PTC Therapeutics (PTCT) 10-Q 5 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 30, 2015
Document and Entity Information
Entity Registrant Name	PTC THERAPEUTICS, INC.
Entity Central Index Key	1070081
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		33,848,276
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$36,825	$49,748
Marketable securities	243,642	265,493
Prepaid expenses and other current assets	6,116	3,885
Receivables, net	3,178	4,445
Total current assets	289,761	323,571
Fixed assets, net	9,408	9,159
Deposits and other assets	351	489
Total assets	299,520	333,219
Current liabilities:
Accounts payable and accrued expenses	23,532	29,121
Deferred revenue	373	3,354
Total current liabilities	23,905	32,475
Other long-term liabilities	2,295	2,277
Total liabilities	26,200	34,752
Common stock, $0.001 par value. Authorized 125,000,000 shares; issued and outstanding 33,483,306 shares at March 31, 2015. Authorized 125,000,000 shares; issued and outstanding 32,898,392 shares at December 31, 2014	33	33
Additional paid-in capital	734,489	721,722
Accumulated other comprehensive loss	-736	-737
Accumulated deficit	-460,466	-422,551
Total stockholders' equity	273,320	298,467
Total liabilities and stockholders' equity	$299,520	$333,219

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$0.00	$0.00
Common stock, authorized shares	125,000,000	125,000,000
Common stock, issued shares	33,483,306	32,898,392
Common stock, outstanding shares	33,483,306	32,898,392

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenues:
Net product revenue	$5,069
Collaboration revenue	338	9,147
Grant revenue	2,075	70
Total revenues	7,482	9,217
Operating expenses:
Research and development	27,938	15,889
Selling, general and administrative	17,615	7,540
Total operating expenses	45,553	23,429
Loss from operations	-38,071	-14,212
Interest income	524	171
Other (expense) income, net	-368	-57
Net loss	($37,915)	($14,098)
Weighted-average shares outstanding:
Basic and diluted (in shares)	33,067,752	24,492,487
Net loss per share - basic and diluted (in dollars per share)	($1.15)	($0.58)

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Consolidated Statements of Comprehensive Loss
Net loss	($37,915)	($14,098)
Other comprehensive loss:
Unrealized gain on marketable securities	125	10
Foreign currency translation loss	-124
Comprehensive loss	($37,914)	($14,088)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities
Net loss	($37,915)	($14,098)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	634	588
Change in valuation of warrant liability	41	55
Amortization of premiums on investments	486	414
Share-based compensation expense	9,748	3,705
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	-2,231	-358
Receivables	1,267	120
Deposits and other assets	138	17
Accounts payable and accrued expenses	-5,589	-3,472
Other long-term liabilities	-23	-23
Deferred revenue	-2,981	-386
Net cash used in operating activities	-36,425	-13,438
Cash flows from investing activities
Purchases of fixed assets	-883	-186
Purchases of marketable securities	-19,108	-25,354
Sale & redemption of marketable securities	40,598	21,273
Net cash provided/ used in investing activities	20,607	-4,267
Cash flows from financing activities
Payments on long-term debt		-37
Proceeds from exercise of options	3,019
Net proceeds from public offerings		118,183
Net cash provided by financing activities	3,019	118,146
Effect of exchange rate changes on cash	-124
Net increase/(decrease) in cash and cash equivalents	-12,923	100,441
Cash and cash equivalents, beginning of period	49,748	15,414
Cash and cash equivalents, end of period	36,825	115,855
Supplemental disclosure of cash information
Cash paid for interest		1
Supplemental disclosures of non-cash information related to investing and financing activities
Change in unrealized gain (loss) on marketable securities	$125	$10

The_Company

The Company	3 Months Ended
	Mar. 31, 2015
The Company
The Company
	1.The Company
	PTC Therapeutics, Inc. (the Company or PTC) was incorporated as a Delaware corporation on March 31, 1998. PTC is a global biopharmaceutical company focused on the discovery, development and commercialization of orally administered, small molecule therapeutics targeting an area of RNA biology referred to as post-transcriptional control. The letters “PTC” in the corporate name are an acronym for post-transcriptional control processes, which are the regulatory events that occur in cells during and after a messenger RNA is copied from DNA through the transcription process. The Company has discovered all of its compounds currently under development using its proprietary technologies. The Company plans to continue to develop these compounds both on its own and through selective collaboration arrangements with leading pharmaceutical and biotechnology companies. The Company believes that systematically targeting post-transcriptional control processes represents an unexploited approach to drug discovery and development. The Company’s internally discovered pipeline addresses multiple therapeutic areas, including rare disorders, oncology and infectious diseases.
	The Company’s lead product, Translarna™ (ataluren) received marketing authorization from the European Commission, or EC, in August 2014 for the treatment of nonsense mutation Duchenne muscular dystrophy, or nmDMD, in ambulatory patients age 5 years and over in the 31 member states of the European Economic Area, or EEA. This marketing authorization is subject to annual review and renewal by the European Medicines Agency, or EMA following its reassessment of the risk-benefit balance of the authorization and is further conditioned on the Company’s ability to complete its global, confirmatory Phase 3 clinical trial in nmDMD, which it refers to as ACT DMD, and submit the final report, including additional efficacy and safety data from the trial, during 2015. See “Risk Factors—Risks Related to Regulatory Approval of our Product Candidates” for further detail regarding the EMA’s approval process, including a description of the risk-benefit balance.
	The Company launched Translarna on a commercial basis in Germany in December 2014 and expects to expand its launch activities across the EEA throughout 2015 and future years, subject to successful completion of pricing and reimbursement negotiations. Concurrently, the Company has been pursuing reimbursed early access programs in selected countries where those mechanisms exist, both within Europe and in those countries outside of Europe that will reference the marketing authorization described above.
	The Company has not generated significant product revenue to date and is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals, the difficulties inherent in the development of commercially usable products, the potential need to obtain additional capital necessary to fund the development of its products, and competition from other companies. As of March 31, 2015, the Company had an accumulated deficit of approximately $460.4 million. The Company has financed its operations to date primarily through 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.

