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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	Apr. 30, 2018
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		39,943,960
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 61,117	$ 99,394
Marketable securities	202,939	201,236
Accounts receivable, net	12,981	13,872
Inventory, net	5,142	5,351
Prepaid expenses and other current assets	2,011	3,112
Prepaid taxes	2,613	2,842
Total current assets	286,803	325,807
Property and equipment, net	3,042	3,230
Other assets	6,457	5,556
Investment-equity	15,000	0
Intangible assets, net	188,556	184,817
Goodwill	936	936
Total assets	500,794	520,346
Current liabilities:
Accounts payable	9,423	18,938
Accrued expenses	31,644	36,018
Guaranteed minimum royalty	2,000	2,000
Other current liabilities	3,958	3,902
Business combination-related contingent consideration	9,500	9,100
Derivative financial instruments, warrants	0	15,710
Total current liabilities	56,525	85,668
Convertible debt	45,238	45,077
Other non-current liabilities	4,617	2,472
Guaranteed minimum royalty, less current portion	12,939	13,095
Business combination-related contingent consideration, less current portion	82,000	80,900
Total liabilities	201,319	227,212
Stockholders' Equity:
Preferred stock $0.001 par value; 20,000,000 shares authorized; 0 issued and outstanding as of March 31, 2018 and December 31, 2017	0	0
Common stock $0.0001 par value; 100,000,000 shares authorized; 39,873,285 and 39,373,745 issued and outstanding as of March 31, 2018 and December 31, 2017, respectively	4	4
Additional paid-in capital	486,717	471,800
Accumulated deficit	(185,717)	(177,655)
Accumulated other comprehensive loss	(1,529)	(1,015)
Total stockholders' equity	299,475	293,134
Total liabilities and stockholders' equity	$ 500,794	$ 520,346

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
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)	39,873,285	39,373,745
Common stock shares outstanding (in shares)	39,873,285	39,373,745

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net product sales	$ 38,432	$ 33,620
Operating expenses:
Cost of goods sold	1,613	709
Research and development	24,636	20,860
Selling, general and administrative	26,468	23,115
Change in fair value of contingent consideration	3,627	3,344
Total operating expenses	56,344	48,028
Operating loss	(17,912)	(14,408)
Other income (expenses), net:
Other income, net	121	126
Interest expense, net	(358)	(132)
Change in fair value of derivative instruments	0	1,260
Total other income (expense), net	(237)	1,254
Loss before provision for income taxes	(18,149)	(13,154)
Income tax benefit (expense)	(229)	2,064
Net loss	$ (18,378)	$ (11,090)
Loss per common share, basic (in dollars per share)	$ (0.46)	$ (0.29)
Loss per common share, diluted (in dollars per share)	$ (0.46)	$ (0.32)
Weighted average common shares outstanding, basic (in shares)	39,657,418	38,045,317
Weighted average common shares outstanding, diluted (in shares)	39,657,418	39,158,922
Comprehensive loss:
Net loss	$ (18,378)	$ (11,090)
Foreign currency translation	22	(76)
Unrealized gain (loss) on marketable securities	(536)	146
Comprehensive loss	$ (18,892)	$ (11,020)

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows From Operating Activities:
Net loss	$ (18,378)	$ (11,090)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,348	4,284
Deferred income tax benefit	0	(2,064)
Interest income from notes receivable	0	(325)
Non-cash interest expense	413	376
Amortization of premiums on marketable securities	356	287
Share based compensation	4,659	7,093
Change in fair value of liability classified warrants	0	(1,260)
Change in fair value of contingent consideration	3,627	3,344
Payments related to change in fair value of contingent consideration	(4,245)	(914)
Inventory Reserve	816	25
Other	75	53
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	886	3,076
Inventory	(593)	(574)
Other current and non-current operating assets	421	(946)
Accounts payable and accrued expenses	(9,330)	(4,626)
Other current and non-current operating liabilities	2,211	(146)
Net cash used in operating activities	(14,734)	(3,407)
Cash Flows From Investing Activities:
Purchase of fixed assets	(39)	(838)
Cash paid for intangible assets	(8,217)	(3,477)
Proceeds from the sale/maturity of marketable securities	26,924	8,440
Purchase of marketable securities	(29,519)	0
Cash paid for investments - equity	(10,000)	0
Net cash provided by (used in) investing activities	(20,851)	4,125
Cash Flows From Financing Activities:
Payment of acquisition-related contingent consideration	(7,066)	(1,068)
Payment of guaranteed minimum royalty	(500)	(500)
Payment of other liability	0	(250)
Proceeds from exercise of warrants	608	0
Proceeds from exercise of stock options	4,256	1,964
Net cash provided by (used in) financing activities	(2,702)	146
Effect of exchange rate changes on cash	10	4
Net change in cash	(38,277)	868
Cash, beginning of year	99,394	41,002
Cash, end of period	$ 61,117	$ 41,870

DESCRIPTION OF BUSINESS

3 Months Ended

Mar. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

DESCRIPTION OF BUSINESS

Organization and Description of Business

Retrophin, Inc. (“we”, “our”, “us”, “Retrophin” and the “Company”) refers to Retrophin, Inc., a Delaware corporation, as well as our direct and indirect subsidiaries. Retrophin is a fully integrated biopharmaceutical company headquartered in San Diego, California focused on the development, acquisition and commercialization of therapies for the treatment of 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. Consequences of PKAN include dystonia, dysarthria, rigidity, retinal degeneration, and severe digestive problems. There are currently no viable treatment options for patients with PKAN. Fosmetpantotenate is a phosphopantothenate replacement therapy that aims to restore levels of this key substrate in PKAN patients.

Sparsentan (RE-021) is an investigational product candidate which acts as both a potent angiotensin receptor blocker (“ARB”), as well as a selective endothelin receptor antagonist (“ERA”), with in vitro selectivity toward endothelin receptor type A. The Company secured a license to sparsentan from Ligand Pharmaceuticals, Inc. and Bristol-Myers Squibb Company (who referred to it as DARA). The Company is developing sparsentan as a treatment for:


▪	Focal segmental glomerulosclerosis ("FSGS"), which is a leading cause of end-stage renal disease and nephrotic syndrome (“NS”). There are no U.S. Food and Drug Administration ("FDA") approved pharmacologic treatments for FSGS and off-label resources are limited to ACE/ARBs, steroids, and immunosuppressant agents, which are effective in only a subset of patients.


▪	Immunoglobulin A nephropathy ("IgAN"), which is characterized by hematuria, proteinuria, and variable rates of progressive renal failure. There is no FDA approved treatment for IgAN.

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"). CNSA-001 is an orally bioavailable form of a natural precursor of tetrahydrobiopterin ("BH4") with the potential to provide improved phenylalanine ("Phe") reduction in patients with PKU when compared to BH4.

PKU is a rare, genetic metabolic condition in which the body cannot breakdown Phe due to a missing or defective phenylalanine hydroxylase ("PAH") enzyme. High Phe levels can lead to developmental and physical growth delay, executive function impairment, seizures, and microcephaly caused by toxic Phe accumulation in the brain.

