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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	May 06, 2019
Document And Entity Information
Entity Registrant Name	Retrophin, Inc.
Entity Central Index Key	0001438533
Trading Symbol	rtrx
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		41,439,478
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Emerging Growth	false
Entity Small Business	false

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 69,838	$ 102,873
Marketable securities	377,808	368,668
Accounts receivable, net	12,713	12,662
Inventory, net	5,571	5,619
Prepaid expenses and other current assets	8,171	4,140
Prepaid taxes	1,412	1,716
Total current assets	475,513	495,678
Property and equipment, net	2,995	3,146
Other non-current assets	13,471	7,709
Investment-equity	15,000	15,000
Intangible assets, net	159,753	186,691
Goodwill	936	936
Total assets	667,668	709,160
Current liabilities:
Accounts payable	7,627	6,954
Accrued expenses	46,619	49,695
Other current liabilities	8,292	6,165
Business combination-related contingent consideration	19,000	19,350
2019 Convertible debt	22,537	22,457
Total current liabilities	104,075	104,621
2025 Convertible debt	197,470	195,091
Other non-current liabilities	23,412	17,545
Business combination-related contingent consideration, less current portion	57,000	73,650
Total liabilities	381,957	390,907
Stockholders' Equity:
Preferred stock $0.0001 par value; 20,000,000 shares authorized; 0 issued and outstanding as of March 31, 2019 and December 31, 2018	0	0
Common stock $0.0001 par value; 100,000,000 shares authorized; 41,438,020 and 41,389,524 issued and outstanding as of March 31, 2019 and December 31, 2018, respectively	4	4
Additional paid-in capital	596,644	589,795
Accumulated deficit	(310,994)	(270,017)
Accumulated other comprehensive income (loss)	57	(1,529)
Total stockholders' equity	285,711	318,253
Total liabilities and stockholders' equity	$ 667,668	$ 709,160

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars 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 dollars per share)	$ 0.0001	$ 0.0001
Common stock shares authorized (in shares)	100,000,000	100,000,000
Common stock shares issued (in shares)	41,438,020	41,389,524
Common stock shares outstanding (in shares)	41,438,020	41,389,524

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net product sales	$ 39,570	$ 38,432
Operating expenses:
Cost of goods sold	1,017	1,613
Research and development	33,443	24,636
Selling, general and administrative	32,669	26,468
Change in fair value of contingent consideration	3,169	3,627
Impairment of L-UDCA IPR&D intangible asset	(25,500)	0
Write off of L-UDCA contingent consideration	(18,000)	0
Total operating expenses	77,798	56,344
Operating loss	(38,228)	(17,912)
Other income (expenses), net:
Other income (expense), net	(302)	121
Interest income	2,819	797
Interest expense	(4,865)	(1,155)
Total other expense, net	(2,348)	(237)
Loss before income taxes	(40,576)	(18,149)
Income tax expense	(401)	(229)
Net loss	$ (40,977)	$ (18,378)
Basic and diluted net loss per common share (in dollars/share)	$ (0.99)	$ (0.46)
Basic and diluted weighted average common shares outstanding (in shares)	41,410,314	39,657,418
Comprehensive loss:
Net loss	$ (40,977)	$ (18,378)
Foreign currency translation	117	22
Unrealized gain (loss) on marketable securities	1,469	(536)
Comprehensive loss	$ (39,391)	$ (18,892)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash Flows From Operating Activities:
Net loss	$ (40,977)	$ (18,378)
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	4,901	4,348
Non-cash interest expense	350	413
Amortization of premiums on marketable securities	(343)	356
Amortization of debt discount and issuance costs	2,459	0
Provision for Inventory	189	816
Share based compensation	6,271	4,659
Change in fair value of contingent consideration	(14,831)	3,627
Payments related to change in fair value of contingent consideration	(1,405)	(4,245)
Impairment of IPR&D intangible assets	25,500	0
Other	62	75
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	40	886
Inventory	(170)	(593)
Other current and non-current operating assets	(9,321)	421
Accounts payable and accrued expenses	(3,103)	(9,330)
Other current and non-current operating liabilities	9,886	2,211
Net cash used in operating activities	(20,492)	(14,734)
Cash Flows From Investing Activities:
Purchase of fixed assets	(19)	(39)
Cash paid for intangible assets	(3,961)	(8,217)
Proceeds from the sale/maturity of marketable securities	72,990	26,924
Purchase of marketable securities	(80,422)	(29,519)
Cash paid for investments - equity	0	(10,000)
Net cash used in investing activities	(11,412)	(20,851)
Cash Flows From Financing Activities:
Payment of acquisition-related contingent consideration	(905)	(7,066)
Payment of guaranteed minimum royalty	(509)	(500)
Proceeds from exercise of warrants	0	608
Proceeds from exercise of stock options	304	4,256
Net cash used in financing activities	(1,110)	(2,702)
Effect of exchange rate changes on cash	(21)	10
Net change in cash and cash equivalents	(33,035)	(38,277)
Cash and cash equivalents, beginning of year	102,873	99,394
Cash and cash equivalents, end of period	$ 69,838	$ 61,117

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2017		39,373,745
Beginning balance at Dec. 31, 2017	$ 293,134	$ 4	$ 471,800	$ (177,655)	$ (1,015)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	4,543		4,543
Exercise of warrants and reclassification of derivative liability (in shares)		168,612
Exercise of warrants and reclassification of derivative liability	608		608
Unrealized gain/(loss) on marketable securities	(536)				(536)
Foreign currency translation adjustments	22				22
Issuance of common stock from stock option exercises and vesting of restricted stock units (in shares)		330,928
Issuance of common stock from stock option exercises and vesting of restricted stock units	4,256		4,256
ESPP stock purchase and expense	116		116
Net loss	(18,378)			(18,378)
Ending balance (in shares) at Mar. 31, 2018		39,873,285
Ending balance at Mar. 31, 2018	299,475	$ 4	486,717	(185,717)	(1,529)
Beginning balance (in shares) at Dec. 31, 2018		41,389,524
Beginning balance at Dec. 31, 2018	318,253	$ 4	589,795	(270,017)	(1,529)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	6,370		6,370
Unrealized gain/(loss) on marketable securities	1,469				1,469
Foreign currency translation adjustments	117				117
Issuance of common stock from stock option exercises and vesting of restricted stock units (in shares)		48,496
Issuance of common stock from stock option exercises and vesting of restricted stock units	304		304
ESPP stock purchase and expense	175		175
Net loss	(40,977)			(40,977)
Ending balance (in shares) at Mar. 31, 2019		41,438,020
Ending balance at Mar. 31, 2019	$ 285,711	$ 4	$ 596,644	$ (310,994)	$ 57

DESCRIPTION OF BUSINESS

3 Months Ended

Mar. 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 biopharmaceutical company headquartered in San Diego, California, focused on identifying, developing and delivering life-changing therapies to people living 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 rare diseases and that we believe offer attractive growth characteristics.

The Company is developing the following pipeline products:

The Company is developing fosmetpantotenate (RE-024), a novel small molecule, as a potential treatment for pantothenate kinase-associated neurodegeneration (“PKAN”). PKAN is a genetic neurodegenerative disorder that is typically diagnosed in the first decade of life.

Sparsentan, also known as RE-021, is an investigational product candidate with a dual mechanism of action, a potent angiotensin receptor blocker (“ARB”) and selective endothelin receptor antagonist (“ERA”), with in vitro selectivity toward endothelin receptor type A. 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.