Summary_of_significant_account

Summary of significant accounting policies	3 Months Ended
	Mar. 31, 2015
Summary of significant accounting policies
Summary of significant accounting policies
	2.Summary of significant accounting policies
	The Company’s complete listing of significant accounting policies are described in Note 2 of the notes to the Company’s audited financial statements as of December 31, 2014 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on March 2, 2015 (2014 Form 10-K).
	Basis of Presentation
	The accompanying financial information as of March 31, 2015 and for the three months ended March 31, 2015 and 2014 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, 2014 and notes thereto included in the 2014 Form 10-K.
	In the opinion of management, the unaudited financial information as of March 31, 2015 and for the three months ended March 31, 2015 and 2014 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 period ended March 31, 2015 are not necessarily indicative of the results to be expected for the year ended December 31, 2015 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 reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Inventories and cost of product revenue
	On August 4, 2014, the Company was notified that the European Commission, or EC, granted marketing authorization for Translarna for the treatment of Duchenne muscular dystrophy caused by nonsense mutations, or nmDMD, in ambulatory patients aged five years and older. The marketing authorization allows the Company to market Translarna in the European Economic Area, or EEA, which is comprised of the 28 member states of the European Union plus Norway, Iceland and Liechtenstein. This marketing authorization is subject to annual review and renewal by the European Medicines Agency, or EMA following its reassessment of the risk-benefit balance of the authorization and is further conditioned on the Company’s ability to complete its global, confirmatory Phase 3 clinical trial in nm DMD, which it refers to as ACT DMD, and submit the final report, including additional efficacy and safety data from the trial during 2015.  The launch in these countries is on a country by country basis. The Company does do not have sufficient history or experience from which to accurately forecast product sales or demand generation. As such, the Company has not capitalized inventory and will not capitalize inventory until the completion of ACT DMD and satisfaction of the EMA conditions or until the Company can reasonably predict future product sales. The costs incurred related to the manufacturing of Translarna have been recorded as research and development expense in the statements of operations. The Company’s cost of product sales includes royalties and other miscellaneous selling costs, which were not material and therefore included as a component of research and development costs in the current year presentation. The time period over which this inventory is consumed will depend on a number of factors, including the amount of future Translarna sales, and the ability to utilize inventory prior to its expiration date.
	Recently issued accounting standard
	In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers. ASU 2014-09 will eliminate transaction- and industry-specific revenue recognition guidance under current GAAP and replace it with a principle-based approach for determining revenue recognition. ASU 2014-09 will require that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also will require additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2016. Early application is not permitted. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. Presently, the Company is assessing what effect the adoption of ASU 2014-09 will have on its financial statements and accompanying notes.
	In August 2014, the FASB issued ASU 2014-15, “Presentation of Financial Statements—Going Concern—Disclosures of Uncertainties about an entity’s Ability to Continue as a Going Concern.” ASU 2014-15 provides new guidance related to management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern by incorporating and expanding upon certain principles that are currently in U.S. auditing standards and to provide related footnote disclosures. This new guidance is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. The requirements of ASU 2014-15 are not expected to have a significant impact on the Condensed Consolidated Financial Statements.
	Revenue Recognition
	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
	PTC’S net product sales have consisted solely of sales of Translarna for the treatment of nmDMD in territories outside of the U.S. The Company applies the revenue recognition guidance in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition—Products. 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.
	The Company records revenue on sales where Translarna is available either on a commercial basis or through a reimbursed early access program and typically paid for by a government authority or institution. Prior to January 1, 2015, the Company recognized revenue for commercial and reimbursed early access program sales on a cash basis once the product was shipped on behalf of the government authority or institution and payment had been received, if all other revenue recognition criteria were met. Beginning in the first quarter of 2015, the Company is recognizing revenue for Translarna as product is shipped, as the Company has established a pattern of collectability.
	The Company records revenue net of estimated discounts and rebates. Allowances are recorded as a reduction of revenue at the time revenues from product sales are recognized. Allowances for government rebates and discounts are established at the time of delivery. These allowances are adjusted to reflect known changes in factors that 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 the Financial Accounting Standards Board (FASB), guidance on the milestone method of revenue recognition. 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 our 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.