The Company is party to a three-way Cooperative Research and Development Agreement ("CRADA") with the National Institutes of Health’s National Center for Advancing Translational Sciences and patient advocacy foundation NGLY1.org to collaborate on research efforts aimed at the identification of potential small molecule therapeutics for N-glycanase deficiency ("NGLY1").

NGLY1 is an extremely rare genetic disorder believed to be caused by a deficiency in an enzyme called N-glycanase-1, which is encoded by the gene NGLY1. The condition has been characterized by symptoms such as developmental delays, seizures, complex hyperkinetic movement disorders, diminished reflexes and an inability to produce tears. There are no approved therapeutic options for NGLY1 deficiency, and current therapeutic strategies are limited to symptom management.

Liquid ursodeoxycholic acid ("L-UDCA") is a liquid formulation of ursodeoxycholic acid being developed for the treatment of a rare liver disease called primary biliary cholangitis ("PBC"). The Company obtained the rights to L-UDCA in 2016 with the intention of making L-UDCA commercially available to the subset of PBC patients who have difficulty swallowing.

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 also 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 (approved and marketed in Europe for select indications as Kolbam) 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.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Mar. 31, 2018
Accounting Policies [Abstract]
SUMMARY OF 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 2017 10-K filed with the SEC on February 27, 2018. 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, 2017 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 Effective January 1, 2018, the Company adopted Accounting Standards Codification (" ASC"), Topic 606, Revenue from Contracts with Customers, using the full retrospective transition method. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. See Note 3 for further discussion. Adoption of New Accounting Standards In May 2014, the Financial Accounting Standard Board ("FASB") issued ASU No. 2014-09, Revenue from Contracts with Customers. Under the new standard, revenue is recognized at the time a good or service is transferred to a customer for the amount of consideration for which the entity expects to be entitled for that specific good or service. Entities may use a full retrospective approach or report the cumulative effect as of the date of adoption. The Company adopted the new standard on January 1, 2018 using the full retrospective approach and there was no impact on the timing or recognition of revenue because its only revenue source is product sales and because no variable consideration exists. The new standard also requires enhanced disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. See Note 3 for further discussion. In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features. These amendments simplify the accounting for certain financial instruments with down round features. The amendments require companies to disregard the down round feature when assessing whether the instrument is indexed to its own stock, for purposes of determining liability or equity classification. See Note 6 for further discussion. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The new guidance dictates that, when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, it should be treated as an acquisition or disposal of an asset. The guidance was adopted as of January 1, 2018. Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its consolidated financial position or results of operations upon adoption. In 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. A modified retrospective transition approach is required for lessees for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. The Company is in the process of evaluating the impact of this guidance on its consolidated financial statements and related disclosures; however, based on the Company's current operating leases, it is expected to have a material impact on the company's consolidated balance sheet by increasing assets and liabilities. 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, 2018, the Company holds $202.9 million in available for sale debt securities that are affected by this ASU. If adopted as of March 31, 2018, this would not have a material impact on the company's financial statements. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The new guidance addresses a specific consequence of the newly enacted federal income tax law (the "Tax Act"). This accounting update allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Act. The amendments eliminate the stranded tax effects that were created as a result of the reduction of historical U.S. federal corporate income tax rates to the newly enacted U.S. federal corporate income tax rates. The accounting update is effective January 1, 2019, with early adoption permitted, and is to be applied either in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act is recognized. The Company is currently evaluating the potential effect of the guidance on its consolidated financial statements.

REVENUE RECOGNITION

3 Months Ended

Mar. 31, 2018

Revenue from Contract with Customer [Abstract]

Revenue Recognition

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 is offered to its customers, health care providers, payors and other indirect customers relating to the Company’s sales of its products. These provisions are based on the amounts earned or to be claimed on the related sales and are classified as a reduction of accounts receivable (if the amount is payable to the customer) or as a current liability (if the amount is payable to a party other than a customer). Where appropriate, these reserves take into consideration the Company’s historical experience, current contractual and statutory requirements, 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 Company had the following net product revenues (in thousands):



	For the three months ended:
	March 31, 2018		March 31, 2017
Bile acid products	$	18,508	$	15,736
Thiola	19,924		17,884
Total net product revenue	$	38,432	$	33,620

MARKETABLE SECURITIES

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

MARKETABLE SECURITIES

The Company's marketable securities as of March 31, 2018 and December 31, 2017 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, 2018, investment activity for the Company included $26.9 million in maturities and $29.7 million in purchases, all relating to debt based marketable securities.

Marketable securities consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Marketable Securities:
Commercial paper	$	10,339	$	6,897
Corporate debt securities	162,648		164,297
Securities of government sponsored entities	29,952		30,042
Total marketable securities:	$	202,939	$	201,236

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



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Losses			Aggregate Estimated Fair Value
Marketable securities:
Commercial paper	Less than 1	$	10,384	$	(45	)	$	10,339
Corporate debt securities	Less than 1	88,525		(439		)	88,086
Securities of government-sponsored entities	Less than 1	30,019		(67		)	29,952
Total maturity less than 1 year		128,928		(551		)	128,377
Corporate debt securities	1 to 2	75,276		(714		)	74,562
Total maturity 1 to 2 years		75,276		(714		)	74,562
Total available-for-sale securities		$	204,204	$	(1,265	)	$	202,939

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2017 (in thousands):



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Losses			Aggregate Estimated Fair Value
Marketable securities:
Commercial paper	Less than 1	$	6,911	$	(14	)	$	6,897
Corporate debt securities	Less than 1	86,531		(198		)	86,333
Securities of government-sponsored entities	Less than 1	30,132		(90		)	30,042
Total maturity less than 1 year		123,574		(302		)	123,272
Corporate debt securities	1 to 2	78,388		(424		)	77,964
Total maturity 1 to 2 years		78,388		(424		)	77,964
Total available-for-sale securities		$	201,962	$	(726	)	$	201,236

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

The Company reviews the available-for-sale investments for other-than-temporary declines in fair value below cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below the cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell the security before recovery of its amortized cost basis. The assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security. As of March 31, 2018 and December 31, 2017, the Company believed the cost basis for available-for-sale investments was recoverable in all material respects.

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT (Notes)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Future Acquisition Right and Joint Development Agreement	FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT Censa Pharmaceuticals Inc. In December 2017, the Company entered into a Future Acquisition Right and Joint Development Agreement (the “Option Agreement”) with Censa Pharmaceuticals Inc. (“Censa”), which became effective in January 2018. The Company has agreed to fund certain development activities of Censa’s CNSA-001 program, in an aggregate amount expected to be approximately $17 million through proof of concept, and has 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. In exchange for the Option, the Company paid $10 million, and an additional $5 million upon Censa’s completion of a specified development milestone set forth in the Option Agreement. If the Company exercises the Option, the Company will acquire Censa for $65 million in upfront consideration, subject to certain adjustments, 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") and 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. As of March 31, 2018, the Company has paid $10.0 million as an upfront payment and $5.0 million in development funding to Censa. In addition, the Company accrued $5.0 million related to a development milestone payable to Censa within 45 days of achievement. The Company capitalized the upfront payment and accrued milestone, and expensed the development funding paid. The Company is treating the upfront payment and milestone, both of which are compensation for the purchase option, as a cost-method investment with a total carrying value of $15.0 million as March 31, 2018. The Company's maximum exposure to loss related to this VIE is limited to the carrying value of its investment.

