

CONVERTIBLE SENIOR NOTES (Tables)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Schedule of fair value of warrants



	Twelve Months Ended December 31,
	2019		2018
Contractual interest expense	$	6,900	$	2,108
Amortization of debt discount	8,874		2,582
Amortization of debt issuance costs	896		273
Total interest expense for the 2025 Notes	$	16,670	$	4,963

The composition of the Company’s 2025 Notes are as follows (in thousands):



	December 31, 2019			December 31, 2018
2.50% convertible senior notes due 2025	$	276,000		$	276,000
Unamortized debt discount	(65,963		)	(74,836		)
Unamortized debt issuance costs	(5,176		)	(6,073		)
Total 2025 Notes, net of unamortized debt discount and debt issuance costs	$	204,861		$	195,091

INCOME TAXES

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

INCOME TAXES

For financial reporting purposes, net loss before income taxes includes the following components (in thousands):



	Year Ended December 31,
	2019			2018			2017
United States	$	(129,452	)	$	(87,573	)	$	(55,611	)
Foreign	(16,996		)	(14,294		)	(2,752		)
Total	$	(146,448	)	$	(101,867	)	$	(58,363	)

The components of the provision (benefit) for income taxes, in the Consolidated Statement of Operations are as follows (in thousands):



	2019			2018		2017
Current
Federal	$	(319	)	$	698	$	6,991
State	298			113		802
	(21		)	811		7,793
Deferred
Federal	—			—		(7,965		)
State	—			—		1,540
	—			—		(6,425		)
Total tax provision (benefit)	$	(21	)	$	811	$	1,368

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate expressed as a percentage of loss before income taxes:



	2019		2018		2017
Statutory rate - federal	(21.00	)%	(21.00	)%	(35.00	)%
State taxes, net of federal benefit	(4.35	)%	(4.44	)%	(3.30	)%
Change in FV of derivative liability (warrants)	—	%	—	%	2.82	%
Change in federal tax rate	—	%	—	%	23.29	%
Convertible Debt	—	%	21.77	%	—	%
Loss on extinguishment of debt	—	%	4.09	%	—	%
Other permanent differences	0.24	%	0.10	%	1.04	%
Tax credits	(15.17	)%	(11.86	)%	(5.79	)%
Return to provision adjustments and other true-ups	0.44	%	1.42	%	(3.48	)%
Other	2.32	%	1.06	%	1.25	%
Change in valuation allowance	37.50	%	9.79	%	21.62	%
Income tax provision (benefit)	(0.02	)%	0.93	%	2.45	%

The significant components of the Company’s deferred tax assets and liabilities as of December 31, 2019 and 2018 are as follows (in thousands):



	2019			2018
Deferred Tax Assets:
Net operating loss	$	27,747		$	9,700
Research and development and other tax credits	33,315			14,715
Contingent consideration	18,029			23,459
Other accrued expenses	4,319			3,710
Stock based compensation	19,458			16,761
Charitable Contributions	1,256			—
Other	—			555
	104,124			68,900
Deferred Tax Liabilities:
Intangible assets	(2,749		)	(14,288		)
Convertible Debt	(16,182		)	(18,419		)
Tax basis depreciation less than book depreciation	(448		)	—
	(19,379		)	(32,707		)

Net deferred tax assets before valuation allowance	84,745			36,194
Valuation allowance	(84,745		)	(36,194		)
Total deferred tax assets	$	—		$	—

The Company has established a full valuation allowance against its U.S. federal and state deferred tax assets due to the uncertainty surrounding the realization of such assets in future periods. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which temporary differences become deductible. Management considers the scheduled reversal of deferred liabilities and tax planning strategies in making this assessment and evaluates the recoverability of the deferred tax assets as of each reporting date. At such time as it is determined that it is more likely than not that deferred assets are realizable, the valuation allowance will be reduced accordingly and recorded as a tax benefit.

The Company has recorded a valuation allowance of $84.7 million as of December 31, 2019 to reflect the estimated amount of deferred tax assets that may not be realized. The Company increased its valuation allowance by $48.6 million for the year ended December 31, 2019.

At December 31, 2019, the Company had available unused U.S. federal and state net operating loss (“NOL”) carryforwards of $113.6 million and $65.8 million, respectively, all of which are fully offset by a valuation allowance. The state NOL carryforwards will begin to expire in 2022. In addition, at December 31, 2019, the Company had federal orphan drug tax credit carryforwards of $28.5 million that begin to expire in 2037 unless utilized, federal research and development tax credit carryforwards of $3.3 million that begin to expire in 2038 unless utilized and California Competes tax credit carryforwards of $2.0 million that begin to expire in 2022. The Company has international subsidiaries whose operations are not material for the year ended December 31, 2019.

The Company accounts for uncertain tax benefits in accordance with the provisions of ASC 740-10 of the Accounting for Uncertainty in Income Taxes. As of December 31, 2019 the Company had $0.2 million in unrecognized tax benefits.

The Company does not anticipate that the amount of unrecognized tax benefits as of December 31, 2019 will change materially within the following 12 months.

A reconciliation of the Company's unrecognized tax benefits for the years 2019 and 2018 is provided in the following table (in thousands):



	2019		2018
Balance as of January 1:	$	—	$	—
Increase in current period positions	235		—
Decrease in prior period positions	—		—
Increase in prior period positions	—		—
Balance as of December 31:	$	235	$	—

The Company files income tax returns in the U.S. federal jurisdiction, various state and local, and foreign jurisdictions. The Company’s income tax returns are open to examination by federal, state and foreign tax authorities, generally for the years ended December 31, 2016 and later.

The Company’s policy is to record estimated interest and penalties related to the underpayment of income taxes or unrecognized tax benefits as a component of its income tax provision. During the years ended 2019, 2018 and 2017, the Company did not recognize any interest or penalties in its Consolidated Statements of Operations and Comprehensive Loss and there were no accruals recorded for interest or penalties at December 31, 2019 and 2018.

INCOME TAXES - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current
Federal									$ (319)	$ 698	$ 6,991
State									298	113	802
Total									(21)	811	7,793
Deferred
Federal									0	0	(7,965)
State									0	0	1,540
Total									0	0	(6,425)
Total tax provision (benefit)	$ 32	$ (523)	$ 69	$ 401	$ 0	$ 415	$ 167	$ 229	$ (21)	$ 811	$ 1,368

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Preferred Stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	43,088,921	41,389,524
Common stock, shares outstanding (in shares)	43,088,921	41,389,524

DESCRIPTION OF BUSINESS

12 Months Ended

Dec. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

DESCRIPTION OF BUSINESS

Organization and Description of Business

Retrophin, Inc. (“we”, “our”, “us”, “Retrophin” and the “Company”) refers to Retrophin, Inc., a Delaware corporation, as well as our direct and indirect subsidiaries. Retrophin is a fully integrated biopharmaceutical company headquartered in San Diego, California focused on identifying, developing and delivering life-changing therapies to people with rare diseases. We regularly evaluate and, where appropriate, act on opportunities to expand our product pipeline through licenses and acquisitions of products in areas that will serve patients with serious or rare diseases and that we believe offer attractive growth characteristics.

Clinical Programs

Sparsentan, also known as RE-021, is an investigational product candidate with a dual mechanism of action, a selective endothelin receptor antagonist (“ERA”), with in vitro selectivity toward endothelin receptor type A and a potent angiotensin receptor blocker (“ARB”). Sparsentan is currently being evaluated in two pivotal Phase 3 clinical studies in the following indications:


•	Focal segmental glomerulosclerosis ("FSGS") is a rare kidney disease characterized by proteinuria where the glomeruli become progressively scarred. FSGS is a leading cause of end-stage renal disease.


•	Immunoglobulin A nephropathy ("IgAN") is an immune-complex-mediated glomerulonephritis characterized by hematuria, proteinuria, and variable rates of progressive renal failure. IgAN is the most common primary glomerular disease.

Chenodal^® has also been the standard of care for cerebrotendinous xanthomatosis (“CTX”) patients for more than three decades but is not currently labeled for this indication. In January 2020, we randomized the first patients in a Phase 3 clinical trial to evaluate the effects of Chenodal in adult and pediatric patients with CTX. The pivotal study, known as the RESTORE study, is intended to support a new drug application (“NDA”) submission for marketing authorization of Chenodal for CTX in the United States.

