PTC Therapeutics (PTCT) 10-Q 6 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Nov. 05, 2014
Document and Entity Information	'	'
Entity Registrant Name	'PTC THERAPEUTICS, INC.	'
Entity Central Index Key	'0001070081	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-14	'
Amendment Flag	'false	'
Current Fiscal Year End Date	'--12-31	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	33,602,541
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'

Balance_sheets

Balance sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$52,873	$15,414
Marketable securities	156,516	127,053
Prepaid expenses and other current assets	2,831	1,599
Receivables, net	1,296	958
Total current assets	213,516	145,024
Fixed assets, net	6,193	6,730
Deposits and other assets	1,086	149
Total assets	220,795	151,903
Current liabilities:	'	'
Accounts payable and accrued expenses	16,493	12,207
Current portion of long-term debt	'	49
Deferred revenue	769	878
Total current liabilities	17,262	13,134
Other long-term liabilities	2,237	2,227
Total liabilities	19,499	15,361
Stockholders' equity:	'	'
Preferred stock, $0.001 par value. Undesignated 5,000,000 shares; issued and outstanding 0 shares at September 30, 2014 and December 31, 2013	'	'
Common stock, $0.001 par value. Authorized 125,000,000 shares; issued and outstanding 29,373,327 shares at September 30, 2014. Authorized 125,000,000 shares; issued and outstanding 23,803,282 shares at December 31, 2013	30	24
Additional paid-in capital	596,617	465,246
Accumulated other comprehensive (loss) income	-69	70
Accumulated deficit	-395,282	-328,798
Total stockholders' equity	201,296	136,542
Total liabilities and stockholders' equity	$220,795	$151,903

Balance_sheets_Parenthetical

Balance sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Balance sheets	'	'
Preferred stock, par value (in dollars per share)	$0.00	$0.00
Preferred stock, undesignated shares	5,000,000	5,000,000
Preferred stock, issued shares	0	0
Preferred stock, outstanding shares	0	0
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	29,373,327	23,803,282
Common stock, outstanding shares	29,373,327	23,803,282

Statements_of_operations

Statements of operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues:	'	'	'	'
Net product sales	$81	'	$81	'
Collaboration revenue	716	15,455	11,280	27,395
Grant revenue	897	834	1,226	2,890
Total revenues	1,694	16,289	12,587	30,285
Operating expenses:	'	'	'	'
Research and development	18,765	13,886	52,967	39,855
General and administrative	10,530	6,679	26,803	17,735
Total operating expenses	29,295	20,565	79,770	57,590
Loss from operations	-27,601	-4,276	-67,183	-27,305
Interest income (expense), net	354	27	774	-6,250
Loss on extinguishment of debt	'	-130	'	-130
Other income (expense), net	-35	-37	-75	-3
Net loss	-27,282	-4,416	-66,484	-33,688
Deemed dividend	'	'	'	-18,249
Gain on exchange of convertible preferred stock in connection with recapitalization	'	'	'	3,391
Net loss attributable to common stockholders	($27,282)	($4,416)	($66,484)	($48,546)
Weighted-average shares outstanding:	'	'	'	'
Basic and diluted (in shares)	29,351,693	23,803,282	28,441,827	8,995,167
Net loss per share applicable to common stockholders-basic and diluted (in dollars per share)	($0.93)	($0.19)	($2.34)	($5.40)

Statements_of_comprehensive_lo

Statements of comprehensive loss (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statements of comprehensive loss	'	'	'	'
Net loss	($27,282)	($4,416)	($66,484)	($33,688)
Other comprehensive loss:	'	'	'	'
Unrealized loss on marketable securities	-159	-40	-139	-40
Comprehensive loss	($27,441)	($4,456)	($66,623)	($33,728)

