PTC Therapeutics (PTCT) 10-Q 9 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 04, 2018
Document and Entity Information
Entity Registrant Name	PTC THERAPEUTICS, INC.
Entity Central Index Key	1,070,081
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		46,445,672
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1

Consolidated Balance Sheets (un

Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 97,675	$ 111,792	$ 54,106	$ 58,321
Marketable securities	80,595	79,454
Trade receivables, net	45,611	40,394
Inventory	12,355	10,754
Prepaid expenses and other current assets	5,760	6,669
Total current assets	241,996	249,063
Fixed assets, net	8,302	8,376
Intangible assets, net	127,565	132,993
Deposits and other assets	1,548	1,221
Total assets	379,411	391,653
Current liabilities:
Accounts payable and accrued expenses	71,437	76,446
Deferred revenue	0	3,937
Other current liabilities	1,279	1,665
Total current liabilities	72,716	82,048
Deferred revenue - long-term	9,300	7,954
Long-term debt	146,878	144,971
Other long-term liabilities	209	243
Total liabilities	229,103	235,216
Stockholders’ equity:
Common stock, $0.001 par value. Authorized 125,000,000 shares; issued and outstanding 41,809,398 shares at March 31, 2018. Authorized 125,000,000 shares; issued and outstanding 41,612,395 shares at December 31, 2017	42	42
Additional paid-in capital	975,418	966,534
Accumulated other comprehensive income	4,953	3,969
Accumulated deficit	(830,105)	(814,108)
Total stockholders’ equity	150,308	156,437
Total liabilities and stockholders’ equity	$ 379,411	$ 391,653

Consolidated Balance Sheets (u3

Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized shares (in shares)	125,000,000	125,000,000
Common stock, issued shares (in shares)	41,809,398	41,612,395
Common stock, outstanding shares (in shares)	41,809,398	41,612,395

Consolidated Statements of Oper

Consolidated Statements of Operations (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Net product revenue	$ 55,981	$ 26,442
Collaboration and grant revenue	81	105
Total revenues	56,062	26,547
Operating expenses:
Cost of product sales, excluding amortization of acquired intangible asset	3,045	39
Amortization of acquired intangible asset	5,428	0
Research and development	31,363	27,363
Selling, general and administrative	32,969	25,500
Total operating expenses	72,805	52,902
Loss from operations	(16,743)	(26,355)
Interest expense, net	(3,303)	(2,219)
Other income (expense), net	1,004	(318)
Loss before income tax expense	(19,042)	(28,892)
Income tax expense	(221)	(165)
Net loss attributable to common stockholders	$ (19,263)	$ (29,057)
Weighted-average shares outstanding:
Basic and diluted (in shares)	41,626,617	34,305,948
Net loss per share-basic and diluted (in dollars per share)
Net loss per share—basic and diluted (in dollars per share)	$ (0.46)	$ (0.85)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (19,263)	$ (29,057)
Other comprehensive loss:
Unrealized loss on marketable securities	(123)	(22)
Foreign currency translation gain	1,107	631
Comprehensive loss	$ (18,279)	$ (28,448)

Consolidated Statements of Cash

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	$ (19,263)	$ (29,057)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	6,022	612
Non-cash interest expense	1,780	1,600
Amortization of premiums on investments	(96)	208
Amortization of debt issuance costs	126	80
Share-based compensation expense	7,748	9,029
Unrealized foreign currency transaction (gains) losses, net	(1,300)	820
Changes in operating assets and liabilities:
Inventory, net	(1,446)	(1,350)
Prepaid expenses and other current assets	958	93
Trade receivables, net	(4,223)	(6,746)
Deposits and other assets	(308)	(226)
Accounts payable and accrued expenses	(6,810)	(3,923)
Other liabilities	(475)	(624)
Deferred revenue	1,409	582
Net cash used in operating activities	(15,878)	(28,902)
Cash flows from investing activities
Purchases of fixed assets	(479)	(225)
Purchases of marketable securities	(22,683)	(19,467)
Sale and redemption of marketable securities	21,514	44,110
Net cash (used in) provided by investing activities	(1,648)	24,418
Cash flows from financing activities
Proceeds from exercise of options	1,136	106
Proceeds from shares issued under employee stock purchase plan	0	557
Net cash provided by financing activities	1,136	663
Effect of exchange rate changes on cash	2,273	(394)
Net decrease in cash and cash equivalents	(14,117)	(4,215)
Cash and cash equivalents, beginning of period	111,792	58,321
Cash and cash equivalents, end of period	97,675	54,106
Supplemental disclosure of cash information
Cash paid for interest	3,023	2,250
Cash paid for income taxes	$ 326	$ 28

The Company

The Company	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company	The Company PTC Therapeutics, Inc. (the “Company” or “PTC”) is a science-led global biopharmaceutical company focused on the discovery, development and commercialization of clinically-differentiated medicines that provide benefits to patients with rare disorders. The Company has launched two rare disease products and has a global commercial footprint. The Company’s recent ability to commercialize products is the foundation that drives its continued investment in a robust pipeline of transformative medicines and its mission to provide access to best-in-class treatments for patients who have an unmet medical need. The Company has two products, Translarna ™ (ataluren) and Emflaza™ (deflazacort), for the treatment of Duchenne muscular dystrophy, or DMD, a rare, life threatening disorder. Translarna received marketing authorization from the European Commission in August 2014 for the treatment of nonsense mutation Duchenne muscular dystrophy, or nmDMD, in ambulatory patients aged five years and older in the 31 member states of the European Economic Area, or EEA. Emflaza is approved in the United States for the treatment of DMD in patients five years and older. The Company’s marketing authorization for Translarna in the EEA is subject to annual review and renewal by the European Commission following reassessment by the European Medicines Agency, or EMA, of the benefit-risk balance of the authorization, which the Company refers to as the annual EMA reassessment. This marketing authorization is further subject to the specific obligation to conduct and submit the results of a multi-center, randomized, double-blind, 18-month, placebo-controlled trial, followed by an 18-month open-label extension, according to an agreed protocol, in order to confirm the efficacy and safety of Translarna in the approved patient population. The final report on the trial and open-label extension is to be submitted by the Company to the EMA by the end of the third quarter of 2021. The Company refers to the trial and open-label extension together as Study 041. The marketing authorization in the EEA was last renewed in June 2017 and is effective, unless extended, through August 5, 2018. In February 2018, the Company submitted a marketing authorization renewal request to the EMA. The renewal was based on the Company’s commitment to conduct Study 041 and the totality of the clinical data available from its trials and studies of Translarna for the treatment of nmDMD, including the safety and efficacy results of the Phase 2b and Phase 3 clinical trials. The primary efficacy endpoint was not achieved in either trial within the pre-specified level of statistical significance. In June 2014, the Company initiated reimbursed early access programs, or EAP programs, for Translarna for nmDMD patients in selected territories in the EEA and recorded its first sales of Translarna in the third quarter of 2014 pursuant to an EAP program. In December 2014, the Company recorded its first commercial sales in Germany. As of March 31, 2018 , Translarna was available in over 25 countries on a commercial basis or pursuant to an EAP program. The Company expects to expand its launch activities across the EEA pursuant to the marketing authorization granted by the EMA throughout 2018 and future years, subject to continued renewal of its marketing authorization following annual EMA reassessments and successful completion of pricing and reimbursement negotiations. Concurrently, the Company plans to continue to pursue EAP programs in select countries where those mechanisms exist, both within the EEA and in other countries that will reference the marketing authorization in the EEA. Translarna is an investigational new drug in the United States. During the first quarter of 2017, the Company filed a New Drug Application, or NDA, over protest with the United States Food and Drug Administration, (the "FDA"), for which the FDA granted a standard review. In October 2017, the Office of Drug Evaluation I of the FDA issued a complete response letter for the NDA, stating that it was unable to approve the application in its current form. In response, the Company filed a formal dispute resolution request with the Office of New Drugs of the FDA. In February 2018, the Office of New Drugs of the FDA denied PTC’s appeal of the Complete Response Letter. In its response, the Office of New Drugs recommended a possible path forward for the ataluren NDA submission based on the accelerated approval pathway. This would involve a re-submission of an NDA containing the current data on effectiveness of ataluren with new data to be generated on dystrophin production in nmDMD patients’ muscles. The Company intends to follow the FDA’s recommendation and will collect such dystrophin data using newer technologies via procedures and methods that it is currently designing and expects to initiate such a study by the end of 2018. Additionally, should a re-submission of an NDA receive accelerated approval, the Office of New Drugs stated that Study 041, which is currently enrolling, could serve as the confirmatory post-approval trial required in connection with the accelerated approval framework. The NDA, which seeks approval of Translarna for the treatment of nmDMD in the United States, was initially submitted by the Company in December 2015. In February 2016, following the submission, the Company received a Refuse to File letter from the FDA regarding the NDA. The FDA stated in the Refuse to File letter that the NDA was not sufficiently complete to permit a substantive review. Specifically, the Company was notified in the letter that, in the view of the FDA, both the Phase 2b and Phase 3 ACT DMD trials were negative and do not provide substantial evidence of effectiveness and that the NDA did not contain adequate information regarding the abuse potential of Translarna. Additionally, the FDA stated that the Company had proposed a post-hoc adjustment of ACT DMD that eliminates data from a majority of enrolled patients. During July 2016, the Company appealed the Refuse to File decision via the formal dispute resolution process within FDA’s Center for Drug Evaluation and Research; however, this appeal was denied by the FDA’s Office of Drug Evaluation I in October 2016. On April 20, 2017, the Company completed its acquisition of all rights to Emflaza, or the Transaction. Emflaza is approved in the United States for the treatment of DMD in patients five years and older. The Transaction was completed pursuant to an asset purchase agreement, dated March 15, 2017, as amended on April 20, 2017, (the "Asset Purchase Agreement"), by and between the Company and Marathon Pharmaceuticals, LLC (now known as Complete Pharma Holdings, LLC), or Marathon. The Transaction was accounted for as an asset acquisition. The assets acquired by the Company in the Transaction include intellectual property rights related to Emflaza, inventories of Emflaza, and certain contractual rights related to Emflaza. The Company assumed certain liabilities and obligations in the Transaction arising out of, or relating to, the assets acquired in the Transaction. Upon the closing of the Transaction, the Company paid to Marathon total upfront consideration comprised of $75.0 million in cash, funded through cash on hand, and 6,683,598 shares of the Company’s common stock. The number of shares of common stock issued at closing was determined by dividing $65.0 million by the volume weighted average price per share of the Company’s common stock on the Nasdaq Stock Market for the 15 trading-day period ending on the third trading day immediately preceding the closing. Marathon will be entitled to receive contingent payments from the Company based on annual net sales of Emflaza beginning in 2018, up to a specified aggregate maximum amount over the expected commercial life of the asset, and a single $50.0 million sales-based milestone, in each case subject to the terms and conditions of the Asset Purchase Agreement. As of March 31, 2018 , the Company had an accumulated deficit of approximately $830.1 million . The Company has financed its operations to date primarily through the private offering in August 2015 of 3.00% convertible senior notes due 2022 (see Note 9), public offerings of common stock in February 2014 and October 2014, its initial public offering of common stock in June 2013, private placements of its convertible preferred stock, collaborations, bank debt, convertible debt financings, grant funding and clinical trial support from governmental and philanthropic organizations and patient advocacy groups in the disease area addressed by the Company’s product candidates. Since 2014, the Company has also relied on revenue generated from net sales of Translarna for the treatment of nmDMD in territories outside of the United States, and in May 2017, the Company began to recognize revenue generated from net sales of Emflaza for the treatment of DMD in the United States. The Company expects that the cash flows from the sales of its products, together with the Company's cash, cash equivalents and marketable securities, including the net proceeds from the Company's underwritten public offering of its common stock that close in April 2018 as discussed in Note 12, will be sufficient to fund its operations for at least the next twelve months.