Cooperative Research and Development Agreements ("CRADAs"):

The Company is a participant in two CRADAs, which form a multi-stakeholder approach to pool resources with leading experts, and incorporates the patient perspective early in the identification and development process. Retrophin has partnered with the National Institutes of Health’s National Center for Advancing Translational Sciences ("NCATS") and leading patient advocacy organizations, NGLY1.org and Alagille Syndrome Alliance ("ALGSA"), aimed at the identification of potential small molecule therapeutics for NGLY1 deficiency and Alagille syndrome, respectively. There are no treatment options currently approved for these diseases.

Approved products:


•	Chenodal (chenodiol tablets) is approved in the United States for the treatment of patients suffering from gallstones in whom surgery poses an unacceptable health risk due to disease or advanced age. Chenodal has been the standard of care for CTX patients for more than three decades.


•	Cholbam^® (cholic acid capsules) is approved in the United States for the treatment of bile acid synthesis disorders due to single enzyme defects and is further indicated for adjunctive treatment of patients with peroxisomal disorders.


•	Thiola^® and Thiola EC^® (tiopronin tablets) are approved in the United States for the prevention of cystine (kidney) stone formation in patients with severe homozygous cystinuria.

Changes in Development Activities:

In August 2019, the Company announced that the Phase 3 FORT Study evaluating the safety and efficacy of fosmetpantotenate compared to placebo in patients with pantothenate kinase-associated neurodegeneration ("PKAN") did not meet its primary endpoint and did not demonstrate a difference between treatment groups. The study also did not meet its secondary endpoint. The Company will not proceed with further development of fosmetpantotenate for PKAN.

In August 2019, following a strategic review of the CNSA-001 program in patients with phenylketonuria ("PKU"), the Company made the decision to decline to exercise its option to acquire Censa Pharmaceuticals and accordingly discontinue its joint development program for CNSA-001. The Company impaired the related $15 million long-term investment during the third quarter of 2019.

During the first quarter of 2019, the Company elected to discontinue development of the L-UDCA program, resulting in impairment of the intangible asset of $25.5 million, originally recorded in 2016, and the related $18.0 million in contingent liability. This resulted in a net $7.5 million non-cash charge to first quarter operations.

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2019

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of derivative warrant issuances and balances outstanding

The following table presents the Company’s derivative warrant issuances and balances outstanding during the year ended December 31, 2018:



		Weighted Average
	Warrants	Exercise Price		Grant Date Fair Value
Outstanding at December 31, 2017	1,159,424	$	7.86	$	4.15
Issued	—	—		—
Canceled	554	5.99		3.33
Exercised	1,158,870	7.88		4.15
Outstanding at December 31, 2018	—	—		—

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Leases On February 7, 2020, the Company notified its landlord, Kilroy Realty, L.P., of its intention to vacate the premises of its existing office leases. The abandonment of this leased office space coincides with the Company’s expected occupancy of the new office lease space in the adjacent building per the office lease made effective April 12, 2019. The expiration of the existing leases is estimated to occur in the third quarter of 2020, depending on the ability of the current tenant to vacate the new leased premises, through which date, the Company is obligated to pay all base rent, operating expenses and other obligations due under the existing lease. The impending expiration of the existing lease will result in an adjustment to the ROU asset and lease liability in the first quarter of 2020, with acceleration of certain costs through the expiration date, at which time the carrying amounts for the ROU asset and related lease liability will be reduced to zero. The ROU asset and lease liability related to the new office lease will be established when the Company is granted access to the premise and has the ability to direct its use. As such, the ROU asset for the new lease will be established prior to the extinguishment of the ROU asset and lease liability for the existing lease, resulting in an overlap of ROU assets during the interim period between inception of the new lease and the expiration of the old lease. At-The-Market Equity Offering Program On February 24, 2020, we entered into an Open Market Sale Agreement with Jefferies LLC, as agent (“Jefferies”), pursuant to which we may offer and sell, from time to time through Jefferies, shares of our common stock having an aggregate offering price of up to $100.0 million (the “ATM Shares”). The ATM Shares will be sold pursuant to our effective registration statement on Form S-3 (Registration Statement No. 333-227182), as previously filed with the Securities and Exchange Commission.

INTANGIBLE ASSETS (Tables)

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of amortizable intangible assets

Amortizable intangible assets as of December 31, 2019 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(24,451	)	$	43,398
Thiola License	15	85,824		(20,417		)	65,407
Economic Interest - U.S. revenue Cholbam	10	75,900		(36,071		)	39,829
Economic Interest - International revenue Cholbam	10	7,544		(3,585		)	3,959
Ligand License	11	7,900		(3,555		)	4,345
Manchester Customer Relationships	10	403		(232		)	171
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(116		)	91
Total		$	245,802	$	(88,602	)	$	157,200

Amortizable intangible assets as of December 31, 2018 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(20,213	)	$	47,636
Thiola License	15	70,009		(14,523		)	55,486
Economic Interest - U.S. revenue Cholbam	10	75,900		(28,487		)	47,413
Economic Interest - International revenue Cholbam	10	7,700		(2,890		)	4,810
Economic Interest - L-UDCA (acquired IPR&D)	Indefinite	25,500		—			25,500
Ligand License	11	7,900		(2,397		)	5,503
Manchester Customer Relationships	10	403		(192		)	211
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(75		)	132
Total		$	255,643	$	(68,952	)	$	186,691

Schedule of amortization expense for the next 5 years

The following table summarizes amortization expense for the twelve months ended December 31, 2019, 2018 and 2017 (in thousands):



	2019		2018		2017
Research and development	$	1,158	$	976	$	327
Selling, general and administrative	18,549		17,052		17,004
Total amortization expense	$	19,707	$	18,028	$	17,331

As of December 31, 2019, amortization expense for the next five years is expected to be as follows (in thousands):



2020	$	20,773
2021	20,773
2022	20,739
2023	20,449
2024	19,543
Thereafter	54,923
Total	$	157,200

COMMITMENTS AND CONTINGENCIES	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Legal Proceedings In August 2017, Martin Shkreli, the Company’s former Chief Executive Officer, was convicted on securities fraud charges. Mr. Shkreli's conviction was subsequently affirmed upon appeal. In connection with the trial and appeal proceedings, the Company advanced a portion of Mr. Shkreli's legal fees, of which $3.8 million was reimbursed by its directors’ and officers’ insurance carriers. Pending the outcome of Mr. Shkreli's appeal, the insurance carriers reserved their rights to assert that certain of the advanced funds pertain to claims excluded from coverage under the relevant insurance policy and are therefore recoverable by the carriers, and therefore the final amount of the reimbursement from the insurance carriers is not currently estimable. In October 2018, Spring Pharmaceuticals, LLC (Spring) filed a lawsuit against the Company, Martin Shkreli, Mission Pharmacal Company and Alamo Pharma Services, Inc. in the United States District Court for the Eastern District of Pennsylvania alleging that the Company violated various federal and state antitrust and unfair competition laws by allegedly refusing to sell samples of the Thiola^® brand drug so that Spring can conduct the bioequivalence testing needed to submit an ANDA to the FDA for approval to market a generic version of the product. The lawsuit sought injunctive relief and damages. In December 2019, the Court granted the Company's motion to dismiss the lawsuit, but granted Spring permission to amend its complaint. On February 10, 2020, Spring filed an amended complaint. Spring’s amended complaint seeks injunctive relief and damages. The Company intends to vigorously defend against Spring’s claims. No amounts have been accrued related to this matter and the outcome cannot be determined. The Company is not aware of any other proceedings or claims that could have, individually or in the aggregate, a material adverse effect on its results of operations or financial condition.