The Company is a party to a joint development agreement with Censa Pharmaceuticals Inc. ("Censa"), a privately held biotechnology company focused on developing therapies for orphan metabolic diseases, to evaluate sepiapterin ("CNSA-001") for the treatment of phenylketonuria (PKU).

In September 2017, the Company entered into a three-way Cooperative Research and Development Agreement ("CRADA") with the National Institutes of Health’s National Center for Advancing Translational Sciences (NCATS) and patient advocacy foundation NGLY1.org to collaborate on research efforts aimed at the identification of potential small molecule therapeutics for NGLY1 deficiency.

The Company sells the following three 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 cerebrotendinous xanthomatosis ("CTX") patients for more than three decades and the Company is currently pursuing adding this indication to the label.


•	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 (tiopronin tablets) is approved in the United States for the prevention of cystine (kidney) stone formation in patients with severe homozygous cystinuria.

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES	BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES The accompanying unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the 2018 10-K filed with the SEC on February 26, 2019. The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information, the instructions for Form 10-Q and the rules and regulations of the SEC. Accordingly, since they are interim statements, the accompanying condensed consolidated financial statements do not include all of the information and notes required by GAAP for annual financial statements, but reflect all adjustments consisting of normal, recurring adjustments, that are necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods presented. Interim results are not necessarily indicative of the results that may be expected for any future periods. The December 31, 2018 balance sheet information was derived from the audited financial statements as of that date. Certain reclassifications have been made to the prior period consolidated financial statements to conform to the current period presentation. A summary of the significant accounting policies applied in the preparation of the accompanying condensed consolidated financial statements follows: Principles of Consolidation The unaudited condensed consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with GAAP. All intercompany accounts and transactions have been eliminated in consolidation. Revenue Recognition The Company 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. See Note 3 for further discussion. Research and Development Expenses Research and development expenses are comprised of salaries and bonuses, benefits, non-cash share-based compensation, license fees, costs paid to third-party contractors to perform research, conduct clinical trials and pre/non-clinical trials, develop drug materials, and associated overhead expenses and facilities. 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 Our clinical trials are conducted pursuant to 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, initiation activities, enrollment, 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, progress of the clinical trials, and completion of patient studies. 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 all the factors set forth above and may fluctuate significantly from quarter to quarter. Adoption of New Accounting Standards 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. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. See Note 6 for further discussion. Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies. Unless otherwise noted, 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 fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. As of March 31, 2019, the Company held $377.8 million in available for sale debt securities. If adopted as of March 31, 2019, this ASU update would not have a material impact on the Company's financial statements.

REVENUE RECOGNITION

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

REVENUE RECOGNITION

Product Revenue, Net

The Company sells Chenodal and Cholbam (Kolbam), which are aggregated as bile acid products, and Thiola through direct-to-patient distributors. The Company sells its products 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.

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 are 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, specific known market events and trends, industry data and forecasted customer buying and payment patterns. 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 other current liabilities 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 other current liabilities 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 three months ended March 31, 2019 and 2018 (in thousands):



	Three Months Ended March 31,
	2019		2018
Bile acid products	$	18,390	$	18,508
Thiola	21,180		19,924
Total net product revenue	$	39,570	$	38,432

MARKETABLE SECURITIES

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

MARKETABLE SECURITIES

The Company's marketable securities as of March 31, 2019 and December 31, 2018 were comprised of available-for-sale marketable securities which are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive income. 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. Interest and dividends on securities classified as available-for-sale are included in interest income. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. During the three months ended March 31, 2019, investment activity for the Company included $73.0 million in maturities and $80.4 million in purchases, all relating to debt based marketable securities.

Marketable securities consisted of the following (in thousands):



	March 31, 2019		December 31, 2018
Commercial paper	$	53,373	$	59,255
Corporate debt securities	324,435		299,413
Securities of government sponsored entities	—		10,000
Total marketable securities:	$	377,808	$	368,668

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



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Commercial paper	Less than 1	$	53,366	$	20	$	(13	)	$	53,373
Corporate debt securities	Less than 1	147,633		28		(200		)	147,461
Total maturity less than 1 year		200,999		48		(213		)	200,834
Corporate debt securities	1 to 2	176,622		436		(84		)	176,974
Total maturity 1 to 2 years		176,622		436		(84		)	176,974
Total available-for-sale securities		$	377,621	$	484	$	(297	)	$	377,808

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



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
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

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. All available for sale securities are held in current assets regardless of contractual maturities exceeding one year, as the Company has the ability to sell them within the next twelve months.

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 March 31, 2019 and December 31, 2018, the Company believed the cost basis for available-for-sale investments was recoverable in all material respects.

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

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 million, agreed to fund certain development activities of Censa’s CNSA-001 program which are expected to be approximately$19.7 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 has expensed the development funding as incurred. The Company is treating the upfront payment and milestone payment, both of which are consideration for the Option, as a cost-method investment with a carrying value of $15.0 million as of March 31, 2019.

If the Company exercises the Option, the Company will acquire Censa for an additional $65 million, which may be reduced by up to $2.6 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 may elect 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 provides a notice of interest to exercise the Option is less than $19.26. In addition, if the Company exercises the Option and acquires Censa, the Company would be required to make further cash payments to Censa’s equity holders of up to an aggregate of $25 million if the CNSA-001 program achieves specified development and commercial milestones.

The Company determined that Censa is a variable interest entity ("VIE"), however concluded that the Company is not the primary beneficiary of the VIE. As such, the Company did not consolidate Censa’s results into its consolidated financial statements. The Company will continue to monitor facts and circumstances for changes that could potentially result in the Company becoming the primary beneficiary.

The following table presents the Company’s development funding roll-forward through March 31, 2019 and its effect on the upfront consideration if the Option exercise is elected (in thousands):



	March 31, 2019
Non-creditable development funding commitment	$	17,091
Development funding creditable against purchase option	2,612
Total development funding	19,703
Development funding paid through March 31, 2019	18,299
Development funding payable	$	1,404

LEASES

3 Months Ended

Mar. 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 a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance 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, CA. The lease was originally signed in July 2016, amended in July 2017, and is for approximately 45,000 square feet of 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 approximately $2.3 million in tenant improvement allowances and seven months of rent abatement. 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 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 approximately 16,000 square feet of office space in adjacent buildings. The 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 $1.0 million.

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



	March 31, 2019
2019	$	2,250
2020	2,958
2021	2,486
2022	2,560
2023	2,637
Thereafter	1,585
Total undiscounted future minimum payments	14,476
Present value discount	(2,530		)
Total lease liability	11,946
Lease incentives	(1,702		)
Straight line lease expense in excess of cash payments	(1,635		)
Total ROU asset	$	8,609

As of March 31, 2019, the current and non-current portions of the ROU asset were recorded to the Condensed Consolidated Balance Sheet as follows (in thousands):



	March 31, 2019
Prepaid expenses and other current assets	$	2,590
Other non-current assets	6,019
Total ROU asset	$	8,609

As of March 31, 2019, the current and non-current portions of the lease liability were recorded to the Condensed Consolidated Balance Sheet as follows (in thousands):



	March 31, 2019
Other current liabilities	$	3,054
Other non-current liabilities	8,892
Total lease liabilities	$	11,946

For the 3 months ended March 31, 2019, the Company recorded $0.7 million in expense related to operating leases .