Summary of significant accounti

Summary of significant accounting policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of significant accounting policies	Summary of significant accounting policies The Company’s complete listing of significant accounting policies is set forth in Note 2 of the notes to the Company’s audited financial statements as of December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the "SEC") on March 6, 2018 (the " 2017 Form 10-K"). Additional significant accounting policies adopted during the three month period ended March 31, 2018 are discussed in further detail below. Basis of presentation The accompanying financial information as of March 31, 2018 and for the three months ended March 31, 2018 and 2017 has been prepared by the Company, without audit, pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (GAAP) have been condensed or omitted pursuant to such rules and regulations. These interim financial statements should be read in conjunction with the Company’s audited financial statements as of December 31, 2017 and notes thereto included in the 2017 Form 10-K. In the opinion of management, the unaudited financial information as of March 31, 2018 and for the three months ended March 31, 2018 and 2017 reflects all adjustments, which are normal recurring adjustments, necessary to present a fair statement of financial position, results of operations and cash flows. The results of operations for the three month periods ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ended December 31, 2018 or for any other interim period or for any other future year. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates in these consolidated financial statements have been made in connection with the calculation of net product sales, certain accruals related to the Company’s research and development expenses, stock-based compensation, valuation procedures for the convertible notes, allowance for doubtful accounts, inventory, acquired intangible assets, and the provision for or benefit from income taxes. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known. Inventory and cost of product sales Inventory Inventories are stated at the lower of cost and net realizable value with cost determined on a first-in, first-out basis by product. The Company capitalizes inventory costs associated with products following regulatory approval when future commercialization is considered probable and the future economic benefit is expected to be realized. Translarna and Emflaza product which may be used in clinical development programs are included in inventory and charged to research and development expense when the product enters the research and development process and no longer can be used for commercial purposes. Inventory used for marketing efforts are charged to selling, general and administrative expense. The following table summarizes the components of the Company’s inventory for the periods indicated: March 31, 2018 December 31, 2017 Raw materials $ 768 $ 452 Work in progress 4,786 3,912 Finished goods 6,801 6,390 Total inventory $ 12,355 $ 10,754 The Company periodically reviews its inventories for excess amounts or obsolescence and writes down obsolete or otherwise unmarketable inventory to its estimated net realizable value. The Company has not recorded any inventory write downs as of the current period. Additionally, though the Company’s product is subject to strict quality control and monitoring which it performs throughout the manufacturing processes, certain batches or units of product may not meet quality specifications resulting in a charge to cost of product sales. Cost of product sales Cost of product sales consists of the cost of inventory sold, manufacturing and supply chain costs, storage costs, amortization of the acquired intangible asset and royalty payments associated with net product sales. Revenue recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-9, “Revenue from Contracts with Customers (Topic 606)”. ASU No. 2014-9 eliminated transaction- and industry-specific revenue recognition guidance under FASB Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition-Products (Topic 605) and replaced it with a principle-based approach for determining revenue recognition. ASC Topic 606 requires entities to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. On January 1, 2018, the Company adopted ASC Topic 606 using the modified retrospective approach, a practical expedient permitted under Topic 606, and applied this approach only to contracts that were not completed as of January 1, 2018. The Company calculated a one-time transition adjustment of $3.3 million , which was recorded on January 1, 2018 to the opening balance of accumulated deficit, related to the product sales of Emflaza. The ASC 606 transition adjustment recorded for Emflaza resulted in sales being recognized earlier than under Topic 605, as the deferred revenue recognition model (sell-through) is not applicable under Topic 606. The one-time adjustment consisted of $3.9 million in deferred revenue offset by $0.6 million of variable consideration. The information presented for the periods prior to January 1, 2018 has not been adjusted and is reported under Topic 605. Periods prior to January 1, 2018 The Company recognizes revenue when amounts are realized or realizable and earned. Revenue is considered realizable and earned when the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred or services have been rendered; (3) the price is fixed or determinable; and (4) collection of the amounts due are reasonably assured. Net product sales Prior to the second quarter of 2017, the Company’s net product sales consisted of sales of Translarna for the treatment of nmDMD in territories outside of the U.S. The Company recognizes revenue from product sales when there is persuasive evidence that an arrangement exists, title to product and associated risk of loss has passed to the customer, the price is fixed or determinable, collectability is reasonably assured and the Company has no further performance obligations in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition—Products. The Company has recorded revenue on sales where Translarna is available either on a commercial basis or through a reimbursed EAP program. Orders for Translarna are generally received from hospital and retail pharmacies and the Company’s third-party partner distributors. Revenue is recognized when risk of ownership has transferred. The Company’s third-party partner distributors act as intermediaries between the Company and end users and do not typically stock significant quantities of Translarna. The ultimate payor for Translarna is typically a government authority or institution or a third-party health insurer. In May 2017, the Company began the commercialization of Emflaza in the U.S. The Company recorded product revenue related to the sales of Emflaza in the U.S. in accordance with ASC 605-15, when persuasive evidence of an arrangement exists, delivery has occurred and title of the product and associated risk of loss has passed to the customer, the price is fixed or determinable and collection from the customer has been reasonably assured. Due to the early stage of the product launch, the Company determined that it was not able to reliably make certain estimates, including returns, necessary to recognize product revenue upon shipment to distributors. As a result, the Company recorded net product revenue for Emflaza using a deferred revenue recognition model (sell-through). Under the deferred revenue model, the Company does not recognize revenue until Emflaza is shipped to the specialty pharmacy. The Company records revenue net of estimated third-party discounts and rebates. Allowances are recorded as a reduction of revenue at the time revenues from product sales are recognized. These allowances are adjusted to reflect known changes in factors and may impact such allowances in the quarter those changes are known. Collaboration and grant revenue The terms of these agreements typically include payments to the Company of one or more of the following: nonrefundable, upfront license fees; milestone payments; research funding and royalties on future product sales. In addition, the Company generates service revenue through agreements that generally provide for fees for research and development services and may include additional payments upon achievement of specified events. The Company evaluates all contingent consideration earned, such as a milestone payment, using the criteria as provided by ASC 605-28, Revenue Recognition—Milestone Method. At the inception of a collaboration arrangement, the Company evaluates if a milestone payment is substantive. The criteria requires that (1) the Company determines if the milestone is commensurate with either its performance to achieve the milestone or the enhancement of value resulting from its activities to achieve the milestone; (2) the milestone be related to past performance; and (3) the milestone be reasonable relative to all deliverable and payment terms of the collaboration arrangement. If these criteria are met then the contingent milestones can be considered a substantive milestone and will be recognized as revenue in the period that the milestone is achieved. The Company recognizes royalties as earned in accordance with the terms of various research and collaboration agreements. If not substantive, the contingent consideration is allocated to the existing units of accounting based on relative selling price and recognized following the same basis previously established for the associated unit of accounting. The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities. Periods commencing January 1, 2018 The Company's net product revenue consists of sales of Translarna in territories outside of the U.S. and sales of Emflaza in the U.S., both for the treatment of DMD. Net product revenue The Company recognizes revenue when its performance obligations with its customers have been satisfied. The Company’s performance obligations are to provide Translarna or Emflaza based on customer orders from distributors, hospitals, specialty pharmacies or retail pharmacies. The performance obligations are satisfied at a point in time when the Company’s customer obtains control of either Translarna or Emflaza, which is typically upon delivery. The Company invoices its customers after the products have been delivered and invoice payments are generally due within 30 to 90 days of invoice date. The Company determines the transaction price based on fixed consideration in its contractual agreements. Contract liabilities arise in certain circumstances when consideration is due for goods the Company has yet to provide. As the Company has identified only one distinct performance obligation, the transaction price is allocated entirely to either product sales of Translarna or Emflaza. In determining the transaction price, a significant financing component does not exist since the timing from when the Company delivers product to when the customers pay for the product is typically less than one year. Customers in certain countries pay in advance of product delivery. In those instances, payment and delivery typically occur in the same month. The Company records product sales net of any variable consideration, which includes discounts, allowances, rebates and distribution fees. The Company uses the expected value or most likely amount method when estimating its variable consideration, unless discount or rebate terms are specified within contracts. Historically, returns of Translarna and Emflaza are immaterial to the financial statements. The identified variable consideration is recorded as a reduction of revenue at the time revenues from product sales are recognized. These estimates for variable consideration are adjusted to reflect known changes in factors and may impact such estimates in the quarter those changes are known. Revenue recognized does not include amounts of variable consideration that are constrained. In relation to customer contracts, the Company incurs costs to fulfill a contract but does not incur costs to obtain a contract. These costs to fulfill a contract do not meet the criteria for capitalization and are expensed as incurred. Upon adoption of ASC Topic 606 on January 1, 2018, the Company elected the following practical expedients: • Portfolio Approach - the Company applied the Portfolio Approach to contract reviews within its identified revenue streams that have similar characteristics and the Company believes this approach would not differ materially than if applying ASC Topic 606 to each individual contract. • Significant Financing Component - the Company expects the period between when it transfers a promised good to a customer and when the customer pays for the good or service to be one year or less. • Immaterial Performance Obligations - the Company disregards promises deemed to be immaterial in the context of the contract. • Shipping and Handling Activities - the Company considers any shipping and handling costs that are incurred after the customer has obtained control of the product as a cost to fulfill a promise. Shipping and handling costs associated with finished goods delivered to customers are recorded as a selling expense. Collaboration revenue The terms of these agreements typically include payments to the Company of one or more of the following: nonrefundable, upfront license fees; milestone payments; research funding and royalties on future product sales. In addition, the Company generates service revenue through agreements that generally provide for fees for research and development services and may include additional payments upon achievement of specified events. At the inception of a collaboration arrangement, the Company needs to first evaluate if the arrangement meets the criteria in ASC Topic 808 “Collaborative Arrangements” to then determine if ASC Topic 606 is applicable by considering whether the collaborator meets the definition of a customer. If the criteria are met, the Company assesses the promises in the arrangement to identify distinct performance obligations. For licenses of intellectual property, the Company assesses, at contract inception, whether the intellectual property is distinct from other performance obligations identified in the arrangement. If the licensing of intellectual property is determined to be distinct, revenue is recognized for nonrefundable, upfront license fees when the license is transferred to the customer and the customer can use and benefit from the license. If the licensing of intellectual property is determined not to be distinct, then the license will be bundled with other promises in the arrangement into one distinct performance obligation. The Company needs to determine if the bundled performance obligation is satisfied over time or at a point in time. If the Company concludes that the nonrefundable, upfront license fees will be recognized over time, the Company will need to assess the appropriate method of measuring proportional performance. For milestone payments, the Company assesses, at contract inception, whether the development or sales-based milestones are considered probable of being achieved. If it is probable that a significant revenue reversal will occur, the Company will not record revenue until the uncertainty has been resolved. Milestone payments that are contingent upon regulatory approval are not considered probable of being achieved until the applicable regulatory approvals or other external conditions are obtained as such conditions are not within the Company's control. If it is probable that a significant revenue reversal will not occur, the Company will estimate the milestone payments using the most likely amount method. The Company will re-assess the development and sales-based milestones each reporting period to determine the probability of achievement. The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities. Allowance for doubtful accounts The Company maintains an allowance for estimated losses resulting from the inability of its customers to make required payments. The Company estimates uncollectible amounts based upon current customer receivable balances, the age of customer receivable balances, the customer’s financial condition and current economic trends. The allowance for doubtful accounts was $0.8 million as of March 31, 2018 and $0.8 million as of December 31, 2017 . Income Taxes On December 22, 2017, the U.S. government enacted the 2017 Tax Cuts and Jobs Act (the 2017 Tax Act), which significantly revises U.S. tax law by, among other provisions, lowering the U.S. federal statutory income tax rate to 21%, imposing a mandatory one-time transition tax on previously deferred foreign earnings, and eliminating or reducing certain income tax deductions. The Global Intangible Low-tax Income (GILTI) provisions of the 2017 Tax Act require the Company to include in its U.S. income tax return foreign subsidiary earnings in excess of an allowable return on the foreign subsidiary’s tangible assets. The Company has elected to account for GILTI tax in the period in which it is incurred, and therefore has not provided any deferred tax impacts of GILTI in its consolidated financial statements for the period ended March 31, 2018 . ASC 740, Income Taxes requires the effects of changes in tax laws to be recognized in the period in which the legislation is enacted. However, due to the complexity and significance of the 2017 Tax Act’s provisions, the SEC issued SAB 118, which allows companies to record the tax effects of the 2017 Tax Act on a provisional basis based on a reasonable estimate, and then, if necessary, subsequently adjust such amounts during a limited measurement period as more information becomes available. The measurement period ends when a company has obtained, prepared, and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year from enactment. The 2017 Tax Act does not have a material impact on the Company’s financial statements since its deferred temporary differences are fully offset by a valuation allowance and the Company does not have any significant off shore earnings from which to record the mandatory transition tax. However, given the significant complexity of the 2017 Tax Act, anticipated guidance from the U.S. Treasury about implementing the 2017 Tax Act, and the potential for additional guidance from the SEC or the FASB related to the 2017 Tax Act, these estimates may be adjusted during the measurement period. The Company continues to analyze the changes in certain income tax deductions, assess calculations of earnings and profits in certain foreign subsidiaries, including if those earnings which are held in cash or other assets and gather additional data to compute the full impacts on the Company’s deferred and current tax assets and liabilities. Recently issued accounting standards In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) No. 2016-2, “Leases (Topic 842)”. This standard will require organizations that lease assets with lease terms of more than 12 months to recognize assets and liabilities for the rights and obligations created by those leases on their balance sheets. The ASU will also require new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. The standard is effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. The Company expects to adopt this guidance when effective and is currently assessing what effect the adoption of ASU No. 2016-2 will have on its consolidated financial statements and accompanying notes. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”. This standard requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected. This standard is effective for public companies who are SEC filers for fiscal years beginning after December 15, 2019, including interim periods within those years. The Company expects to adopt this guidance when effective and is assessing what effect the adoption of ASU 2016-13 will have on its consolidated financial statements and accompanying notes. In February 2018, the FASB issued ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income". This standard permits the reclassification of tax effects stranded in other comprehensive income as a result of tax reform to retained earnings related to the change in federal tax rate in addition to other stranded effects that relate to the Tax Cuts and Job Act ("the Act") but do not directly relate to the change in the federal rate. ASU 2018-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years with early adoption permitted for periods for which financial statements have not yet been issued or made available for issuance. The Company expects to adopt this guidance when effective and is currently assessing what effect the adoption of ASU No. 2018-02 will have on its consolidated financial statements and accompanying notes. Impact of recently adopted accounting pronouncements In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”. ASU No. 2014-09 eliminated transaction- and industry-specific revenue recognition guidance under FASB Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition-Products and replaced it with a principle-based approach for determining revenue recognition. ASC Topic 606 requires entities to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. On January 1, 2018, the Company adopted ASC Topic 606 using the modified retrospective approach and applied this approach only to contracts that were not completed as of January 1, 2018. The Company calculated a one-time transition adjustment of $3.3 million , which was recorded on January 1, 2018 to deferred revenue and accumulated deficit, related to the product sales of Emflaza. The information presented for the periods prior to January 1, 2018 has not been restated and is reported under ASC Topic 605. In January 2016, the FASB issued ASU No. 2016-01, “Financial Instruments — Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities”. This standard enhances the reporting model for financial instruments, which includes amendments to address aspects of recognition, measurement, presentation and disclosure. The new guidance affects all reporting organizations (whether public or private) that hold financial assets or owe financial liabilities. The Company adopted ASU 2016-01 during the three months ended March 31, 2018. In March 2018, the FASB issued ASU 2018-04, "Investments - Debt Securities (Topic 320) and Regulated Operations (Topic 980): Amendments to SEC Paragraphs Pursuant to the SEC Staff Accounting Bulletin ("SAB") No. 117 and SEC Release No. 33-9273 (SEC Update)". This standard supersedes SEC paragraphs in ASC 320, Investments- Debt Securities, as a result of the issuance of SAB 117 and also updates the Codification for a 2011 SEC release and are effective when a registrant adopts ASU 2016-01, which in the case of the Company was during the three months ended March 31, 2018. The adoption of these standards did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 . In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments”. This standard clarifies the presentation of certain specific cash flow issues in the Statement of Cash Flows. The Company adopted ASU 2016-15 during the three months ended March 31, 2018. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 . In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash”. This standard requires entities to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows and no longer present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents in the statement of cash flows. The Company adopted ASU 2016-18 during the three months ended March 31, 2018. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 . In May 2017, the FASB issued ASU No. 2017-09, "Stock Compensation (Topic 718): Scope of Modification Accounting". This standard clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as a modification, with entities applying the modification accounting guidance if the value, vesting conditions or classification of the award changes. In addition to all disclosures about modifications that are required under the current guidance, entities will be also required to disclose that compensation expense has not changed if applicable. The Company adopted ASU 2017-09 during the three months ended March 31, 2018. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 .