Fair_value_of_financial_instru

Fair value of financial instruments and marketable securities	3 Months Ended
	Mar. 31, 2015
Fair value of financial instruments and marketable securities
Fair value of financial instruments and marketable securities
	3.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 are reflected in the accompanying financial statements at fair value. The carrying amount of grant and collaboration 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 in Note 3 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, 2015 and December 31, 2014:
			March 31, 2015
			Total		Quoted prices		Significant			Significant
					in active		other			unobservable
					markets for		observable			inputs
					identical assets		inputs			(level 3)
					(level 1)		(level 2)
	Marketable securities		$	243,642	$	—	$	243,642		$	—
	Warrant liability		229		—		—			229
			December 31, 2014
			Total		Quoted		Significant			Significant
					prices		other			unobservable
					in active		observable			inputs
					markets for		inputs			(level 3)
					identical		(level 2)
					assets
					(level 1)
	Marketable securities		$	265,493	$	—	$	265,493		$	—
	Warrant Liability		188		—		—			188
	The following is a summary of marketable securities accounted for as available-for-sale securities at March 31, 2015 and December 31, 2014:
			March 31, 2015
			Amortized		Gross Unrealized					Fair
			Cost		Gains		Losses			Value
	Commercial paper		$	19,748	$	26	$	—		$	19,774
	Corporate debt securities		186,810		44		(320		)	186,534
	Government obligations		37,346		21		(33		)	37,334
			$	243,904	$	91	$	(353	)	$	243,642
			December 31, 2014
			Amortized		Gross Unrealized					Fair
			Cost		Gains		Losses			Value
	Corporate debt securities		$	230,379	$	80	$	(428	)	$	230,031
	Government obligations		35,501		7		(46		)	35,462
			$	265,880	$	87	$	(474	)	$	265,493
	At March 31, 2015 and December 31, 2014, 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.
	Marketable securities on the balance sheet at March 31, 2015 and December 31, 2014 mature as follows:
			March 31, 2015
			Less Than		More Than
			12 Months		12 Months
	Commercial paper		$	19,774	$	—
	Corporate debt securities		138,306		48,228
	Government obligations		11,312		26,022
	Total Marketable securities		$	169,392	$	74,250
			December 31, 2014
			Less Than		More Than
			12 Months		12 Months
	Corporate debt securities		$	157,758	$	72,273
	Government obligations		6,003		29,459
	Total Marketable securities		$	163,761	$	101,732
	Level 3 valuation
	The warrant liability is classified in Other long-term liabilities on the Company’s balance sheet. The warrant liability is marked-to-market each reporting period with the change in fair value recorded as a gain or loss within Other income (expense), net on the Company’s statement 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 table presented below is a summary of changes in the fair value of the Company’s Level 3 valuation for warrant liability for the period ended March 31, 2015:
			Level 3 assets
	Beginning balance as of December 31, 2014		$	188
	Change in fair value of warrant liability		41
	Ending balance as of March 31, 2015		$	229
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, 2015 include (i) volatility (68%—70%), (ii) risk free interest rate (0.56%—1.13%), (iii) strike price ($128-$2,520), (iv) fair value of common stock ($60.85), and (v) expected life (2.21—4.48 years). The significant assumptions used in preparing the option pricing model for valuing the Company’s warrants as of December 31, 2014 include (i) volatility (68%-70%), (ii) risk free interest rate (0.89%—1.65%), (iii) strike price ($128—$2,520), (iv) fair value of common stock ($51.77), and (v) expected life (2.50—4.70 years). See Note 6 for a description of the warrants issued in connection with the convertible notes.

Other_comprehensive_income_los

Other comprehensive income (loss) and accumulated other comprehensive items	3 Months Ended
	Mar. 31, 2015
Other comprehensive income (loss) and accumulated other comprehensive items
Other comprehensive income (loss) and accumulated other comprehensive items
	4.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, 2015:
		Unrealized			Foreign			Total
		Gains/(Losses)			Currency			Accumulated
		On			Translation			Other
		Marketable						Comprehensive
		Securities						Items
	Balance at December 31, 2014	$	(387	)	$	(350	)	$	(737	)
	Other comprehensive income/(loss) before reclassifications	125			(124		)	1
	Amounts reclassified from other comprehensive items	—			—			—
	Other comprehensive income/(loss)	125			(124		)	1
	Balance at March 31, 2015	$	(262	)	$	(474	)	$	(736	)

Accounts_payable_and_accrued_e

Accounts payable and accrued expenses	3 Months Ended
	Mar. 31, 2015
Accounts payable and accrued expenses
Accounts payable and accrued expenses
	5.Accounts payable and accrued expenses
	Accounts payable and accrued expenses at March 31, 2015 and December 31, 2014 consist of the following:
		March 31,		December 31,
		2015		2014
	Employee compensation, benefits, and related accruals	$	3,365	$	9,312
	Consulting and contracted research	11,691		9,349
	Professional fees	3,382		3,334
	Accounts payable	3,139		4,128
	Other	1,955		2,998
		$	23,532	$	29,121