Statements_of_cash_flows

Statements of cash flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities	'	'
Net loss	($66,484)	($33,688)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'
Depreciation	1,693	1,811
Change in valuation of warrant liability	78	3
Non-cash interest expense	'	6,049
Loss on extinguishment of debt	'	130
Amortization of premiums on investments	1,225	'
Share-based compensation expense	12,605	5,142
Changes in operating assets and liabilities:	'	'
Prepaid expenses and other current assets	-1,232	-1,288
Grant and collaboration receivables	-338	230
Deposits and other assets	-937	34
Accounts payable and accrued expenses	4,286	3,181
Other long-term liabilities	-68	-262
Deferred revenue	-109	-13,801
Net cash used in operating activities	-49,281	-32,459
Cash flows from investing activities	'	'
Purchases of fixed assets	-1,156	-474
Purchases of marketable securities	-132,602	-139,731
Sale & redemption of marketable securities	101,775	6,508
Net cash used in investing activities	-31,983	-133,697
Cash flows from financing activities	'	'
Payments on long-term debt	-49	-4,960
Net proceeds from sale of Series Four convertible preferred stock	'	60,785
Proceeds from exercise of options	389	'
Net proceeds from public offerings	118,383	131,650
Net cash provided by financing activities	118,723	187,475
Net increase in cash and cash equivalents	37,459	21,319
Cash and cash equivalents, beginning of period	15,414	2,726
Cash and cash equivalents, end of period	52,873	24,045
Supplemental disclosure of cash information	'	'
Cash paid for interest	1	366
Supplemental disclosures of non-cash information related to investing and financing activities	'	'
Change in unrealized gain (loss) on marketable securities	-139	-40
Change in carry value of preferred securities resulting from recapitalization	'	$3,391

The_Company

The Company	9 Months Ended
	Sep. 30, 2014
The Company	'
The Company	'
	1.The Company
	PTC Therapeutics, Inc. (the Company or PTC) was incorporated as a Delaware corporation on March 31, 1998. During the second quarter of 2014, a wholly-owned subsidiary was established in Bermuda to hold certain intellectual property rights of the Company.  In addition, wholly-owned subsidiaries in Ireland, Denmark, Italy, Germany, Switzerland and France were established during 2014.  PTC is a biopharmaceutical company focused on the discovery and development of orally administered, proprietary small molecule drugs that target post-transcriptional control processes. The Company’s internally discovered pipeline addresses multiple therapeutic areas, including rare disorders, oncology and infectious diseases. PTC has developed proprietary technologies that PTC applies in our drug discovery activities and in collaborations with leading biopharmaceutical companies.
	The Company’s lead candidate is ataluren, an investigational new drug in the US, for the treatment of patients with genetic disorders that arise from a type of genetic mutation known as a nonsense mutation. The brand name of ataluren is Translarna™. On August 4, 2014, the Company was notified that the European Commission, or EC, granted conditional 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 conditional 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. The conditional marketing authorization is subject to an annual review by the EMA and the Company will seek to renew the approval on an annual basis until its obligations have been fulfilled and the approval is converted from a conditional approval into a full approval.
	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 September 30, 2014, the Company had an accumulated deficit of approximately $395.3 million. The Company has financed its operations to date primarily through public offerings of common stock in February 2014 and October 2014 (see Notes 6 and 10 below), its initial public offering of common stock in June 2013 (see Note 6 below), 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	9 Months Ended
	Sep. 30, 2014
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, 2013 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on March 6, 2014 (2013 Form 10-K). There have been no changes to our accounting policies during the quarter.
	Basis of Presentation
	The accompanying financial information as of September 30, 2014 and for the three and nine months ended September 30, 2014 and 2013 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, 2013 and notes thereto included in the 2013 Form 10-K.
	In the opinion of management, the unaudited financial information as of September 30, 2014 and for the three and nine months ended September 30, 2014 and 2013 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 and nine month periods ended September 30, 2014 are not necessarily indicative of the results to be expected for the year ended December 31, 2014 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.
	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
	To date, PTC’s net product sales have consisted solely of sales of Translarna for the treatment of DMD caused by nonsense mutations. 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 has recorded revenue on sales where Translarna is available on a reimbursed early access program and typically paid for by a government authority or institution. The Company generally recognizes revenue for these named patient or cohort early access programs once the product is shipped through to the government authority or institution on a cash basis if all other revenue recognition criteria have been met.
	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 based on the actual payer information, which is known at the time of delivery, and the government-mandated discounts applicable to government-funded programs. These allowances are adjusted to reflect known changes in the factors that may impact such allowances in the quarter those changes are known.