Fair value of financial instrum

Fair value of financial instruments and marketable securities	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair value of financial instruments and marketable securities	Fair value of financial instruments and marketable securities The Company follows the fair value measurement rules, which provides guidance on the use of fair value in accounting and disclosure for assets and liabilities when such accounting and disclosure is called for by other accounting literature. These rules establish a fair value hierarchy for inputs to be used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority). · Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date. · Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs). · Level 3—Inputs are unobservable and reflect the Company’s assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available. Cash equivalents and investments are reflected in the accompanying financial statements at fair value. The carrying amount of receivables, accounts payable and accrued expenses, and debt approximates fair value due to the short-term nature of those instruments. Fair value of certain marketable securities is based upon market prices using quoted prices in active markets for identical assets quoted on the last day of the period. In establishing the estimated fair value of the remaining investments, the Company used the fair value as determined by its investment advisors using observable inputs other than quoted prices. The Company reviews its investments on a periodic basis for other-than-temporary impairments. This review is subjective, as it requires management to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the fair value of the investment. The following represents the fair value using the hierarchy described above for the Company’s financial assets and liabilities that are required to be measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 : March 31, 2018 Total Quoted prices Significant Significant Marketable securities $ 80,595 $ — $ 80,595 $ — Warrant liability $ 1 $ — $ — $ 1 Stock appreciation rights liability $ 1,279 $ — $ — $ 1,279 December 31, 2017 Total Quoted prices in active markets for identical assets (level 1) Significant other observable inputs (level 2) Significant unobservable inputs (level 3) Marketable securities $ 79,454 $ — $ 79,454 $ — Warrant Liability $ 1 $ — $ — $ 1 Stock appreciation rights liability $ 1,665 $ — $ — $ 1,665 No transfers of assets between Level 1 and Level 2 of the fair value measurement hierarchy occurred during the periods ended March 31, 2018 and December 31, 2017 . The following is a summary of marketable securities accounted for as available-for-sale securities at March 31, 2018 and December 31, 2017 : March 31, 2018 Amortized Cost Gross Unrealized Fair Value Gains Losses Commercial paper $ 26,191 $ 30 $ — $ 26,221 Corporate debt securities 54,505 — (131 ) 54,374 $ 80,696 $ 30 $ (131 ) $ 80,595 December 31, 2017 Amortized Cost Gross Unrealized Fair Value Gains Losses Commercial paper $ 13,775 $ 52 $ — $ 13,827 Corporate debt securities 65,657 — (30 ) 65,627 $ 79,432 $ 52 $ (30 ) $ 79,454 At March 31, 2018 and December 31, 2017 , the Company held securities with an unrealized loss position that were not considered to be other-than-temporarily impaired as the Company has the ability to hold such investments until recovery of their fair value. Unrealized gains and losses are reported as a component of accumulated other comprehensive (loss) income in stockholders’ equity. As of March 31, 2018 and December 31, 2017 , the Company did not have any realized gains/losses from the sale of marketable securities. The unrealized losses and fair values of available-for-sale securities that have been in an unrealized loss position for a period of less than and greater than 12 months as of March 31, 2018 are as follows: March 31, 2018 Securities in an unrealized loss position less than 12 months Securities in an unrealized loss position greater than 12 months Total Unrealized losses Fair Value Unrealized losses Fair Value Unrealized losses Fair Value Corporate debt securities $ (131 ) $ 54,374 $ — $ — $ (131 ) $ 54,374 The unrealized losses and fair values of available-for-sale securities that have been in an unrealized loss position for a period of less than and greater than 12 months as of December 31, 2017 are as follows: December 31, 2017 Securities in an unrealized loss position less than 12 months Securities in an unrealized loss position greater than 12 months Total Unrealized losses Fair Value Unrealized losses Fair Value Unrealized losses Fair Value Corporate debt securities $ (28 ) $ 59,108 $ (2 ) $ 6,519 $ (30 ) $ 65,627 Marketable securities on the balance sheet at March 31, 2018 and December 31, 2017 mature as follows: March 31, 2018 Less Than 12 Months More Than 12 Months Commercial paper $ 26,221 $ — Corporate debt securities 54,374 — Total Marketable securities $ 80,595 $ — December 31, 2017 Less Than 12 Months More Than 12 Months Commercial paper $ 13,827 $ — Corporate debt securities 55,550 10,077 Total Marketable securities $ 69,377 $ 10,077 The Company classifies all of its securities as current as they are all available for sale and are available for current operations. Convertible 3.0% senior notes In August 2015, the Company issued $150.0 million of 3.0% convertible senior notes due August 15, 2022 (the “Convertible Notes”). Interest is payable semi-annually on February 15 and August 15 of each year, beginning on February 15, 2016. The Company separately accounted for the liability and equity components of the Convertible Notes by allocating the proceeds between the liability component and equity component, as further discussed in Note 9. The fair value of the Convertible Notes, which differs from their carrying values, is influenced by interest rates, the Company’s stock price and stock price volatility and is determined by prices for the Convertible Notes observed in market trading which are Level 2 inputs. The estimated fair value of the Convertible Notes at March 31, 2018 and December 31, 2017 was $139.3 million and $115.7 million , respectively. The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents, accounts receivable, accounts payable and borrowings under the credit and security agreement with MidCap Financial Trust and other financial institutions (as further discussed in Note 9) approximate fair value because of the immediate or short-term maturity of these financial instruments. The carrying amounts for the credit and security agreement approximate fair value based on market activity for other debt instruments with similar characteristics and comparable risk. Level 3 valuation The warrant liability is classified in Other long-term liabilities on the Company’s consolidated balance sheets. The warrant liability is marked-to-market each reporting period with the change in fair value recorded as a gain or loss within Other expense, net, on the Company’s consolidated statements of operations until the warrants are exercised, expire or other facts and circumstances lead the warrant liability to be reclassified as an equity instrument. The fair value of the warrant liability is determined at each reporting period by utilizing the Black-Scholes option pricing model. The stock appreciation rights (SARs) liability is classified in Other liabilities on the Company’s consolidated balance sheets. The SARs liability is marked-to-market each reporting period with the change in fair value recorded as compensation expense on the Company’s consolidated statements of operations until the SARS vest. The fair value of the SARs liability is determined at each reporting period by utilizing the Black-Scholes option pricing model. The table presented below is a summary of changes in the fair value of the Company’s Level 3 valuations for the warrant liability and SARs liability for the period ended March 31, 2018 : Level 3 liabilities Warrants SARs Beginning balance as of December 31, 2017 $ 1 $ 1,665 Change in fair value — 1,605 Payments — (1,991 ) Ending balance as of March 31, 2018 $ 1 $ 1,279 Fair value of the warrant liability is estimated using an option-pricing model, which includes variables such as the expected volatility based on guideline public companies, the stock fair value, and the estimated time to a liquidity event. The significant assumptions used in preparing the option pricing model for valuing the Company’s warrants as of March 31, 2018 include (i) volatility ( 54% - 56% ), (ii) risk free interest rate ( 2.18% - 2.18% ), (iii) strike price ( $128.00 - $2,520.00 ), (iv) fair value of common stock ( $27.06 ), and (v) expected life ( 1.3 — 1.5 years). The significant assumptions used in preparing the option pricing model for valuing the Company’s warrants as of December 31, 2017 include (i) volatility ( 69% - 69% ), (ii) risk free interest rate ( 1.89% — 1.89% ), (iii) strike price ( $128.00 — $2,520.00 ), (iv) fair value of common stock ( $16.68 ), and (v) expected life ( 1.6 — 1.7 years). Fair value of the SARs liability is estimated using an option-pricing model, which includes variables such as the expected volatility based on guideline public companies, the stock fair value, and the estimated time to a liquidity event. The significant assumptions used in preparing the option pricing model for valuing the Company’s SARs as of March 31, 2018 include (i) volatility ( 55% — 58% ), (ii) risk free interest rate ( 2.01% — 2.18% ), (iii) strike price ( $6.76 - $30.86 ), (iv) fair value of common stock ( $27.06 ), and (v) expected life ( 0.8 — 1.8 years). The significant assumptions used in preparing the option pricing model for valuing the Company’s SARs as of December 31, 2017 include (i) volatility ( 31% - 70% ), (ii) risk free interest rate ( 1.28% — 1.89% ), (iii) strike price ( $6.76 — $30.86 ), (iv) fair value of common stock ( $16.68 ), and (v) expected life ( 0.0 — 2.0 years).

Other comprehensive income (los

Other comprehensive income (loss) and accumulated other comprehensive items	3 Months Ended
	Mar. 31, 2018
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other comprehensive income (loss) and accumulated other comprehensive items	Other comprehensive income (loss) and accumulated other comprehensive items Other comprehensive income (loss) includes changes in equity that are excluded from net income (loss), such as unrealized gains and losses on marketable securities. The following tables summarize other comprehensive income (loss) and the changes in accumulated other comprehensive items for the three months ended March 31, 2018 : Unrealized Gains/(Losses) On Marketable Securities, net of tax Foreign Currency Translation Total Accumulated Other Comprehensive Items Balance at December 31, 2017 $ 22 $ 3,947 $ 3,969 Other comprehensive (loss) income before reclassifications (123 ) 1,107 984 Amounts reclassified from other comprehensive items — — — Other comprehensive (loss) income (123 ) 1,107 984 Balance at March 31, 2018 $ (101 ) $ 5,054 $ 4,953

Accounts payable and accrued ex

Accounts payable and accrued expenses	3 Months Ended
	Mar. 31, 2018
Payables and Accruals [Abstract]
Accounts payable and accrued expenses	Accounts payable and accrued expenses Accounts payable and accrued expenses at March 31, 2018 and December 31, 2017 consist of the following: March 31, December 31, Employee compensation, benefits, and related accruals $ 9,243 $ 17,711 Consulting and contracted research 6,570 5,137 Professional fees 3,100 2,116 Sales allowance and other costs 25,098 22,257 Sales rebates and royalties 16,380 11,657 Accounts payable 3,104 15,282 Other 7,942 2,286 $ 71,437 $ 76,446

Warrants

Warrants	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Warrants	Warrants All of the Company’s outstanding warrants were classified as liabilities as of March 31, 2018 and December 31, 2017 because they contained non-standard antidilution provisions. The following is a summary of the Company’s outstanding warrants as of March 31, 2018 and December 31, 2017 : Warrant shares Exercise price Expiration Common stock 7,030 $ 128.00 2019 Common stock 130 $ 2,520.00 2019

Net loss per share

Net loss per share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Net loss per share	Net loss per share Basic earnings per share is computed by dividing net loss by the weighted-average number of common shares outstanding. Diluted earnings per share is computed by dividing net loss by the weighted-average number of common shares plus the effect of any dilutive potential common shares outstanding during the period. The following tables set forth the computation of basic and diluted net loss per share: Three Months Ended March 31, 2018 2017 Numerator Net loss $ (19,263 ) $ (29,057 ) Denominator Denominator for basic and diluted net loss per share 41,626,617 34,305,948 Net loss per share: Basic and diluted $ (0.46 ) * $ (0.85 ) * *In the three months ended March 31, 2018 and 2017 , the Company experienced a net loss and therefore did not report any dilutive share impact. The following table shows historical dilutive common share equivalents outstanding, which are not included in the above historical calculation, as the effect of their inclusion is anti-dilutive during each period As of March 31, 2018 2017 Stock Options 8,176,777 7,007,290 Unvested restricted stock awards and units 615,375 566,594 Total 8,792,152 7,573,884

Stock award plan

Stock award plan	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock award plan	Stock award plan On March 5, 2013, the Company’s Board of Directors approved the 2013 Stock Incentive Plan, which provides for the granting of stock option awards, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards in the aggregate of 739,937 shares of common stock. On March 5, 2013, the Board approved a grant of 735,324 shares of restricted stock and 4,613 stock options. There are no additional shares available for issuance under this plan. In 2009, the Company’s shareholders approved the 2009 Equity and Long-Term Incentive Plan, which provides for the granting of stock option awards, restricted stock awards, and other stock-based and cash-based awards, subject to certain adjustments and annual increases. In May 2013, the Company’s Board of Directors and stockholders increased by 2,500,000 the number of shares authorized under the 2009 Equity and Long Term Incentive Plan, which provides for the granting of stock option awards, restricted stock awards, and other stock-based and cash-based awards. There are no additional shares available for issuance under this plan. In May 2013, the Company’s Board of Directors and stockholders approved the 2013 Long Term Incentive Plan, which became effective upon the closing of the Company’s IPO. The 2013 Long Term Incentive Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards and other stock-based awards. The number of shares of common stock reserved for issuance under the 2013 Long Term Incentive Plan is the sum of (1) 122,296 shares of common stock available for issuance under the Company’s 2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan, (2) the number of shares (up to 3,040,444 shares) equal to the sum of the number of shares of common stock subject to outstanding awards under the Company’s 1998 Employee, Director and Consultant Stock Option Plan, 2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right plus (3) an annual increase, to be added on the first day of each fiscal year until the expiration of the 2013 Long Term Incentive Plan, equal to the lowest of 2,500,000 shares of common stock, 4% of the number of shares of common stock outstanding on the first day of the fiscal year and an amount determined by the Company’s Board of Directors. As of March 31, 2018 , awards for 574,778 shares of common stock are available for issuance. From January 1, 2018 through March 31, 2018 , the Company issued a total of 1,916,939 stock options to various employees. Of those, 155,150 were inducement grants for non-statutory stock options. The inducement grant awards were made pursuant to the Nasdaq inducement grant exception as a material component of the Company's new hires’ employment compensation and not under the 2013 Long Term Incentive Plan. A summary of stock option activity is as follows: Number of Weighted- Weighted- Aggregate (in Outstanding at December 31, 2017 6,448,642 $ 29.00 Granted 1,916,939 $ 18.71 Exercised (77,312 ) $ 14.70 Forfeited/Cancelled (111,492 ) $ 34.42 Outstanding at March 31, 2018 8,176,777 $ 26.65 7.67 years $ 56,205 Vested or Expected to vest at March 31, 2018 3,711,261 $ 21.15 8.98 years $ 32,239 Exercisable at March 31, 2018 4,166,448 $ 32.12 6.40 years $ 21,177 The fair value of grants made in the three months ended March 31, 2018 was contemporaneously estimated on the date of grant using the following assumptions: Three months ended Risk-free interest rate 2.25% — 2.73% Expected volatility 64%—90% Expected term 5.04 – 10.00 years The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the three -month period ended March 31, 2018 was $12.50 per share. The Company uses the “simplified method” to determine the expected term of options. Under this method, the expected term represents the average of the vesting period and the contractual term. The expected volatility of share options was estimated based on a historical volatility analysis of peers that were similar to the Company with respect to industry, stage of life cycle, size, and financial leverage. The risk-free rate of the option is based on U.S. Government Securities Treasury Constant Maturities yields at the date of grant for a term similar to the expected term of the option. Restricted Stock Awards —Restricted stock awards are granted subject to certain restrictions, including in some cases service or time conditions (restricted stock). The grant-date fair value of restricted stock awards, which has been determined based upon the market value of the Company’s shares on the grant date, is expensed over the vesting period. Restricted Stock Units —Restricted stock units are granted subject to certain restrictions, including in some cases service or time conditions (restricted stock). The grant-date fair value of restricted stock units, which has been determined based upon the market value of the Company’s shares on the grant date, is expensed over the vesting period. The following table summarizes information on the Company’s restricted stock awards and units: Restricted Stock Awards and Units Number of Weighted January 1, 2018 393,011 $ 15.64 Granted 338,991 $ 18.01 Vested (97,545 ) $ 16.89 Forfeited (19,082 ) $ 17.06 Unvested at March 31, 2018 615,375 $ 16.74 Stock Appreciation Rights —Stock appreciation rights (SARs) entitle the holder to receive, upon exercise, an amount of the Company's common stock or cash (or a combination thereof) determined by reference to appreciation, from and after the date of grant, in the fair market value of a share of the Company's common stock over the measurement price based on the exercise date. In May 2016, a total of 897,290 SARs were granted to non-executive employees (the 2016 SARs). The 2016 SARs will vest annually in equal installments over four years and will be settled in cash on each vest date, requiring the Company to remeasure the SARs at each reporting period until vesting occurs. For the period ending March 31, 2018 , a total of 177,329 SARs vested. For the period ending March 31, 2018 , the Company recorded $1.6 million in compensation expense related to the 2016 SARs. Employee Stock Purchase Plan —In June 2016, the Company established an Employee Stock Purchase Plan (“ESPP” or “the Plan”) for certain eligible employees. The Plan is administered by the Company’s Board of Directors or a committee appointed by the Board. The total number of shares available for purchase under the Plan is one million shares of the Company’s common stock. Employees may participate over a six -month period through payroll withholdings and may purchase, at the end of the six -month period, the Company’s common stock at a purchase price of at least 85% of the closing price of a share of the Company’s common stock on the first business day of the offering period or the closing price of a share of the Company’s common stock on the last business day of the offering period, whichever is lower. No participant will be granted a right to purchase the Company’s common stock under the Plan if such participant would own more than 5% of the total combined voting power of the Company or any subsidiary of the Company after such purchase. For the period ending March 31, 2018 , the Company recorded $0.2 million in compensation expense related to the ESPP. The Company recorded share-based compensation expense in the statement of operations related to incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units and the ESPP as follows: Three Months Ended March 31, 2018 2017 Research and development $ 3,747 $ 4,467 Selling, general and administrative 4,001 4,562 Total $ 7,748 $ 9,029 As of March 31, 2018 , there was approximately $60.0 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 2009 Equity and Long Term Incentive Plan, the 2013 Long Term Incentive Plan and equity awards made pursuant to the Nasdaq inducement grant exception for new hires. This cost is expected to be recognized as share-based compensation expense over the weighted average remaining service period of approximately 2.63 years.