Warrants

Warrants	3 Months Ended
	Mar. 31, 2015
Warrants
Warrants
	6.Warrants
	All of the Company’s outstanding warrants were classified as liabilities as of March 31, 2015 and December 31, 2014 because they contained non-standard antidilution provisions.
	The following is a summary of the Company’s outstanding warrants as of March 31, 2015:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019 and 2020
	Common stock	130	$	2,520.00	2019
	The following is a summary of the Company’s outstanding warrants as of December 31, 2014:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019 and 2020
	Common stock	130	$	2,520.00	2019

Net_loss_per_share

Net loss per share	3 Months Ended
	Mar. 31, 2015
Net loss per share
Net loss per share
	7.Net loss per share
	Basic earnings per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding. Diluted earnings per share is computed by dividing net income (loss) by the weighted-average number of common shares plus the effect of 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,
		2015			2014
	Numerator
	Net loss	$	(37,915	)	$	(14,098	)
	Denominator
	Denominator for basic and diluted net loss per share	33,067,752			24,492,487
	Net loss per share:
	Basic and diluted	$	(1.15	)*	$	(0.58	)*
	*In the three months ended March 31, 2015 and 2014, 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,
		2015		2014
	Stock Options	4,627,833		3,133,830
	Unvested restricted stock	364,970		748,456
	Total	4,992,803		3,882,286

Stock_award_plan

Stock award plan	3 Months Ended
	Mar. 31, 2015
Stock award plan
Stock award plan
	8.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 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.
	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) 245,000 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.
	From January 1, 2015 through March 31, 2015, the Company issued a total of 1,456,550 stock options to various employees.  Of those, 93,350 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 our new hires’ employment compensation.
	A summary of stock option activity is as follows:
		Number of		Weighted-			Weighted-	Aggregate
		options		average			average	intrinsic
				exercise			remaining	value
				price			contractual
							term
								(in
								thousands)
	Outstanding at December 31, 2014	3,432,972		$	25
	Granted	1,456,550		$	51.02
	Exercised	(234,830	)	$	12.86
	Forfeited	(26,265	)	$	47.52
	Expired	(594	)	$	388.53
	Outstanding at March 31, 2015	4,627,833		$	33.6		8.9 years	$	140,399
	Vested or Expected to vest at March 31, 2015	4,332,726		$	32.74		8.9 years	$	133,232
	Exercisable at March 31, 2015	1,037,262		$	30.98		8.2 years	$	45,137
	The fair value of grants made in the three months ended March 31, 2015 was contemporaneously estimated on the date of grant using the following assumptions:
		Three months
		ended March
		31, 2015
	Risk-free interest rate	1.54% — 1.77%
	Expected volatility	67%-69%
	Expected term	5.50 - 6.11 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, 2015 was $31.82 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.
	The following table summarizes information on the Company’s restricted stock:
		Restricted Stock
		Number of		Weighted
		Shares		Average
				Grant
				Date Fair
				Value
	January 1, 2015	718,400		$	10.72
	Granted	—		—
	Vested	(350,084	)	$	10.59
	Forfeited	(3,346	)	$	10.82
	Unvested at March 31, 2015	364,970		$	10.85
	The Company recorded share-based compensation expense in the statement of operations as follows:
		Three Months Ended March
		31,
		2015			2014
	Research and development	$	4,667		$	1,944
	Selling, general and administrative	5,081			1,761
	Total	$	9,748		$	3,705
	As of March 31, 2015 there was approximately $70.6 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 2009 Equity and Long Term Incentive Plan, 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 3.0 years.

Commitments_and_contingencies

Commitments and contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and contingencies
Commitments and contingencies
	9. Commitments and contingencies
	Operating leases
	The Company leases office space under a noncancelable operating lease through February 2019. Rent expense was approximately $0.3 million for the three months ended March 31, 2015. The Company also leases certain office equipment under operating leases. Future minimum lease payments as of March 31, 2015 are as follows:
	2015	$	1,016
	2016	946
	2017	923
	2018	1,035
	2019	176
		$	4,096
	Other 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. To the extent that the Company develops and commercializes program intellectual property on a for-profit basis, it may become obligated to pay to Wellcome Trust development and regulatory milestone payments of up to an aggregate of $68.9 million 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 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 we successfully develop and subsequently commercialize or, if the Company outlicenses rights to a collaboration product, a specified percentage of certain payments the Company receives from the 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 its payment to the SMA Foundation of a specified amount.
	The Company has employment agreements with certain employees that require the funding of a specific level of payments, if certain events, such as a change in control or termination without cause, occur.

Collaboration_Revenue

Collaboration Revenue	3 Months Ended
	Mar. 31, 2015
Collaboration Revenue
Collaboration Revenue
	10.Collaboration Revenue
	In January 2014, the Company announced the initiation of a Phase 1 clinical program in its spinal muscular atrophy collaboration with F. Hoffman-La Roche Ltd and Hoffman-La Roche Inc. (Roche) and the Spinal Muscular Atrophy Foundation which triggered a $7.5 million milestone payment from Roche. 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 three months ended March 31, 2014.