Fair_value_of_financial_instru

Fair value of financial instruments and marketable securities	9 Months Ended
	Sep. 30, 2014
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 September 30, 2014 and December 31, 2013:
		September 30, 2014
		Total		Quoted prices		Significant			Significant
				in active		other			unobservable
				markets for		observable			inputs
				identical assets		inputs			(level 3)
				(level 1)		(level 2)
	Marketable securities	$	156,516	$	—	$	156,516		$	—
	Warrant liability	136		—		—			136
		December 31, 2013
		Total		Quoted prices		Significant			Significant
				in active		other			unobservable
				markets for		observable			inputs
				identical assets		inputs			(level 3)
				(level 1)		(level 2)
	Marketable securities	$	127,053	$	—	$	127,053		$	—
	Warrant Liability	58		—		—			58
	The following is a summary of marketable securities accounted for as available-for-sale securities at September 30, 2014 and December 31, 2013:
		September 30, 2014
		Amortized		Gross Unrealized					Fair
		Cost		Gains		Losses			Value
	Corporate debt securities	$	122,561	$	112	$	(156	)	$	122,517
	Government obligations	34,024		8		(33		)	33,999
		$	156,585	$	120	$	(189	)	$	156,516
		December 31, 2013
		Amortized		Gross Unrealized					Fair
		Cost		Gains		Losses			Value
	Commercial paper	$	14,993	$	5	$	—		$	14,998
	Corporate debt securities	111,989		97		(31		)	112,055
		$	126,982	$	102	$	(31	)	$	127,053
	At September 30, 2014 and December 31, 2013, 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 September 30, 2014 and December 31, 2013 mature as follows:
		September 30, 2014
		Less Than		More Than
		12 Months		12 Months
	Corporate debt securities	$	65,860	$	56,657
	Government obligations	—		33,999
	Total Marketable securities	$	65,860	$	90,656
		December 31, 2013
		Less Than		More Than
		12 Months		12 Months
	Commercial paper	$	14,998	$	—
	Corporate debt securities	54,159		57,896
	Total Marketable securities	$	69,157	$	57,896
	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 September 30, 2014:
		Level 3 assets
	Beginning balance as of December 31, 2013	$	58
	Change in fair value of warrant liability	78
	Ending balance as of September 30, 2014	$	136
	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 September 30, 2014 include (i) volatility (64%—72%), (ii) risk free interest rate (0.83%—1.78%), (iii) strike price ($128.00-$2,520), (iv) fair value of common stock ($44.01), and (v) expected life (2.71—4.98 years). The significant assumptions used in preparing the option pricing model for valuing the Company’s warrants as of December 31, 2013 include (i) volatility (61-89%), (ii) risk free interest rate (0.07%—2.10%), (iii) strike price ($128.00—$2,520.00), (iv) fair value of common stock ($16.97), and (v) expected life (0.30—5.70 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	9 Months Ended
	Sep. 30, 2014
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 and nine months ended September 30, 2014:
		Unrealized Gains/			Total
		(Losses)			Accumulated
		On Marketable			Other
		Securities			Comprehensive
					Items
	Balance at June 30, 2014	$	90		$	90
	Other comprehensive income/(loss) before reclassifications	(159		)	(159		)
	Amounts reclassified from other comprehensive items	—			—
	Other comprehensive income/(loss)	(159		)	(159		)
	Balance at September 30, 2014	$	(69	)	$	(69	)
		Unrealized Gains/			Total
		(Losses)			Accumulated
		On Marketable			Other
		Securities			Comprehensive
					Items
	Balance at December 31, 2013	$	70		$	70
	Other comprehensive income/(loss) before reclassifications	(139		)	(139		)
	Amounts reclassified from other comprehensive items	—			—
	Other comprehensive income/(loss)	(139		)	(139		)
	Balance at September 30, 2014	$	(69	)	$	(69	)

Accounts_payable_and_accrued_e

Accounts payable and accrued expenses	9 Months Ended
	Sep. 30, 2014
Accounts payable and accrued expenses	'
Accounts payable and accrued expenses	'
	5.Accounts payable and accrued expenses
	Accounts payable and accrued expenses at September 30, 2014 and December 31, 2013 consist of the following:
		September 30,		December 31,
		2014		2013
	Employee compensation, benefits, and related accruals	$	5,729	$	5,103
	Consulting and contracted research	5,709		4,006
	Professional fees	3,592		1,294
	Accounts payable	518		1,124
	Other	945		680
		$	16,493	$	12,207