Debt

Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt 2017 Credit Facility In May 2017, the Company entered into a credit and security agreement (the "Credit Facility") with MidCap Financial Trust, a Delaware statutory trust (“MidCap”), as administrative agent and MidCap and certain other financial institutions as lenders thereunder (the “Credit Agreement”) that provides for a senior secured term loan facility of $60.0 million , of which $40.0 million was drawn by the Company on May 5, 2017. The remaining $20.0 million under the senior secured term loan facility will become available to the Company upon its demonstration (on or prior to December 31, 2018) of net product revenue equaling or exceeding $120.0 million for the trailing 12 month period. The Company capitalized approximately $0.4 million of debt issuance costs, which were netted against the carrying value of the Credit Facility and will be amortized over the term of the Credit Facility. Borrowings under the Credit Agreement bear interest at a rate per annum equal to LIBOR (with a LIBOR floor rate of 1.00% ) plus 6.15% . The Company is obligated to make interest only payments (payable monthly in arrears) through April 30, 2019. Commencing on May 1, 2019 and continuing for the remaining twenty-four months of the facility, the Company will be required to make monthly interest payments and monthly principal payments. The principal payments are to be made based on straight-line amortization of the principal over the twenty-four month period. The maturity date of the Credit Agreement is May 1, 2021, unless terminated earlier. The Credit Facility is subject to certain financial covenants. As of March 31, 2018 , the Company was in compliance with all required covenants. Convertible Notes In August 2015, the Company issued, at par value, $150.0 million aggregate principal amount of 3.0% convertible senior notes due 2022 (the "Convertible Notes"). The Convertible Notes bear cash interest at a rate of 3.0% per year, payable semi-annually on February 15 and August 15 of each year, beginning on February 15, 2016. The Convertible Notes will mature on August 15, 2022, unless earlier repurchased or converted. The net proceeds to the Company from the offering were $145.4 million after deducting the initial purchasers’ discounts and commissions and the offering expenses payable by the Company. The Convertible Notes are governed by an indenture (the Convertible Notes Indenture) with U.S Bank National Association as trustee (the Convertible Notes Trustee). Holders may convert their Convertible Notes at their option at any time prior to the close of business on the business day immediately preceding February 15, 2022 only under the following circumstances: · during any calendar quarter commencing on or after September 30, 2015 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; · during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price (as defined in the Convertible Notes Indenture) per $1,000 principal amount of Convertible Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; · during any period after the Company has issued notice of redemption until the close of business on the scheduled trading day immediately preceding the relevant redemption date; or · upon the occurrence of specified corporate events. On or after February 15, 2022, until the close of business on the business day immediately preceding the maturity date, holders may convert their Convertible Notes at any time, regardless of the foregoing circumstances. Upon conversion, the Company will pay cash up to the aggregate principal amount of the Convertible Notes to be converted and deliver shares of its common stock in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of Convertible Notes being converted. The conversion rate for the Convertible Notes was initially, and remains, 17.7487 shares of the Company’s common stock per $1,000 principal amount of the Convertible Notes, which is equivalent to an initial conversion price of approximately $56.34 per share of the Company’s common stock. The Company may not redeem the Convertible Notes prior to August 20, 2018. The Company may redeem for cash all or any portion of the Convertible Notes, at its option, on or after August 20, 2018 if the last reported sale price of its common stock has been at least 130% of the conversion price then in effect on the last trading day of, and for at least 19 other trading days (whether or not consecutive) during, any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption, at a redemption price equal to 100% of the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. No sinking fund is provided for the Convertible Notes, which means that the Company is not required to redeem or retire the Convertible Notes periodically. If the Company undergoes a “fundamental change” (as defined in the Indenture governing the Convertible Notes Indenture), subject to certain conditions, holders of the Convertible Notes may require the Company to repurchase for cash all or part of their Convertible Notes at a repurchase price equal to 100% of the principal amount of the Convertible Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. The Convertible Notes Indenture contains customary events of default with respect to the Convertible Notes, including that upon certain events of default (including the Company’s failure to make any payment of principal or interest on the Convertible Notes when due and payable) occurring and continuing, the Convertible Notes Trustee by notice to the Company, or the holders of at least 25% in principal amount of the outstanding Convertible Notes by notice to the Company and the Convertible Notes Trustee, may, and the Convertible Notes Trustee at the request of such holders (subject to the provisions of the Convertible Notes Indenture) shall, declare 100% of the principal of and accrued and unpaid interest, if any, on all the Convertible Notes to be due and payable. In case of certain events of bankruptcy, insolvency or reorganization, involving the Company or a significant subsidiary, 100% of the principal of and accrued and unpaid interest on the Convertible Notes will automatically become due and payable. Upon such a declaration of acceleration, such principal and accrued and unpaid interest, if any, will be due and payable immediately. The Company accounts for the Convertible Notes as a liability and equity component where the carrying value of the liability component will be valued based on a similar instrument. In accounting for the issuance of the Convertible Notes, the Company separated the Convertible Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the Convertible Notes as a whole. The excess of the principal amount of the liability component over its carrying amount, referred to as the debt discount, is amortized to interest expense over the seven -year term of the Convertible Notes. The equity component is not re-measured as long as it continues to meet the conditions for equity classification. The equity component recorded at issuance related to the Convertible Notes is $57.5 million and was recorded in additional paid-in capital. In accounting for the transaction costs related to the issuance of the Convertible Notes, the Company allocated the total costs incurred to the liability and equity components of the Convertible Notes based on their relative values. Transaction costs attributable to the liability component are amortized to interest expense over the seven -year term of the Convertible Notes, and transaction costs attributable to the equity component are netted with the equity components in stockholders’ equity. Additionally, the Company initially recorded a net deferred tax liability of $22.3 million in connection with the Notes. The Convertible Notes consist of the following: Liability component March 31, 2018 December 31, 2017 Principal $ 150,000 $ 150,000 Less: Debt issuance costs (2,032 ) (2,121 ) Less: Debt discount, net(1) (40,791 ) (42,572 ) Net carrying amount $ 107,177 $ 105,307 (1) Included in the consolidated balance sheets within convertible senior notes (due 2022) and amortized to interest expense over the remaining life of the Convertible Notes using the effective interest rate method. The fair value of the Convertible Notes was approximately $139.3 million as of March 31, 2018 . The Company estimates the fair value of its Convertible Notes utilizing market quotations for debt that have quoted prices in active markets. As of March 31, 2018 , the remaining contractual life of the Convertible Notes is approximately 4.4 years. The following table sets forth total interest expense recognized related to the Convertible Notes: Three Months Ended March 31, 2018 2017 Contractual interest expense $ 1,110 $ 1,110 Amortization of debt issuance costs 89 80 Amortization of debt discount 1,780 1,600 Total $ 2,979 $ 2,790 Effective interest rate of the liability component 11 % 11 %

Commitments and contingencies

Commitments and contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Under various agreements, the Company will be required to pay royalties and milestone payments upon the successful development and commercialization of products. The Company has entered into funding agreements with The Wellcome Trust Limited ("Wellcome Trust") for the research and development of small molecule compounds in connection with the Company's oncology and antibacterial programs. As the Company has discontinued development under its antibacterial program, it no longer expects that milestone and royalty payments from the Company to Wellcome Trust will apply under that agreement, resulting in a change to the total amount of development and regulatory milestone payments the Company may become obligated to pay for this program. Under the oncology program funding agreement, to the extent that the Company develops and commercializes program intellectual property on a for-profit basis itself or in collaboration with a partner (provided the Company retains overall control of worldwide commercialization), the Company may become obligated to pay to Wellcome Trust development and regulatory milestone payments and single-digit royalties on sales of any research program product. The Company’s obligation to pay such royalties would continue on a country-by-country basis until the longer of the expiration of the last patent in the program intellectual property in such country covering the research program product and the expiration of market exclusivity of such product in such country. The Company’s first such milestone payment of $0.8 million payable to Wellcome Trust occurred in the second quarter of 2016. Additional milestone payments of up to an aggregate of $22.4 million may become payable by the Company to Wellcome Trust under this agreement. The Company has also entered into a collaboration agreement with the SMA Foundation. The Company may become obligated to pay the SMA Foundation single- digit royalties on worldwide net product sales of any collaboration product that is successfully developed and subsequently commercialized or, if the Company outlicenses rights to a collaboration product, a specified percentage of certain payments the Company receives from its licensee. The Company is not obligated to make such payments unless and until annual sales of a collaboration product exceed a designated threshold. The Company’s obligation to make such payments would end upon our payment to the SMA Foundation of a specified amount. The Company has employment agreements with certain employees which require the funding of a specific level of payments, if certain events, such as a change in control or termination without cause, occur. Additionally, the Company has royalty payments associated with Translarna and Emflaza product net sales, payable quarterly or annually in accordance with the terms of the related agreements. The Company is currently involved in various legal proceedings (refer to Item 1. Legal Proceedings for further details on the lawsuits filed). The Company denies any allegations of wrongdoing and intends to vigorously defend against these lawsuits. The Company is unable, however, to predict the outcome of these matters at this time. Moreover, any conclusion of this matter in a manner adverse to the Company and for which it incurs substantial costs or damages not covered by the Company's directors’ and officers’ liability insurance would have a material adverse effect on its financial condition and business. In addition, the litigation could adversely impact the Company's reputation and divert management’s attention and resources from other priorities, including the execution of business plans and strategies that are important to the Company's ability to grow its business, any of which could have a material adverse effect on the Company's business.

Revenue recognition

Revenue recognition	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue recognition	Revenue recognition Net product sales The Company views its operations and manages its business in one operating segment. During the three months ended March 31, 2018 , net product sales in the United States was $19.2 million , consisting solely of Emflaza, and net product sales not in the United States was $36.8 million , consisting solely of Translarna. The following table presents changes in the Company’s contract liabilities for the three months ended March 31, 2018 : Balance as of Additions Deductions ASC 606 Adjustment Balance as of Deferred Revenue $ 11,891 $ 1,346 $ — $ (3,937 ) $ 9,300.265 The Company did not have any contract assets for the three months ended March 31, 2018 . During the three months ended March 31, 2018 , the Company recognized revenue in the period from: March 31, Amounts included in contract liabilities at the beginning of the period $ — Performance obligations satisfied in previous period — Performance obligations satisfied in current period 55,981 Total product revenue $ 55,981 The Company has not made significant changes to the judgments made in applying ASC Topic 606 for the three months ended March 31, 2018 . Remaining performance obligations Remaining performance obligations represent the transaction price for goods the Company has yet to provide. As of March 31, 2018 , the aggregate amount of transaction price allocated to remaining performance obligations relating to Translarna net product revenue was $9.3 million . The Company expects to recognize revenue over the next two to four years as the specific timing for satisfying the performance obligations is contingent upon a number of factors, including customers’ needs and schedules. The impact of adoption using the modified retrospective method on the Company’s consolidated financial statements is as follows: i. Consolidated balance sheets Impact of changes in accounting policies As reported March 31, Adjustments As reported Balances without adoption of Topic 606 Assets Current assets: Cash and cash equivalents $ 97,675 $ — $ 97,675 Marketable securities 80,595 — 80,595 Trade receivables, net 45,611 — 45,611 Inventory 12,355 80 12,435 Prepaid expenses and other current assets 5,760 — 5,760 Total current assets 241,996 80 242,076 Fixed assets, net 8,302 — 8,302 Intangible assets, net 127,565 — 127,565 Deposits and other assets 1,548 — 1,548 Total assets $ 379,411 $ 80 $ 379,491 Liabilities and stockholders’ equity Current liabilities: Accounts payable and accrued expenses $ 71,437 $ (839 ) $ 70,598 Deferred revenue — 4,935 4,935 Other current liabilities 1,279 — 1,279 Total current liabilities 72,716 4,096 76,812 Deferred revenue - long-term 9,300 — 9,300 Long-term debt 146,878 — 146,878 Other long-term liabilities 209 — 209 Total liabilities 229,103 4,096 233,199 Stockholders’ equity: Common stock 42 — 42 Additional paid-in capital 975,418 — 975,418 Accumulated other comprehensive income 4,953 — 4,953 Accumulated deficit (830,105 ) (4,016 ) (834,121 ) Total stockholders’ equity 150,308 (4,016 ) 146,292 Total liabilities and stockholders’ equity $ 379,411 $ 80 $ 379,491 ii. Consolidated statements of operations Impact of changes in accounting policies As reported for the period ended March 31, Adjustments As reported Balances without adoption of Topic 606 Revenues: Net product revenue $ 55,981 $ (829 ) $ 55,152 Collaboration and grant revenue 81 — 81 Total revenues 56,062 (829 ) 55,233 Operating expenses: Cost of product sales, excluding amortization of acquired intangible asset 3,045 (80 ) 2,965 Amortization of acquired intangible asset 5,428 — 5,428 Research and development 31,363 — 31,363 Selling, general and administrative 32,969 — 32,969 Total operating expenses 72,805 (80 ) 72,725 Loss from operations (16,743 ) (749 ) (17,492 ) Interest expense, net (3,303 ) — (3,303 ) Other income, net 1,004 — 1,004 Loss before income tax expense (19,042 ) (749 ) (19,791 ) Income tax expense (221 ) — (221 ) Net loss attributable to common stockholders $ (19,263 ) $ (749 ) $ (20,012 ) iii. Consolidated statements of comprehensive loss Impact of changes in accounting policies As reported for the period ended March 31, Adjustments As reported Balances without adoption of Topic 606 Net loss $ (19,263 ) $ (749 ) $ (20,012 ) Other comprehensive loss: Unrealized loss on marketable securities, net of tax (123 ) — (123 ) Foreign currency translation gain 1,107 — 1,107 Comprehensive loss $ (18,279 ) $ (749 ) $ (19,028 ) iv. Consolidated statements of cash flows Impact of changes in accounting policies As reported for the period ended March 31, Adjustments Balances without adoption of Topic 606 Cash flows from operating activities Net loss $ (19,263 ) $ (749 ) $ (20,012 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 6,022 — 6,022 Non-cash interest expense 1,780 — 1,780 Amortization of premiums on investments (96 ) — (96 ) Amortization of debt issuance costs 126 — 126 Share-based compensation expense 7,748 — 7,748 Unrealized foreign currency transaction losses, net (1,300 ) — (1,300 ) Changes in operating assets and liabilities: 0 Inventory, net (1,446 ) (80 ) (1,526 ) Prepaid expenses and other current assets 958 — 958 Trade receivables, net (4,223 ) — (4,223 ) Deposits and other assets (308 ) — (308 ) Accounts payable and accrued expenses (6,810 ) (839 ) (7,649 ) Other liabilities (475 ) — (475 ) Deferred revenue 1,409 1,668 3,077 Net cash used in operating activities (15,878 ) — (15,878 ) Cash flows from investing activities Purchases of fixed assets (479 ) — (479 ) Purchases of marketable securities (22,683 ) — (22,683 ) Sale and redemption of marketable securities 21,514 — 21,514 Net cash used in investing activities (1,648 ) — (1,648 ) Cash flows from financing activities Proceeds from exercise of options 1,136 — 1,136 Net cash provided by financing activities 1,136 — 1,136 Effect of exchange rate changes on cash 2,273 — 2,273 Net decrease in cash and cash equivalents (14,117 ) — (14,117 ) Cash and cash equivalents, beginning of period 111,792 — 111,792 Cash and cash equivalents, end of period $ 97,675 $ — $ 97,675 Collaboration revenue The Company has ongoing collaborations with the Spinal Muscular Atrophy Foundation (SMA Foundation) and F. Hoffman-La Roche Ltd and Hoffman- La Roche Inc. (collectively, Roche) and early stage discovery arrangements with other institutions. The following are the key terms to the Company’s (i) ongoing collaborations and (ii) early stage discovery and development arrangements. Roche and SMA Foundation In November 2011, the Company and the SMA Foundation entered into a licensing and collaboration agreement with Roche for a spinal muscular atrophy program. Under the terms of the agreement, Roche acquired an exclusive worldwide license to the Company’s spinal muscular atrophy program, which includes three compounds currently in preclinical development, as well as potential back-up compounds. The Company received a nonrefundable upfront cash payment of $30.0 million during the research term, which was terminated effective December 31, 2014, after which Roche provided the Company with funding, based on an agreed- upon full-time equivalent rate, for an agreed-upon number of full- time equivalent employees that the Company contributed to the research program. The Company identified two material promises in the collaboration agreement, the license and the research activities. The Company evaluated whether these material promises are distinct and determined that the license does not have standalone functionality and there is a significant integration of the license and research activities. As such, both promises were bundled into one distinct performance obligation. As a result, the Company deferred the $30.0 million upfront payment which was recognized over the estimated performance period of two years, which was the contracted research period. As of adoption of ASC Topic 606 on January 1, 2018, all performance obligations had been satisfied and the balance of the remaining deferred upfront payment was fully recognized. Under the agreement, the Company is eligible to receive additional payments from Roche if specified events are achieved with respect to each licensed product, including up to $135.0 million in research and development event milestones, up to $325.0 million in sales milestones upon achievement of sales events, and up to double digit royalties on worldwide annual net sales of a commercial product. In January 2014, the Company announced the initiation of a Phase 1 clinical program in its spinal muscular atrophy collaboration with Roche and the SMA Foundation which triggered a $7.5 million milestone payment from Roche. Under ASC Topic 605, the Company considered this milestone event substantive because the applicable criteria of its revenue recognition policy would be satisfied and recorded it as collaboration revenue for the year ended December 31, 2014. In November 2014, the Company announced the initiation of a Phase 2 study in adult and pediatric patients in its spinal muscular atrophy collaboration with Roche and the SMA Foundation which triggered a $10 million payment from Roche. Under ASC Topic 605, the Company considered this milestone event substantive because the applicable criteria of its revenue recognition policy would be satisfied and recorded it as collaboration revenue for the year ended December 31, 2014. In October 2017, the Company announced that the Sunfish, a two-part clinical trial in pediatric and adult type 2 and type 3 spinal muscular atrophy initiated in the fourth quarter of 2016 with Roche and SMA Foundation, had transitioned into the pivotal second part of its study. The achievement of this milestone triggered a $20.0 million payment to the Company from Roche. Under ASC Topic 605, the Company considered this milestone event substantive because the applicable criteria of its revenue recognition policy would be satisfied and recorded it as collaboration revenue for the year ended December 31, 2017. For the three months ended March 31, 2018 and 2017 , the Company recognized revenue related to the licensing and collaboration agreement with Roche of $0.1 million and $0.1 million , respectively. Early stage collaboration and discovery agreements From time to time, the Company has arrangements with several organizations pursuant to which the Company uses its discovery technologies to help identify potential drug candidates. The Company does not take ownership of the potential compounds, but rather provides research services to the collaborator using its specialized technology platform. Generally, these arrangements are structured such that the collaborator and the Company work together to jointly select targets from which to apply its discovery technologies. The research period for the Company to apply its technology is generally three to four years. The Company will typically receive a nonrefundable, upfront cash payment and the collaborator agrees to provide funding for research activities performed on its behalf. Generally, the two material promises in these arrangements are the license and the research activities. The Company evaluated whether these material promises are distinct and determined that the license does not have standalone functionality and there is a significant integration of the license and research activities. As such, both promises are bundled into one distinct performance obligation. As of adoption of ASC Topic 606 on January 1, 2018, all deferred revenue related to these arrangements had been recognized. For the three months ended March 31, 2018 and 2017 , the Company did not recognize any revenue related to discovery agreements. The Company is eligible to receive additional payments from its early stage discovery research arrangements if the discovery compounds are ultimately developed and commercialized. The aggregate potential payments the Company is eligible for if all products are developed is $143.0 million and up to $252.0 million in sales milestones upon achievement of specified sales events and up to double digit royalties on worldwide annual net sales of the licensed product. The Company will recognize revenue when it is probable the milestones will be achieved (see Note 2). For the three months ended March 31, 2018 and 2017 , the Company did not recognize any revenue related to early stage collaborations.