QUARTERLY FINANCIAL INFORMATION (UNAUDITED)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

QUARTERLY FINANCIAL INFORMATION (UNAUDITED)



	Fourth Quarter			Third Quarter				Second Quarter			First Quarter

For the year ended December 31, 2019:
Net product sales	$	46,688		$	44,373			$	44,707		$	39,570
Total operating expenses	74,855			78,810			¹	81,236			77,798			²
Operating loss	(28,167		)	(34,437		)		(36,529		)	(38,228		)
Total other expense, net	(2,060		)	(2,576		)		(2,103		)	(2,348		)
Loss before provision for income taxes	(30,227		)	(37,013		)		(38,632		)	(40,576		)
Income tax benefit (provision)	(32		)	523				(69		)	(401		)
Net income (loss)	$	(30,259	)	$	(36,490	)		$	(38,701	)	$	(40,977	)
Net Loss per common share
Basic and diluted	$	(0.70	)	$	(0.85	)		$	(0.92	)	$	(0.99	)
For the year ended December 31, 2018:
Net product sales	$	43,771		$	40,706			$	41,337		$	38,432
Total operating expenses	48,756			76,289			³	62,897			56,344
Operating loss	(4,985		)	(35,583		)		(21,560		)	(17,912		)
Total other income (expense), net	(2,470		)	(18,518		)	⁴	(602		)	(237		)
Income (loss) before provision for income taxes	(7,455		)	(54,101		)		(22,162		)	(18,149		)
Income tax benefit (provision)	—			(415		)		(167		)	(229		)
Net income (loss)	$	(7,455	)	$	(54,516	)		$	(22,329	)	$	(18,378	)
Net loss per common share
Basic and diluted	$	(0.18	)	$	(1.34	)		$	(0.56	)	$	(0.46	)

⁴In September 2018, the Company executed a partial repurchase of the 2019 Notes that resulted in a $17.0 million loss on early extinguishment of debt. See Note 7 for further discussion.

ACCRUED EXPENSES

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

ACCRUED EXPENSES

Accrued expenses consist of the following at December 31, 2019 and 2018 (in thousands):



	2019		2018
Compensation related costs	$	14,045	$	10,446
Research and development	16,067		16,515
Government rebate reserves	6,584		8,464
Selling, general and administrative	3,552		2,990
Royalty/contingent consideration	7,272		6,805
Miscellaneous accrued expenses	4,225		4,475
Total accrued expenses	$	51,745	$	49,695

RETIREMENT PLAN	12 Months Ended
RETIREMENT PLAN	Dec. 31, 2019
Retirement Benefits [Abstract]
RETIREMENT PLAN	RETIREMENT PLAN The Company has a 401(k) defined contribution savings plan for the benefit of all eligible employees. Employer matching contributions were $1.0 million, $0.9 million, and $0.6 million for the years ended December 31, 2019, 2018 and 2017, respectively.

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net product sales	$ 175,338	$ 164,246	$ 154,937
Operating expenses:
Cost of goods sold	5,234	5,527	3,605
Research and development	140,963	123,757	78,168
Selling, general and administrative	128,951	103,654	101,333
Change in fair value of contingent consideration	15,051	11,590	19,389
Restructuring	0	(242)	3,608
Legal fee settlement	0	0	2,625
Impairment of L-UDCA IPR&D intangible asset	25,500	0	0
Write off of L-UDCA contingent consideration	(18,000)	0	0
Impairment of long-term investment	15,000	0	0
Total operating expenses	312,699	244,286	208,728
Operating loss	(137,361)	(80,040)	(53,791)
Other Income (expense), net:
Other income (expense), net	(314)	(474)	1,107
Interest income	10,055	5,499	3,234
Interest expense	(18,828)	(9,810)	(4,422)
Loss on extinguishment of debt	0	(17,042)	0
Change in fair value of derivative instruments	0	0	(4,491)
Total other expense, net	(9,087)	(21,827)	(4,572)
Loss before benefit (provision) for income taxes	(146,448)	(101,867)	(58,363)
Income tax benefit (provision)	21	(811)	(1,368)
Net loss	$ (146,427)	$ (102,678)	$ (59,731)
Net loss per common share:
Basic and diluted net loss per common share (in USD per share)	$ (3.46)	$ (2.54)	$ (1.54)
Weighted average common shares outstanding:
Basic and diluted weighted average common shares outstanding (in shares)	42,339,961	40,433,171	38,769,816
Comprehensive loss:
Net loss	$ (146,427)	$ (102,678)	$ (59,731)
Foreign currency translation gain (loss)	92	39	(339)
Unrealized gain (loss) on marketable securities	2,163	(553)	(186)
Comprehensive loss	$ (144,172)	$ (103,192)	$ (60,256)

INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Thousands		1 Months Ended				3 Months Ended	12 Months Ended
	Jun. 20, 2016	Nov. 30, 2018	Mar. 31, 2018	Nov. 30, 2017	Sep. 30, 2015	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net							$ 157,200
Payments to date under terms of licensing agreement							15,370	$ 18,974	$ 13,122
Amortization expense							19,707	18,028	17,331
Impairment of intangible assets						$ 25,500	25,500	0	$ 0
Economic Interest - L-UDCA (acquired IPR&D)
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives	$ 25,500
Assets useful life (in years)	17 years
Total purchase price	$ 25,500
Ligand License Agreement
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net											$ 2,500
Require to make substantial payments payable upon achievement of milestones											$ 114,100
Payments to date under terms of licensing agreement							$ 7,200
Payment of amendment consideration					$ 1,000
Ligand License Agreement \| Minimum
Finite-Lived Intangible Assets [Line Items]
Annual royalty percentage							15.00%
Ligand License Agreement \| Maximum
Finite-Lived Intangible Assets [Line Items]
Annual royalty percentage							17.00%
Licensing Agreements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired			$ 4,600
Product rights
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net							$ 43,398	$ 47,636
Assets useful life (in years)							16 years	16 years
Finite-lived intangible asset							$ 67,849	$ 67,849
Product rights \| Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives										$ 67,800
Assets useful life (in years)										16 years
Trade Name
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net							$ 0	$ 0
Assets useful life (in years)							1 year	1 year
Finite-lived intangible asset							$ 175	$ 175
Trade Name \| Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives										$ 200
Assets useful life (in years)										1 year
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net							$ 171	$ 211
Assets useful life (in years)							10 years	10 years
Finite-lived intangible asset							$ 403	$ 403
Customer relationships \| Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives										$ 400
Assets useful life (in years)										10 years
Thiola License Agreement
Finite-Lived Intangible Assets [Line Items]
Assets useful life (in years)										10 years
Automatic renewal periods										1 year
Remaining weighed average period of amortization (in years)							9 years 4 months 24 days
Thiola License Agreement \| Mission Pharmacal Company
Finite-Lived Intangible Assets [Line Items]
Annual royalty percentage							20.00%
Mission an up-front license fee							$ 3,000
Guaranteed minimum royalties							2,000
Present value of guaranteed minimum royalties payable							14,300	15,200
Thiola License Agreement \| Mission Pharmacal Company \| Other Current Liabilities
Finite-Lived Intangible Assets [Line Items]
Guaranteed minimum royalties							2,100	2,100
Thiola License Agreement \| Mission Pharmacal Company \| Other Noncurrent Liabilities
Finite-Lived Intangible Assets [Line Items]
Guaranteed minimum royalties							$ 12,200	13,100
Thiola License Agreement \| Mission Pharmacal Company \| Minimum
Finite-Lived Intangible Assets [Line Items]
Discount rate							7.00%
Thiola License Agreement \| Mission Pharmacal Company \| Maximum
Finite-Lived Intangible Assets [Line Items]
Discount rate							11.00%
Acquired Product Rights L-UDCA
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets						$ 25,500
Thiola
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net							$ 65,407	$ 55,486
Assets useful life (in years)							15 years	15 years
Licensing agreement, extension term				5 years
Finite-lived intangible asset				$ 5,900			$ 85,824	$ 70,009
Payments for the option to acquire business		$ 300
Payment of guaranteed minimum royalty		$ 100
Minimum royalty, percentage		20.00%
Amortization expense		$ 1,000
Guaranteed minimum liability		$ 700
Increase in intangible assets							$ 15,800
United States \| Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Capitalized economic interest												$ 75,900
International \| Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Capitalized economic interest												$ 7,300

LOSS PER SHARE - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	15,875,963	16,299,349	11,039,901
Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	7,632,414	8,410,932	2,642,160
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	599,298	395,034	157,319
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	7,644,251	7,210,576	7,080,998
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	0	282,807	1,159,424

STOCKHOLDERS’ EQUITY / DEFICIT - Unvested Restricted Stock (Details) - Restricted shares $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to restricted shares granted \| $	$ 11.9
Weighted average period for unrecognized costs (in years)	2 years 7 months 6 days
Number of shares
Unvested beginning balance (in shares) \| shares	400,426
Granted (in shares) \| shares	559,815
Vested (in shares) \| shares	(137,203)
Forfeited/cancelled (in shares) \| shares	(59,310)
Unvested ending balance (in shares) \| shares	763,728
Weighted Average Grant Date Fair Value
Unvested beginning balance (in USD per share) \| $ / shares	$ 24.95
Granted (in USD per share) \| $ / shares	17.15
Vested (in USD per share) \| $ / shares	24.43
Forfeited/cancelled (in USD per share) \| $ / shares	20.97
Unvested ending balance (in USD per share) \| $ / shares	$ 19.64

LOSS PER SHARE

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

LOSS PER SHARE

Basic earnings (loss) per share (“EPS”) represents net income (loss) attributable to common shareholders divided by the weighted average number of common shares outstanding during the measurement period. Diluted EPS represents net income attributable to common shareholders divided by the weighted average number of common shares outstanding during the measurement period while also giving effect to all potentially dilutive common shares that were outstanding during the period using the treasury stock method.