Capital_structure

Capital structure	9 Months Ended
	Sep. 30, 2014
Capital structure	'
Capital structure	'
	6.Capital structure
	2013 Recapitalization
	During January and February of 2013, the Company entered into a “bridge” financing arrangement with certain existing investors providing for the issuance by the Company of an aggregate of $6 million of convertible promissory notes and warrants to purchase 2,527,675 shares of Series One convertible preferred stock (Series One) and Series Two convertible preferred stock (Series Two). The warrants have a per share exercise price of $0.01, and as such, they are referred to as “penny warrants”. This bridge financing was closed in anticipation of the March 2013 Series Four financing event, which the Company refers to as the “2013 recapitalization”.
	The Company allocated the proceeds of the convertible promissory notes between debt and warrant liability. Since the value of the warrants exceeded the proceeds from the convertible notes issued to existing investors, the value of the warrant in excess of the proceeds is considered a deemed dividend and reflected as an equity transaction in the financial statements. The Company recorded $6.0 million to interest expense related to the debt discount associated with the convertible debt during the quarter ended March 31, 2013.
	On March 7, 2013, the Company closed a private placement of a new series of convertible preferred stock that resulted in the 2013 recapitalization. In this private placement, the Company issued and sold an aggregate of 4,497,035 shares of its Series Four senior preferred stock (Series Four) for an aggregate purchase price of approximately $54.0 million. Including the $6.0 million raised with the bridge financing, total gross proceeds raised during the quarter ended March 31, 2013 was approximately $60.0 million. In addition, the Company issued an aggregate of 502,919 shares of Series Four upon the share settlement of the convertible promissory notes described above that were issued in January and February 2013.
	In connection with this private placement, the Company effected a one-for-120 reverse stock split of its common stock and an exchange of outstanding shares of Series One, Series Two and Series Three convertible preferred stock (Series Three) into an aggregate of 6,700,487 shares of a new series of Series Five junior preferred stock (Series Five). In addition, the Company issued an aggregate of 2,527,675 shares of Series One and Series Two upon the exercise of the warrants issued in connection with the bridge loan that were immediately exchanged for 2,095,515 shares of Series Five during the 2013 recapitalization.
	The Company accounted for the 2013 recapitalization as an extinguishment of its Series One, Series Two and Series Three convertible preferred stock and recorded the Series Five shares at their fair value as of the recapitalization date. In accordance with authoritative accounting guidance, the Company recorded a gain attributable to the common stockholders on the extinguishment of the Series One, Series Two and Series Three. The gain of approximately $3.4 million represents the excess of the Series One, Series Two and Series Three over the fair value of the shares Series Five issued in connection with the recapitalization.
	Initial Public Offering
	In June 2013, the Company closed the initial public offering of its common stock pursuant to a registration statement on Form S-1, as amended. The Company issued and sold an aggregate of 9,627,800 shares of common stock under the registration statement at a public offering price of $15.00 per share, including 1,255,800 shares pursuant to the exercise by the underwriters of an over-allotment option. The Company received net proceeds from the initial public offering of approximately $131.6 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company.
	Upon closing the initial public offering, all outstanding shares of the Series Four and Series Five were converted into 14,170,956 shares of common stock.
	Follow-On Offering
	In February 2014, the Company closed a follow-on public offering of its common stock pursuant to a registration statement on Form S-1, as amended. The Company issued and sold an aggregate of 5,163,265 shares of common stock under the registration statement at a public offering price of $24.50 per share, including 673,469 shares pursuant to the exercise by the underwriters of an over-allotment option. The Company received net proceeds from the follow –on public offering of approximately $118.4 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company.
	Warrants
	All of the Company’s outstanding warrants were classified as liabilities as of September 30, 2014 and December 31, 2013 because they contained non-standard antidilution provisions.
	The following is a summary of the Company’s outstanding warrants as of September 30, 2014:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019-2020
	Common stock	130	$	2,520.00	2019
	The following is a summary of the Company’s outstanding warrants as of December 31, 2013:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	1,428	$	128.00	2014
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019 and 2020
	Common stock	452	$	2,520.00	2014
	In connection with the 2013 recapitalization, all of the Series Two outstanding warrants became warrants to purchase Series Five. In connection with the Company’s initial public offering all of the Series Five outstanding warrants became warrants to purchase common stock.