Subsequent events

Subsequent events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent events	Subsequent events In April 2018, the Company closed an underwritten public offering of its common stock pursuant to a registration statement on Form S-3. The Company issued and sold an aggregate of 4,600,000 shares of common stock under the registration statement at a public offering price of $27.04 per share, including 600,000 shares issued upon exercise by the underwriters of their option to purchase additional shares. The Company received net proceeds of approximately $117.9 million after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

Summary of significant accoun19

Summary of significant accounting policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying financial information as of March 31, 2018 and for the three months ended March 31, 2018 and 2017 has been prepared by the Company, without audit, pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (GAAP) have been condensed or omitted pursuant to such rules and regulations. These interim financial statements should be read in conjunction with the Company’s audited financial statements as of December 31, 2017 and notes thereto included in the 2017 Form 10-K. In the opinion of management, the unaudited financial information as of March 31, 2018 and for the three months ended March 31, 2018 and 2017 reflects all adjustments, which are normal recurring adjustments, necessary to present a fair statement of financial position, results of operations and cash flows. The results of operations for the three month periods ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ended December 31, 2018 or for any other interim period or for any other future year.
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates in these consolidated financial statements have been made in connection with the calculation of net product sales, certain accruals related to the Company’s research and development expenses, stock-based compensation, valuation procedures for the convertible notes, allowance for doubtful accounts, inventory, acquired intangible assets, and the provision for or benefit from income taxes. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known.
Inventory and cost of product sales	Inventory and cost of product sales Inventory Inventories are stated at the lower of cost and net realizable value with cost determined on a first-in, first-out basis by product. The Company capitalizes inventory costs associated with products following regulatory approval when future commercialization is considered probable and the future economic benefit is expected to be realized. Translarna and Emflaza product which may be used in clinical development programs are included in inventory and charged to research and development expense when the product enters the research and development process and no longer can be used for commercial purposes. Inventory used for marketing efforts are charged to selling, general and administrative expense. The following table summarizes the components of the Company’s inventory for the periods indicated: March 31, 2018 December 31, 2017 Raw materials $ 768 $ 452 Work in progress 4,786 3,912 Finished goods 6,801 6,390 Total inventory $ 12,355 $ 10,754 The Company periodically reviews its inventories for excess amounts or obsolescence and writes down obsolete or otherwise unmarketable inventory to its estimated net realizable value. The Company has not recorded any inventory write downs as of the current period. Additionally, though the Company’s product is subject to strict quality control and monitoring which it performs throughout the manufacturing processes, certain batches or units of product may not meet quality specifications resulting in a charge to cost of product sales. Cost of product sales Cost of product sales consists of the cost of inventory sold, manufacturing and supply chain costs, storage costs, amortization of the acquired intangible asset and royalty payments associated with net product sales.
Revenue recognition	Revenue recognition In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-9, “Revenue from Contracts with Customers (Topic 606)”. ASU No. 2014-9 eliminated transaction- and industry-specific revenue recognition guidance under FASB Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition-Products (Topic 605) and replaced it with a principle-based approach for determining revenue recognition. ASC Topic 606 requires entities to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. On January 1, 2018, the Company adopted ASC Topic 606 using the modified retrospective approach, a practical expedient permitted under Topic 606, and applied this approach only to contracts that were not completed as of January 1, 2018. The Company calculated a one-time transition adjustment of $3.3 million , which was recorded on January 1, 2018 to the opening balance of accumulated deficit, related to the product sales of Emflaza. The ASC 606 transition adjustment recorded for Emflaza resulted in sales being recognized earlier than under Topic 605, as the deferred revenue recognition model (sell-through) is not applicable under Topic 606. The one-time adjustment consisted of $3.9 million in deferred revenue offset by $0.6 million of variable consideration. The information presented for the periods prior to January 1, 2018 has not been adjusted and is reported under Topic 605. Periods prior to January 1, 2018 The Company recognizes revenue when amounts are realized or realizable and earned. Revenue is considered realizable and earned when the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred or services have been rendered; (3) the price is fixed or determinable; and (4) collection of the amounts due are reasonably assured. Net product sales Prior to the second quarter of 2017, the Company’s net product sales consisted of sales of Translarna for the treatment of nmDMD in territories outside of the U.S. The Company recognizes revenue from product sales when there is persuasive evidence that an arrangement exists, title to product and associated risk of loss has passed to the customer, the price is fixed or determinable, collectability is reasonably assured and the Company has no further performance obligations in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition—Products. The Company has recorded revenue on sales where Translarna is available either on a commercial basis or through a reimbursed EAP program. Orders for Translarna are generally received from hospital and retail pharmacies and the Company’s third-party partner distributors. Revenue is recognized when risk of ownership has transferred. The Company’s third-party partner distributors act as intermediaries between the Company and end users and do not typically stock significant quantities of Translarna. The ultimate payor for Translarna is typically a government authority or institution or a third-party health insurer. In May 2017, the Company began the commercialization of Emflaza in the U.S. The Company recorded product revenue related to the sales of Emflaza in the U.S. in accordance with ASC 605-15, when persuasive evidence of an arrangement exists, delivery has occurred and title of the product and associated risk of loss has passed to the customer, the price is fixed or determinable and collection from the customer has been reasonably assured. Due to the early stage of the product launch, the Company determined that it was not able to reliably make certain estimates, including returns, necessary to recognize product revenue upon shipment to distributors. As a result, the Company recorded net product revenue for Emflaza using a deferred revenue recognition model (sell-through). Under the deferred revenue model, the Company does not recognize revenue until Emflaza is shipped to the specialty pharmacy. The Company records revenue net of estimated third-party discounts and rebates. Allowances are recorded as a reduction of revenue at the time revenues from product sales are recognized. These allowances are adjusted to reflect known changes in factors and may impact such allowances in the quarter those changes are known. Collaboration and grant revenue The terms of these agreements typically include payments to the Company of one or more of the following: nonrefundable, upfront license fees; milestone payments; research funding and royalties on future product sales. In addition, the Company generates service revenue through agreements that generally provide for fees for research and development services and may include additional payments upon achievement of specified events. The Company evaluates all contingent consideration earned, such as a milestone payment, using the criteria as provided by ASC 605-28, Revenue Recognition—Milestone Method. At the inception of a collaboration arrangement, the Company evaluates if a milestone payment is substantive. The criteria requires that (1) the Company determines if the milestone is commensurate with either its performance to achieve the milestone or the enhancement of value resulting from its activities to achieve the milestone; (2) the milestone be related to past performance; and (3) the milestone be reasonable relative to all deliverable and payment terms of the collaboration arrangement. If these criteria are met then the contingent milestones can be considered a substantive milestone and will be recognized as revenue in the period that the milestone is achieved. The Company recognizes royalties as earned in accordance with the terms of various research and collaboration agreements. If not substantive, the contingent consideration is allocated to the existing units of accounting based on relative selling price and recognized following the same basis previously established for the associated unit of accounting. The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities. Periods commencing January 1, 2018 The Company's net product revenue consists of sales of Translarna in territories outside of the U.S. and sales of Emflaza in the U.S., both for the treatment of DMD. Net product revenue The Company recognizes revenue when its performance obligations with its customers have been satisfied. The Company’s performance obligations are to provide Translarna or Emflaza based on customer orders from distributors, hospitals, specialty pharmacies or retail pharmacies. The performance obligations are satisfied at a point in time when the Company’s customer obtains control of either Translarna or Emflaza, which is typically upon delivery. The Company invoices its customers after the products have been delivered and invoice payments are generally due within 30 to 90 days of invoice date. The Company determines the transaction price based on fixed consideration in its contractual agreements. Contract liabilities arise in certain circumstances when consideration is due for goods the Company has yet to provide. As the Company has identified only one distinct performance obligation, the transaction price is allocated entirely to either product sales of Translarna or Emflaza. In determining the transaction price, a significant financing component does not exist since the timing from when the Company delivers product to when the customers pay for the product is typically less than one year. Customers in certain countries pay in advance of product delivery. In those instances, payment and delivery typically occur in the same month. The Company records product sales net of any variable consideration, which includes discounts, allowances, rebates and distribution fees. The Company uses the expected value or most likely amount method when estimating its variable consideration, unless discount or rebate terms are specified within contracts. Historically, returns of Translarna and Emflaza are immaterial to the financial statements. The identified variable consideration is recorded as a reduction of revenue at the time revenues from product sales are recognized. These estimates for variable consideration are adjusted to reflect known changes in factors and may impact such estimates in the quarter those changes are known. Revenue recognized does not include amounts of variable consideration that are constrained. In relation to customer contracts, the Company incurs costs to fulfill a contract but does not incur costs to obtain a contract. These costs to fulfill a contract do not meet the criteria for capitalization and are expensed as incurred. Upon adoption of ASC Topic 606 on January 1, 2018, the Company elected the following practical expedients: • Portfolio Approach - the Company applied the Portfolio Approach to contract reviews within its identified revenue streams that have similar characteristics and the Company believes this approach would not differ materially than if applying ASC Topic 606 to each individual contract. • Significant Financing Component - the Company expects the period between when it transfers a promised good to a customer and when the customer pays for the good or service to be one year or less. • Immaterial Performance Obligations - the Company disregards promises deemed to be immaterial in the context of the contract. • Shipping and Handling Activities - the Company considers any shipping and handling costs that are incurred after the customer has obtained control of the product as a cost to fulfill a promise. Shipping and handling costs associated with finished goods delivered to customers are recorded as a selling expense. Collaboration revenue The terms of these agreements typically include payments to the Company of one or more of the following: nonrefundable, upfront license fees; milestone payments; research funding and royalties on future product sales. In addition, the Company generates service revenue through agreements that generally provide for fees for research and development services and may include additional payments upon achievement of specified events. At the inception of a collaboration arrangement, the Company needs to first evaluate if the arrangement meets the criteria in ASC Topic 808 “Collaborative Arrangements” to then determine if ASC Topic 606 is applicable by considering whether the collaborator meets the definition of a customer. If the criteria are met, the Company assesses the promises in the arrangement to identify distinct performance obligations. For licenses of intellectual property, the Company assesses, at contract inception, whether the intellectual property is distinct from other performance obligations identified in the arrangement. If the licensing of intellectual property is determined to be distinct, revenue is recognized for nonrefundable, upfront license fees when the license is transferred to the customer and the customer can use and benefit from the license. If the licensing of intellectual property is determined not to be distinct, then the license will be bundled with other promises in the arrangement into one distinct performance obligation. The Company needs to determine if the bundled performance obligation is satisfied over time or at a point in time. If the Company concludes that the nonrefundable, upfront license fees will be recognized over time, the Company will need to assess the appropriate method of measuring proportional performance. For milestone payments, the Company assesses, at contract inception, whether the development or sales-based milestones are considered probable of being achieved. If it is probable that a significant revenue reversal will occur, the Company will not record revenue until the uncertainty has been resolved. Milestone payments that are contingent upon regulatory approval are not considered probable of being achieved until the applicable regulatory approvals or other external conditions are obtained as such conditions are not within the Company's control. If it is probable that a significant revenue reversal will not occur, the Company will estimate the milestone payments using the most likely amount method. The Company will re-assess the development and sales-based milestones each reporting period to determine the probability of achievement. The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities.
Allowance for doubtful accounts	Allowance for doubtful accounts The Company maintains an allowance for estimated losses resulting from the inability of its customers to make required payments. The Company estimates uncollectible amounts based upon current customer receivable balances, the age of customer receivable balances, the customer’s financial condition and current economic trends.
Income Taxes	Income Taxes On December 22, 2017, the U.S. government enacted the 2017 Tax Cuts and Jobs Act (the 2017 Tax Act), which significantly revises U.S. tax law by, among other provisions, lowering the U.S. federal statutory income tax rate to 21%, imposing a mandatory one-time transition tax on previously deferred foreign earnings, and eliminating or reducing certain income tax deductions. The Global Intangible Low-tax Income (GILTI) provisions of the 2017 Tax Act require the Company to include in its U.S. income tax return foreign subsidiary earnings in excess of an allowable return on the foreign subsidiary’s tangible assets. The Company has elected to account for GILTI tax in the period in which it is incurred, and therefore has not provided any deferred tax impacts of GILTI in its consolidated financial statements for the period ended March 31, 2018 . ASC 740, Income Taxes requires the effects of changes in tax laws to be recognized in the period in which the legislation is enacted. However, due to the complexity and significance of the 2017 Tax Act’s provisions, the SEC issued SAB 118, which allows companies to record the tax effects of the 2017 Tax Act on a provisional basis based on a reasonable estimate, and then, if necessary, subsequently adjust such amounts during a limited measurement period as more information becomes available. The measurement period ends when a company has obtained, prepared, and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year from enactment. The 2017 Tax Act does not have a material impact on the Company’s financial statements since its deferred temporary differences are fully offset by a valuation allowance and the Company does not have any significant off shore earnings from which to record the mandatory transition tax. However, given the significant complexity of the 2017 Tax Act, anticipated guidance from the U.S. Treasury about implementing the 2017 Tax Act, and the potential for additional guidance from the SEC or the FASB related to the 2017 Tax Act, these estimates may be adjusted during the measurement period. The Company continues to analyze the changes in certain income tax deductions, assess calculations of earnings and profits in certain foreign subsidiaries, including if those earnings which are held in cash or other assets and gather additional data to compute the full impacts on the Company’s deferred and current tax assets and liabilities.
Recently issued accounting standards	Recently issued accounting standards In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) No. 2016-2, “Leases (Topic 842)”. This standard will require organizations that lease assets with lease terms of more than 12 months to recognize assets and liabilities for the rights and obligations created by those leases on their balance sheets. The ASU will also require new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. The standard is effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted. The Company expects to adopt this guidance when effective and is currently assessing what effect the adoption of ASU No. 2016-2 will have on its consolidated financial statements and accompanying notes. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”. This standard requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected. This standard is effective for public companies who are SEC filers for fiscal years beginning after December 15, 2019, including interim periods within those years. The Company expects to adopt this guidance when effective and is assessing what effect the adoption of ASU 2016-13 will have on its consolidated financial statements and accompanying notes. In February 2018, the FASB issued ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income". This standard permits the reclassification of tax effects stranded in other comprehensive income as a result of tax reform to retained earnings related to the change in federal tax rate in addition to other stranded effects that relate to the Tax Cuts and Job Act ("the Act") but do not directly relate to the change in the federal rate. ASU 2018-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years with early adoption permitted for periods for which financial statements have not yet been issued or made available for issuance. The Company expects to adopt this guidance when effective and is currently assessing what effect the adoption of ASU No. 2018-02 will have on its consolidated financial statements and accompanying notes. Impact of recently adopted accounting pronouncements In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”. ASU No. 2014-09 eliminated transaction- and industry-specific revenue recognition guidance under FASB Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition-Products and replaced it with a principle-based approach for determining revenue recognition. ASC Topic 606 requires entities to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. On January 1, 2018, the Company adopted ASC Topic 606 using the modified retrospective approach and applied this approach only to contracts that were not completed as of January 1, 2018. The Company calculated a one-time transition adjustment of $3.3 million , which was recorded on January 1, 2018 to deferred revenue and accumulated deficit, related to the product sales of Emflaza. The information presented for the periods prior to January 1, 2018 has not been restated and is reported under ASC Topic 605. In January 2016, the FASB issued ASU No. 2016-01, “Financial Instruments — Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities”. This standard enhances the reporting model for financial instruments, which includes amendments to address aspects of recognition, measurement, presentation and disclosure. The new guidance affects all reporting organizations (whether public or private) that hold financial assets or owe financial liabilities. The Company adopted ASU 2016-01 during the three months ended March 31, 2018. In March 2018, the FASB issued ASU 2018-04, "Investments - Debt Securities (Topic 320) and Regulated Operations (Topic 980): Amendments to SEC Paragraphs Pursuant to the SEC Staff Accounting Bulletin ("SAB") No. 117 and SEC Release No. 33-9273 (SEC Update)". This standard supersedes SEC paragraphs in ASC 320, Investments- Debt Securities, as a result of the issuance of SAB 117 and also updates the Codification for a 2011 SEC release and are effective when a registrant adopts ASU 2016-01, which in the case of the Company was during the three months ended March 31, 2018. The adoption of these standards did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 . In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments”. This standard clarifies the presentation of certain specific cash flow issues in the Statement of Cash Flows. The Company adopted ASU 2016-15 during the three months ended March 31, 2018. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 . In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash”. This standard requires entities to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows and no longer present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents in the statement of cash flows. The Company adopted ASU 2016-18 during the three months ended March 31, 2018. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 . In May 2017, the FASB issued ASU No. 2017-09, "Stock Compensation (Topic 718): Scope of Modification Accounting". This standard clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as a modification, with entities applying the modification accounting guidance if the value, vesting conditions or classification of the award changes. In addition to all disclosures about modifications that are required under the current guidance, entities will be also required to disclose that compensation expense has not changed if applicable. The Company adopted ASU 2017-09 during the three months ended March 31, 2018. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations for the period ended and as of March 31, 2018 .