DERIVATIVE FINANCIAL INSTRUMENTS

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVE FINANCIAL INSTRUMENTS

Since 2013, the Company has issued five tranches of common stock purchase warrants to secure financing, remediate covenant violations and provide consideration for amendments with respect to a credit facility extinguished in 2015.

Historically, the Company accounted for these instruments, which do not have fixed settlement provisions, as derivative instruments in accordance with FASB ASC 815-40, Derivative and Hedging – Contracts in Entity’s Own Equity. This was due to an anti-dilution provision for the warrants that provides for a reduction to the exercise price if the Company issues equity or equity linked instruments in the future at an effective price per share less than the exercise price then in effect for the warrant ("down round provision"). As such, the warrants were re-measured at each balance sheet date based on estimated fair value. Changes in estimated fair value were recorded as non-cash adjustments within other income (expenses), net, in the Company’s accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss. The Company recorded a gain on the change in the estimated fair value of warrants of $1.3 million for the three months ended March 31, 2017.

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

In accordance with the guidance presented in the ASU, the fair value of the derivative liability balance as of December 31, 2017 of $15.7 million was reclassified by means of a cumulative-effect adjustment to equity as of January 1, 2018.

Impact of the adoption of ASU 2017-11 on equity (in thousands):



	Common stock		Additional paid in capital		Accumulated other comprehensive loss			Accumulated deficit			Total stockholders' equity (deficit)
Balance–December 31, 2017	$	4	$	471,800	$	(1,015	)	$	(177,655	)	$	293,134
Balance-March 31, 2018 before effect of ASU 17-11	4		481,323		(1,529		)	(196,033		)	283,765
Effect of ASU 17-11	—		5,394					10,316			15,710
Balance–March 31, 2018	$	4	$	486,717	$	(1,529	)	$	(185,717	)	$	299,475

The Company calculated the fair value of the warrants using the Black-Scholes Model as of December 31, 2017, using the following assumptions:



	December 31, 2017
Fair value of common stock	$	21.07
Remaining life of the warrants (in years)	0.1 - 2.0 years
Risk-free interest rate*	1.39 - 1.89%
Expected volatility**	33 - 43%
Dividend yield	—		%

*The risk-free interest rate is based on the U.S. Treasury security rates for the remaining term of the warrants at the measurement date.

**Expected volatility is based on an analysis of the Company’s historical volatility.

FAIR VALUE MEASUREMENTS

3 Months Ended

Mar. 31, 2018

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 derivative liabilities, the Company used the Black Scholes Model as of December 31, 2017. Based on the fair value hierarchy, the Company classified the derivative liability within Level 3. The Company adopted ASU 2017-11 as of January 1, 2018 and is no longer required to treat outstanding warrants as derivative liabilities measured at fair value. See Note 6 for further discussion.

In estimating the fair value of the Company’s contingent consideration, the Company used the probability-based expected method for royalty payments based on projected revenues. Based on the fair value hierarchy, the Company classified contingent consideration within Level 3 because valuation inputs are based on projected revenues discounted to a present value.

Financial instruments with carrying values approximating fair value include cash and cash equivalents, accounts receivable, and accounts payable, due to their short term nature. As of March 31, 2018, the estimated fair value of convertible debt was $63.4 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, 2018 (in thousands):



	As of March 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	$	61,117	$	61,117	$	—	$	—
Marketable securities, available-for-sale	202,939		—		202,939		—
Total	$	264,056	$	61,117	$	202,939	$	—
Liabilities:
Business combination-related contingent consideration	$	91,500	$	—	$	—	$	91,500
Total	$	91,500	$	—	$	—	$	91,500



	As of December 31, 2017
	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	$	99,394	$	92,726	$	6,668	$	—
Marketable securities, available-for-sale	201,236		—		201,236		—
Total	$	300,630	$	92,726	$	207,904	$	—
Liabilities:
Derivative liability related to warrants	$	15,710	$	—	$	—	$	15,710
Business combination-related contingent consideration	90,000		—		—		90,000
Total	$	105,710	$	—	$	—	$	105,710

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, 2018 (in thousands):



	Fair Value Measurements of Acquisition-Related Contingent Consideration (Level 3)
Balance at January 1, 2018	$	90,000
Increase from revaluation of contingent consideration	3,627
Contractual payments included in accrued liabilities at March 31, 2018	(2,127		)
Contractual payments	—
Balance at March 31, 2018	$	91,500

The fair value of contingent consideration liabilities was determined by applying a form of the income approach (a level 3 input), based upon the probability-weighted projected payment amounts discounted to present value at a rate appropriate for the risk of achieving the performance targets. The key assumptions included in the calculations were the earn-out period payment probabilities, 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, 2018, the Company incurred charges of $3.6 million in operating expenses on the Condensed Consolidated Statements of Operations and Comprehensive Loss for the revaluation 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 changes in the estimated timing of payments. During the three months ended March 31, 2017, the Company incurred charges of $3.3 million in operating expenses on the Condensed Consolidated Statement of Operations and Comprehensive Loss for the revaluation of the contingent consideration liabilities. For the three months ended March 31, 2017, $1.4 million, $1.1 million, and $0.8 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 changes in the estimated timing of payments.

- 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, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLE ASSETS

As of March 31, 2018, the net book value of amortizable intangible assets was approximately $188.6 million.

The following table sets forth amortizable intangible assets as of March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Finite-lived intangible assets	$	243,865		$	235,863
Less: accumulated amortization	(55,309		)	(51,046		)
Net carrying value	$	188,556		$	184,817

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



	Three Months Ended March 31,
	2018		2017
Research and development	$	103	$	81
Selling, general and administrative	4,096		4,090
Total amortization expense	$	4,199	$	4,171

During the three months ended March 31, 2018, the Company made a development payment to Ligand Pharmaceuticals for $4.6 million relating to sparsentan which was recorded as an increase to the Ligand license intangible asset.

CONVERTIBLE NOTES PAYABLE	3 Months Ended
CONVERTIBLE NOTES PAYABLE	Mar. 31, 2018
Debt Disclosure [Abstract]
CONVERTIBLE NOTES PAYABLE	CONVERTIBLE NOTES PAYABLE 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 senior convertible notes due in 2019 (the “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 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 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. At March 31, 2018 and December 31, 2017, the aggregate carrying value of the Notes was $45.2 million and $45.1 million, respectively.