FAIR VALUE MEASUREMENTS

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

Financial Instruments and Fair Value

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 valuation techniques used to measure the fair value of the Company’s marketable securities and all other financial instruments, all of which have counter-parties with high credit ratings, were valued based on quoted market prices or model driven valuations using significant inputs derived from or corroborated by observable market data. Based on the fair value hierarchy, the Company classified marketable securities within Level 2.

In estimating the fair value of the Company’s contingent consideration, the Company used the Monte Carlo Simulation model as of March 31, 2019 and December 31, 2018. Based on the fair value hierarchy, the Company classified the fair value measurement of contingent consideration within Level 3.

Financial instruments with carrying values approximating fair value include cash and cash equivalents, accounts receivable, and accounts payable, due to their short term nature. As of March 31, 2019, the estimated fair value of the Company's 4.5% Senior Convertible Notes due 2019 was $29.7 million and the estimated fair value of the Company's 2.5% Convertible Senior Notes due 2025 was $262.4 million, considering factors such as market conditions, prepayment and make-whole provisions, variability in pricing from multiple lenders and the term of the debt.

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



	As of March 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)
Assets:
Cash and Cash Equivalents	$	69,838	$	49,173	$	20,665	—
Marketable securities, available-for-sale	377,808		—		377,808		—
Total	$	447,646	$	49,173	$	398,473	$	—
Liabilities:
Business combination-related contingent consideration	$	76,000	$	—	$	—	$	76,000
Total	$	76,000	$	—	$	—	$	76,000



	As of 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)
Assets:
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 business combination-related contingent consideration for the three months ended March 31, 2019 (in thousands):



	Fair Value Measurements of Acquisition-Related Contingent Consideration (Level 3)
Balance at January 1, 2019	$	93,000
L-UDCA write-off	(18,000		)
Changes in the fair value of contingent consideration	3,169
Contractual payments included in accrued liabilities at March 31, 2019	(2,093		)
Contractual payments	—
Foreign currency impact	(76		)
Balance at March 31, 2019	$	76,000

The key assumptions included in the calculations for contingent consideration were the future number of patients in treatment, projected revenues, discount rate, and the timing of payments. The present value of the expected payments considers the time at which the obligations are expected to be settled and a discount rate that reflects the risk associated with the performance payments.

During the three months ended March 31, 2019, the Company recognized $3.2 million in operating expense on the Condensed Consolidated Statement of Operations and Comprehensive Loss for the change in fair value of the contingent consideration liabilities. For the three months ended March 31, 2019, $1.5 million and $1.6 million of the charges were related to the increase in contingent consideration liabilities for the products Chenodal and Cholbam, respectively. In each case, the value increased due to passage of time. In addition, the Company made a portfolio decision not to pursue further development of L-UDCA. The related contingent consideration of $18.0 million was accordingly considered fully written off. See Note 17 for further discussion.

During the three months ended March 31, 2018, the Company incurred charges of $3.6 million in operating expenses on the Condensed Consolidated Statement of Operations and Comprehensive Loss for the change in fair value of the contingent consideration liabilities. For the three months ended March 31, 2018, $0.8 million, $1.8 million, and $1.0 million of the charges were related to the increase in contingent consideration liabilities for the products Chenodal and Cholbam and product candidate L-UDCA, respectively. In each case, the value increased due to passage of time.

- 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

INTANGIBLE ASSETS

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLE ASSETS

As of March 31, 2019, the net book value of amortizable intangible assets was approximately $159.8 million.

The following table sets forth amortizable intangible assets as of March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019			December 31, 2018
Finite-lived intangible assets	$	233,375		$	255,643
Less: accumulated amortization	(73,622		)	(68,952		)
Net carrying value	$	159,753		$	186,691

During the three months ended March 31, 2019, the Company made a portfolio decision not to pursue further development of L-UDCA, acquired in 2016. The related in-progress research and development intangible asset ("IPR&D") of $25.5 million was accordingly considered fully impaired and written off. As of December 31, 2018, the value of the IPR&D was $25.5 million. See Note 17 for further discussion.

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



	Three Months Ended March 31,
	2019		2018
Research and development	$	286	$	103
Selling, general and administrative	4,445		4,096
Total amortization expense	$	4,731	$	4,199

CONVERTIBLE NOTES PAYABLE

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

CONVERTIBLE NOTES PAYABLE

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. The first payment was made on March 15, 2019.

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



	March 31, 2019			December 31, 2018
2.50% convertible senior notes due 2025	$	276,000		$	276,000
Unamortized debt discount	(72,681		)	(74,836		)
Unamortized debt issuance costs	(5,849		)	(6,073		)
Total 2025 Notes, net of unamortized debt discount and debt issuance costs	$	197,470		$	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 then-outstanding 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.

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 March 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 March 31, 2019 was 7.7%. The following table sets forth total interest expense recognized related to the 2025 Notes (in thousands):



	Three Months Ended March 31,
	2019		2018
Contractual interest expense	1,725		—
Amortization of debt discount	2,155		—
Amortization of debt issuance costs	224		—
Total interest expense for the 2025 Notes	$	4,104	$	—

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.

Senior Convertible Notes Due 2019

On May 29, 2014, the Company entered into a Note Purchase Agreement relating to a private placement by the Company of $46.0 million aggregate principal 4.50% senior convertible notes due in 2019 (the “2019 Notes”) which are convertible into shares of the Company’s common stock at an initial conversion price of $17.41 per share. The conversion price is subject to customary anti-dilution protection. The 2019 Notes bear interest at a rate of 4.5% per annum, payable semiannually in arrears on May 15 and November 15 of each year. The 2019 Notes mature on May 30, 2019 unless earlier converted or repurchased in accordance with their terms, and there are no contractual payments due prior to that date.

In September 2018, the Company used part of the net proceeds from the issuance of the 2025 Notes noted 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 in September 2018. At March 31, 2019, approximately $22.6 million of principal remained outstanding on the 2019 Notes.

The composition of the Company’s 2019 Notes are as follows (in thousands):



	March 31, 2019			December 31, 2018
4.50% senior convertible notes due 2019	$	22,590		$	22,590
Unamortized debt discount	(50		)	(125		)
Unamortized debt issuance costs	(3		)	(8		)
Total 2019 Notes, net of unamortized debt discount and debt issuance costs	$	22,537		$	22,457

ACCRUED EXPENSES

3 Months Ended

Mar. 31, 2019

Payables and Accruals [Abstract]

ACCRUED EXPENSES

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



	March 31, 2019		December 31, 2018
Government rebates payable	$	8,988	$	8,464
Compensation related costs	7,856		10,446
Accrued royalties and contingent consideration	6,042		6,805
Research and development	17,955		16,515
Selling, general and administrative	3,812		2,990
Miscellaneous accrued	1,966		4,475
Total accrued expenses	$	46,619	$	49,695

LOSS PER COMMON SHARE

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

LOSS PER COMMON SHARE

Basic and diluted net loss per common share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. The Company’s potentially dilutive shares, which include outstanding stock options, restricted stock units, warrants, and shares issuable upon conversion of the 2019 Notes and 2025 Notes, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.