Summary of significant accoun20

Summary of significant accounting policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Schedule of Inventory	The following table summarizes the components of the Company’s inventory for the periods indicated: March 31, 2018 December 31, 2017 Raw materials $ 768 $ 452 Work in progress 4,786 3,912 Finished goods 6,801 6,390 Total inventory $ 12,355 $ 10,754

Fair value of financial instr21

Fair value of financial instruments and marketable securities (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of financial assets and liabilities that are required to be measured at fair value on a recurring basis	The following represents the fair value using the hierarchy described above for the Company’s financial assets and liabilities that are required to be measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 : March 31, 2018 Total Quoted prices Significant Significant Marketable securities $ 80,595 $ — $ 80,595 $ — Warrant liability $ 1 $ — $ — $ 1 Stock appreciation rights liability $ 1,279 $ — $ — $ 1,279 December 31, 2017 Total Quoted prices in active markets for identical assets (level 1) Significant other observable inputs (level 2) Significant unobservable inputs (level 3) Marketable securities $ 79,454 $ — $ 79,454 $ — Warrant Liability $ 1 $ — $ — $ 1 Stock appreciation rights liability $ 1,665 $ — $ — $ 1,665
Summary of marketable securities accounted for as available-for-sale securities	The following is a summary of marketable securities accounted for as available-for-sale securities at March 31, 2018 and December 31, 2017 : March 31, 2018 Amortized Cost Gross Unrealized Fair Value Gains Losses Commercial paper $ 26,191 $ 30 $ — $ 26,221 Corporate debt securities 54,505 — (131 ) 54,374 $ 80,696 $ 30 $ (131 ) $ 80,595 December 31, 2017 Amortized Cost Gross Unrealized Fair Value Gains Losses Commercial paper $ 13,775 $ 52 $ — $ 13,827 Corporate debt securities 65,657 — (30 ) 65,627 $ 79,432 $ 52 $ (30 ) $ 79,454
Summary of unrealized losses and fair values of available-for-sale securities in a continuous unrealized loss position	The unrealized losses and fair values of available-for-sale securities that have been in an unrealized loss position for a period of less than and greater than 12 months as of March 31, 2018 are as follows: March 31, 2018 Securities in an unrealized loss position less than 12 months Securities in an unrealized loss position greater than 12 months Total Unrealized losses Fair Value Unrealized losses Fair Value Unrealized losses Fair Value Corporate debt securities $ (131 ) $ 54,374 $ — $ — $ (131 ) $ 54,374 The unrealized losses and fair values of available-for-sale securities that have been in an unrealized loss position for a period of less than and greater than 12 months as of December 31, 2017 are as follows: December 31, 2017 Securities in an unrealized loss position less than 12 months Securities in an unrealized loss position greater than 12 months Total Unrealized losses Fair Value Unrealized losses Fair Value Unrealized losses Fair Value Corporate debt securities $ (28 ) $ 59,108 $ (2 ) $ 6,519 $ (30 ) $ 65,627
Schedule of marketable securities on the balance sheet	Marketable securities on the balance sheet at March 31, 2018 and December 31, 2017 mature as follows: March 31, 2018 Less Than 12 Months More Than 12 Months Commercial paper $ 26,221 $ — Corporate debt securities 54,374 — Total Marketable securities $ 80,595 $ — December 31, 2017 Less Than 12 Months More Than 12 Months Commercial paper $ 13,827 $ — Corporate debt securities 55,550 10,077 Total Marketable securities $ 69,377 $ 10,077
Summary of changes in the fair value of the Company's Level 3 valuation for warrant liability and SARs liability	The table presented below is a summary of changes in the fair value of the Company’s Level 3 valuations for the warrant liability and SARs liability for the period ended March 31, 2018 : Level 3 liabilities Warrants SARs Beginning balance as of December 31, 2017 $ 1 $ 1,665 Change in fair value — 1,605 Payments — (1,991 ) Ending balance as of March 31, 2018 $ 1 $ 1,279

Other comprehensive income (l22

Other comprehensive income (loss) and accumulated other comprehensive items (Tables)	3 Months Ended
	Mar. 31, 2018
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Summary of other comprehensive income (loss) and the changes in accumulated other comprehensive items	The following tables summarize other comprehensive income (loss) and the changes in accumulated other comprehensive items for the three months ended March 31, 2018 : Unrealized Gains/(Losses) On Marketable Securities, net of tax Foreign Currency Translation Total Accumulated Other Comprehensive Items Balance at December 31, 2017 $ 22 $ 3,947 $ 3,969 Other comprehensive (loss) income before reclassifications (123 ) 1,107 984 Amounts reclassified from other comprehensive items — — — Other comprehensive (loss) income (123 ) 1,107 984 Balance at March 31, 2018 $ (101 ) $ 5,054 $ 4,953

Accounts payable and accrued 23

Accounts payable and accrued expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Payables and Accruals [Abstract]
Schedule of components of accounts payable and accrued expenses	Accounts payable and accrued expenses at March 31, 2018 and December 31, 2017 consist of the following: March 31, December 31, Employee compensation, benefits, and related accruals $ 9,243 $ 17,711 Consulting and contracted research 6,570 5,137 Professional fees 3,100 2,116 Sales allowance and other costs 25,098 22,257 Sales rebates and royalties 16,380 11,657 Accounts payable 3,104 15,282 Other 7,942 2,286 $ 71,437 $ 76,446

Warrants (Tables)

Warrants (Tables)	3 Months Ended
	Mar. 31, 2018
Stockholders' Equity Note [Abstract]
Summary of the Company's outstanding warrants	The following is a summary of the Company’s outstanding warrants as of March 31, 2018 and December 31, 2017 : Warrant shares Exercise price Expiration Common stock 7,030 $ 128.00 2019 Common stock 130 $ 2,520.00 2019

Net loss per share (Tables)

Net loss per share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of computation of basic and diluted net loss available to common stockholders	The following tables set forth the computation of basic and diluted net loss per share: Three Months Ended March 31, 2018 2017 Numerator Net loss $ (19,263 ) $ (29,057 ) Denominator Denominator for basic and diluted net loss per share 41,626,617 34,305,948 Net loss per share: Basic and diluted $ (0.46 ) * $ (0.85 ) * *In the three months ended March 31, 2018 and 2017 , the Company experienced a net loss and therefore did not report any dilutive share impact.
Schedule of historical dilutive common share equivalents outstanding	The following table shows historical dilutive common share equivalents outstanding, which are not included in the above historical calculation, as the effect of their inclusion is anti-dilutive during each period As of March 31, 2018 2017 Stock Options 8,176,777 7,007,290 Unvested restricted stock awards and units 615,375 566,594 Total 8,792,152 7,573,884

Stock award plan (Tables)

Stock award plan (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of stock option activity	A summary of stock option activity is as follows: Number of Weighted- Weighted- Aggregate (in Outstanding at December 31, 2017 6,448,642 $ 29.00 Granted 1,916,939 $ 18.71 Exercised (77,312 ) $ 14.70 Forfeited/Cancelled (111,492 ) $ 34.42 Outstanding at March 31, 2018 8,176,777 $ 26.65 7.67 years $ 56,205 Vested or Expected to vest at March 31, 2018 3,711,261 $ 21.15 8.98 years $ 32,239 Exercisable at March 31, 2018 4,166,448 $ 32.12 6.40 years $ 21,177
Schedule of assumptions used to estimate fair values of grants made on the date of grant	The fair value of grants made in the three months ended March 31, 2018 was contemporaneously estimated on the date of grant using the following assumptions: Three months ended Risk-free interest rate 2.25% — 2.73% Expected volatility 64%—90% Expected term 5.04 – 10.00 years
Summary of information on the Company's restricted stock	The following table summarizes information on the Company’s restricted stock awards and units: Restricted Stock Awards and Units Number of Weighted January 1, 2018 393,011 $ 15.64 Granted 338,991 $ 18.01 Vested (97,545 ) $ 16.89 Forfeited (19,082 ) $ 17.06 Unvested at March 31, 2018 615,375 $ 16.74
Schedule of share-based compensation expense recorded in the statement of operations	The Company recorded share-based compensation expense in the statement of operations related to incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units and the ESPP as follows: Three Months Ended March 31, 2018 2017 Research and development $ 3,747 $ 4,467 Selling, general and administrative 4,001 4,562 Total $ 7,748 $ 9,029

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Summary of convertible notes	The Convertible Notes consist of the following: Liability component March 31, 2018 December 31, 2017 Principal $ 150,000 $ 150,000 Less: Debt issuance costs (2,032 ) (2,121 ) Less: Debt discount, net(1) (40,791 ) (42,572 ) Net carrying amount $ 107,177 $ 105,307 (1) Included in the consolidated balance sheets within convertible senior notes (due 2022) and amortized to interest expense over the remaining life of the Convertible Notes using the effective interest rate method.
Summary of interest expense recognized related to the Convertible Notes	The following table sets forth total interest expense recognized related to the Convertible Notes: Three Months Ended March 31, 2018 2017 Contractual interest expense $ 1,110 $ 1,110 Amortization of debt issuance costs 89 80 Amortization of debt discount 1,780 1,600 Total $ 2,979 $ 2,790 Effective interest rate of the liability component 11 % 11 %

Revenue recognition (Tables)

Revenue recognition (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract liabilities, rollforward and revenue recognition	The following table presents changes in the Company’s contract liabilities for the three months ended March 31, 2018 : Balance as of Additions Deductions ASC 606 Adjustment Balance as of Deferred Revenue $ 11,891 $ 1,346 $ — $ (3,937 ) $ 9,300.265 During the three months ended March 31, 2018 , the Company recognized revenue in the period from: March 31, Amounts included in contract liabilities at the beginning of the period $ — Performance obligations satisfied in previous period — Performance obligations satisfied in current period 55,981 Total product revenue $ 55,981
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The impact of adoption using the modified retrospective method on the Company’s consolidated financial statements is as follows: i. Consolidated balance sheets Impact of changes in accounting policies As reported March 31, Adjustments As reported Balances without adoption of Topic 606 Assets Current assets: Cash and cash equivalents $ 97,675 $ — $ 97,675 Marketable securities 80,595 — 80,595 Trade receivables, net 45,611 — 45,611 Inventory 12,355 80 12,435 Prepaid expenses and other current assets 5,760 — 5,760 Total current assets 241,996 80 242,076 Fixed assets, net 8,302 — 8,302 Intangible assets, net 127,565 — 127,565 Deposits and other assets 1,548 — 1,548 Total assets $ 379,411 $ 80 $ 379,491 Liabilities and stockholders’ equity Current liabilities: Accounts payable and accrued expenses $ 71,437 $ (839 ) $ 70,598 Deferred revenue — 4,935 4,935 Other current liabilities 1,279 — 1,279 Total current liabilities 72,716 4,096 76,812 Deferred revenue - long-term 9,300 — 9,300 Long-term debt 146,878 — 146,878 Other long-term liabilities 209 — 209 Total liabilities 229,103 4,096 233,199 Stockholders’ equity: Common stock 42 — 42 Additional paid-in capital 975,418 — 975,418 Accumulated other comprehensive income 4,953 — 4,953 Accumulated deficit (830,105 ) (4,016 ) (834,121 ) Total stockholders’ equity 150,308 (4,016 ) 146,292 Total liabilities and stockholders’ equity $ 379,411 $ 80 $ 379,491 ii. Consolidated statements of operations Impact of changes in accounting policies As reported for the period ended March 31, Adjustments As reported Balances without adoption of Topic 606 Revenues: Net product revenue $ 55,981 $ (829 ) $ 55,152 Collaboration and grant revenue 81 — 81 Total revenues 56,062 (829 ) 55,233 Operating expenses: Cost of product sales, excluding amortization of acquired intangible asset 3,045 (80 ) 2,965 Amortization of acquired intangible asset 5,428 — 5,428 Research and development 31,363 — 31,363 Selling, general and administrative 32,969 — 32,969 Total operating expenses 72,805 (80 ) 72,725 Loss from operations (16,743 ) (749 ) (17,492 ) Interest expense, net (3,303 ) — (3,303 ) Other income, net 1,004 — 1,004 Loss before income tax expense (19,042 ) (749 ) (19,791 ) Income tax expense (221 ) — (221 ) Net loss attributable to common stockholders $ (19,263 ) $ (749 ) $ (20,012 ) iii. Consolidated statements of comprehensive loss Impact of changes in accounting policies As reported for the period ended March 31, Adjustments As reported Balances without adoption of Topic 606 Net loss $ (19,263 ) $ (749 ) $ (20,012 ) Other comprehensive loss: Unrealized loss on marketable securities, net of tax (123 ) — (123 ) Foreign currency translation gain 1,107 — 1,107 Comprehensive loss $ (18,279 ) $ (749 ) $ (19,028 ) iv. Consolidated statements of cash flows Impact of changes in accounting policies As reported for the period ended March 31, Adjustments Balances without adoption of Topic 606 Cash flows from operating activities Net loss $ (19,263 ) $ (749 ) $ (20,012 ) Adjustments to reconcile net loss to net cash used in operating activities: Depreciation and amortization 6,022 — 6,022 Non-cash interest expense 1,780 — 1,780 Amortization of premiums on investments (96 ) — (96 ) Amortization of debt issuance costs 126 — 126 Share-based compensation expense 7,748 — 7,748 Unrealized foreign currency transaction losses, net (1,300 ) — (1,300 ) Changes in operating assets and liabilities: 0 Inventory, net (1,446 ) (80 ) (1,526 ) Prepaid expenses and other current assets 958 — 958 Trade receivables, net (4,223 ) — (4,223 ) Deposits and other assets (308 ) — (308 ) Accounts payable and accrued expenses (6,810 ) (839 ) (7,649 ) Other liabilities (475 ) — (475 ) Deferred revenue 1,409 1,668 3,077 Net cash used in operating activities (15,878 ) — (15,878 ) Cash flows from investing activities Purchases of fixed assets (479 ) — (479 ) Purchases of marketable securities (22,683 ) — (22,683 ) Sale and redemption of marketable securities 21,514 — 21,514 Net cash used in investing activities (1,648 ) — (1,648 ) Cash flows from financing activities Proceeds from exercise of options 1,136 — 1,136 Net cash provided by financing activities 1,136 — 1,136 Effect of exchange rate changes on cash 2,273 — 2,273 Net decrease in cash and cash equivalents (14,117 ) — (14,117 ) Cash and cash equivalents, beginning of period 111,792 — 111,792 Cash and cash equivalents, end of period $ 97,675 $ — $ 97,675