ACCRUED EXPENSES

3 Months Ended

Mar. 31, 2018

Payables and Accruals [Abstract]

ACCRUED EXPENSES

Accrued expenses at March 31, 2018 and December 31, 2017 consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Government rebates payable	$	6,372	$	5,883
Compensation related costs	5,693		7,749
Accrued royalties and contingent consideration	5,870		6,429
Research and development	9,553		6,989
Selling, general and administrative	2,058		3,896
Restructuring expenses	42		3,549
Miscellaneous accrued	2,056		1,523
Total accrued expenses	$	31,644	$	36,018

LOSS PER COMMON SHARE

3 Months Ended

Mar. 31, 2018

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 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,
	2018							2017
	Shares	Net Loss			EPS			Shares	Net Loss			EPS
Basic loss per share	39,657,418	$	(18,378	)	$	(0.46	)	38,045,317	$	(11,090	)	$	(0.29	)
Dilutive shares related to warrants	—	—						1,113,605	—
Change in fair value of derivative instruments	—	—						—	(1,260		)
Dilutive loss per share	39,657,418	$	(18,378	)	$	(0.46	)	39,158,922	$	(12,350	)	$	(0.32	)

The following shares were excluded because they were anti-dilutive (in thousands):



	Three Months Ended March 31,
	2018	2017
Restricted stock units	139	332
Convertible debt	2,642	2,642
Options	7,025	6,405
Warrants	633	—
Total anti-dilutive shares	10,439	9,379

COMMITMENTS AND CONTINGENCIES

3 Months Ended

Mar. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Leases and Sublease Agreements



Facilities	Annual Base Rent	Lease Expiration	Comments
Occupied Locations
Corporate Headquarters San Diego, CA	$2.1 million	July 2024
Vacated Locations
New York, NY	$0.5 million	November 2018	Sublet through expiration

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. In connection with these proceedings, Mr. Shkreli sought advancement of his legal fees from the Company. The Company disputed its obligation to pay these amounts in full, and in November 2016, the Company and Mr. Shkreli entered into a binding settlement arrangement under which the Company advanced $2.8 million in legal fees to Mr. Shkreli’s counsel. The Company also advanced an additional $2 million in legal fees once the matter proceeded to trial. In December 2017, the Company agreed to advance Mr. Shkreli $625,000 in full satisfaction of its obligation to advance fees to Mr. Shkreli in connection with his appeal of his conviction. The Company has been reimbursed by its directors’ and officers’ insurance carriers for $3.3 million of the legal fees the Company advanced in connection with the pre-trial and trial proceedings. 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 the 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. The federal Court granted a stay of the federal lawsuit pending a determination by the arbitration panel whether the Company’s counterclaims would be litigated in the arbitration, as the Company is seeking. In April 2016, the arbitration panel granted the parties’ request for a stay of the proceedings pending settlement discussions. 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. Pursuant to the November 2016 binding term sheet, the significant majority of the existing legal fees related to these proceedings that Mr. Shkreli claimed should be advanced were offset and satisfied by a $2.025 million judgment against Mr. Shkreli in a different case, and the Company paid $0.4 million in legal fees to Mr. Shkreli's counsel. The legal fees the Company has advanced 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. The Company will also be subject to additional obligations when the litigation resumes, as well as advancement obligations in the interim.

For the three months ended March 31, 2018 and 2017, the Company recorded no expenses under the settlement agreement. For the three months ended March 31, 2017, the Company paid $1.0 million under the settlement. No reimbursements from the Company's directors’ and officers’ insurance carriers were received during the three months ended March 31, 2018 and 2017. Of the $3.3 million reimbursed by the insurance carriers, $2.6 million is recorded as a liability on the Consolidated Balance Sheet pending the outcome of Mr. Shkreli's appeal.

From time to time the Company is involved in legal proceedings arising in the ordinary course of business. The Company believes there is no litigation pending 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, 2018

Equity [Abstract]

SHARE BASED COMPENSATION

Restricted Shares

Service and Performance Based Restricted Stock Units

The following table summarizes the Company’s restricted stock activity during the three months ended March 31, 2018:



	Number of Restricted Stock Units		Weighted Average Grant Date Fair Value
Unvested December 31, 2017	345,332		$	20.51
Granted	18,061		22.18
Vested	(11,377	)	18.33
Forfeited/canceled	(12,666	)	22.84
Unvested March 31, 2018	339,350		$	20.58

At March 31, 2018, unamortized stock compensation for restricted stock units was $2.1 million, with a weighted-average recognition period of 1.2 years.

Performance Based Restricted Stock Units

The Company did not grant any performance based restricted stock units during the three months ended March 31, 2018.

Stock Options

The following table summarizes stock option activity during the three months ended March 31, 2018:



	Shares Underlying Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2017	7,153,668		$	17.16	6.95	$	39,010
Granted	136,500		24.08
Exercised	(319,551	)	13.32
Forfeited/canceled	(198,002	)	25.35
Outstanding at March 31, 2018	6,772,615		$	17.25	7.02	$	43,054

At March 31, 2018, unamortized stock compensation for stock options was $24.7 million, with a weighted-average recognition period of 2.6 years.

At March 31, 2018, outstanding options to purchase 4.5 million shares of common stock were exercisable with a weighted-average exercise price per share of $16.16.

Share Based Compensation

The following table sets forth total non-cash stock-based compensation for the three months ended March 31, 2018 and 2017 (in thousands):



	Three Months Ended March 31,
	2018		2017
Research and development	$	1,407	$	2,656
Selling, general & administrative	3,202		4,437
Total	$	4,609	$	7,093

Exercise of Warrants

During the three months ended March 31, 2018, the Company issued 168,612 shares of common stock upon the exercise of outstanding warrants for cash received by the Company in the amount of $0.6 million. See Note 6 for changes in warrant accounting.

At March 31, 2018 and December 31, 2017, warrants to purchase 990,810 and 1,159,424 shares of common stock, respectively, were outstanding.

INCOME TAXES

3 Months Ended

Mar. 31, 2018

Income Tax Disclosure [Abstract]

INCOME TAXES

The following table summarizes our effective tax rate and income tax benefit (expense) for the three months ended March 31, 2018 and 2017 (dollars in millions):



	Three Months Ended March 31,
	2018			2017
Effective tax rate	(1.3		)%	15.7		%
Income tax benefit (expense)	$	(0.2	)	$	2.1

For the three months ended March 31, 2018 and 2017, we recognized an income tax expense of $0.2 million and an income tax benefit of $2.1 million, respectively, representing an effective tax rate of (1.3)% and 15.7%, respectively. Under GAAP, quarterly effective tax rates may vary significantly depending on the actual operating results in the various tax jurisdictions, and significant transactions, as well as changes in the valuation allowance related to the expected recovery of deferred tax assets.

For the three months ended March 31, 2018, when compared to the same period in 2017, the change in the tax benefit and decrease in the effective income tax rate was primarily attributable to the increase of the U.S. federal valuation allowance in 2018.

At March 31, 2018, we had no unrecognized tax benefits. We did not recognize any interest or penalties related to unrecognized tax benefits during the three months ended March 31, 2018.