Net_loss_per_share

Net loss per share	9 Months Ended
	Sep. 30, 2014
Net loss per share	'
Net loss per share	'
	7.Net loss per share
	Basic earnings per share is computed by dividing net loss available to common stockholders by the weighted-average number of common shares outstanding. Diluted earnings per share is computed by dividing net income (loss) available to common stockholders 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 income (loss) per share for common stockholders:
			Three months ended September 30,
			2014			2013
	Numerator
	Net loss attributable to common stockholders		$	(27,282	)	$	(4,416	)
	Denominator
	Denominator for basic and diluted net loss per share		29,351,693			23,803,282
	Net loss per share:
	Basic and diluted		$	(0.93	)*	$	(0.19	)*
		·		In the three months ended September 30, 2014 and 2013, the Company experienced a net loss and therefore did not report any dilutive share impact.
			Nine months ended September 30,
			2014			2013
	Numerator
	Net loss		$	(66,484	)	$	(33,688	)
	Deemed dividend		—			(18,249		)
	Gain on exchange of convertible preferred stock in connection with recapitalization		—			3,391
	Net loss attributable to common stockholders		$	(66,484	)	$	(48,546	)
	Denominator
	Denominator for basic and diluted net loss per share		28,441,827			8,995,167
	Net loss per share:
	Basic and diluted		$	(2.34	)*	$	(5.40	)*
	*In the nine months ended September 30, 2014 and 2013, 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 September 30,
			2014		2013
	Stock Options		3,443,778		1,987,860
	Unvested restricted stock		729,320		1,113,807
	Total		4,173,098		3,101,667

Stock_option_plan

Stock option plan	9 Months Ended
	Sep. 30, 2014
Stock option plan	'
Stock option 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 Stock 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) 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 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, 2014 through September 30, 2014, the Company issued a total of 1,469,496 stock options to various employees.  Of those, 448,800 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, 2013	2,095,592		$	20.24
	Granted	1,469,496		$	29.57
	Exercised	(35,500	)	$	10.96
	Forfeited	(85,775	)	$	11.78
	Expired	(35	)	$	646.66
	Outstanding at September 30, 2014	3,443,778		$	24.52		8.9 yrs		$	84,456
	Vested or Expected to vest at September 30, 2014	3,217,812		$	23.01		9.0 yrs		$	79,675
	Exercisable at September 30, 2014	722,835		$	36.23		8.3 yrs		$	22,463
	The fair value of grants made in the period ended September 30, 2014 was contemporaneously estimated on the date of grant using the following assumptions:
		Nine months ended
		September 30, 2014
	Risk-free interest rate	0.11%—2.04%
	Expected volatility	79%—91%
	Expected term	5.5 years—6.25 years
	The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the nine month period ended September 30, 2014 was $21.70 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, 2014	1,110,226		$	10.68
	Granted	—		—
	Vested	(371,280	)	$	10.6
	Forfeited	(9,626	)	$	10.66
	Unvested at September 30, 2014	729,320		$	10.72
	The Company recorded share-based compensation expense in the statement of operations as follows:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2014			2013			2014			2013
	Research and development	$	2,363		$	677		$	6,517		$	1,378
	General and administrative	2,258			1,963			6,088			3,764
	Total	$	4,621		$	2,640		$	12,605		$	5,142
	As of September 30, 2014 there was approximately $38.7 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 1998, 2009 and 2013 Plans and the inducement grants pursuant to the NASDAQ inducement grant exception. This cost is expected to be recognized as share-based compensation expense over the weighted average remaining service period of approximately 2.70 years.

Collaboration_Revenue

Collaboration Revenue	9 Months Ended
	Sep. 30, 2014
Collaboration Revenue	'
Collaboration Revenue	'
	9.Collaboration Revenue
	On January 22, 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.