The Company (Details)

The Company (Details) $ in Thousands	Apr. 20, 2017USD ($)shares	Aug. 31, 2014member_state	Mar. 31, 2018USD ($)number_country	Dec. 31, 2017USD ($)	Aug. 31, 2015
Long-term debt
Minimum age of ambulatory patient		5 years
Number of member states of the European Economic Area | member_state		31
Retained earnings (accumulated deficit)			$ (830,105)	$ (814,108)
Convertible debt | 3.00% Convertible senior notes due 2022
Long-term debt
Interest rate					3.00%
Non-collaborative Arrangement Transactions | Marathon Pharmaceuticals, LLC
Long-term debt
Cash consideration	$ 75,000
Equity Interest Issued, number of shares (in shares) | shares	6,683,598
Numerator for calculation of number of shares of equity interests issued to acquire entity	$ 65,000
Trading day period	15 days
Development and regulatory milestone payments which the entity may be obligated to pay	$ 50,000
Translarna
Long-term debt
Number of countries | number_country			25

Summary of significant accoun30

Summary of significant accounting policies - Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Raw materials	$ 768	$ 452
Work in progress	4,786	3,912
Finished goods	6,801	6,390
Total inventory	$ 12,355	$ 10,754

Summary of significant accoun31

Summary of significant accounting policies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings (accumulated deficit)	$ (830,105)		$ (814,108)
ASC 606 Adjustment	(3,937)
Allowance for doubtful accounts receivable	800		$ 800
Adjustments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings (accumulated deficit)		$ 3,300
Variable consideration	$ 600

Fair value of financial instr32

Fair value of financial instruments and marketable securities - Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	$ 80,595	$ 79,454
Recurring basis | Total
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	80,595	79,454
Warrant Liability	1	1
Stock appreciation rights liability	1,279	1,665
Recurring basis | Quoted prices in active markets for identical assets (level 1)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	0	0
Warrant Liability	0	0
Stock appreciation rights liability	0	0
Recurring basis | Significant other observable inputs (level 2)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	80,595	79,454
Warrant Liability	0	0
Stock appreciation rights liability	0	0
Recurring basis | Significant unobservable inputs (level 3)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	0	0
Warrant Liability	1	1
Stock appreciation rights liability	$ 1,279	$ 1,665

Fair value of financial instr33

Fair value of financial instruments and marketable securities - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Aug. 31, 2015
Financial assets and liabilities measured at fair value on recurring basis
Transfers of assets between Level 1 and Level 2 of the fair value measurement hierarchy	$ 0	$ 0
Realized gains	$ 0	$ 0
Minimum | Warrants
Financial assets and liabilities measured at fair value on recurring basis
Volatility	54.00%	69.00%
Risk-free interest rate (as a percent)	2.18%	1.89%
Strike price (in dollars per share)	$ 128	$ 128
Expected life	1 year 4 months 6 days	1 year 7 months 6 days
Maximum | Warrants
Financial assets and liabilities measured at fair value on recurring basis
Volatility	56.00%	69.00%
Risk-free interest rate (as a percent)	2.18%	1.89%
Strike price (in dollars per share)	$ 2,520	$ 2,520
Expected life	1 year 5 months 23 days	1 year 8 months 12 days
Common stock | Warrants
Financial assets and liabilities measured at fair value on recurring basis
Fair value of shares (in dollars per share)	$ 27.06	$ 16.68
SARs | Minimum
Financial assets and liabilities measured at fair value on recurring basis
Volatility	55.00%	31.00%
Risk-free interest rate (as a percent)	2.01%	1.28%
Strike price (in dollars per share)	$ 6.76	$ 6.76
Expected life	9 months 4 days	0 days
SARs | Maximum
Financial assets and liabilities measured at fair value on recurring basis
Volatility	58.00%	70.00%
Risk-free interest rate (as a percent)	2.18%	1.89%
Strike price (in dollars per share)	$ 30.86	$ 30.86
Expected life	1 year 9 months 4 days	2 years
SARs | Common stock
Financial assets and liabilities measured at fair value on recurring basis
Fair value of shares (in dollars per share)	$ 27.06	$ 16.68
3.00% Convertible senior notes due 2022 | Convertible debt
Financial assets and liabilities measured at fair value on recurring basis
Principal	$ 150,000,000	$ 150,000,000	$ 150,000,000
Interest rate			3.00%
Fair value of convertible notes	$ 139,300,000	$ 115,700,000

Fair value of financial instr34

Fair value of financial instruments and marketable securities - Available for sale (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 80,696	$ 79,432
Gross Unrealized Gains	30	52
Gross Unrealized Losses	(131)	(30)
Fair Value	80,595	79,454
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,191	13,775
Gross Unrealized Gains	30	52
Gross Unrealized Losses	0	0
Fair Value	26,221	13,827
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	54,505	65,657
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(131)	(30)
Fair Value	$ 54,374	$ 65,627

Fair value of financial instr35

Fair value of financial instruments and marketable securities - Unrealized Loss Positions (Details) - Corporate debt securities - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Unrealized losses
Securities in an unrealized loss position less than 12 months	$ (131)	$ (28)
Securities in an unrealized loss position greater than 12 months	0	(2)
Total	(131)	(30)
Fair Value
Securities in an unrealized loss position less than 12 months	54,374	59,108
Securities in an unrealized loss position greater than 12 months	0	6,519
Total	$ 54,374	$ 65,627

Fair value of financial instr36

Fair value of financial instruments and marketable securities - Marketable securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	$ 80,595	$ 69,377
Total Marketable securities, More Than 12 Months	0	10,077
Commercial paper
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	26,221	13,827
Total Marketable securities, More Than 12 Months	0	0
Corporate debt securities
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	54,374	55,550
Total Marketable securities, More Than 12 Months	$ 0	$ 10,077

Fair value of financial instr37

Fair value of financial instruments and marketable securities - Warrants and SARs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
SARs
Changes in the fair value of warrant liability and SARs liability
December 31, 2017	$ 1,665
Change in fair value	1,605
Payments	(1,991)
March 31, 2018	1,279
Warrants
Changes in the fair value of warrant liability and SARs liability
December 31, 2017	1
Change in fair value	0
Payments	0
March 31, 2018	$ 1

Other comprehensive income (l38

Other comprehensive income (loss) and accumulated other comprehensive items (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Other comprehensive income (loss) and accumulated other comprehensive items
Beginning balance	$ 156,437
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income before reclassifications	984
Amounts reclassified from other comprehensive items	0
Other comprehensive (loss) income	984
Ending balance	150,308
Unrealized Gains/(Losses) On Marketable Securities, net of tax
Other comprehensive income (loss) and accumulated other comprehensive items
Beginning balance	22
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income before reclassifications	(123)
Amounts reclassified from other comprehensive items	0
Other comprehensive (loss) income	(123)
Ending balance	(101)
Foreign Currency Translation
Other comprehensive income (loss) and accumulated other comprehensive items
Beginning balance	3,947
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income before reclassifications	1,107
Amounts reclassified from other comprehensive items	0
Other comprehensive (loss) income	1,107
Ending balance	5,054
AOCI Attributable to Parent
Other comprehensive income (loss) and accumulated other comprehensive items
Beginning balance	3,969
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance	$ 4,953

Accounts payable and accrued 39

Accounts payable and accrued expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Employee compensation, benefits, and related accruals	$ 9,243	$ 17,711
Consulting and contracted research	6,570	5,137
Professional fees	3,100	2,116
Sales allowance and other costs	25,098	22,257
Sales rebates and royalties	16,380	11,657
Accounts payable	3,104	15,282
Other	7,942	2,286
Accounts payable and accrued expenses	$ 71,437	$ 76,446

Warrants (Details)

Warrants (Details) - Warrants - Common stock - 2019	Mar. 31, 2018$ / sharesshares
Warrants
Warrant shares (in shares) | shares	7,030
Exercise price (in dollars per share) | $ / shares	$ 128
Warrant shares (in shares) | shares	130
Exercise price (in dollars per share) | $ / shares	$ 2,520

Net loss per share - Numerator

Net loss per share - Numerator and Denominator (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator
Net loss	$ (19,263)	$ (29,057)
Denominator
Denominator for basic and diluted net loss per share (in shares)	41,626,617	34,305,948
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.46)	$ (0.85)

Net loss per share - Antidiluti

Net loss per share - Antidilutive (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net loss per share
Total shares excluded from calculation (in shares)	8,792,152	7,573,884
Stock Options
Net loss per share
Total shares excluded from calculation (in shares)	8,176,777	7,007,290
Unvested restricted stock awards and units
Net loss per share
Total shares excluded from calculation (in shares)	615,375	566,594

Stock award plan - Narrative (D

Stock award plan - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 05, 2013	Jun. 30, 2016	May 31, 2016	May 31, 2013	Mar. 31, 2018	Mar. 31, 2017
Stock option plan
Share-based compensation expense					$ 7,748	$ 9,029
Unrecognized compensation cost					$ 60,000
Weighted average remaining service period for recognition of unrecognized compensation cost					2 years 7 months 17 days
Common stock
Stock option plan
Number of shares available for issuance (in shares)					574,778
Unvested restricted stock
Stock option plan
Grants in period (in shares)					338,991
Stock option
Stock option plan
Granted (in shares)					1,916,939
Inducement grants for non-statutory stock options (in shares)					155,150
Expected dividend yield (as a percent)					0.00%
Weighted average grant date fair value (in dollars per share)					$ 12.50
SARs
Stock option plan
Granted (in shares)			897,290
Vesting period					4 years
Vested (in shares)					177,329
Share-based compensation expense					$ 1,600
2013 Stock Incentive Plan
Stock option plan
Number of shares available for issuance (in shares)	0
2013 Stock Incentive Plan | Common stock
Stock option plan
Number of shares authorized (in shares)	739,937
2013 Stock Incentive Plan | Unvested restricted stock
Stock option plan
Grants in period (in shares)	735,324
2013 Stock Incentive Plan | Stock option
Stock option plan
Granted (in shares)	4,613
2009 Equity and Long Term Incentive Plan
Stock option plan
Number of shares available for issuance (in shares)					0
Number of additional shares authorized (in shares)				2,500,000
2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan | Common stock
Stock option plan
Number of shares available for issuance (in shares)				122,296
2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan | 1998 Employee, Director and Consultant Stock Option Plan | Common stock | Maximum
Stock option plan
Number of shares subject to outstanding awards (in shares)				3,040,444
2013 Long Term Incentive Plan | Minimum
Stock option plan
Annual increase in the number of shares (in shares) on the first day of the fiscal year				2,500,000
Annual increase in the number of shares outstanding on the first day of the fiscal year				4.00%
Employee Stock Purchase Plan
Stock option plan
Number of shares authorized (in shares)		1,000,000
Share-based compensation expense					$ 200
Award requisite service period		6 months
Purchase price of common stock, percent		85.00%
Employee stock purchase plan, voting percentage limit		5.00%

Stock award plan - Share Base C

Stock award plan - Share Base Compensation (Details) - Stock option $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares
Number of options
Outstanding at the beginning of the period (in shares) | shares	6,448,642
Granted (in shares) | shares	1,916,939
Exercised (in shares) | shares	(77,312)
Forfeited/Cancelled (in shares) | shares	(111,492)
Outstanding at the end of the period (in shares) | shares	8,176,777
Vested or Expected to vest at the end of the period (in shares) | shares	3,711,261
Exercisable at the end of the period (in shares) | shares	4,166,448
Weighted- average exercise price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 29
Granted (in dollars per share) | $ / shares	18.71
Exercised (in dollars per share) | $ / shares	14.70
Forfeited/Cancelled (in dollars per share) | $ / shares	34.42
Outstanding at the end of the period (in dollars per share) | $ / shares	26.65
Vested or Expected to vest at the end of the period (in dollars per share) | $ / shares	21.15
Exercisable at the end of the period (in dollars per share) | $ / shares	$ 32.12
Weighted- average remaining contractual term
Outstanding at the end of the period	7 years 8 months 1 day
Vested or Expected to vest at the end of the period	8 years 11 months 23 days
Exercisable at the end of the period	6 years 4 months 24 days
Aggregate intrinsic value
Outstanding at the end of the period (in dollars) | $	$ 56,205
Vested or Expected to vest at the end of the period (in dollars) | $	32,239
Exercisable at the end of the period (in dollars) | $	$ 21,177
Minimum
Valuation assumptions
Risk-free interest rate (as a percent)	2.25%
Expected volatility (as a percent)	64.00%
Expected term	5 years 16 days
Maximum
Valuation assumptions
Risk-free interest rate (as a percent)	2.73%
Expected volatility (as a percent)	90.00%
Expected term	10 years

Stock award plan - Restricted S

Stock award plan - Restricted Stock (Details) - Unvested restricted stock	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Number of Shares
Balance at the beginning of the period (in shares) | shares	393,011
Granted (in shares) | shares	338,991
Vested (in shares) | shares	(97,545)
Forfeited (in shares) | shares	(19,082)
Balance at the end of the period (in shares) | shares	615,375
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) | $ / shares	$ 15.64
Granted (in dollars per share) | $ / shares	18.01
Vested (in dollars per share) | $ / shares	16.89
Forfeited (in dollars per share) | $ / shares	17.06
Balance at the end of the period (in dollars per share) | $ / shares	$ 16.74

Stock award plan - Share-based

Stock award plan - Share-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock option plan
Share-based compensation expense	$ 7,748	$ 9,029
Research and development
Stock option plan
Share-based compensation expense	3,747	4,467
Selling, general and administrative
Stock option plan
Share-based compensation expense	$ 4,001	$ 4,562

Debt - Narrative (Details)