Basic and diluted EPS is calculated as follows (net loss amounts are stated in thousands):



	For the year ended December 31,
	2019							2018							2017
	Shares	Net loss			EPS			Shares	Net loss			EPS			Shares	Net Loss			EPS
Basic and dilutive loss per share	42,339,961	$	(146,427	)	$	(3.46	)	40,433,171	$	(102,678	)	$	(2.54	)	38,769,816	$	(59,731	)	$	(1.54	)

For the years ended December 31, 2019, 2018 and 2017, the following shares were excluded because they were anti-dilutive:



	For the year ended December 31,
	2019	2018	2017
Convertible Debt	7,632,414	8,410,932	2,642,160
Restricted Stock	599,298	395,034	157,319
Options	7,644,251	7,210,576	7,080,998
Warrants	—	282,807	1,159,424
Total Anti-Dilutive Shares	15,875,963	16,299,349	11,039,901

INTANGIBLE ASSETS - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 19,707	$ 18,028	$ 17,331
Research and development
Finite-Lived Intangible Assets [Line Items]
Amortization expense	1,158	976	327
Selling, general and administrative
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 18,549	$ 17,052	$ 17,004

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Vesting Award Terms



	Vesting Term
Stock Options	3 to 4 years
Restricted Stock Units	1 to 4 years

Schedule of inventory, net of reserve

Inventory, net of reserve, consisted of the following at December 31, 2019 and 2018 (in thousands):



	December 31, 2019		December 31, 2018
Raw material	$	2,713	$	2,883
Finished goods	3,369		2,736
Total inventory	$	6,082	$	5,619

Schedule of major classifications of property, equipment and software, including their respective expected useful lives

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Property, plant and equipment, net consisted of the following (in thousands):



	December 31,
	2019			2018
Computers and equipment	$	577		$	506
Furniture and fixtures	1,251			1,150
Leasehold improvements	2,654			2,628
Construction-in-progress	249			—
	4,731			4,284
Less: Accumulated depreciation	(1,840		)	(1,138		)
Total property and equipment, net	$	2,891		$	3,146

REVENUE RECOGNITION

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

REVENUE RECOGNITION

Product Revenue, Net

Product sales for the year ended December 31, 2019 consisted of sales of Bile Acid products (Chenodal and Cholbam) and Tiopronin products (Thiola and Thiola EC). Prior to 2019 product sales consisted of Chenodal, Cholbam and Thiola.

The Company sells its products through direct-to-patient distributors worldwide, with more than 95% of the revenue generated in North America.

Revenues from product sales are recognized when the customer obtains control of the Company’s product, which occurs upon delivery to the customer. The Company receives payments from its product sales based on terms that generally are within 30 days of delivery of product to the patient.

Deductions from Revenue

Revenues from product sales are recorded at the net sales price, which includes provisions resulting from discounts, rebates and co-pay assistance that is offered to its customers, health care providers, payors and other indirect customers relating to the Company’s sales of its products. These provisions are based on the amounts earned or to be claimed on the related sales and are classified as a reduction of accounts receivable (if the amount is payable to the customer) or as a current liability (if the amount is payable to a party other than a customer). Where appropriate, these reserves take into consideration the Company’s historical experience, current contractual and statutory requirements and specific known market events and trends. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contract. If actual results in the future vary from the Company’s provisions, the Company will adjust the provision, which would affect net product revenue and earnings in the period such variances become known. Our historical experience is that such adjustments have been immaterial.

Government Rebates: We calculate the rebates that we will be obligated to provide to government programs and deduct these estimated amounts from our gross product sales at the time the revenues are recognized. Allowances for government rebates and discounts are established based on actual payer information, which is reasonably estimated at the time of delivery, and the government-mandated discounts applicable to government-funded programs. Rebate discounts are included in accrued expenses in the accompanying consolidated balance sheets.

Commercial Rebates: We calculate the rebates that we incur due to contracts with certain commercial payors and deduct these amounts from our gross product sales at the time the revenues are recognized. Allowances for commercial rebates are established based on actual payer information, which is reasonably estimated at the time of delivery. Rebate discounts are included in accrued expenses in the accompanying consolidated balance sheets.

Prompt Pay Discounts: We offer discounts to certain customers for prompt payments. We accrue for the calculated prompt pay discount based on the gross amount of each invoice for those customers at the time of sale.

Product Returns: Consistent with industry practice, we offer our customers a limited right to return product purchased directly from the Company, which is principally based upon the product’s expiration date. Generally, shipments are only made upon a patient prescription thus returns are minimal.

Co-pay Assistance: We offer a co-pay assistance program, which is intended to provide financial assistance to qualified commercially insured patients with prescription drug co-payments required by payors. The calculation of the accrual for co-pay assistance is based on an identification of claims and the cost per claim associated with product that has been recognized as revenue.

The following table summarizes net product revenues for the twelve months ended December 31, 2019, 2018 and 2017 (in thousands):



	Twelve Months Ended December 31,
	2019		2018		2017
Tiopronin products	$	95,638	$	89,176	$	82,311
Bile acid products	79,700		75,070		72,626
Total net product revenue	$	175,338	$	164,246	$	154,937

ACQUISITIONS AND DISPOSITIONS	12 Months Ended
ACQUISITIONS AND DISPOSITIONS	Dec. 31, 2019
Business Combinations [Abstract]
ACQUISITIONS AND DISPOSITIONS	FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT Censa Pharmaceuticals Inc. In December 2017, the Company entered into a Future Acquisition Right and Joint Development Agreement (the “Option Agreement”) with Censa, which became effective in January 2018. The Company made an upfront payment of $10.0 million, agreed to fund certain development activities of Censa’s CNSA-001 program which were approximately $19.9 million through proof of concept, and paid $5.0 million related to a development milestone for the right, but not the obligation, to acquire Censa (the “Option”) on the terms and subject to the conditions set forth in a separate Agreement and Plan of Merger. The Company capitalized the upfront and milestone payments and expensed the development funding as incurred. The Company treated the upfront payment and milestone payment, both of which were consideration for the Option, as a cost-method investment with a carrying value of $15.0 million. The Company determined that Censa was a variable interest entity ("VIE"), and concluded that the Company was not the primary beneficiary of the VIE. As such, the Company did not consolidate Censa’s results into its consolidated financial statements. In August 2019, following a strategic review of the CNSA-001 program in patients with PKU, the Company made the decision to decline to exercise its option to acquire Censa Pharmaceuticals and accordingly discontinue its joint development program for CNSA-001. The Company impaired the $15 million long-term investment during the third quarter of 2019. If the Company had exercised the Option, the Company would have acquired Censa for an additional $65.0 million, which would have been reduced by up to $2.8 million of development funding ("creditable"), paid as a combination of 20% in cash and 80% in shares of the Company’s common stock, valued at a fixed price of $21.40 per share; provided, however, that Censa could have elected on behalf of its equity holders to receive the upfront consideration in 100% cash if the average price per share of the Company’s common stock for the ten trading days ending on the date the Company provided notice of interest to exercise the Option was less than $19.26. In addition, if the Company had exercised the Option and acquired Censa, the Company would have been required to make further cash payments to Censa’s equity holders of up to an aggregate of $25.0 million if the CNSA-001 program had achieved specified development and commercial milestones. ACQUISITIONS AND DISPOSITIONS Amendment to Trademark License and Supply Agreement In November 2017, the Company amended their agreement with the manufacturer of Thiola to extend the term of the current exclusive U.S. and Canada licensing agreement by an additional five years, to 2029. The royalty rate and guaranteed minimum payment were also extended through the new agreement term. In November 2018, the license agreement was amended to extend the territorial rights beyond the United States and Canada. As consideration for the expanded territory the Company paid an up-front fee of $0.3 million and will pay guaranteed minimum royalties equaling the greater of $0.1 million or 20% of our Thiola net sales generated from outside of the United States during each calendar year. Upon execution of the amendment, the Company capitalized an additional $1.0 million in intangible assets and recorded a guaranteed minimum liability of $0.7 million related to this amendment. Acquisition and disposition of Liquid Ursodeoxycholic Acid (L-UDCA) On June 20, 2016, the Company signed a definitive agreement to purchase the rights, titles, licenses and ownership of L-UDCA from Asklepion Pharmaceuticals, LLC ("Asklepion"). The acquisition was accounted for under the acquisition method of accounting in accordance with Accounting Standard Codification ("ASC") 805. The fair value of assets acquired and liabilities assumed was based upon an independent third-party valuation and the Company’s estimates. Critical estimates in valuing certain intangible assets include but are not limited to future expected cash flows from acquired product rights for L-UDCA, licenses, trade names and developed technologies, present value and discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. The purchase included $25.5 million for an intangible asset with a definite life related to product rights in the U.S. The useful life related to the acquired product rights was expected to be approximately 17 years once the NDA was approved by the FDA. Until approval, the asset was considered IPR&D with an indefinite life and was not amortized. The contingent consideration of $25.0 million (present value) recorded during the period ended June 30, 2016, was related to an agreement to pay an additional cash amount in the form of milestones and sales royalties through 2035. During the first quarter of 2019, the Company elected to discontinue development of the L-UDCA program and wrote off the $25.5 million intangible asset and related contingent consideration liability of $18 million.