Summary_of_significant_account1

Summary of significant accounting policies (Policies)	3 Months Ended
	Mar. 31, 2015
Summary of significant accounting policies
Basis of presentation
	Basis of Presentation
	The accompanying financial information as of March 31, 2015 and for the three months ended March 31, 2015 and 2014 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, 2014 and notes thereto included in the 2014 Form 10-K.
	In the opinion of management, the unaudited financial information as of March 31, 2015 and for the three months ended March 31, 2015 and 2014 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 period ended March 31, 2015 are not necessarily indicative of the results to be expected for the year ended December 31, 2015 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 reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Inventories and cost of product revenue
	Inventories and cost of product revenue
	On August 4, 2014, the Company was notified that the European Commission, or EC, granted marketing authorization for Translarna for the treatment of Duchenne muscular dystrophy caused by nonsense mutations, or nmDMD, in ambulatory patients aged five years and older. The marketing authorization allows the Company to market Translarna in the European Economic Area, or EEA, which is comprised of the 28 member states of the European Union plus Norway, Iceland and Liechtenstein. This marketing authorization is subject to annual review and renewal by the European Medicines Agency, or EMA following its reassessment of the risk-benefit balance of the authorization and is further conditioned on the Company’s ability to complete its global, confirmatory Phase 3 clinical trial in nm DMD, which it refers to as ACT DMD, and submit the final report, including additional efficacy and safety data from the trial during 2015.  The launch in these countries is on a country by country basis. The Company does do not have sufficient history or experience from which to accurately forecast product sales or demand generation. As such, the Company has not capitalized inventory and will not capitalize inventory until the completion of ACT DMD and satisfaction of the EMA conditions or until the Company can reasonably predict future product sales. The costs incurred related to the manufacturing of Translarna have been recorded as research and development expense in the statements of operations. The Company’s cost of product sales includes royalties and other miscellaneous selling costs, which were not material and therefore included as a component of research and development costs in the current year presentation. The time period over which this inventory is consumed will depend on a number of factors, including the amount of future Translarna sales, and the ability to utilize inventory prior to its expiration date.
Recently issued accounting standard
	Recently issued accounting standard
	In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers. ASU 2014-09 will eliminate transaction- and industry-specific revenue recognition guidance under current GAAP and replace it with a principle-based approach for determining revenue recognition. ASU 2014-09 will require that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also will require additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2016. Early application is not permitted. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. Presently, the Company is assessing what effect the adoption of ASU 2014-09 will have on its financial statements and accompanying notes.
	In August 2014, the FASB issued ASU 2014-15, “Presentation of Financial Statements—Going Concern—Disclosures of Uncertainties about an entity’s Ability to Continue as a Going Concern.” ASU 2014-15 provides new guidance related to management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern by incorporating and expanding upon certain principles that are currently in U.S. auditing standards and to provide related footnote disclosures. This new guidance is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. The requirements of ASU 2014-15 are not expected to have a significant impact on the Condensed Consolidated Financial Statements.
Revenue recognition
	Revenue Recognition
	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
	PTC’S net product sales have consisted solely of sales of Translarna for the treatment of nmDMD in territories outside of the U.S. The Company applies the revenue recognition guidance in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Subtopic 605-15, Revenue Recognition—Products. 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.
	The Company records revenue on sales where Translarna is available either on a commercial basis or through a reimbursed early access program and typically paid for by a government authority or institution. Prior to January 1, 2015, the Company recognized revenue for commercial and reimbursed early access program sales on a cash basis once the product was shipped on behalf of the government authority or institution and payment had been received, if all other revenue recognition criteria were met. Beginning in the first quarter of 2015, the Company is recognizing revenue for Translarna as product is shipped, as the Company has established a pattern of collectability.
	The Company records revenue net of estimated discounts and rebates. Allowances are recorded as a reduction of revenue at the time revenues from product sales are recognized. Allowances for government rebates and discounts are established at the time of delivery. These allowances are adjusted to reflect known changes in factors that 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 the Financial Accounting Standards Board (FASB), guidance on the milestone method of revenue recognition. 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 our 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.

Fair_value_of_financial_instru1

Fair value of financial instruments and marketable securities (Tables)	3 Months Ended
	Mar. 31, 2015
Fair value of financial instruments and marketable securities
Schedule of financial assets and liabilities that are required to be measured at fair value on a recurring basis		March 31, 2015
		Total		Quoted prices		Significant			Significant
				in active		other			unobservable
				markets for		observable			inputs
				identical assets		inputs			(level 3)
				(level 1)		(level 2)
	Marketable securities	$	243,642	$	—	$	243,642		$	—
	Warrant liability	229		—		—			229
		December 31, 2014
		Total		Quoted		Significant			Significant
				prices		other			unobservable
				in active		observable			inputs
				markets for		inputs			(level 3)
				identical		(level 2)
				assets
				(level 1)
	Marketable securities	$	265,493	$	—	$	265,493		$	—
	Warrant Liability	188		—		—			188
Summary of marketable securities accounted for as available-for-sale securities		March 31, 2015
		Amortized		Gross Unrealized					Fair
		Cost		Gains		Losses			Value
	Commercial paper	$	19,748	$	26	$	—		$	19,774
	Corporate debt securities	186,810		44		(320		)	186,534
	Government obligations	37,346		21		(33		)	37,334
		$	243,904	$	91	$	(353	)	$	243,642
		December 31, 2014
		Amortized		Gross Unrealized					Fair
		Cost		Gains		Losses			Value
	Corporate debt securities	$	230,379	$	80	$	(428	)	$	230,031
	Government obligations	35,501		7		(46		)	35,462
		$	265,880	$	87	$	(474	)	$	265,493
Schedule of marketable securities on the balance sheet		March 31, 2015
		Less Than		More Than
		12 Months		12 Months
	Commercial paper	$	19,774	$	—
	Corporate debt securities	138,306		48,228
	Government obligations	11,312		26,022
	Total Marketable securities	$	169,392	$	74,250
		December 31, 2014
		Less Than		More Than
		12 Months		12 Months
	Corporate debt securities	$	157,758	$	72,273
	Government obligations	6,003		29,459
	Total Marketable securities	$	163,761	$	101,732
Summary of changes in the fair value of the Company's Level 3 valuation for warrant liability
		Level 3 assets
	Beginning balance as of December 31, 2014	$	188
	Change in fair value of warrant liability	41
	Ending balance as of March 31, 2015	$	229