Debt - Narrative (Details)	May 05, 2017USD ($)	May 31, 2017USD ($)	Aug. 31, 2015USD ($)day$ / shares	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Convertible debt | 3.00% Convertible senior notes due 2022
Long-term debt
Debt principal amount			$ 150,000,000	$ 150,000,000	$ 150,000,000
Interest rate			3.00%
Net proceeds from issuance of convertible notes			$ 145,400,000
Trading days, number | day			20
Consecutive trading days, period | day			30
Stock price trigger			130.00%
Business days, period			5 days
Consecutive trading-day period			5 days
Common stock per principal amount			$ 1,000
Maximum product of the closing sale price of shares of the Company's common stock and the applicable conversion rate for such trading day			98.00%
Conversion ratio			17.7487
Conversion price per share (in dollars per share) | $ / shares			$ 56.34
Convertible instruments principal and unpaid interest payable upon events of default			100.00%
Minimum percentage of principal held by convertible debt instrument holders required to issue notice for declaration of principal and unpaid interest payable upon events of default			25.00%
Term of the convertible notes			7 years
Adjustments to additional paid in capital, equity component of convertible debt			$ 57,500,000
Net deferred tax liability in connection with convertible notes			$ 22,300,000
Fair value of convertible notes				$ 139,300,000	$ 115,700,000
Remaining contractual life of the convertible notes				4 years 4 months 24 days
Convertible debt | 3.00% Convertible senior notes due 2022 | Redemption on or after August 20, 2018
Long-term debt
Trading days, number | day			19
Consecutive trading days, period | day			30
Stock price trigger			130.00%
Redemption price			100.00%
Sinking fund			$ 0
MidCap Financial Trust
Long-term debt
Line of credit facility, maximum borrowing capacity		$ 60,000,000
Proceeds from lines of credit	$ 40,000,000
Line of credit facility, additional capacity available, net product revenue threshold		20,000,000
Line of credit facility, net product revenue threshold, additional capacity		$ 120,000,000
Line of credit facility, net product revenue threshold, additional capacity, trailing period		12 months
Debt issuance costs		$ 400,000
Debt instrument, floor interest rate		1.00%
Debt instrument, basis spread on variable rate		6.15%
Debt instrument, interest payment period		24 months

Debt - Convertible Notes (Detai

Debt - Convertible Notes (Details) - 3.00% Convertible senior notes due 2022 - Convertible debt - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Aug. 31, 2015
Long-term debt
Principal	$ 150,000,000	$ 150,000,000	$ 150,000,000
Less: Debt issuance costs	(2,032,000)	(2,121,000)
Less: Debt discount, net	(40,791,000)	(42,572,000)
Net carrying amount	$ 107,177,000	$ 105,307,000

Debt - Interest Expense (Detail

Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Long-term debt
Amortization of debt issuance costs	$ 126	$ 80
Convertible debt | 3.00% Convertible senior notes due 2022
Long-term debt
Contractual interest expense	1,110	1,110
Amortization of debt issuance costs	89	80
Amortization of debt discount	1,780	1,600
Total	$ 2,979	$ 2,790
Effective interest rate of the liability component	11.00%	11.00%

Commitments and contingencies (

Commitments and contingencies (Details) - Funding agreement - Wellcome trust - USD ($) $ in Millions	Mar. 31, 2018	Jun. 30, 2016
Other Commitments [Abstract]
Development and regulatory milestone payments which the entity may be obligated to pay		$ 0.8
Maximum
Other Commitments [Abstract]
Development and regulatory milestone payments which the entity may be obligated to pay	$ 22.4

Revenue recognition - Narrative

Revenue recognition - Narrative (Details)	1 Months Ended				3 Months Ended		12 Months Ended
	Oct. 31, 2017USD ($)	Nov. 30, 2014USD ($)	Jan. 31, 2014USD ($)	Nov. 30, 2011USD ($)compound	Mar. 31, 2018USD ($)segmentdeliverable	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)deliverable
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Number of operating segments | segment					1
Net product revenue					$ 55,981,000	$ 26,442,000
Contract with customer, liability							$ 11,891,000
Upfront cash payment					1,346,000
Licensing And Collaboration Agreement
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Upfront cash payment				$ 30,000,000
Revenue recognition, milestone method, revenue recognized	$ 20,000,000	$ 10,000,000	$ 7,500,000
Revenues					100,000	100,000
Licensing And Collaboration Agreement | Research And Development Event Milestones
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognition, milestone, potential achievements					135,000,000
Licensing And Collaboration Agreement | Sales Milestones
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognition, milestone, potential achievements					325,000,000
Discovery Agreements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues					0	0
Early Stage Collaborations
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues					0	$ 0
Early Stage Collaborations | Research And Development Event Milestones
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognition, milestone, potential achievements					143,000,000
Early Stage Collaborations | Sales Milestones
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognition, milestone, potential achievements					252,000,000
United States | Emflaza
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net product revenue					19,200,000
Non-US | Translarna
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net product revenue					$ 36,800,000
Collaborative Arrangement | Roche And Sma Foundation
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Number of compounds in preclinical development | compound				3
Number of significant deliverables | deliverable							2
Collaboration And Discovery Agreements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Number of significant deliverables | deliverable					2
Minimum | Collaboration And Discovery Agreements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Collaborative arrangements research period for applying discovery technology					3 years
Maximum | Collaboration And Discovery Agreements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Collaborative arrangements research period for applying discovery technology					4 years

Revenue recognition - Contract

Revenue recognition - Contract Liabilities, Rollforward (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Movement in Deferred Revenue [Roll Forward]
Beginning balance	$ 11,891
Additions	1,346
Deductions	0
ASC 606 Adjustment	$ (3,937)

Revenue recognition - Recognize

Revenue recognition - Recognized revenue in the period (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue from Contract with Customer [Abstract]
Amounts included in contract liabilities at the beginning of the period	$ 0
Performance obligations satisfied in previous period	0
Performance obligations satisfied in current period	55,981
Total product revenue	$ 55,981	$ 26,442

Revenue recognition - Balance S

Revenue recognition - Balance Sheet Impacts (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 97,675		$ 111,792	$ 54,106	$ 58,321
Marketable securities	80,595		79,454
Trade receivables, net	45,611		40,394
Inventory	12,355		10,754
Prepaid expenses and other current assets	5,760		6,669
Total current assets	241,996		249,063
Fixed assets, net	8,302		8,376
Intangible assets, net	127,565		132,993
Deposits and other assets	1,548		1,221
Total assets	379,411		391,653
Current liabilities:
Accounts payable and accrued expenses	71,437		76,446
Deferred revenue	0		3,937
Other current liabilities	1,279		1,665
Total current liabilities	72,716		82,048
Deferred revenue - long-term	9,300		7,954
Long-term debt	146,878		144,971
Other long-term liabilities	209		243
Total liabilities	229,103		235,216
Stockholders’ equity:
Common stock, $0.001 par value. Authorized 125,000,000 shares; issued and outstanding 41,809,398 shares at March 31, 2018. Authorized 125,000,000 shares; issued and outstanding 41,612,395 shares at December 31, 2017	42		42
Additional paid-in capital	975,418		966,534
Accumulated other comprehensive income	4,953		3,969
Accumulated deficit	(830,105)		(814,108)
Total stockholders’ equity	150,308		156,437
Total liabilities and stockholders’ equity	379,411		391,653
Adjustments
Stockholders’ equity:
Accumulated deficit		$ 3,300
Adjustments | ASU 2014-09
Current assets:
Cash and cash equivalents	0		0
Marketable securities	0
Trade receivables, net	0
Inventory	80
Prepaid expenses and other current assets	0
Total current assets	80
Fixed assets, net	0
Intangible assets, net	0
Deposits and other assets	0
Total assets	80
Current liabilities:
Accounts payable and accrued expenses	(839)
Deferred revenue	4,935
Other current liabilities	0
Total current liabilities	4,096
Deferred revenue - long-term	0
Long-term debt	0
Other long-term liabilities	0
Total liabilities	4,096
Stockholders’ equity:
Common stock, $0.001 par value. Authorized 125,000,000 shares; issued and outstanding 41,809,398 shares at March 31, 2018. Authorized 125,000,000 shares; issued and outstanding 41,612,395 shares at December 31, 2017	0
Additional paid-in capital	0
Accumulated other comprehensive income	0
Accumulated deficit	(4,016)
Total stockholders’ equity	(4,016)
Total liabilities and stockholders’ equity	80
Balances without adoption of Topic 606
Current assets:
Cash and cash equivalents	97,675		$ 111,792
Marketable securities	80,595
Trade receivables, net	45,611
Inventory	12,435
Prepaid expenses and other current assets	5,760
Total current assets	242,076
Fixed assets, net	8,302
Intangible assets, net	127,565
Deposits and other assets	1,548
Total assets	379,491
Current liabilities:
Accounts payable and accrued expenses	70,598
Deferred revenue	4,935
Other current liabilities	1,279
Total current liabilities	76,812
Deferred revenue - long-term	9,300
Long-term debt	146,878
Other long-term liabilities	209
Total liabilities	233,199
Stockholders’ equity:
Common stock, $0.001 par value. Authorized 125,000,000 shares; issued and outstanding 41,809,398 shares at March 31, 2018. Authorized 125,000,000 shares; issued and outstanding 41,612,395 shares at December 31, 2017	42
Additional paid-in capital	975,418
Accumulated other comprehensive income	4,953
Accumulated deficit	(834,121)
Total stockholders’ equity	146,292
Total liabilities and stockholders’ equity	$ 379,491

Revenue recognition - Income St

Revenue recognition - Income Statement Impacts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Net product revenue	$ 55,981	$ 26,442
Collaboration and grant revenue	81	105
Total revenues	56,062	26,547
Operating expenses:
Cost of product sales, excluding amortization of acquired intangible asset	3,045	39
Amortization of acquired intangible asset	5,428	0
Research and development	31,363	27,363
Selling, general and administrative	32,969	25,500
Total operating expenses	72,805	52,902
Loss from operations	(16,743)	(26,355)
Interest expense, net	(3,303)	(2,219)
Other income (expense), net	1,004	(318)
Loss before income tax expense	(19,042)	(28,892)
Income tax expense	(221)	(165)
Net loss attributable to common stockholders	(19,263)	$ (29,057)
Adjustments | ASU 2014-09
Revenues:
Net product revenue	(829)
Collaboration and grant revenue	0
Total revenues	(829)
Operating expenses:
Cost of product sales, excluding amortization of acquired intangible asset	(80)
Amortization of acquired intangible asset	0
Research and development	0
Selling, general and administrative	0
Total operating expenses	(80)
Loss from operations	(749)
Interest expense, net	0
Other income (expense), net	0
Loss before income tax expense	(749)
Income tax expense	0
Net loss attributable to common stockholders	(749)
Balances without adoption of Topic 606
Revenues:
Net product revenue	55,152
Collaboration and grant revenue	81
Total revenues	55,233
Operating expenses:
Cost of product sales, excluding amortization of acquired intangible asset	2,965
Amortization of acquired intangible asset	5,428
Research and development	31,363
Selling, general and administrative	32,969
Total operating expenses	72,725
Loss from operations	(17,492)
Interest expense, net	(3,303)
Other income (expense), net	1,004
Loss before income tax expense	(19,791)
Income tax expense	(221)
Net loss attributable to common stockholders	$ (20,012)

Revenue recognition - Comprehen

Revenue recognition - Comprehensive Income Impacts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ (19,263)	$ (29,057)
Other comprehensive loss:
Unrealized loss on marketable securities	(123)	(22)
Foreign currency translation gain	1,107	631
Comprehensive loss	(18,279)	$ (28,448)
Adjustments | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	(749)
Other comprehensive loss:
Unrealized loss on marketable securities	0
Foreign currency translation gain	0
Comprehensive loss	(749)
Balances without adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	(20,012)
Other comprehensive loss:
Unrealized loss on marketable securities	(123)
Foreign currency translation gain	1,107
Comprehensive loss	$ (19,028)

Revenue recognition - Cash Flow

Revenue recognition - Cash Flow Impacts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net loss	$ (19,263)	$ (29,057)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	6,022	612
Non-cash interest expense	1,780	1,600
Amortization of premiums on investments	(96)	208
Amortization of debt issuance costs	126	80
Share-based compensation expense	7,748	9,029
Unrealized foreign currency transaction (gains) losses, net	(1,300)	820
Changes in operating assets and liabilities:
Inventory, net	(1,446)	(1,350)
Prepaid expenses and other current assets	958	93
Trade receivables, net	(4,223)	(6,746)
Deposits and other assets	(308)	(226)
Accounts payable and accrued expenses	(6,810)	(3,923)
Other liabilities	(475)	(624)
Deferred revenue	1,409	582
Net cash used in operating activities	(15,878)	(28,902)
Cash flows from investing activities
Purchases of fixed assets	(479)	(225)
Purchases of marketable securities	(22,683)	(19,467)
Sale and redemption of marketable securities	21,514	44,110
Net cash (used in) provided by investing activities	(1,648)	24,418
Cash flows from financing activities
Proceeds from exercise of options	1,136	106
Net cash provided by financing activities	1,136	663
Effect of exchange rate changes on cash	2,273	(394)
Net decrease in cash and cash equivalents	(14,117)	(4,215)
Cash and cash equivalents, beginning of period	111,792	58,321
Cash and cash equivalents, end of period	97,675	$ 54,106
Adjustments | ASU 2014-09
Cash flows from operating activities
Net loss	(749)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	0
Non-cash interest expense	0
Amortization of premiums on investments	0
Amortization of debt issuance costs	0
Share-based compensation expense	0
Unrealized foreign currency transaction (gains) losses, net	0
Changes in operating assets and liabilities:
Inventory, net	(80)
Prepaid expenses and other current assets	0
Trade receivables, net	0
Deposits and other assets	0
Accounts payable and accrued expenses	(839)
Other liabilities	0
Deferred revenue	1,668
Net cash used in operating activities	0
Cash flows from investing activities
Purchases of fixed assets	0
Purchases of marketable securities	0
Sale and redemption of marketable securities	0
Net cash (used in) provided by investing activities	0
Cash flows from financing activities
Proceeds from exercise of options	0
Net cash provided by financing activities	0
Effect of exchange rate changes on cash	0
Net decrease in cash and cash equivalents	0
Cash and cash equivalents, beginning of period	0
Cash and cash equivalents, end of period	0
Balances without adoption of Topic 606
Cash flows from operating activities
Net loss	(20,012)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	6,022
Non-cash interest expense	1,780
Amortization of premiums on investments	(96)
Amortization of debt issuance costs	126
Share-based compensation expense	7,748
Unrealized foreign currency transaction (gains) losses, net	(1,300)
Changes in operating assets and liabilities:
Inventory, net	(1,526)
Prepaid expenses and other current assets	958
Trade receivables, net	(4,223)
Deposits and other assets	(308)
Accounts payable and accrued expenses	(7,649)
Other liabilities	(475)
Deferred revenue	3,077
Net cash used in operating activities	(15,878)
Cash flows from investing activities
Purchases of fixed assets	(479)
Purchases of marketable securities	(22,683)
Sale and redemption of marketable securities	21,514
Net cash (used in) provided by investing activities	(1,648)
Cash flows from financing activities
Proceeds from exercise of options	1,136
Net cash provided by financing activities	1,136
Effect of exchange rate changes on cash	2,273
Net decrease in cash and cash equivalents	(14,117)
Cash and cash equivalents, beginning of period	111,792
Cash and cash equivalents, end of period	$ 97,675

Revenue recognition - Performan

Revenue recognition - Performance Obligations (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01 - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Nov. 30, 2011	Mar. 31, 2018
Translarna
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation		$ 9,300
Translarna | Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, performance obligation, period		2 years
Translarna | Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, performance obligation, period		4 years
Licensing And Collaboration Agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation	$ 30,000
Revenue, performance obligation, period	2 years

Subsequent events (Details)

Subsequent events (Details) - Subsequent Event $ / shares in Units, $ in Millions	1 Months Ended
	Apr. 30, 2018USD ($)$ / sharesshares
Subsequent Event [Line Items]
Stock issued during period (in shares)	4,600,000
Shares issued (in dollars per share) | $ / shares	$ 27.04
Proceeds from issuance of common stock | $	$ 117.9
Over-Allotment Option
Subsequent Event [Line Items]
Stock issued during period (in shares)	600,000