INTANGIBLE ASSETS - Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (88,602)	$ (68,952)
Intangible assets finite-lived, net	157,200
Intangible assets, gross (excluding goodwill)	245,802	255,643
Intangible assets, net (excluding goodwill)	$ 157,200	$ 186,691
Chenodal Product Rights
Finite-Lived Intangible Assets [Line Items]
Useful Life	16 years	16 years
Gross Carrying Amount	$ 67,849	$ 67,849
Accumulated Amortization	(24,451)	(20,213)
Intangible assets finite-lived, net	$ 43,398	$ 47,636
Thiola License
Finite-Lived Intangible Assets [Line Items]
Useful Life	15 years	15 years
Gross Carrying Amount	$ 85,824	$ 70,009	$ 5,900
Accumulated Amortization	(20,417)	(14,523)
Intangible assets finite-lived, net	$ 65,407	$ 55,486
Economic Interest - U.S. revenue Cholbam
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Gross Carrying Amount	$ 75,900	$ 75,900
Accumulated Amortization	(36,071)	(28,487)
Intangible assets finite-lived, net	$ 39,829	$ 47,413
Economic Interest - International revenue Cholbam
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Gross Carrying Amount	$ 7,544	$ 7,700
Accumulated Amortization	(3,585)	(2,890)
Intangible assets finite-lived, net	$ 3,959	4,810
Economic Interest - L-UDCA (acquired IPR&D)
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets		$ 25,500
Ligand License
Finite-Lived Intangible Assets [Line Items]
Useful Life	11 years	11 years
Gross Carrying Amount	$ 7,900	$ 7,900
Accumulated Amortization	(3,555)	(2,397)
Intangible assets finite-lived, net	$ 4,345	$ 5,503
Manchester Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Gross Carrying Amount	$ 403	$ 403
Accumulated Amortization	(232)	(192)
Intangible assets finite-lived, net	$ 171	$ 211
Manchester Trade Name
Finite-Lived Intangible Assets [Line Items]
Useful Life	1 year	1 year
Gross Carrying Amount	$ 175	$ 175
Accumulated Amortization	(175)	(175)
Intangible assets finite-lived, net	$ 0	$ 0
Internal Use Software
Finite-Lived Intangible Assets [Line Items]
Useful Life	5 years	5 years
Gross Carrying Amount	$ 207	$ 207
Accumulated Amortization	(116)	(75)
Intangible assets finite-lived, net	$ 91	$ 132

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Inventory, Net of Reserve (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Raw material	$ 2,713	$ 2,883
Finished goods	3,369	2,736
Total inventory	$ 6,082	$ 5,619

REVENUE RECOGNITION (Tables)

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Summary of Net Product Revenue

The following table summarizes net product revenues for the twelve months ended December 31, 2019, 2018 and 2017 (in thousands):



	Twelve Months Ended December 31,
	2019		2018		2017
Tiopronin products	$	95,638	$	89,176	$	82,311
Bile acid products	79,700		75,070		72,626
Total net product revenue	$	175,338	$	164,246	$	154,937

FAIR VALUE MEASUREMENTS - Fair Value of Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1	$ 93,000
Balance at December 31	70,900	$ 93,000
Significant unobservable inputs (Level 3)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1	93,000	90,000
L-UDCA write-off	(18,000)	0
Increase from revaluation of contingent consideration	15,051	11,590
Contractual Payments	(6,696)	(6,373)
Contractual Payments accrued at December 31	(12,253)	(2,171)
Foreign currency impact	(202)	(46)
Balance at December 31	$ 70,900	$ 93,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Principles of Consolidation

Use of Estimates

Revenue Recognition

Patents

Research and Development Costs

Clinical Trial Expenses

Employee Stock-Based Compensation



	Vesting Term
Stock Options	3 to 4 years
Restricted Stock Units	1 to 4 years

Earnings (Loss) Per Share

Cash and Cash Equivalents

Marketable Securities

Trade Receivables, Net

Segment Information

Property and Equipment, net

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Intangible Assets, Net

Goodwill

Impairment of Long-Lived Assets

During the first quarter of 2019, the Company elected to discontinue development of the L-UDCA program, resulting in the write off of the IPR&D intangible asset, see Note 5 for further discussion.

Fair Value Measurements

Contingent Consideration

Level 1 – Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 2 – Quoted prices in markets that are not active or financial instruments for which all significant inputs are observable, either directly or indirectly; and

Level 3 – Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

Income Taxes

Reclassifications

Certain reclassifications have been made to the prior year financial statements in order to conform to the current year’s presentation.