On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act. The Tax Legislation reduces the US federal corporate tax rate from 35% to 21%, as well as making several other significant changes to the tax law, effective January 1, 2018. Pursuant to the Securities and Exchange Commission Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), given the amount and complexity of the changes in tax law resulting from the Tax Legislation, the Company has not finalized the accounting for the income tax effects of the Tax Legislation. This includes the provisional amounts recorded related to the re-measurement of the deferred taxes and the change to our valuation allowance. The impact of the Tax Legislation may differ from this estimate during the one-year measurement period due to, among other things, further refinement of the Company's calculation, changes in interpretations and assumptions the Company has made, guidance that may be issued and actions the Company may take as a result of the Tax Legislation.

At March 31, 2018, the Company is still analyzing certain aspects of the Tax Legislation and refining its calculations, which could potentially affect the analysis of the Company’s deferred tax assets and liabilities and its valuation allowance. Any subsequent adjustment is not expected to be material to the Company’s financial position or results of operations.

INVENTORY

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

INVENTORY

Inventory, net of reserves, consisted of the following at March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018		December 31, 2017
Raw materials	$	3,743	$	3,435
Finished goods	1,399		1,916
Total inventory	$	5,142	$	5,351

The inventory reserve was $1.3 million and $0.7 million at March 31, 2018 and December 31, 2017, respectively.

ACCOUNTS RECEIVABLES	3 Months Ended
ACCOUNTS RECEIVABLES	Mar. 31, 2018
Receivables [Abstract]
Accounts Receivables	ACCOUNTS RECEIVABLES Accounts receivable, net of reserves for prompt pay discounts and doubtful accounts, was $13.0 million and $13.9 million at March 31, 2018 and December 31, 2017, respectively. The total reserves for both periods were immaterial.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Mar. 31, 2018
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 Effective January 1, 2018, the Company adopted Accounting Standards Codification (" ASC"), Topic 606, Revenue from Contracts with Customers, using the full retrospective transition method. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. See Note 3 for further discussion.
Adoption of New Accounting Standards and Recently Issued Accounting Pronouncements	Adoption of New Accounting Standards In May 2014, the Financial Accounting Standard Board ("FASB") issued ASU No. 2014-09, Revenue from Contracts with Customers. Under the new standard, revenue is recognized at the time a good or service is transferred to a customer for the amount of consideration for which the entity expects to be entitled for that specific good or service. Entities may use a full retrospective approach or report the cumulative effect as of the date of adoption. The Company adopted the new standard on January 1, 2018 using the full retrospective approach and there was no impact on the timing or recognition of revenue because its only revenue source is product sales and because no variable consideration exists. The new standard also requires enhanced disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. See Note 3 for further discussion. In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features. These amendments simplify the accounting for certain financial instruments with down round features. The amendments require companies to disregard the down round feature when assessing whether the instrument is indexed to its own stock, for purposes of determining liability or equity classification. See Note 6 for further discussion. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The new guidance dictates that, when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, it should be treated as an acquisition or disposal of an asset. The guidance was adopted as of January 1, 2018. Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its consolidated financial position or results of operations upon adoption. In 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. A modified retrospective transition approach is required for lessees for capital and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. The Company is in the process of evaluating the impact of this guidance on its consolidated financial statements and related disclosures; however, based on the Company's current operating leases, it is expected to have a material impact on the company's consolidated balance sheet by increasing assets and liabilities. 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, 2018, the Company holds $202.9 million in available for sale debt securities that are affected by this ASU. If adopted as of March 31, 2018, this would not have a material impact on the company's financial statements. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The new guidance addresses a specific consequence of the newly enacted federal income tax law (the "Tax Act"). This accounting update allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Act. The amendments eliminate the stranded tax effects that were created as a result of the reduction of historical U.S. federal corporate income tax rates to the newly enacted U.S. federal corporate income tax rates. The accounting update is effective January 1, 2019, with early adoption permitted, and is to be applied either in the period of adoption or retrospectively to each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act is recognized. The Company is currently evaluating the potential effect of the guidance on its consolidated financial statements.
Deductions from Revenue	Deductions from Revenue Revenues from product sales are recorded at the net sales price, which includes provisions resulting from discounts, rebates and co-pay assistance that is offered to its customers, health care providers, payors and other indirect customers relating to the Company’s sales of its products. These provisions are based on the amounts earned or to be claimed on the related sales and are classified as a reduction of accounts receivable (if the amount is payable to the customer) or as a current liability (if the amount is payable to a party other than a customer). Where appropriate, these reserves take into consideration the Company’s historical experience, current contractual and statutory requirements, 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.
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. 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.
Derivative Financial Instruments	Historically, the Company accounted for these instruments, which do not have fixed settlement provisions, as derivative instruments in accordance with FASB ASC 815-40, Derivative and Hedging – Contracts in Entity’s Own Equity. This was due to an anti-dilution provision for the warrants that provides for a reduction to the exercise price if the Company issues equity or equity linked instruments in the future at an effective price per share less than the exercise price then in effect for the warrant ("down round provision"). As such, the warrants were re-measured at each balance sheet date based on estimated fair value. Changes in estimated fair value were recorded as non-cash adjustments within other income (expenses), net, in the Company’s accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss.
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 derivative liabilities, the Company used the Black Scholes Model as of December 31, 2017. Based on the fair value hierarchy, the Company classified the derivative liability within Level 3. The Company adopted ASU 2017-11 as of January 1, 2018 and is no longer required to treat outstanding warrants as derivative liabilities measured at fair value. See Note 6 for further discussion. In estimating the fair value of the Company’s contingent consideration, the Company used the probability-based expected method for royalty payments based on projected revenues. Based on the fair value hierarchy, the Company classified contingent consideration within Level 3 because valuation inputs are based on projected revenues discounted to a present value. Financial instruments with carrying values approximating fair value include cash and cash equivalents, accounts receivable, and accounts payable, due to their short term nature.
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 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.

- Definition

Disclosure of accounting policy for investments in debt and equity securities that are classified as available-for-sale. This policy also may describe the entity's accounting treatment for transfers between investment categories, how the entity determines whether impairments of available-for-sale securities are other than temporary, and how the fair values of such securities are determined.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.M)
-URI http://asc.fasb.org/extlink&oid=65877573&loc=d3e87990-122713

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

REVENUE RECOGNITION (Tables)

3 Months Ended

Mar. 31, 2018

Revenue from Contract with Customer [Abstract]

Summary of Net Product Revenue

The Company had the following net product revenues (in thousands):



	For the three months ended:
	March 31, 2018		March 31, 2017
Bile acid products	$	18,508	$	15,736
Thiola	19,924		17,884
Total net product revenue	$	38,432	$	33,620

MARKETABLE SECURITIES (Tables)

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of marketable securities

Marketable securities consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Marketable Securities:
Commercial paper	$	10,339	$	6,897
Corporate debt securities	162,648		164,297
Securities of government sponsored entities	29,952		30,042
Total marketable securities:	$	202,939	$	201,236