Subsequent_events

Subsequent events	9 Months Ended
	Sep. 30, 2014
Subsequent events	'
Subsequent events	'
	10.Subsequent events
	On October 16, 2014, 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 3,450,000 shares of common stock under the registration statement at a public offering price of $36.25 per share, including 450,000 shares issued upon exercise by the underwriters of their option to purchase additional shares.  The Company received net proceeds of approximately $117.5 million after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

Summary_of_significant_account1

Summary of significant accounting policies (Policies)	9 Months Ended
	Sep. 30, 2014
Summary of significant accounting policies	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying financial information as of September 30, 2014 and for the three and nine months ended September 30, 2014 and 2013 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, 2013 and notes thereto included in the 2013 Form 10-K.
	In the opinion of management, the unaudited financial information as of September 30, 2014 and for the three and nine months ended September 30, 2014 and 2013 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 and nine month periods ended September 30, 2014 are not necessarily indicative of the results to be expected for the year ended December 31, 2014 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.
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
	To date, PTC’s net product sales have consisted solely of sales of Translarna for the treatment of DMD caused by nonsense mutations. 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 has recorded revenue on sales where Translarna is available on a reimbursed early access program and typically paid for by a government authority or institution. The Company generally recognizes revenue for these named patient or cohort early access programs once the product is shipped through to the government authority or institution on a cash basis if all other revenue recognition criteria have been met.
	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 based on the actual payer information, which is known at the time of delivery, and the government-mandated discounts applicable to government-funded programs. These allowances are adjusted to reflect known changes in the factors that may impact such allowances in the quarter those changes are known.

Fair_value_of_financial_instru1

Fair value of financial instruments and marketable securities (Tables)	9 Months Ended
	Sep. 30, 2014
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	'
		September 30, 2014
		Total		Quoted prices		Significant			Significant
				in active		other			unobservable
				markets for		observable			inputs
				identical assets		inputs			(level 3)
				(level 1)		(level 2)
	Marketable securities	$	156,516	$	—	$	156,516		$	—
	Warrant liability	136		—		—			136
		December 31, 2013
		Total		Quoted prices		Significant			Significant
				in active		other			unobservable
				markets for		observable			inputs
				identical assets		inputs			(level 3)
				(level 1)		(level 2)
	Marketable securities	$	127,053	$	—	$	127,053		$	—
	Warrant Liability	58		—		—			58
Summary of marketable securities accounted for as available-for-sale securities	'
		September 30, 2014
		Amortized		Gross Unrealized					Fair
		Cost		Gains		Losses			Value
	Corporate debt securities	$	122,561	$	112	$	(156	)	$	122,517
	Government obligations	34,024		8		(33		)	33,999
		$	156,585	$	120	$	(189	)	$	156,516
		December 31, 2013
		Amortized		Gross Unrealized					Fair
		Cost		Gains		Losses			Value
	Commercial paper	$	14,993	$	5	$	—		$	14,998
	Corporate debt securities	111,989		97		(31		)	112,055
		$	126,982	$	102	$	(31	)	$	127,053
Schedule of marketable securities on the balance sheet	'
		September 30, 2014
		Less Than		More Than
		12 Months		12 Months
	Corporate debt securities	$	65,860	$	56,657
	Government obligations	—		33,999
	Total Marketable securities	$	65,860	$	90,656
		December 31, 2013
		Less Than		More Than
		12 Months		12 Months
	Commercial paper	$	14,998	$	—
	Corporate debt securities	54,159		57,896
	Total Marketable securities	$	69,157	$	57,896
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, 2013	$	58
	Change in fair value of warrant liability	78
	Ending balance as of September 30, 2014	$	136

Other_comprehensive_income_los1

Other comprehensive income (loss) and accumulated other comprehensive items (Tables)	9 Months Ended
	Sep. 30, 2014
Other comprehensive income (loss) and accumulated other comprehensive items	'
Summary of other comprehensive income (loss) and the changes in accumulated other comprehensive items	'
		Unrealized Gains/			Total
		(Losses)			Accumulated
		On Marketable			Other
		Securities			Comprehensive
					Items
	Balance at June 30, 2014	$	90		$	90
	Other comprehensive income/(loss) before reclassifications	(159		)	(159		)
	Amounts reclassified from other comprehensive items	—			—
	Other comprehensive income/(loss)	(159		)	(159		)
	Balance at September 30, 2014	$	(69	)	$	(69	)
		Unrealized Gains/			Total
		(Losses)			Accumulated
		On Marketable			Other
		Securities			Comprehensive
					Items
	Balance at December 31, 2013	$	70		$	70
	Other comprehensive income/(loss) before reclassifications	(139		)	(139		)
	Amounts reclassified from other comprehensive items	—			—
	Other comprehensive income/(loss)	(139		)	(139		)
	Balance at September 30, 2014	$	(69	)	$	(69	)