Derivative Financial Instruments, Warrants

Recently Issued Accounting Pronouncements

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net loss	$ (146,427)	$ (102,678)	$ (59,731)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	20,408	18,668	17,804
Deferred income tax	0	0	(6,425)
Settlement expense	0	0	2,625
Loss on extinguishment of debt	0	17,042	0
Impairment of intangible assets	25,500	0	0
Loss on allowance for inventory	1,468	2,457	609
Loss on impairment of long-term investment	(15,000)	0	0
Accretion of notes receivable	0	0	(651)
Accretion of contingent consideration	1,485	1,357	1,723
Amortization of debt discount and deferred financing costs	9,903	3,398	656
Amortization of (discounts) premiums on investments	(788)	382	1,338
Share based compensation	21,105	19,774	26,874
Change in estimated fair value of contingent consideration	(2,948)	11,590	19,389
Payments from change in fair value of contingent consideration	(5,661)	(8,085)	(3,949)
Change in estimated fair value of liability classified warrants	0	0	4,491
Foreign currency transaction gain	112	464	(1,081)
Other operating activities	(51)	(396)	(83)
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	(5,184)	152	4,945
Inventory	(1,958)	(2,773)	(1,706)
Prepaid expenses and other current assets	(7,931)	(1,358)	(2,702)
Prepaid income taxes	555	1,126	621
Accounts payable	9,255	(2,708)	2,060
Accrued expenses and other current liabilities	7,943	16,630	596
Net cash provided by (used in) operating activities	(58,214)	(24,958)	7,403
Cash Flows from Investing Activities:
Purchase of fixed assets	(195)	(727)	(887)
Purchase of intangible assets	(15,370)	(18,974)	(13,122)
Investment - Equity	0	(15,000)	0
Proceeds from the sale/maturity of marketable securities	259,140	162,755	114,526
Purchase of marketable securities	(223,712)	(331,345)	(102,415)
Proceeds from the maturity of notes receivable	0	0	47,500
Net cash provided by (used in) investing activities	19,863	(203,291)	45,602
Cash Flows from Financing Activities:
Payment of acquisition-related contingent consideration	(3,388)	(9,721)	(4,099)
Payment of other liability	0	(1,000)	(852)
Payment of guaranteed minimum royalty	(2,084)	(2,000)	(2,000)
Proceeds from exercise of warrants	0	5,305	3,645
Proceeds from exercise of stock options	1,618	10,588	8,087
Proceeds from issuance of 2025 convertible senior notes	0	276,000	0
Repurchase of 2019 convertible senior notes including premium	0	(40,203)	0
Payment of debt issuance and financing costs	0	(8,820)	0
Other financing activities	1,777	1,714	664
Net cash provided by (used in) financing activities	(2,077)	231,863	5,445
Effect of exchange rate changes on cash	(9)	(135)	(58)
Net increase (decrease) in cash and cash equivalents	(40,437)	3,479	58,392
Cash and cash equivalents, beginning of year	102,873	99,394	41,002
Cash and cash equivalents, end of year	62,436	102,873	99,394
Supplemental Disclosure of Cash Flow Information:
Cash paid for interest	7,669	1,880	2,070
Cash paid for income taxes	656	218	7,172
Non-cash Investing and financing activities:
Reclassification of derivative liability to equity due to exercise of warrants	0	0	11,221
Accrued royalty in excess of minimum payable to the sellers of Thiola	15,815	14,572	13,247
Term extension of current Thiola agreement	0	0	5,885
Adoption of ASU 2017-11 - reclassification of derivative liability of warrants with down round provisions	$ 0	$ 15,710	$ 0

LEASES (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Schedule of future minimum rent commitments

Following is a schedule of the future minimum rental commitments for our commenced operating lease reconciled to the lease liability and ROU assets as of December 31, 2019 (in thousands):



	December 31, 2019
2020	$	2,613
2021	2,486
2022	2,561
2023	2,637
2024	1,584
Thereafter	—
Total undiscounted future minimum payments	11,881
Present value discount	(1,874		)
Total lease liability	10,007
Lease incentives	(1,463		)
Straight line lease expense in excess of cash payments	(1,549		)
Total ROU asset	$	6,995

Supplemental balance sheet information

The current and non-current portions of the lease liability were recorded to the Consolidated Balance Sheets as follows (in thousands):



	December 31, 2019
Other current liabilities	$	2,613
Other non-current liabilities	7,394
Total lease liabilities	$	10,007

Supplemental cash flow information

Supplemental cash flow information related to leases is as follows (in thousands):



	December 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flow for operating leases	$	1,710
Right-of-use assets obtained in exchange for lease obligations:
Operating leases¹	$	11,717

¹Includes leases that commenced during the year ended December 31, 2019, as well as balances related to leases in existence as of the date of the adoption of Topic 842.

FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of fair value on a recurring basis



	As of December, 2019		Fair Value Hierarchy at December 31, 2019
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	62,436	$	62,436	$	—	$	—
Marketable securities, available-for-sale	336,088		—		336,088		—
Total	$	398,524	$	62,436	$	336,088	$	—
Liabilities:
Business combination-related contingent consideration	$	70,900	$	—	$	—	$	70,900
Total	$	70,900	$	—	$	—	$	70,900



	As of December, 2018		Fair Value Hierarchy at December 31, 2018
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	102,873	$	62,978	$	39,895	$	—
Marketable securities, available-for-sale	368,668		—		368,668		—
Total	$	471,541	$	62,978	$	408,563	$	—
Liabilities:
Business combination-related contingent consideration	93,000		—		—		93,000
Total	$	93,000	$	—	$	—	$	93,000

Schedule of fair value measurements of acquisition-related contingent consideration



	Contingent Consideration (Level 3)
	2019			2018
Balance at January 1,	$	93,000		$	90,000
L-UDCA write-off	(18,000		)	—
Increase from revaluation of contingent consideration	15,051			11,590
Contractual Payments	(6,696		)	(6,373		)
Contractual Payments accrued at December 31	(12,253		)	(2,171		)
Foreign currency impact	(202		)	(46		)
Balance at December 31,	$	70,900		$	93,000

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 4,731	$ 4,284
Less: Accumulated depreciation	(1,840)	(1,138)
Total property and equipment, net	2,891	3,146
Depreciation	700	600	$ 500
Computers and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	577	506
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,251	1,150
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,654	2,628
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 249	$ 0

DESCRIPTION OF BUSINESS (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
DESCRIPTION OF BUSINESS (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of long-term investment	$ 15,000		$ 15,000	$ 0	$ 0
Impairment of L-UDCA IPR&D intangible asset		$ 25,500	25,500	0	0
Write off of L-UDCA contingent consideration		18,000	$ 18,000	$ 0	$ 0
Loss on write-off of L-UDCA		7,500
Acquired Product Rights L-UDCA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of L-UDCA IPR&D intangible asset		25,500
Write off of L-UDCA contingent consideration		$ 18,000

INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets:
Net operating loss	$ 27,747	$ 9,700
Research and development and other tax credits	33,315	14,715
Contingent consideration	18,029	23,459
Other accrued expenses	4,319	3,710
Stock based compensation	19,458	16,761
Charitable Contributions	1,256	0
Other	0	555
Deferred tax assets	104,124	68,900
Deferred Tax Liabilities:
Intangible assets	(2,749)	(14,288)
Convertible Debt	(16,182)	(18,419)
Tax basis depreciation less than book depreciation	(448)	0
Deferred tax liabilities	(19,379)	(32,707)
Net deferred tax assets before valuation allowance	84,745	36,194
Valuation allowance	(84,745)	(36,194)
Total deferred tax assets	$ 0	$ 0

STOCKHOLDERS’ EQUITY / DEFICIT - Common Stock and Preferred Stock (Details)	12 Months Ended
	Dec. 31, 2019 vote $ / shares shares	Dec. 31, 2018 $ / shares shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, par value (in USD per share) \| $ / shares	$ 0.0001	$ 0.0001
Number of votes per common share owned \| vote	1
Preferred Stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, par value (in USD per share) \| $ / shares	$ 0.0001	$ 0.0001
Series A Preferred Stock
Class of Stock [Line Items]
Preferred Stock, shares authorized (in shares)	1,000

LOSS PER SHARE (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of basic and diluted net loss per share

Basic and diluted EPS is calculated as follows (net loss amounts are stated in thousands):



	For the year ended December 31,
	2019							2018							2017
	Shares	Net loss			EPS			Shares	Net loss			EPS			Shares	Net Loss			EPS
Basic and dilutive loss per share	42,339,961	$	(146,427	)	$	(3.46	)	40,433,171	$	(102,678	)	$	(2.54	)	38,769,816	$	(59,731	)	$	(1.54	)

Schedule of common stock options, convertible debt and restricted stock units anti-dilutive

For the years ended December 31, 2019, 2018 and 2017, the following shares were excluded because they were anti-dilutive:



	For the year ended December 31,
	2019	2018	2017
Convertible Debt	7,632,414	8,410,932	2,642,160
Restricted Stock	599,298	395,034	157,319
Options	7,644,251	7,210,576	7,080,998
Warrants	—	282,807	1,159,424
Total Anti-Dilutive Shares	15,875,963	16,299,349	11,039,901

ACQUISITIONS AND DISPOSITIONS - Acquisition of Liquid Ursodeoxycholic Acid (L-UDCA) Narrative (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Jun. 20, 2016	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Impairment of L-UDCA IPR&D intangible asset		$ 25,500	$ 25,500	$ 0	$ 0
Write off of L-UDCA contingent consideration		$ 18,000	$ 18,000	$ 0	$ 0
Economic Interest - L-UDCA (acquired IPR&D)
Business Acquisition [Line Items]
Intangible assets acquired with definite lives	$ 25,500
Assets useful life (in years)	17 years
Present value of contingent consideration	$ 25,000