Schedule of available for sale securities

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



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Losses			Aggregate Estimated Fair Value
Marketable securities:
Commercial paper	Less than 1	$	10,384	$	(45	)	$	10,339
Corporate debt securities	Less than 1	88,525		(439		)	88,086
Securities of government-sponsored entities	Less than 1	30,019		(67		)	29,952
Total maturity less than 1 year		128,928		(551		)	128,377
Corporate debt securities	1 to 2	75,276		(714		)	74,562
Total maturity 1 to 2 years		75,276		(714		)	74,562
Total available-for-sale securities		$	204,204	$	(1,265	)	$	202,939

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2017 (in thousands):



	Remaining Contractual Maturity (in years)	Amortized Cost		Unrealized Losses			Aggregate Estimated Fair Value
Marketable securities:
Commercial paper	Less than 1	$	6,911	$	(14	)	$	6,897
Corporate debt securities	Less than 1	86,531		(198		)	86,333
Securities of government-sponsored entities	Less than 1	30,132		(90		)	30,042
Total maturity less than 1 year		123,574		(302		)	123,272
Corporate debt securities	1 to 2	78,388		(424		)	77,964
Total maturity 1 to 2 years		78,388		(424		)	77,964
Total available-for-sale securities		$	201,962	$	(726	)	$	201,236

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of New Accounting Pronouncements and Changes in Accounting Principles

Impact of the adoption of ASU 2017-11 on equity (in thousands):



	Common stock		Additional paid in capital		Accumulated other comprehensive loss			Accumulated deficit			Total stockholders' equity (deficit)
Balance–December 31, 2017	$	4	$	471,800	$	(1,015	)	$	(177,655	)	$	293,134
Balance-March 31, 2018 before effect of ASU 17-11	4		481,323		(1,529		)	(196,033		)	283,765
Effect of ASU 17-11	—		5,394					10,316			15,710
Balance–March 31, 2018	$	4	$	486,717	$	(1,529	)	$	(185,717	)	$	299,475

Schedule of assumptions for valuation of warrants

The Company calculated the fair value of the warrants using the Black-Scholes Model as of December 31, 2017, using the following assumptions:



	December 31, 2017
Fair value of common stock	$	21.07
Remaining life of the warrants (in years)	0.1 - 2.0 years
Risk-free interest rate*	1.39 - 1.89%
Expected volatility**	33 - 43%
Dividend yield	—		%

*The risk-free interest rate is based on the U.S. Treasury security rates for the remaining term of the warrants at the measurement date.

**Expected volatility is based on an analysis of the Company’s historical volatility.

FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of fair value on a recurring basis



	As of March 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	$	61,117	$	61,117	$	—	$	—
Marketable securities, available-for-sale	202,939		—		202,939		—
Total	$	264,056	$	61,117	$	202,939	$	—
Liabilities:
Business combination-related contingent consideration	$	91,500	$	—	$	—	$	91,500
Total	$	91,500	$	—	$	—	$	91,500



	As of December 31, 2017
	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	$	99,394	$	92,726	$	6,668	$	—
Marketable securities, available-for-sale	201,236		—		201,236		—
Total	$	300,630	$	92,726	$	207,904	$	—
Liabilities:
Derivative liability related to warrants	$	15,710	$	—	$	—	$	15,710
Business combination-related contingent consideration	90,000		—		—		90,000
Total	$	105,710	$	—	$	—	$	105,710

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, 2018	$	90,000
Increase from revaluation of contingent consideration	3,627
Contractual payments included in accrued liabilities at March 31, 2018	(2,127		)
Contractual payments	—
Balance at March 31, 2018	$	91,500

INTANGIBLE ASSETS (Tables)

3 Months Ended

Mar. 31, 2018

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, 2018 and December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Finite-lived intangible assets	$	243,865		$	235,863
Less: accumulated amortization	(55,309		)	(51,046		)
Net carrying value	$	188,556		$	184,817

Schedule of amortization expense

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



	Three Months Ended March 31,
	2018		2017
Research and development	$	103	$	81
Selling, general and administrative	4,096		4,090
Total amortization expense	$	4,199	$	4,171

ACCRUED EXPENSES (Tables)

3 Months Ended

Mar. 31, 2018

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses at March 31, 2018 and December 31, 2017 consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Government rebates payable	$	6,372	$	5,883
Compensation related costs	5,693		7,749
Accrued royalties and contingent consideration	5,870		6,429
Research and development	9,553		6,989
Selling, general and administrative	2,058		3,896
Restructuring expenses	42		3,549
Miscellaneous accrued	2,056		1,523
Total accrued expenses	$	31,644	$	36,018

LOSS PER COMMON SHARE (Tables)

3 Months Ended

Mar. 31, 2018

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,
	2018							2017
	Shares	Net Loss			EPS			Shares	Net Loss			EPS
Basic loss per share	39,657,418	$	(18,378	)	$	(0.46	)	38,045,317	$	(11,090	)	$	(0.29	)
Dilutive shares related to warrants	—	—						1,113,605	—
Change in fair value of derivative instruments	—	—						—	(1,260		)
Dilutive loss per share	39,657,418	$	(18,378	)	$	(0.46	)	39,158,922	$	(12,350	)	$	(0.32	)

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

The following shares were excluded because they were anti-dilutive (in thousands):



	Three Months Ended March 31,
	2018	2017
Restricted stock units	139	332
Convertible debt	2,642	2,642
Options	7,025	6,405
Warrants	633	—
Total anti-dilutive shares	10,439	9,379

COMMITMENTS AND CONTINGENCIES (Tables)

3 Months Ended

Mar. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of property subject to or available for operating lease

Leases and Sublease Agreements



Facilities	Annual Base Rent	Lease Expiration	Comments
Occupied Locations
Corporate Headquarters San Diego, CA	$2.1 million	July 2024
Vacated Locations
New York, NY	$0.5 million	November 2018	Sublet through expiration

Schedule of principal contractual commitments

SHARE BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Schedule of restricted stock activity

The following table summarizes the Company’s restricted stock activity during the three months ended March 31, 2018:



	Number of Restricted Stock Units		Weighted Average Grant Date Fair Value
Unvested December 31, 2017	345,332		$	20.51
Granted	18,061		22.18
Vested	(11,377	)	18.33
Forfeited/canceled	(12,666	)	22.84
Unvested March 31, 2018	339,350		$	20.58

Schedule of stock option issuances and balances outstanding

The following table summarizes stock option activity during the three months ended March 31, 2018:



	Shares Underlying Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2017	7,153,668		$	17.16	6.95	$	39,010
Granted	136,500		24.08
Exercised	(319,551	)	13.32
Forfeited/canceled	(198,002	)	25.35
Outstanding at March 31, 2018	6,772,615		$	17.25	7.02	$	43,054

Schedule of Share based compensation expenses

The following table sets forth total non-cash stock-based compensation for the three months ended March 31, 2018 and 2017 (in thousands):



	Three Months Ended March 31,
	2018		2017
Research and development	$	1,407	$	2,656
Selling, general & administrative	3,202		4,437
Total	$	4,609	$	7,093

INCOME TAXES (Tables)

3 Months Ended

Mar. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax (Expense) Benefit

The following table summarizes our effective tax rate and income tax benefit (expense) for the three months ended March 31, 2018 and 2017 (dollars in millions):