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



	Three Months Ended March 31,
	2019							2018
	Shares	Net Loss			EPS			Shares	Net Loss			EPS
Basic and diluted loss per share	41,410,314	$	(40,977	)	$	(0.99	)	39,657,418	$	(18,378	)	$	(0.46	)

The following common stock equivalents have been excluded because they were anti-dilutive (in thousands):



	Three Months Ended March 31,
	2019	2018
Restricted stock units	549	139
Convertible debt	8,411	2,642
Options	7,654	7,025
Warrants	—	633
Total anti-dilutive shares	16,614	10,439

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Research Collaboration and Licensing Agreements As part of the Company's research and development efforts, the Company enters into research collaboration and licensing agreements with unrelated companies, scientific collaborators, universities, and consultants. These agreements contain varying terms and provisions which include fees and milestones to be paid by the Company, services to be provided, and ownership rights to certain proprietary technology developed under the agreements. Some of these agreements contain provisions which require the Company to pay royalties, in the event the Company sells or licenses any proprietary products developed under the respective agreements. Legal Proceedings In August 2017, Martin Shkreli, the Company’s former Chief Executive Officer, was convicted on securities fraud charges following investigations by the U.S. Attorney for the Eastern District of New York and the U.S Securities and Exchange Commission. The Company was not a target of these investigations and cooperated with them fully. Mr. Shkreli has appealed his conviction to the United States Court of Appeals for the Second Circuit. In connection with the trial and pending appeal proceedings, Mr. Shkreli sought advancement of his legal fees from the Company, and the Company has advanced a total of $5.4 million in legal fees, of which $3.8 million has been reimbursed by its directors’ and officers’ insurance carriers. Pending the outcome of Mr. Shkreli's appeal, the insurance carriers have 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. As a result, the final amount of the reimbursement from the insurance carriers is not currently estimable. In addition, a portion of these and the other legal fees the Company has advanced to Mr. Shkreli will be subject to reimbursement by Mr. Shkreli under Delaware law in the event it is ultimately determined that Mr. Shkreli is not entitled to be indemnified by the Company in these proceedings. In August 2015, the Company filed a lawsuit in federal district court for the Southern District of New York against Mr. Shkreli, asserting that he breached his fiduciary duty of loyalty during his tenure as the Company’s Chief Executive Officer and a member of its Board of Directors. Mr. Shkreli served a demand for JAMS arbitration on Retrophin, claiming that Retrophin had breached his December 2013 employment agreement. In response to Mr. Shkreli’s arbitration demand, the Company asserted counterclaims in the arbitration that are substantially similar to the claims it previously asserted in the federal lawsuit against Mr. Shkreli. In October 2018, after the arbitration panel determined that Retrophin's counterclaims were arbitrable, the Company voluntarily dismissed the federal action without prejudice. The Company does not expect the claims and counterclaims in the arbitration to be heard by the arbitration panel before mid-2019. In connection with these proceedings, Mr. Shkreli sought advancement of his legal fees from the Company relating to his defense of the Company’s claims against him. The Company has advanced, and expects to continue to advance, certain of these legal fees to Mr. Shkreli. On October 23, 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. Spring is seeking injunctive relief and damages. The Company intends to vigorously defend against Spring’s claims. On January 15, 2019, the Company filed a motion to dismiss the lawsuit. On April 10, 2019, the Court stayed the Company's motion to dismiss for 90 days to allow for discovery limited to the question of whether Spring has standing to sue. 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.

SHARE BASED COMPENSATION

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

SHARE BASED COMPENSATION

Restricted Shares

Service Based Restricted Stock Units

The following table summarizes the Company’s service based restricted stock unit activity during the three months ended March 31, 2019:



	Number of Restricted Stock Units		Weighted Average Grant Date Fair Value
Unvested December 31, 2018	400,426		$	24.95
Granted	62,850		23.12
Vested	(24,769	)	20.88
Forfeited/canceled	(1,250	)	25.25
Unvested March 31, 2019	437,257		$	24.92

At March 31, 2019, unamortized stock compensation for service based restricted stock units was $8.3 million, with a weighted-average recognition period of 3.0 years.

Performance Based Restricted Stock Units

The following table summarizes the Company’s performance based restricted stock unit activity during the three months ended March 31, 2019:



	Number of Restricted Stock Units	Weighted Average Grant Date Fair Value
Unvested December 31, 2018	226,750	$	21.54
Granted	50,000	23.34
Vested	—	—
Forfeited/canceled	—	—
Unvested March 31, 2019	276,750	$	21.86

At March 31, 2019, unamortized stock compensation for performance based restricted stock units was $1.8 million, with a weighted-average recognition period of 1.2 years.

Stock Options

The following table summarizes stock option activity during the three months ended March 31, 2019:



	Shares Underlying Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018	7,277,337		$	18.55	6.94	$	40,650
Granted	440,700		23.20
Exercised	(23,727	)	12.81
Forfeited/canceled	(33,134	)	24.94
Outstanding at March 31, 2019	7,661,176		$	18.81	6.87	$	40,435

At March 31, 2019, unamortized stock compensation for stock options was $30.9 million, with a weighted-average recognition period of 2.8 years.

At March 31, 2019, outstanding options to purchase 5.0 million shares of common stock were exercisable with a weighted-average exercise price per share of $16.92.

Share Based Compensation

The following table sets forth total stock-based compensation for the three months ended March 31, 2019 and 2018 (in thousands):



	Three Months Ended March 31,
	2019		2018
Research and development	$	1,670	$	1,407
Selling, general & administrative	4,850		3,202
Total	$	6,520	$	4,609

Exercise of Warrants

The Company issued 168,612 shares of common stock upon the exercise of outstanding warrants during the three months ended March 31, 2018, for cash received by the Company in the amount of $0.6 million. As of March 31, 2019 and December 31, 2018, there were zero warrants exercisable for common shares outstanding.

INCOME TAXES

3 Months Ended

Mar. 31, 2019

Income Tax Disclosure [Abstract]

INCOME TAXES

The following table summarizes our effective tax rate and income tax expense for the three months ended March 31, 2019 and 2018 (dollars in millions):



	Three Months Ended March 31,
	2019			2018
Effective tax rate	(1.0		)%	(1.3		)%
Income tax expense	$	(0.4	)	$	(0.2	)

INVENTORY

3 Months Ended

Mar. 31, 2019

Inventory Disclosure [Abstract]

INVENTORY

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



	March 31, 2019		December 31, 2018
Raw materials	$	4,377	$	4,689
Finished goods	1,194		930
Total inventory	$	5,571	$	5,619

The inventory reserve was $1.9 million and $1.8 million at March 31, 2019 and December 31, 2018, respectively.

ACCOUNTS RECEIVABLE	3 Months Ended
ACCOUNTS RECEIVABLE	Mar. 31, 2019
Receivables [Abstract]
ACCOUNTS RECEIVABLE	ACCOUNTS RECEIVABLE Accounts receivable, net of reserves for prompt pay discounts and doubtful accounts, was $12.7 million and $12.7 million at March 31, 2019 and December 31, 2018, respectively. The total reserves for both periods were immaterial.

DISPOSITIONS	3 Months Ended
DISPOSITIONS	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
DISPOSITIONS	DISPOSITIONS In June 2016, the company acquired certain rights to L-UDCA for $0.5 million cash. At the same time the company established a related non-cash asset of $25.5 million for IPR&D and a liability of $25.0 million for contingent consideration (deferred financing) related net sales royalties and milestones. As a result of our quarterly valuation update process during 2016 and 2017, the contingent liability was decreased by $2.3 million and $5.7 million, respectively, and increased by $1.0 million during 2018. The resulting balance of the L-UDCA contingent liability at December 31, 2018 was $18.0 million. 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 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.