INTANGIBLE ASSETS - Amortization Expense Next Five Years (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2020	$ 20,773
2021	20,773
2022	20,739
2023	20,449
2024	19,543
Thereafter	54,923
Intangible assets finite-lived, net	$ 157,200

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT	12 Months Ended
	Dec. 31, 2019
Future Acquisition Right And Joint Development Agreement [Abstract]
FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT	FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT Censa Pharmaceuticals Inc. In December 2017, the Company entered into a Future Acquisition Right and Joint Development Agreement (the “Option Agreement”) with Censa, which became effective in January 2018. The Company made an upfront payment of $10.0 million, agreed to fund certain development activities of Censa’s CNSA-001 program which were approximately $19.9 million through proof of concept, and paid $5.0 million related to a development milestone for the right, but not the obligation, to acquire Censa (the “Option”) on the terms and subject to the conditions set forth in a separate Agreement and Plan of Merger. The Company capitalized the upfront and milestone payments and expensed the development funding as incurred. The Company treated the upfront payment and milestone payment, both of which were consideration for the Option, as a cost-method investment with a carrying value of $15.0 million. The Company determined that Censa was a variable interest entity ("VIE"), and concluded that the Company was not the primary beneficiary of the VIE. As such, the Company did not consolidate Censa’s results into its consolidated financial statements. In August 2019, following a strategic review of the CNSA-001 program in patients with PKU, the Company made the decision to decline to exercise its option to acquire Censa Pharmaceuticals and accordingly discontinue its joint development program for CNSA-001. The Company impaired the $15 million long-term investment during the third quarter of 2019. If the Company had exercised the Option, the Company would have acquired Censa for an additional $65.0 million, which would have been reduced by up to $2.8 million of development funding ("creditable"), paid as a combination of 20% in cash and 80% in shares of the Company’s common stock, valued at a fixed price of $21.40 per share; provided, however, that Censa could have elected on behalf of its equity holders to receive the upfront consideration in 100% cash if the average price per share of the Company’s common stock for the ten trading days ending on the date the Company provided notice of interest to exercise the Option was less than $19.26. In addition, if the Company had exercised the Option and acquired Censa, the Company would have been required to make further cash payments to Censa’s equity holders of up to an aggregate of $25.0 million if the CNSA-001 program had achieved specified development and commercial milestones. ACQUISITIONS AND DISPOSITIONS Amendment to Trademark License and Supply Agreement In November 2017, the Company amended their agreement with the manufacturer of Thiola to extend the term of the current exclusive U.S. and Canada licensing agreement by an additional five years, to 2029. The royalty rate and guaranteed minimum payment were also extended through the new agreement term. In November 2018, the license agreement was amended to extend the territorial rights beyond the United States and Canada. As consideration for the expanded territory the Company paid an up-front fee of $0.3 million and will pay guaranteed minimum royalties equaling the greater of $0.1 million or 20% of our Thiola net sales generated from outside of the United States during each calendar year. Upon execution of the amendment, the Company capitalized an additional $1.0 million in intangible assets and recorded a guaranteed minimum liability of $0.7 million related to this amendment. Acquisition and disposition of Liquid Ursodeoxycholic Acid (L-UDCA) On June 20, 2016, the Company signed a definitive agreement to purchase the rights, titles, licenses and ownership of L-UDCA from Asklepion Pharmaceuticals, LLC ("Asklepion"). The acquisition was accounted for under the acquisition method of accounting in accordance with Accounting Standard Codification ("ASC") 805. The fair value of assets acquired and liabilities assumed was based upon an independent third-party valuation and the Company’s estimates. Critical estimates in valuing certain intangible assets include but are not limited to future expected cash flows from acquired product rights for L-UDCA, licenses, trade names and developed technologies, present value and discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. The purchase included $25.5 million for an intangible asset with a definite life related to product rights in the U.S. The useful life related to the acquired product rights was expected to be approximately 17 years once the NDA was approved by the FDA. Until approval, the asset was considered IPR&D with an indefinite life and was not amortized. The contingent consideration of $25.0 million (present value) recorded during the period ended June 30, 2016, was related to an agreement to pay an additional cash amount in the form of milestones and sales royalties through 2035. During the first quarter of 2019, the Company elected to discontinue development of the L-UDCA program and wrote off the $25.5 million intangible asset and related contingent consideration liability of $18 million.

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of components of net income before incomes taxes

For financial reporting purposes, net loss before income taxes includes the following components (in thousands):



	Year Ended December 31,
	2019			2018			2017
United States	$	(129,452	)	$	(87,573	)	$	(55,611	)
Foreign	(16,996		)	(14,294		)	(2,752		)
Total	$	(146,448	)	$	(101,867	)	$	(58,363	)

Schedule of income tax provision

The components of the provision (benefit) for income taxes, in the Consolidated Statement of Operations are as follows (in thousands):



	2019			2018		2017
Current
Federal	$	(319	)	$	698	$	6,991
State	298			113		802
	(21		)	811		7,793
Deferred
Federal	—			—		(7,965		)
State	—			—		1,540
	—			—		(6,425		)
Total tax provision (benefit)	$	(21	)	$	811	$	1,368

Schedule of reconciliation of the statutory federal income tax expense (benefit)

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate expressed as a percentage of loss before income taxes:



	2019		2018		2017
Statutory rate - federal	(21.00	)%	(21.00	)%	(35.00	)%
State taxes, net of federal benefit	(4.35	)%	(4.44	)%	(3.30	)%
Change in FV of derivative liability (warrants)	—	%	—	%	2.82	%
Change in federal tax rate	—	%	—	%	23.29	%
Convertible Debt	—	%	21.77	%	—	%
Loss on extinguishment of debt	—	%	4.09	%	—	%
Other permanent differences	0.24	%	0.10	%	1.04	%
Tax credits	(15.17	)%	(11.86	)%	(5.79	)%
Return to provision adjustments and other true-ups	0.44	%	1.42	%	(3.48	)%
Other	2.32	%	1.06	%	1.25	%
Change in valuation allowance	37.50	%	9.79	%	21.62	%
Income tax provision (benefit)	(0.02	)%	0.93	%	2.45	%

Schedule of deferred tax assets and liabilities

The significant components of the Company’s deferred tax assets and liabilities as of December 31, 2019 and 2018 are as follows (in thousands):



	2019			2018
Deferred Tax Assets:
Net operating loss	$	27,747		$	9,700
Research and development and other tax credits	33,315			14,715
Contingent consideration	18,029			23,459
Other accrued expenses	4,319			3,710
Stock based compensation	19,458			16,761
Charitable Contributions	1,256			—
Other	—			555
	104,124			68,900
Deferred Tax Liabilities:
Intangible assets	(2,749		)	(14,288		)
Convertible Debt	(16,182		)	(18,419		)
Tax basis depreciation less than book depreciation	(448		)	—
	(19,379		)	(32,707		)

Net deferred tax assets before valuation allowance	84,745			36,194
Valuation allowance	(84,745		)	(36,194		)
Total deferred tax assets	$	—		$	—

Schedule of unrecognized tax benefits

A reconciliation of the Company's unrecognized tax benefits for the years 2019 and 2018 is provided in the following table (in thousands):



	2019		2018
Balance as of January 1:	$	—	$	—
Increase in current period positions	235		—
Decrease in prior period positions	—		—
Increase in prior period positions	—		—
Balance as of December 31:	$	235	$	—

STOCKHOLDERS’ EQUITY / DEFICIT - Black Scholes Assumptions (Details) - Stock Options - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issued (in shares)	1,360,925
Risk free rate	2.30%	2.80%	2.10%
Expected volatility	68.00%	68.00%	70.00%
Expected life (in years)	6 years 2 months 12 days	6 years 2 months 12 days	6 years 1 month 6 days
Expected dividend yield	0.00%	0.00%	0.00%

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	1 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Aug. 31, 2017 USD ($)
Martin Shkreli
Other Commitments [Line Items]
Legal fees reimbursed from director and officer insurance carriers	$ 3.8

MARKETABLE SECURITIES (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of marketable securities

Marketable securities consist of the following (in thousands):



	As of December 31,
	2019		2018
Marketable Securities:
Commercial paper	$	17,152	$	59,255
Corporate debt securities	306,436		299,413
Securities of government sponsored entities	12,500		10,000
Total Marketable Securities:	$	336,088	$	368,668