	Three Months Ended March 31,
	2018			2017
Effective tax rate	(1.3		)%	15.7		%
Income tax benefit (expense)	$	(0.2	)	$	2.1

INVENTORY (Tables)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Schedule of Inventory

Inventory, net of reserves, consisted of the following at March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018		December 31, 2017
Raw materials	$	3,743	$	3,435
Finished goods	1,399		1,916
Total inventory	$	5,142	$	5,351

DESCRIPTION OF BUSINESS - Narrative (Details)	Mar. 31, 2018 product
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of products sold	3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Marketable securities	$ 202,939	$ 201,236

REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended
REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 38,432	$ 33,620
Bile acid products
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	18,508	15,736
Thiola
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 19,924	$ 17,884
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, 2018	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Proceeds from the sale/maturity of marketable securities	$ 26,924	$ 8,440
Purchases of debt based marketable securities	$ 29,700

MARKETABLE SECURITIES - Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	$ 202,939	$ 201,236
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	10,339	6,897
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	162,648	164,297
Securities of government sponsored entities
Schedule of Available-for-sale Securities [Line Items]
Marketable securities	$ 29,952	$ 30,042

MARKETABLE SECURITIES - Available for Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 204,204	$ 201,962
Unrealized Losses	(1,265)	(726)
Aggregate Estimated Fair Value	202,939	201,236
Less than 1 year
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	128,928	123,574
Unrealized Losses	(551)	(302)
Aggregate Estimated Fair Value	128,377	123,272
1 to 2 years
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	75,276	78,388
Unrealized Losses	(714)	(424)
Aggregate Estimated Fair Value	74,562	77,964
Commercial paper \| Less than 1 year
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,384	6,911
Unrealized Losses	(45)	(14)
Aggregate Estimated Fair Value	10,339	6,897
Corporate debt securities \| Less than 1 year
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	88,525	86,531
Unrealized Losses	(439)	(198)
Aggregate Estimated Fair Value	88,086	86,333
Corporate debt securities \| 1 to 2 years
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	75,276	78,388
Unrealized Losses	(714)	(424)
Aggregate Estimated Fair Value	74,562	77,964
Securities of government sponsored entities \| Less than 1 year
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,019	30,132
Unrealized Losses	(67)	(90)
Aggregate Estimated Fair Value	$ 29,952	$ 30,042

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Business combination, option agreement, purchase price	$ 65,000
Business combination, option agreement, purchase price, percent transfered in cash	20.00%
Business combination, option agreement, purchase price, percent transfered 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, weighted average ten day share price, which requires all cash payment (in dollars per share)	$ 19.26
Business combination, option agreement, contingent consideration	$ 25,000
Development milestone payment, period		45 days
Investment		$ 15,000	$ 0
Censa Pharmaceuticals Inc. \| CNSA-001 Program \| Purchase Provision Terms
Variable Interest Entity [Line Items]
Research and development arrangement, contract to perform for others, compensation earned	17,000
Censa Pharmaceuticals Inc.
Variable Interest Entity [Line Items]
Payments for the option to acquire business	10,000	10,000
Censa Pharmaceuticals, Inc, Equity Holders
Variable Interest Entity [Line Items]
Additional required payments for the option to acquire business, successful development milestones	$ 5,000	$ 5,000

DERIVATIVE FINANCIAL INSTRUMENTS (Details) $ in Thousands	3 Months Ended
DERIVATIVE FINANCIAL INSTRUMENTS (Details) $ in Thousands	Mar. 31, 2018 USD ($) tranche	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Loss on derivative instruments, pretax	$ 0	$ 1,260
Derivative liability related to warrants	$ 0		$ 15,710
Warrant
Derivative [Line Items]
Number of tranches \| tranche	5

DERIVATIVE FINANCIAL INSTRUMENTS - Affect Of New Accounting Pronouncement (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	$ 283,765	$ 293,134
Adjusted stockholders' equity	299,475
Common stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	4	4
Adjusted stockholders' equity	4
Additional paid in capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	481,323	471,800
Adjusted stockholders' equity	486,717
Accumulated other comprehensive loss
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	(1,529)	(1,015)
Adjusted stockholders' equity	(1,529)
Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity	(196,033)	(177,655)
Adjusted stockholders' equity	$ (185,717)
Accounting Standards Update 2017-11
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of ASU 17-11		15,710
Accounting Standards Update 2017-11 \| Common stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of ASU 17-11		0
Accounting Standards Update 2017-11 \| Additional paid in capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of ASU 17-11		5,394
Accounting Standards Update 2017-11 \| Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of ASU 17-11		$ 10,316

DERIVATIVE FINANCIAL INSTRUMENTS - Valuation Assumptions (Details) - Warrants	12 Months Ended
	Dec. 31, 2017 $ / shares
Derivative [Line Items]
Fair value of common stock (in dollars per share)	$ 21.07
Dividend yield	0.00%
Minimum
Derivative [Line Items]
Remaining life of the warrants (in years)	1 month 6 days
Risk-free interest rate	1.39%
Expected volatility	33.00%
Maximum
Derivative [Line Items]
Remaining life of the warrants (in years)	2 years
Risk-free interest rate	1.89%
Expected volatility	43.00%

FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Fair value of convertible debt	$ 63,400
Change in fair value of contingent consideration	3,627	$ 3,344
Increase from revaluation of contingent consideration	(4,245)	(914)
Product Rights Chenodal
Business Acquisition [Line Items]
Increase from revaluation of contingent consideration		1,400
Acquired Product Rights Cholbam
Business Acquisition [Line Items]
Increase from revaluation of contingent consideration	1,800	1,100
Acquired Product Rights L-UDCA
Business Acquisition [Line Items]
Increase from revaluation of contingent consideration	$ 1,000	$ 800

FAIR VALUE MEASUREMENTS - Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Marketable securities, available-for-sale	$ 202,939	$ 201,236
Liabilities:
Derivative liability related to warrants	0	15,710
Recurring basis
Assets:
Cash and cash equivalents	61,117	99,394
Marketable securities, available-for-sale	202,939	201,236
Total	264,056	300,630
Liabilities:
Derivative liability related to warrants		15,710
Business combination-related contingent consideration	91,500	90,000
Total	91,500	105,710
Recurring basis \| Quoted prices in active markets (Level 1)
Assets:
Cash and cash equivalents	61,117	92,726
Marketable securities, available-for-sale	0	0
Total	61,117	92,726
Liabilities:
Derivative liability related to warrants		0
Business combination-related contingent consideration	0	0
Total	0	0
Recurring basis \| Significant other observable inputs (Level 2)
Assets:
Cash and cash equivalents	0	6,668
Marketable securities, available-for-sale	202,939	201,236
Total	202,939	207,904
Liabilities:
Derivative liability related to warrants		0
Business combination-related contingent consideration	0	0
Total	0	0
Recurring basis \| Significant unobservable inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Marketable securities, available-for-sale	0	0
Total	0	0
Liabilities:
Derivative liability related to warrants		15,710
Business combination-related contingent consideration	91,500	90,000
Total	$ 91,500	$ 105,710