SUBSEQUENT EVENT	3 Months Ended
SUBSEQUENT EVENT	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Event	SUBSEQUENT EVENT On April 23, 2019, Retrophin, Inc. (the “Company”) entered into an office lease with an effective date of April 12, 2019 (the “Lease”) with Kilroy Realty, L.P. (the “Landlord”) for the lease of approximately 77,242 square feet of the building located at 3611 Valley Centre Drive, San Diego, California 92130 (the “Premises”). 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 in adjacent buildings at 3721 and 3661 Valley Centre Drive, San Diego, California 92130. 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 (the “Initial Term”), and the Landlord has granted the Company an option to extend the term of the Lease by a period of five years. The aggregate base rent due over the Initial Term under the terms of the Lease is approximately $36.5 million.

BASIS OF PRESENTATION AND SIGNIFICANT ACCCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The unaudited condensed consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with GAAP. All intercompany accounts and transactions have been eliminated in consolidation.
Revenue Recognition	Revenue Recognition The Company 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. 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 are 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, specific known market events and trends, industry data and forecasted customer buying and payment patterns. 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 other current liabilities 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 other current liabilities 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.
Research and Development Expense	Research and Development Expenses Research and development expenses are comprised of salaries and bonuses, benefits, non-cash share-based compensation, license fees, costs paid to third-party contractors to perform research, conduct clinical trials and pre/non-clinical trials, develop drug materials, and associated overhead expenses and facilities. 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	Clinical Trial Expenses Our clinical trials are conducted pursuant to 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, initiation activities, enrollment, 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, progress of the clinical trials, and completion of patient studies. 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 all the factors set forth above and may fluctuate significantly from quarter to quarter.
Adoption of New Accounting Standards and Recently Issued Accounting Pronouncements	Adoption of New Accounting Standards 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. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. See Note 6 for further discussion. Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies. Unless otherwise noted, 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 fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. As of March 31, 2019, the Company held $377.8 million in available for sale debt securities. If adopted as of March 31, 2019, this ASU update would not have a material impact on the Company's financial statements.
Marketable Securities	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. All available for sale securities are held in current assets regardless of contractual maturities exceeding one year, as the Company has the ability to sell them within the next twelve months. 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.
Fair Value Measurement	Financial Instruments and Fair Value 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 valuation techniques used to measure the fair value of the Company’s marketable securities and all other financial instruments, all of which have counter-parties with high credit ratings, were valued based on quoted market prices or model driven valuations using significant inputs derived from or corroborated by observable market data. Based on the fair value hierarchy, the Company classified marketable securities within Level 2. In estimating the fair value of the Company’s contingent consideration, the Company used the Monte Carlo Simulation model as of March 31, 2019 and December 31, 2018. Based on the fair value hierarchy, the Company classified the fair value measurement of contingent consideration within Level 3. Financial instruments with carrying values approximating fair value include cash and cash equivalents, accounts receivable, and accounts payable, due to their short term nature.
Income (Loss) Per Share	Basic and diluted net loss per common share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents. The Company’s potentially dilutive shares, which include outstanding stock options, restricted stock units, warrants, and shares issuable upon conversion of the 2019 Notes and 2025 Notes, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.

REVENUE RECOGNITION (Tables)

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Summary of Net Product Revenue

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



	Three Months Ended March 31,
	2019		2018
Bile acid products	$	18,390	$	18,508
Thiola	21,180		19,924
Total net product revenue	$	39,570	$	38,432

MARKETABLE SECURITIES (Tables)

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of marketable securities

Marketable securities consisted of the following (in thousands):



	March 31, 2019		December 31, 2018
Commercial paper	$	53,373	$	59,255
Corporate debt securities	324,435		299,413
Securities of government sponsored entities	—		10,000
Total marketable securities:	$	377,808	$	368,668

Debt Securities Available For Sale

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



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Commercial paper	Less than 1	$	53,366	$	20	$	(13	)	$	53,373
Corporate debt securities	Less than 1	147,633		28		(200		)	147,461
Total maturity less than 1 year		200,999		48		(213		)	200,834
Corporate debt securities	1 to 2	176,622		436		(84		)	176,974
Total maturity 1 to 2 years		176,622		436		(84		)	176,974
Total available-for-sale securities		$	377,621	$	484	$	(297	)	$	377,808

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



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
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

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT (Tables)

3 Months Ended

Mar. 31, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of development funding

The following table presents the Company’s development funding roll-forward through March 31, 2019 and its effect on the upfront consideration if the Option exercise is elected (in thousands):



	March 31, 2019
Non-creditable development funding commitment	$	17,091
Development funding creditable against purchase option	2,612
Total development funding	19,703
Development funding paid through March 31, 2019	18,299
Development funding payable	$	1,404

LEASES (Tables)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Schedule of future minimum rent commitments

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



	March 31, 2019
2019	$	2,250
2020	2,958
2021	2,486
2022	2,560
2023	2,637
Thereafter	1,585
Total undiscounted future minimum payments	14,476
Present value discount	(2,530		)
Total lease liability	11,946
Lease incentives	(1,702		)
Straight line lease expense in excess of cash payments	(1,635		)
Total ROU asset	$	8,609

Supplemental balance sheet information

As of March 31, 2019, the current and non-current portions of the ROU asset were recorded to the Condensed Consolidated Balance Sheet as follows (in thousands):



	March 31, 2019
Prepaid expenses and other current assets	$	2,590
Other non-current assets	6,019
Total ROU asset	$	8,609

As of March 31, 2019, the current and non-current portions of the lease liability were recorded to the Condensed Consolidated Balance Sheet as follows (in thousands):



	March 31, 2019
Other current liabilities	$	3,054
Other non-current liabilities	8,892
Total lease liabilities	$	11,946

FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of fair value on a recurring basis



	As of March 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)
Assets:
Cash and Cash Equivalents	$	69,838	$	49,173	$	20,665	—
Marketable securities, available-for-sale	377,808		—		377,808		—
Total	$	447,646	$	49,173	$	398,473	$	—
Liabilities:
Business combination-related contingent consideration	$	76,000	$	—	$	—	$	76,000
Total	$	76,000	$	—	$	—	$	76,000



	As of 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)
Assets:
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 summary of changes in estimated acquisition related contingent consideration



	Fair Value Measurements of Acquisition-Related Contingent Consideration (Level 3)
Balance at January 1, 2019	$	93,000
L-UDCA write-off	(18,000		)
Changes in the fair value of contingent consideration	3,169
Contractual payments included in accrued liabilities at March 31, 2019	(2,093		)
Contractual payments	—
Foreign currency impact	(76		)
Balance at March 31, 2019	$	76,000

INTANGIBLE ASSETS (Tables)

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Amortizable Intangible Assets

The following table sets forth amortizable intangible assets as of March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019			December 31, 2018
Finite-lived intangible assets	$	233,375		$	255,643
Less: accumulated amortization	(73,622		)	(68,952		)
Net carrying value	$	159,753		$	186,691

Schedule of Amortization Expense

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



	Three Months Ended March 31,
	2019		2018
Research and development	$	286	$	103
Selling, general and administrative	4,445		4,096
Total amortization expense	$	4,731	$	4,199

CONVERTIBLE NOTES PAYABLE CONVERTIBLE NOTES PAYABLE (Tables)

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

The composition of the Company’s 2019 Notes are as follows (in thousands):