Schedule of available for sale securities

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2019 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	17,136	$	16	$	—		$	17,152
Corporate debt securities	Less than 1	191,770		582		(10		)	192,342
Total maturity less than 1 year		208,906		598		(10		)	209,494
Corporate debt securities	1 to 2	113,799		351		(56		)	114,094
Securities of government-sponsored entities	1 to 2	12,501		—		(1		)	12,500
Total maturity 1 to 2 years		126,300		351		(57		)	126,594
Total available-for-sale securities		$	335,206	$	949	$	(67	)	$	336,088

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2018 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	59,313	$	—	$	(58	)	$	59,255
Corporate debt securities	Less than 1	149,824		—		(604		)	149,220
Total maturity less than 1 year		209,137		—		(662		)	208,475
Corporate debt securities	1 to 2	150,813		18		(638		)	150,193
Securities of government-sponsored entities	1 to 2	9,997		4		(1		)	10,000
Total maturity 1 to 2 years		160,810		22		(639		)	160,193
Total available-for-sale securities		$	369,947	$	22	$	(1,301	)	$	368,668

MARKETABLE SECURITIES

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

MARKETABLE SECURITIES

The Company's marketable securities as of December 31, 2019 and 2018 were comprised of available-for-sale marketable debt securities which are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive income (loss). The amortized cost of debt securities in this category are adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income (loss). Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. All available-for-sale securities are classified as current assets, even if the maturity when acquired by the Company is greater than one year due to the ability to liquidate within the next 12 months.

Marketable securities consist of the following (in thousands):



	As of December 31,
	2019		2018
Marketable Securities:
Commercial paper	$	17,152	$	59,255
Corporate debt securities	306,436		299,413
Securities of government sponsored entities	12,500		10,000
Total Marketable Securities:	$	336,088	$	368,668

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2019 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	17,136	$	16	$	—		$	17,152
Corporate debt securities	Less than 1	191,770		582		(10		)	192,342
Total maturity less than 1 year		208,906		598		(10		)	209,494
Corporate debt securities	1 to 2	113,799		351		(56		)	114,094
Securities of government-sponsored entities	1 to 2	12,501		—		(1		)	12,500
Total maturity 1 to 2 years		126,300		351		(57		)	126,594
Total available-for-sale securities		$	335,206	$	949	$	(67	)	$	336,088

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2018 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	59,313	$	—	$	(58	)	$	59,255
Corporate debt securities	Less than 1	149,824		—		(604		)	149,220
Total maturity less than 1 year		209,137		—		(662		)	208,475
Corporate debt securities	1 to 2	150,813		18		(638		)	150,193
Securities of government-sponsored entities	1 to 2	9,997		4		(1		)	10,000
Total maturity 1 to 2 years		160,810		22		(639		)	160,193
Total available-for-sale securities		$	369,947	$	22	$	(1,301	)	$	368,668

During 2019 and 2018, the Company had no realized gains or losses on marketable securities. The Company received proceeds from the sale or maturity of marketable securities of $259.1 million, $162.8 million and $114.5 million for 2019, 2018 and 2017, respectively.

The primary objective of the Company’s investment portfolio is to enhance overall returns while preserving capital and liquidity. The Company’s investment policy limits interest-bearing security investments to certain types of instruments issued by institutions with primarily investment grade credit ratings and places restrictions on maturities and concentration by asset class and issuer.

The Company reviews the available-for-sale investments for other-than-temporary declines in fair value below cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below the cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell the security before recovery of its amortized cost basis. The assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security. As of December 31, 2019 and 2018, the Company believed the cost basis for available-for-sale investments were recoverable in all material respects. For both December 31, 2019 and 2018, any investments in an unrealized loss position for longer than 12 months were immaterial.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) tranche clinical_trial segment reporting_unit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2018 USD ($)	Jan. 01, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of Phase 3 clinical trials \| clinical_trial	3
Marketable securities	$ 336,088,000	$ 368,668,000
Allowance for doubtful accounts	0	0
Bad debt expense	100,000	0	$ 200,000
Inventory reserve	$ 3,100,000	1,800,000
Number of segments \| segment	1
Number of reporting units \| reporting_unit	1
Goodwill, impairment	$ 0	0	0
Impairment of intangible assets		0	0
Number of tranches \| tranche	5
Cumulative effect of new accounting principle				$ 15,710,000	$ (4,868,000)
Restructuring adjustment		$ 200,000	$ 3,600,000
Accounting Standards Update 2016-16
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of new accounting principle					$ 4,900,000

QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net product sales		$ 46,688	$ 44,373	$ 44,707	$ 39,570	$ 43,771	$ 40,706	$ 41,337	$ 38,432	$ 175,338	$ 164,246	$ 154,937
Total operating expenses		74,855	78,810	81,236	77,798	48,756	76,289	62,897	56,344	312,699	244,286	208,728
Operating loss		(28,167)	(34,437)	(36,529)	(38,228)	(4,985)	(35,583)	(21,560)	(17,912)	(137,361)	(80,040)	(53,791)
Total other expense, net		(2,060)	(2,576)	(2,103)	(2,348)	(2,470)	(18,518)	(602)	(237)	(9,087)	(21,827)	(4,572)
Loss before benefit (provision) for income taxes		(30,227)	(37,013)	(38,632)	(40,576)	(7,455)	(54,101)	(22,162)	(18,149)	(146,448)	(101,867)	(58,363)
Income tax benefit (provision)		(32)	523	(69)	(401)	0	(415)	(167)	(229)	21	(811)	(1,368)
Net loss		$ (30,259)	$ (36,490)	$ (38,701)	$ (40,977)	$ (7,455)	$ (54,516)	$ (22,329)	$ (18,378)	$ (146,427)	$ (102,678)	$ (59,731)
Net Loss per common share
Basic and diluted net loss per common share (in USD per share)		$ (0.70)	$ (0.85)	$ (0.92)	$ (0.99)	$ (0.18)	$ (1.34)	$ (0.56)	$ (0.46)	$ (3.46)	$ (2.54)	$ (1.54)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of long-term investment			$ 15,000							$ 15,000	$ 0	$ 0
Impairment of L-UDCA IPR&D intangible asset					$ 25,500					25,500	0	0
Write off of L-UDCA contingent consideration					18,000					18,000	0	0
Loss on write-off of L-UDCA					7,500
Loss on extinguishment of debt										$ 0	$ 17,042	$ 0
Acquired Product Rights L-UDCA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of L-UDCA IPR&D intangible asset					25,500
Write off of L-UDCA contingent consideration					$ 18,000
Convertible Notes Due 2019 \| Senior Notes
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on extinguishment of debt	$ 17,000

LOSS PER SHARE - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Basic and diluted weighted average common shares outstanding (in shares)									42,339,961	40,433,171	38,769,816
Net loss	$ (30,259)	$ (36,490)	$ (38,701)	$ (40,977)	$ (7,455)	$ (54,516)	$ (22,329)	$ (18,378)	$ (146,427)	$ (102,678)	$ (59,731)
Basic and diluted net loss per common share (in USD per share)	$ (0.70)	$ (0.85)	$ (0.92)	$ (0.99)	$ (0.18)	$ (1.34)	$ (0.56)	$ (0.46)	$ (3.46)	$ (2.54)	$ (1.54)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

LEASES - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Leases [Abstract]
Other current liabilities	$ 2,613
Other non-current liabilities	7,394
Total lease liabilities	$ 10,007	$ 11,300

STOCKHOLDERS’ EQUITY / DEFICIT - Performance-based Stock Options (Details) - Performance Shares $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to restricted shares granted \| $	$ 0.5
Weighted average period for unrecognized costs (in years)	1 year
Number of shares
Unvested beginning balance (in shares) \| shares	226,750
Granted (in shares) \| shares	80,000
Vested (in shares) \| shares	0
Forfeited/cancelled (in shares) \| shares	(73,250)
Unvested ending balance (in shares) \| shares	233,500
Weighted Average Grant Date Fair Value
Unvested beginning balance (in USD per share) \| $ / shares	$ 21.54
Granted (in USD per share) \| $ / shares	21.32
Vested (in USD per share) \| $ / shares	0
Forfeited/cancelled (in USD per share) \| $ / shares	23.33
Unvested ending balance (in USD per share) \| $ / shares	$ 20.90