Other_comprehensive_income_los1

Other comprehensive income (loss) and accumulated other comprehensive items (Tables)	3 Months Ended
	Mar. 31, 2015
Other comprehensive income (loss) and accumulated other comprehensive items
Summary of other comprehensive income (loss) and the changes in accumulated other comprehensive items		Unrealized			Foreign			Total
		Gains/(Losses)			Currency			Accumulated
		On			Translation			Other
		Marketable						Comprehensive
		Securities						Items
	Balance at December 31, 2014	$	(387	)	$	(350	)	$	(737	)
	Other comprehensive income/(loss) before reclassifications	125			(124		)	1
	Amounts reclassified from other comprehensive items	—			—			—
	Other comprehensive income/(loss)	125			(124		)	1
	Balance at March 31, 2015	$	(262	)	$	(474	)	$	(736	)

Accounts_payable_and_accrued_e1

Accounts payable and accrued expenses (Tables)	3 Months Ended
	Mar. 31, 2015
Accounts payable and accrued expenses
Schedule of components of accounts payable and accrued expenses
		March 31,		December 31,
		2015		2014
	Employee compensation, benefits, and related accruals	$	3,365	$	9,312
	Consulting and contracted research	11,691		9,349
	Professional fees	3,382		3,334
	Accounts payable	3,139		4,128
	Other	1,955		2,998
		$	23,532	$	29,121

Warrants_Tables

Warrants (Tables)	3 Months Ended
	Mar. 31, 2015
Warrants
Summary of the Company's outstanding warrants
	The following is a summary of the Company’s outstanding warrants as of March 31, 2015:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019 and 2020
	Common stock	130	$	2,520.00	2019
	The following is a summary of the Company’s outstanding warrants as of December 31, 2014:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019 and 2020
	Common stock	130	$	2,520.00	2019

Net_loss_per_share_Tables

Net loss per share (Tables)	3 Months Ended
	Mar. 31, 2015
Net loss per share
Schedule of computation of basic and diluted net loss per share for common stockholders		Three months ended March
		31,
		2015			2014
	Numerator
	Net loss	$	(37,915	)	$	(14,098	)
	Denominator
	Denominator for basic and diluted net loss per share	33,067,752			24,492,487
	Net loss per share:
	Basic and diluted	$	(1.15	)*	$	(0.58	)*
	*In the three months ended March 31, 2015 and 2014, the Company experienced a net loss and therefore did not report any dilutive share impact.
Schedule of historical dilutive common share equivalents outstanding
		As of March 31,
		2015		2014
	Stock Options	4,627,833		3,133,830
	Unvested restricted stock	364,970		748,456
	Total	4,992,803		3,882,286

Stock_award_plan_Tables

Stock award plan (Tables)	3 Months Ended
	Mar. 31, 2015
Stock award plan
Summary of stock option activity		Number of		Weighted-			Weighted-	Aggregate
		options		average			average	intrinsic
				exercise			remaining	value
				price			contractual
							term
								(in
								thousands)
	Outstanding at December 31, 2014	3,432,972		$	25
	Granted	1,456,550		$	51.02
	Exercised	(234,830	)	$	12.86
	Forfeited	(26,265	)	$	47.52
	Expired	(594	)	$	388.53
	Outstanding at March 31, 2015	4,627,833		$	33.6		8.9 years	$	140,399
	Vested or Expected to vest at March 31, 2015	4,332,726		$	32.74		8.9 years	$	133,232
	Exercisable at March 31, 2015	1,037,262		$	30.98		8.2 years	$	45,137
Schedule of assumptions used to estimate fair value of grants made on the date of grant
		Three months
		ended March
		31, 2015
	Risk-free interest rate	1.54% — 1.77%
	Expected volatility	67%-69%
	Expected term	5.50 - 6.11 years
Summary of information on the Company's restricted stock
		Restricted Stock
		Number of		Weighted
		Shares		Average
				Grant
				Date Fair
				Value
	January 1, 2015	718,400		$	10.72
	Granted	—		—
	Vested	(350,084	)	$	10.59
	Forfeited	(3,346	)	$	10.82
	Unvested at March 31, 2015	364,970		$	10.85
Schedule of share-based compensation expense recorded in the statement of operations
		Three Months Ended March
		31,
		2015			2014
	Research and development	$	4,667		$	1,944
	Selling, general and administrative	5,081			1,761
	Total	$	9,748		$	3,705