FAIR VALUE MEASUREMENTS - Acquisition-related Contingent Consideration (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase from revaluation of contingent consideration	$ (4,245)	$ (914)
Recurring basis \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance at January 1, 2018	90,000
Increase from revaluation of contingent consideration	3,627
Contractual payments included in accrued liabilities at March 31, 2018	(2,127)
Contractual payments	0
Balance at March 31, 2018	$ 91,500

INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended
INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Net book value of amortizable intangible assets	$ 188,556	$ 184,817
Licensing Agreements
Finite-Lived Intangible Assets [Line Items]
Development payment made during the period	$ 4,600

INTANGIBLE ASSETS - Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Finite-lived intangible assets	$ 243,865	$ 235,863
Less: accumulated amortization	(55,309)	(51,046)
Net carrying value	$ 188,556	$ 184,817

INTANGIBLE ASSETS - Amortization (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 4,199	$ 4,171
Research and development
Finite-Lived Intangible Assets [Line Items]
Total amortization expense	103	81
Selling, general and administrative
Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 4,096	$ 4,090

CONVERTIBLE NOTES PAYABLE (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	May 29, 2014
Debt Instrument [Line Items]
Convertible debt	$ 45,238,000	$ 45,077,000
Note Purchase Agreement \| Senior convertible notes due 2019
Debt Instrument [Line Items]
Credit agreement amount			$ 46,000,000.0
Initial conversion price (in dollars per share)			$ 17.41
Interest rate percentage			4.50%

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Government rebates payable	$ 6,372	$ 5,883
Compensation related costs	5,693	7,749
Accrued royalties and contingent consideration	5,870	6,429
Research and development	9,553	6,989
Selling, general and administrative	2,058	3,896
Restructuring expenses	42	3,549
Miscellaneous accrued	2,056	1,523
Total accrued expenses	$ 31,644	$ 36,018

LOSS PER COMMON SHARE - EPS Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Shares
Basic loss per share (in shares)	39,657,418	38,045,317
Dilutive shares related to warrants (in shares)	0	1,113,605
Change in fair value of derivative instruments (in shares)	0	0
Weighted average common shares outstanding, diluted (in shares)	39,657,418	39,158,922
Net Loss
Net loss	$ (18,378)	$ (11,090)
Change in fair value of derivative instruments	0	(1,260)
Dilutive net earnings (loss) per share	$ (18,378)	$ (12,350)
Loss per common share, basic (in dollars per share)	$ (0.46)	$ (0.29)
Loss per common share, diluted (in dollars per share)	$ (0.46)	$ (0.32)
Warrant \| Warrant
Net Loss
Dilutive shares related to warrants	$ 0	$ 0

LOSS PER COMMON SHARE - Antidilutive Shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	10,439	9,379
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	139	332
Convertible debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	2,642	2,642
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	7,025	6,405
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation	633	0

COMMITMENTS AND CONTINGENCIES - Leases and Subleases Commitment (Details) - Lease Agreement	3 Months Ended
	Mar. 31, 2018 USD ($)
San Diego CA
Other Commitments [Line Items]
Annual Base Rent	$ 2,100,000.0
NEW YORK
Other Commitments [Line Items]
Annual Base Rent	$ 500,000.0

COMMITMENTS AND CONTINGENCIES - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended		2 Months Ended	12 Months Ended
	Dec. 31, 2017	Nov. 30, 2016	Sep. 30, 2017	Dec. 31, 2016	Mar. 31, 2018
Commitment And Contingency [Line Items]
Judgment against the counterparty		$ 2,025
Martin Shkreli
Commitment And Contingency [Line Items]
Legal fees paid in advance		$ 2,800
Contingent future legal fee advance payment			$ 2,000
Legal fees reimbursed from director and officer insurance carriers			$ 3,300
Payments for legal settlements				$ 1,000
Retrophin, Inc. v. Shkreli
Commitment And Contingency [Line Items]
Loss Contingency Accrual					$ 2,600
Retrophin, Inc. v. Shkreli \| Martin Shkreli
Commitment And Contingency [Line Items]
Legal fees paid in advance	$ 625			$ 400

SHARE BASED COMPENSATION - Restricted Stock Activity (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Restricted stock units
Number of Restricted Stock Units
Beginning Balance (in shares)	345,332,000
Granted (in shares)	18,061,000
Vested (in shares)	(11,377,000)
Forfeited/canceled (in shares)	(12,666,000)
Ending Balance (in share)	339,350,000
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share) \| $ / shares	$ 20.51
Granted (in dollars per share) \| $ / shares	22.18
Vested (in dollars per share) \| $ / shares	18.33
Forfeited/canceled (in dollars per share) \| $ / shares	22.84
Ending balance (in dollars per share) \| $ / shares	$ 20.58
Unamortized stock compensation expense \| $	$ 2.1
Weighted-average recognition period (in years)	1 year 2 months 12 days
Performance Based Restricted Stock Awards
Number of Restricted Stock Units
Granted (in shares)	0

SHARE BASED COMPENSATION - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Weighted Average Exercise Price
Number of shares exercisable (in shares)	4,500,000
Weighted average exercise price (in dollars per share)	$ 16.16
Stock Options
Shares Underlying Options
Beginning Balance (in shares)	7,153,668
Granted (in shares)	136,500
Exercised (in shares)	(319,551)
Forfeited/canceled (in shares)	(198,002)
Ending Balance (in shares)	6,772,615	7,153,668
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 17.16
Granted (in dollars per share)	24.08
Exercised (in dollars per share)	13.32
Forfeited/canceled (in dollars per share)	25.35
Ending balance (in dollars per share)	$ 17.25	$ 17.16
Weighted Average Remaining Contractual Life (years)	7 years 7 days	6 years 11 months 12 days
Aggregate Intrinsic Value (in thousands)	$ 43,054	$ 39,010
Unamortized stock compensation expense	$ 24,700
Weighted-average recognition period (in years)	2 years 7 months 6 days

SHARE BASED COMPENSATION - Stock based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4,609	$ 7,093
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,407	2,656
Selling, general & administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,202	$ 4,437

SHARE BASED COMPENSATION - Exercise of Warrants (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Warrants exercised (in shares)	168,612
Proceeds from warrant exercises	$ 0.6
Warrants outstanding (in shares)	990,810	1,159,424

INCOME TAXES - Summary of Effective Tax Rate and Income Tax Benefit (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Effective tax rate	(1.30%)	15.70%
Income Tax Expense (Benefit)	$ 229	$ (2,064)

INCOME TAXES - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income tax benefit (expense)	$ (229,000)	$ 2,064,000
Effective income tax rate reconciliation, percent	(1.30%)	15.70%
Unrecognized tax benefits	$ 0
Unrecognized tax benefits, income tax penalties expense	$ 0

INVENTORY (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 3,743	$ 3,435
Finished goods	1,399	1,916
Total inventory	5,142	5,351
Inventory Reserve	$ 1,300	$ 700

ACCOUNTS RECEIVABLES (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Accounts receivable, net of reserves	$ 12,981	$ 13,872