	March 31, 2019			December 31, 2018
4.50% senior convertible notes due 2019	$	22,590		$	22,590
Unamortized debt discount	(50		)	(125		)
Unamortized debt issuance costs	(3		)	(8		)
Total 2019 Notes, net of unamortized debt discount and debt issuance costs	$	22,537		$	22,457

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



	March 31, 2019			December 31, 2018
2.50% convertible senior notes due 2025	$	276,000		$	276,000
Unamortized debt discount	(72,681		)	(74,836		)
Unamortized debt issuance costs	(5,849		)	(6,073		)
Total 2025 Notes, net of unamortized debt discount and debt issuance costs	$	197,470		$	195,091



	Three Months Ended March 31,
	2019		2018
Contractual interest expense	1,725		—
Amortization of debt discount	2,155		—
Amortization of debt issuance costs	224		—
Total interest expense for the 2025 Notes	$	4,104	$	—

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 235
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-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
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-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

ACCRUED EXPENSES (Tables)

3 Months Ended

Mar. 31, 2019

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

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



	March 31, 2019		December 31, 2018
Government rebates payable	$	8,988	$	8,464
Compensation related costs	7,856		10,446
Accrued royalties and contingent consideration	6,042		6,805
Research and development	17,955		16,515
Selling, general and administrative	3,812		2,990
Miscellaneous accrued	1,966		4,475
Total accrued expenses	$	46,619	$	49,695

LOSS PER COMMON SHARE (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Schedule of basic and diluted net income (loss) per share

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



	Three Months Ended March 31,
	2019							2018
	Shares	Net Loss			EPS			Shares	Net Loss			EPS
Basic and diluted loss per share	41,410,314	$	(40,977	)	$	(0.99	)	39,657,418	$	(18,378	)	$	(0.46	)

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

The following common stock equivalents have been excluded because they were anti-dilutive (in thousands):



	Three Months Ended March 31,
	2019	2018
Restricted stock units	549	139
Convertible debt	8,411	2,642
Options	7,654	7,025
Warrants	—	633
Total anti-dilutive shares	16,614	10,439

SHARE BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Schedule of service based restricted stock activity

The following table summarizes the Company’s service based restricted stock unit activity during the three months ended March 31, 2019:



	Number of Restricted Stock Units		Weighted Average Grant Date Fair Value
Unvested December 31, 2018	400,426		$	24.95
Granted	62,850		23.12
Vested	(24,769	)	20.88
Forfeited/canceled	(1,250	)	25.25
Unvested March 31, 2019	437,257		$	24.92

Schedule of performance based restricted stock activity

The following table summarizes the Company’s performance based restricted stock unit activity during the three months ended March 31, 2019:



	Number of Restricted Stock Units	Weighted Average Grant Date Fair Value
Unvested December 31, 2018	226,750	$	21.54
Granted	50,000	23.34
Vested	—	—
Forfeited/canceled	—	—
Unvested March 31, 2019	276,750	$	21.86

Schedule of stock option issuances and balances outstanding

The following table summarizes stock option activity during the three months ended March 31, 2019:



	Shares Underlying Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018	7,277,337		$	18.55	6.94	$	40,650
Granted	440,700		23.20
Exercised	(23,727	)	12.81
Forfeited/canceled	(33,134	)	24.94
Outstanding at March 31, 2019	7,661,176		$	18.81	6.87	$	40,435

Schedule of Share based compensation expenses

The following table sets forth total stock-based compensation for the three months ended March 31, 2019 and 2018 (in thousands):



	Three Months Ended March 31,
	2019		2018
Research and development	$	1,670	$	1,407
Selling, general & administrative	4,850		3,202
Total	$	6,520	$	4,609

INCOME TAXES (Tables)

3 Months Ended

Mar. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax (Expense) Benefit

The following table summarizes our effective tax rate and income tax expense for the three months ended March 31, 2019 and 2018 (dollars in millions):



	Three Months Ended March 31,
	2019			2018
Effective tax rate	(1.0		)%	(1.3		)%
Income tax expense	$	(0.4	)	$	(0.2	)

INVENTORY (Tables)

3 Months Ended

Mar. 31, 2019

Inventory Disclosure [Abstract]

Schedule of Inventory

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



	March 31, 2019		December 31, 2018
Raw materials	$	4,377	$	4,689
Finished goods	1,194		930
Total inventory	$	5,571	$	5,619

DESCRIPTION OF BUSINESS (Details)	Mar. 31, 2019 product
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of products sold	3

BASIS OF PRESENTATION AND SIGNIFICANT ACCCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Marketable securities	$ 377,808	$ 368,668

REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended
REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 39,570	$ 38,432
Bile acid products
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	18,390	18,508
Thiola
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 21,180	$ 19,924
Geographic Concentration Risk \| Revenue from Contract with Customer \| United States
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	95.00%

MARKETABLE SECURITIES - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Proceeds from the sale/maturity of marketable securities	$ 72,990	$ 26,924
Purchases of debt based marketable securities	$ 80,422	$ 29,519

MARKETABLE SECURITIES - Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Marketable securities	$ 377,808	$ 368,668
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Marketable securities	53,373	59,255
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities	324,435	299,413
Securities of government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Marketable securities	$ 0	$ 10,000

MARKETABLE SECURITIES - Available for Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	$ 200,999	$ 209,137
Debt securities available for sale, unrealized gain, current	48	0
Debt securities available for sale unrealized loss, current	(213)	(662)
Debt securities, available-for-sale, current	200,834	208,475
Debt securities, available-for-sale, amortized cost basis, noncurrent	176,622	160,810
Debt securities, available for sale unrealized gain, noncurrent	436	22
Debt securities available for sale unrealized gain loss, noncurrent	(84)	(639)
Debt securities, available-for-sale, noncurrent	176,974	160,193
Debt securities, available-for-sale, amortized cost	377,621	369,947
Debt securities, available for sale, unrealized gains	484	22
Debt securities, available-for-sale, unrealized gain (loss)	(297)	(1,301)
Aggregate Estimated Fair Value	377,808	368,668
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	53,366	59,313
Debt securities available for sale, unrealized gain, current	20	0
Debt securities available for sale unrealized loss, current	(13)	(58)
Debt securities, available-for-sale, current	53,373	59,255
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	147,633	149,824
Debt securities available for sale, unrealized gain, current	28	0
Debt securities available for sale unrealized loss, current	(200)	(604)
Debt securities, available-for-sale, current	147,461	149,220
Debt securities, available-for-sale, amortized cost basis, noncurrent	176,622	150,813
Debt securities, available for sale unrealized gain, noncurrent	436	18
Debt securities available for sale unrealized gain loss, noncurrent	(84)	(638)
Debt securities, available-for-sale, noncurrent	$ 176,974	150,193
Securities of government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, noncurrent		9,997
Debt securities, available for sale unrealized gain, noncurrent		4
Debt securities available for sale unrealized gain loss, noncurrent		(1)
Debt securities, available-for-sale, noncurrent		$ 10,000

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended
	Jan. 31, 2018	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2016
Variable Interest Entity [Line Items]
Non-creditable development funding commitment		$ 17,091
Business combination-related contingent consideration		76,000	$ 93,000	$ 25,000
Business combination, option agreement, purchase price	$ 65,000
Business combination, development funding		19,703
Business combination, option agreement, purchase price, percent transfered 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
Investment		$ 15,000	$ 15,000
Censa Pharmaceuticals Inc.
Variable Interest Entity [Line Items]
Payments for the option to acquire business	10,000
Business combination-related contingent consideration	19,700
Business combination, development funding	$ 2,600
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
Variable Interest Entity [Line Items]
Additional required payments for the option to acquire business, successful development milestones	$ 5,000