Commitments_and_contingencies_

Commitments and contingencies (Tables)	3 Months Ended
	Mar. 31, 2015
Commitments and contingencies
Schedule of future minimum lease payments	2015	$	1,016
	2016	946
	2017	923
	2018	1,035
	2019	176
		$	4,096

The_Company1

The Company (USD $)	0 Months Ended
In Thousands, unless otherwise specified	Aug. 04, 2014	Mar. 31, 2015	Dec. 31, 2014
	state
The Company
Minimum age of ambulatory patient	5 years
Number of member states of the European Union	31
Accumulated deficit		($460,466)	($422,551)

Fair_value_of_financial_instru2

Fair value of financial instruments and marketable securities (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	$243,642	$265,493
Recurring basis | Total
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	243,642	265,493
Warrant liability	229	188
Recurring basis | Significant other observable inputs (level 2)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	243,642	265,493
Recurring basis | Significant unobservable inputs (level 3)
Financial assets and liabilities measured at fair value on recurring basis
Warrant liability	$229	$188

Fair_value_of_financial_instru3

Fair value of financial instruments and marketable securities (Details 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Marketable securities accounted for as available-for-sale securities
Amortized Cost	$243,904	$265,880
Gross Unrealized Gains	91	87
Gross Unrealized Losses	-353	-474
Fair Value	243,642	265,493
Commercial paper
Marketable securities accounted for as available-for-sale securities
Amortized Cost	19,748
Gross Unrealized Gains	26
Fair Value	19,774
Corporate debt securities
Marketable securities accounted for as available-for-sale securities
Amortized Cost	186,810	230,379
Gross Unrealized Gains	44	80
Gross Unrealized Losses	-320	-428
Fair Value	186,534	230,031
Government obligations
Marketable securities accounted for as available-for-sale securities
Amortized Cost	37,346	35,501
Gross Unrealized Gains	21	7
Gross Unrealized Losses	-33	-46
Fair Value	$37,334	$35,462

Fair_value_of_financial_instru4

Fair value of financial instruments and marketable securities (Details 3) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	$169,392	$163,761
Total Marketable securities, More Than 12 Months	74,250	101,732
Commercial paper
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	19,774
Corporate debt securities
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	138,306	157,758
Total Marketable securities, More Than 12 Months	48,228	72,273
Government obligations
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	11,312	6,003
Total Marketable securities, More Than 12 Months	$26,022	$29,459

Fair_value_of_financial_instru5

Fair value of financial instruments and marketable securities (Details 4) (Warrants, USD $)	3 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Changes in the fair value of warrant liability
Beginning balance	$188
Change in fair value of warrant liability	41
Ending balance	$229
Minimum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)	68.00%	68.00%
Risk-free interest rate (as a percent)	0.56%	0.89%
Strike price (in dollars per share)	$128	$128
Expected life	2 years 2 months 16 days	2 years 6 months
Maximum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)	70.00%	70.00%
Risk-free interest rate (as a percent)	1.13%	1.65%
Strike price (in dollars per share)	$2,520	$2,520
Expected life	4 years 5 months 23 days	4 years 8 months 12 days
Common stock
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Fair value of shares (in dollars per share)	$60.85	$51.77

Other_comprehensive_income_los2

Other comprehensive income (loss) and accumulated other comprehensive items (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Other comprehensive income and accumulated other comprehensive items
Balance at the beginning of the period	($737)
Other comprehensive income/(loss) before reclassifications	1
Other comprehensive income/(loss)	1
Balance at the end of the period	-736
Unrealized Gains/(Losses) On Marketable Securities
Other comprehensive income and accumulated other comprehensive items
Balance at the beginning of the period	-387
Other comprehensive income/(loss) before reclassifications	125
Other comprehensive income/(loss)	125
Balance at the end of the period	-262
Foreign Currency Translation
Other comprehensive income and accumulated other comprehensive items
Balance at the beginning of the period	-350
Other comprehensive income/(loss) before reclassifications	-124
Other comprehensive income/(loss)	-124
Balance at the end of the period	($474)

Accounts_payable_and_accrued_e2

Accounts payable and accrued expenses (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Accounts payable and accrued expenses
Employee compensation, benefits, and related accruals	$3,365	$9,312
Consulting and contracted research	11,691	9,349
Professional fees	3,382	3,334
Accounts payable	3,139	4,128
Other	1,955	2,998
Accounts payable and accrued expenses	$23,532	$29,121

Warrants_Details

Warrants (Details) (Warrants, Common stock, USD $)	Mar. 31, 2015	Dec. 31, 2014
2017
Warrants
Warrant shares	6,250	6,250
Exercise price (in dollars per share)	$128	$128
2019 and 2020
Warrants
Warrant shares	7,030	7,030
Exercise price (in dollars per share)	$128	$128
2019
Warrants
Warrant shares	130	130
Exercise price (in dollars per share)	$2,520	$2,520