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT - Schedule of Funding (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Non-creditable development funding commitment	$ 17,091
Development funding creditable against purchase option	2,612
Total development funding	19,703
Development funding paid through March 31, 2019	18,299
Development funding payable	$ 1,404

LEASES - Additional Information (Details) ft² in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) ft²	Jan. 01, 2019 USD ($)	Jul. 31, 2016 USD ($) ft²
Lessee, Lease, Description [Line Items]
Square footage leased \| ft²			45
Future minimum lease payments	$ 14,476	$ 14,000
Operating lease term			7 years 7 months
Lease incentives	1,702	$ 1,800	$ 2,300
Operating lease extension term		5 years
Operating lease discount rate		7.70%
Remaining lease term		5 years 7 months
Operating lease right-of-use asset	8,609	$ 7,900
Total lease liability	11,946	$ 11,300
Operating lease expense	$ 700
March 2019 Operating Lease Amendment [Member]
Lessee, Lease, Description [Line Items]
Square footage leased \| ft²	16
Future minimum lease payments	$ 1,000
Operating lease right-of-use asset	1,000
Total lease liability	$ 1,000

LEASES - Future Minimum Rent Commitments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Jul. 31, 2016
Leases [Abstract]
2019	$ 2,250
2020	2,958
2021	2,486
2022	2,560
2023	2,637
Thereafter	1,585
Total future minimum rent commitments	14,476	$ 14,000
Present value discount	(2,530)
Total lease liability	11,946	11,300
Lease incentives	(1,702)	(1,800)	$ (2,300)
Straight line lease expense in excess of cash payments	(1,635)
Total ROU asset	$ 8,609	$ 7,900

LEASES - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Total lease liability	$ 11,946	$ 11,300
Operating lease right-of-use asset	8,609	$ 7,900
Prepaid expenses and other current assets
Lessee, Lease, Description [Line Items]
Operating lease right-of-use asset	2,590
Other noncurrent assets
Lessee, Lease, Description [Line Items]
Operating lease right-of-use asset	6,019
Other current liabilities
Lessee, Lease, Description [Line Items]
Total lease liability	3,054
Other noncurrent liabilities
Lessee, Lease, Description [Line Items]
Total lease liability	$ 8,892

FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 10, 2018
Business Acquisition [Line Items]
Change in fair value of contingent consideration	$ 3,169	$ 3,627
Write off of L-UDCA contingent consideration	18,000	0
Adjustments to contingent consideration	(1,405)	(4,245)	$ 1,000	$ (5,700)	$ (2,300)
Product Rights Chenodal
Business Acquisition [Line Items]
Change in fair value of contingent consideration	1,500
Adjustments to contingent consideration		800
Acquired Product Rights Cholbam
Business Acquisition [Line Items]
Change in fair value of contingent consideration	$ 1,600
Adjustments to contingent consideration		1,800
Acquired Product Rights L-UDCA
Business Acquisition [Line Items]
Adjustments to contingent consideration		$ 1,000
Senior Notes \| Convertible Notes Due 2019
Business Acquisition [Line Items]
Interest rate percentage	4.50%
Fair value of convertible debt	$ 29,700
Senior Notes \| Senior Notes Due 2025
Business Acquisition [Line Items]
Interest rate percentage	2.50%					2.50%
Fair value of convertible debt	$ 262,400

FAIR VALUE MEASUREMENTS - Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2016
Assets:
Cash and Cash Equivalents	$ 69,838	$ 102,873	$ 61,117	$ 99,394
Marketable securities, available-for-sale	377,808	368,668
Total	447,646	471,541
Liabilities:
Business combination-related contingent consideration	76,000	93,000			$ 25,000
Total	76,000	93,000
Quoted prices in active markets (Level 1)
Assets:
Cash and Cash Equivalents	49,173	62,978
Marketable securities, available-for-sale	0	0
Total	49,173	62,978
Liabilities:
Business combination-related contingent consideration	0	0
Total	0	0
Significant other observable inputs (Level 2)
Assets:
Cash and Cash Equivalents	20,665	39,895
Marketable securities, available-for-sale	377,808	368,668
Total	398,473	408,563
Liabilities:
Business combination-related contingent consideration	0	0
Total	0	0
Significant unobservable inputs (Level 3)
Assets:
Cash and Cash Equivalents	0	0
Marketable securities, available-for-sale	0	0
Total	0	0
Liabilities:
Business combination-related contingent consideration	76,000	93,000
Total	$ 76,000	$ 93,000

FAIR VALUE MEASUREMENTS - Acquisition-related Contingent Consideration (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
L-UDCA write-off	$ 1,405	$ 4,245	$ (1,000)	$ 5,700	$ 2,300
Change in fair value of contingent consideration	3,169	$ 3,627
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	93,000
L-UDCA write-off	(18,000)
Contractual payments included in accrued liabilities at March 31, 2019	(2,093)
Contractual payments	0
Foreign currency impact	(76)
Ending balance	$ 76,000		$ 93,000

INTANGIBLE ASSETS - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jun. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Net book value of amortizable intangible assets	$ 159,753		$ 186,691
Impairment of IPR&D intangibles	25,500	$ 0
IPR&D asset	233,375		255,643
Acquired Product Rights L-UDCA
Finite-Lived Intangible Assets [Line Items]
Impairment of IPR&D intangibles	$ 25,500
IPR&D asset			$ 25,500	$ 25,500

INTANGIBLE ASSETS - Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Finite-lived intangible assets	$ 233,375	$ 255,643
Less: accumulated amortization	(73,622)	(68,952)
Net carrying value	$ 159,753	$ 186,691

INTANGIBLE ASSETS - Amortization (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 4,731	$ 4,199
Research and development
Finite-Lived Intangible Assets [Line Items]
Total amortization expense	286	103
Selling, general and administrative
Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 4,445	$ 4,096

CONVERTIBLE NOTES PAYABLE - Additional Information (Details)	1 Months Ended	3 Months Ended
	Sep. 30, 2018 USD ($)	Mar. 31, 2019 USD ($) day $ / shares	Sep. 10, 2018 USD ($)	May 29, 2014 USD ($) $ / shares
Debt Instrument [Line Items]
Debt instrument, repurchase amount		$ 23,400,000
Senior Notes Due 2025
Debt Instrument [Line Items]
Debt instrument term		7 years
Note Purchase Agreement \| Senior convertible notes due 2019
Debt Instrument [Line Items]
Interest rate percentage				4.50%
Initial conversion price (in dollars per share) \| $ / shares				$ 17.41
Credit agreement amount				$ 46,000,000.0
Senior Notes \| Senior Notes Due 2025
Debt Instrument [Line Items]
Long-term debt, excluding current maturities		$ 276,000,000	$ 276,000,000
Interest rate percentage		2.50%	2.50%
Debt conversion, liability		$ 198,600,000
Debt conversion, equity		77,400,000
Proceeds from issuance of debt		$ 267,200,000
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
Conversion ratio		0.0257739
Initial conversion price (in dollars per share) \| $ / shares		$ 38.80
Debt issuance costs, net		$ 8,800,000
Debt instrument, interest rate, effective percentage		7.70%
Senior Notes \| Convertible Notes Due 2019
Debt Instrument [Line Items]
Interest rate percentage		4.50%
Debt instrument, convertible, threshold trading days \| day		20
Debt instrument, convertible, threshold consecutive trading days \| day		30
Debt instrument, repurchase amount		$ 23,400,000
Repayments of debt	$ 40,200,000
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%
Gain (loss) on extinguishment of debt		$ (17,000,000)
Long-term debt and capital lease obligations		$ 22,600,000

CONVERTIBLE NOTES PAYABLE - Composition of Notes (Details) - Senior Notes - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Sep. 10, 2018
Senior Notes Due 2025
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.50%		2.50%
Long-term Debt, Gross	$ 276,000	$ 276,000
Unamortized debt discount	(72,681)	(74,836)
Unamortized debt issuance costs	(5,849)	(6,073)
Long-term Debt	$ 197,470	195,091
Convertible Notes Due 2019
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Long-term Debt, Gross	$ 22,590	22,590
Unamortized debt discount	(50)	(125)
Unamortized debt issuance costs	(3)	(8)
Long-term Debt	$ 22,537	$ 22,457

CONVERTIBLE NOTES PAYABLE - Schedule of Interest Expense (Details) - Senior Notes - Senior Notes Due 2025 - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Contractual interest expense	$ 1,725	$ 0
Amortization of debt discount	2,155	0
Amortization of debt issuance costs	224	0
Total interest expense for the 2025 Notes	$ 4,104	$ 0

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Government rebates payable	$ 8,988	$ 8,464
Compensation related costs	7,856	10,446
Accrued royalties and contingent consideration	6,042	6,805
Research and development	17,955	16,515
Selling, general and administrative	3,812	2,990
Miscellaneous accrued	1,966	4,475
Total accrued expenses	$ 46,619	$ 49,695

LOSS PER COMMON SHARE - EPS Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Weighted average number of shares outstanding, basic and diluted	41,410,314	39,657,418
Net loss	$ (40,977)	$ (18,378)
Basic and Diluted (in dollars/share)	$ (0.99)	$ (0.46)

- Definition

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

+ References + Details

LOSS PER COMMON SHARE - Antidilutive Shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	16,614	10,439
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	549	139
Convertible debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	8,411	2,642
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	7,654	7,025
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	0	633

COMMITMENTS AND CONTINGENCIES (Details) - Martin Shkreli $ in Millions	1 Months Ended
	Aug. 31, 2017 USD ($)
Commitment And Contingency [Line Items]
Contingent future legal fee advance payment	$ 5.4
Legal fees reimbursed from director and officer insurance carriers	$ 3.8

SHARE BASED COMPENSATION - Service Based Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Class of Warrant or Right, Outstanding	0	0
Restricted stock units
Number of Shares
Beginning Balance (in shares)	400,426
Granted (in shares)	62,850
Vested (in shares)	(24,769)
Forfeited/canceled (in shares)	(1,250)
Ending Balance (in share)	437,257
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 24.95
Granted (in dollars per share)	23.12
Vested (in dollars per share)	20.88
Forfeited/canceled (in dollars per share)	25.25
Ending balance (in dollars per share)	$ 24.92
Unamortized stock compensation expense	$ 8.3
Weighted-average recognition period (in years)	3 years
Performance Shares
Number of Shares
Beginning Balance (in shares)	226,750
Granted (in shares)	50,000
Vested (in shares)	0
Forfeited/canceled (in shares)	0
Ending Balance (in share)	276,750
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 21.54
Granted (in dollars per share)	23.34
Vested (in dollars per share)	0.00
Forfeited/canceled (in dollars per share)	0.00
Ending balance (in dollars per share)	$ 21.86
Unamortized stock compensation expense	$ 1.8
Weighted-average recognition period (in years)	1 year 2 months 10 days

SHARE BASED COMPENSATION - Performance Based Restricted Stock Activity (Details) - Performance Shares $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized stock compensation expense \| $	$ 1.8
Weighted-average recognition period (in years)	1 year 2 months 10 days
Beginning Balance (in shares) \| shares	226,750
Beginning balance (in dollars per share) \| $ / shares	$ 21.54
Granted (in shares) \| shares	50,000
Granted (in dollars per share) \| $ / shares	$ 23.34
Vested (in shares) \| shares	0
Vested (in dollars per share) \| $ / shares	$ 0.00
Forfeited/canceled (in shares) \| shares	0
Forfeited/canceled (in dollars per share) \| $ / shares	$ 0.00

SHARE BASED COMPENSATION - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Weighted Average Exercise Price
Number of shares exercisable (in shares)	5,000,000
Weighted average exercise price (in dollars per share)	$ 16.92
Stock Options
Shares Underlying Options
Beginning Balance (in shares)	7,277,337
Granted (in shares)	440,700
Exercised (in shares)	(23,727)
Forfeited/canceled (in shares)	(33,134)
Ending Balance (in shares)	7,661,176	7,277,337
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 18.55
Granted (in dollars per share)	23.20
Exercised (in dollars per share)	12.81
Forfeited/canceled (in dollars per share)	24.94
Ending balance (in dollars per share)	$ 18.81	$ 18.55
Weighted Average Remaining Contractual Life (years)	6 years 10 months 15 days	6 years 11 months 10 days
Aggregate Intrinsic Value (in thousands)	$ 40,435	$ 40,650
Unamortized stock compensation expense	$ 30,900
Weighted-average recognition period (in years)	2 years 9 months

SHARE BASED COMPENSATION - Stock based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6,520	$ 4,609
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,670	1,407
Selling, general & administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4,850	$ 3,202

SHARE BASED COMPENSATION - Exercise of Warrants (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Warrants exercised (in shares)	168,612
Proceeds from warrant exercises	$ 0.6
Warrants outstanding (in shares)		0	0

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended
INCOME TAXES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Effective tax rate	(1.00%)	(1.30%)
Income tax expense	$ (401)	$ (229)

INVENTORY (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 4,377	$ 4,689
Finished goods	1,194	930
Total inventory	5,571	5,619
Inventory Reserve	$ 1,900	$ 1,800

ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Accounts receivable, net of reserves	$ 12,713	$ 12,662

DISPOSITIONS (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
DISPOSITIONS (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to acquire L-UDCA	$ 500
IPR&D asset		$ 233,375		$ 255,643
Business combination-related contingent consideration	25,000	76,000		93,000
Adjustments to contingent consideration		(1,405)	$ (4,245)	1,000	$ (5,700)	$ (2,300)
Impairment of IPR&D intangibles		25,500	0
Write off of L-UDCA contingent consideration		18,000	$ 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]
IPR&D asset	$ 25,500			25,500
Business combination-related contingent consideration				$ 18,000
Impairment of IPR&D intangibles		$ 25,500

SUBSEQUENT EVENT (Details) $ in Thousands	Apr. 23, 2019 USD ($) ft²	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Jul. 31, 2016 ft²
Subsequent Event [Line Items]
Square footage leased \| ft²				45,000
Operating lease term				7 years 7 months
Operating lease extension term			5 years
Total lease liability \| $		$ 11,946	$ 11,300
Subsequent Event
Subsequent Event [Line Items]
Square footage leased \| ft²	77,242
Operating lease term	7 years 7 months
Operating lease extension term	5 years
Total lease liability \| $	$ 36,500

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 15,710,000
Additional Paid-in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	5,394,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 10,316,000