Net_loss_per_share_Details

Net loss per share (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Numerator
Net loss	($37,915)	($14,098)
Denominator
Denominator for basic and diluted net loss per share (in shares)	33,067,752	24,492,487
Net loss per share:
Basic and diluted (in dollars per share)	($1.15)	($0.58)

Net_loss_per_share_Details_2

Net loss per share (Details 2)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Net loss per share
Total shares excluded from calculation	4,992,803	3,882,286
Stock options
Net loss per share
Total shares excluded from calculation	4,627,833	3,133,830
Restricted stock
Net loss per share
Total shares excluded from calculation	364,970	748,456

Stock_award_plan_Details

Stock award plan (Details) (USD $)	3 Months Ended	1 Months Ended	0 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	31-May-13	Mar. 05, 2013
Stock option
Number of options
Outstanding at the beginning of the period (in shares)	3,432,972
Granted (in shares)	1,456,550
Exercised (in shares)	-234,830
Forfeited (in shares)	-26,265
Expired (in shares)	-594
Outstanding at the end of the period (in shares)	4,627,833
Vested or expected to vest at the end of the period (in shares)	4,332,726
Exercisable at the end of the period (in shares)	1,037,262
Weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share)	$25
Granted (in dollars per share)	$51.02
Exercised (in dollars per share)	$12.86
Forfeited (in dollars per share)	$47.52
Expired (in dollars per share)	$389
Outstanding at the end of the period (in dollars per share)	$33.60
Vested or expected to vest at the end of the period (in dollars per share)	$32.74
Exercisable at the end of the period (in dollars per share)	$30.98
Weighted-average remaining contractual term
Outstanding at the beginning of the period	8 years 10 months 24 days
Vested or expected to vest at the end of the period	8 years 10 months 24 days
Exercisable at the end of the period	8 years 2 months 12 days
Valuation assumptions
Inducement grants for non-statutory stock options	93,350
Weighted average grant date fair value (in dollars per share)	$31.82
Aggregate intrinsic value
Outstanding at the end of the period (in dollars)	$140,399
Vested or expected to vest at the end of the period (in dollars)	133,232
Exercisable at the end of the period (in dollars)	$45,137
Stock option | Minimum
Valuation assumptions
Risk-free interest rate (as a percent)	1.54%
Expected volatility (as a percent)	67.00%
Expected term	5 years 6 months
Stock option | Maximum
Valuation assumptions
Risk-free interest rate (as a percent)	1.77%
Expected volatility (as a percent)	69.00%
Expected term	6 years 1 month 10 days
2009 Equity and Long Term Incentive Plan
Stock option plan
Number of additional shares authorized		2,500,000
2013 Stock Incentive Plan
Stock option plan
Number of shares available for issuance			0
2013 Stock Incentive Plan | Stock option
Stock option plan
Number of shares of restricted stock granted			4,613
2013 Stock Incentive Plan | Restricted stock
Stock option plan
Number of shares of restricted stock granted			735,324
2013 Stock Incentive Plan | Common stock
Stock option plan
Number of shares authorized			739,937
2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan | Common stock
Stock option plan
Number of shares available for issuance		245,000
2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan | Common stock | Maximum
Stock option plan
Number of shares subject to outstanding awards		3,040,444
2013 Long Term Incentive Plan | Minimum
Stock option plan
Annual increase in the number of 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 (as a percent)		4.00%

Stock_award_plan_Details_2

Stock award plan - (Details 2) (Restricted stock, USD $)	3 Months Ended
	Mar. 31, 2015
Restricted stock
Number of Shares
Balance at the beginning of the period (in shares)	718,400
Vested (in shares)	-350,084
Forfeited (in shares)	-3,346
Balance at the end of the period (in shares)	364,970
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share)	$10.72
Vested	$10.59
Forfeited (in dollars per share)	$10.82
Balance at the end of the period (in dollars per share)	$10.85

Stock_award_plan_Details_3

Stock award plan (Details 3) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	$9,748,000	$3,705,000
Unrecognized compensation cost	70,600,000
Weighted average remaining service period for recognition of unrecognized compensation cost	3 years
Research and development
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	4,667,000	1,944,000
Selling, general and administrative
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	$5,081,000	$1,761,000

Commitments_and_contingencies_1

Commitments and contingencies (Details) (USD $)	3 Months Ended
	Mar. 31, 2015
Commitments and contingencies
Operating Leases, Rent Expense, Net	$300,000
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity
2015	1,016,000
2016	946,000
2017	923,000
2018	1,035,000
2019	176,000
Total future minimum lease payments	4,096,000
Funding agreement | Wellcome trust | Maximum
Other contingencies
Development and regulatory milestone payments which the entity may be obligated to pay	$68,900,000

Collaboration_Revenue_Details

Collaboration Revenue (Details) (Collaboration agreement, Roche and SMA Foundation, Clinical development milestones, USD $)	0 Months Ended
In Millions, unless otherwise specified	Jan. 22, 2014
Collaboration agreement | Roche and SMA Foundation | Clinical development milestones
Collaboration Revenue
Milestone payment received from Roche	$7.50