Accounts_payable_and_accrued_e1

Accounts payable and accrued expenses (Tables)	9 Months Ended
	Sep. 30, 2014
Accounts payable and accrued expenses	'
Schedule of components of accounts payable and accrued expenses	'
		September 30,		December 31,
		2014		2013
	Employee compensation, benefits, and related accruals	$	5,729	$	5,103
	Consulting and contracted research	5,709		4,006
	Professional fees	3,592		1,294
	Accounts payable	518		1,124
	Other	945		680
		$	16,493	$	12,207

Capital_structure_Tables

Capital structure (Tables)	9 Months Ended
	Sep. 30, 2014
Capital structure	'
Summary of the Company's outstanding warrants	'
	The following is a summary of the Company’s outstanding warrants as of September 30, 2014:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019-2020
	Common stock	130	$	2,520.00	2019
	The following is a summary of the Company’s outstanding warrants as of December 31, 2013:
		Warrant	Exercise		Expiration
		shares	price
	Common stock	1,428	$	128.00	2014
	Common stock	6,250	$	128.00	2017
	Common stock	7,030	$	128.00	2019 and 2020
	Common stock	452	$	2,520.00	2014

Net_loss_per_share_Tables

Net loss per share (Tables)	9 Months Ended
	Sep. 30, 2014
Net loss per share	'
Schedule of computation of basic and diluted net loss per share for common stockholders	'
			Three months ended September 30,
			2014			2013
	Numerator
	Net loss attributable to common stockholders		$	(27,282	)	$	(4,416	)
	Denominator
	Denominator for basic and diluted net loss per share		29,351,693			23,803,282
	Net loss per share:
	Basic and diluted		$	(0.93	)*	$	(0.19	)*
		·		In the three months ended September 30, 2014 and 2013, the Company experienced a net loss and therefore did not report any dilutive share impact.
			Nine months ended September 30,
			2014			2013
	Numerator
	Net loss		$	(66,484	)	$	(33,688	)
	Deemed dividend		—			(18,249		)
	Gain on exchange of convertible preferred stock in connection with recapitalization		—			3,391
	Net loss attributable to common stockholders		$	(66,484	)	$	(48,546	)
	Denominator
	Denominator for basic and diluted net loss per share		28,441,827			8,995,167
	Net loss per share:
	Basic and diluted		$	(2.34	)*	$	(5.40	)*
	*In the nine months ended September 30, 2014 and 2013, 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 September 30,
			2014		2013
	Stock Options		3,443,778		1,987,860
	Unvested restricted stock		729,320		1,113,807
	Total		4,173,098		3,101,667

Stock_option_plan_Tables

Stock option plan (Tables)	9 Months Ended
	Sep. 30, 2014
Stock option 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, 2013	2,095,592		$	20.24
	Granted	1,469,496		$	29.57
	Exercised	(35,500	)	$	10.96
	Forfeited	(85,775	)	$	11.78
	Expired	(35	)	$	646.66
	Outstanding at September 30, 2014	3,443,778		$	24.52		8.9 yrs		$	84,456
	Vested or Expected to vest at September 30, 2014	3,217,812		$	23.01		9.0 yrs		$	79,675
	Exercisable at September 30, 2014	722,835		$	36.23		8.3 yrs		$	22,463
Schedule of assumptions used to estimate fair value of grants made on the date of grant	'
		Nine months ended
		September 30, 2014
	Risk-free interest rate	0.11%—2.04%
	Expected volatility	79%—91%
	Expected term	5.5 years—6.25 years
Summary of information on the Company's restricted stock	'
		Restricted Stock
		Number of		Weighted
		Shares		Average Grant
				Date Fair Value
	January 1, 2014	1,110,226		$	10.68
	Granted	—		—
	Vested	(371,280	)	$	10.6
	Forfeited	(9,626	)	$	10.66
	Unvested at September 30, 2014	729,320		$	10.72
Schedule of share-based compensation expense recorded in the statement of operations	'
		Three Months Ended September 30,						Nine Months Ended September 30,
		2014			2013			2014			2013
	Research and development	$	2,363		$	677		$	6,517		$	1,378
	General and administrative	2,258			1,963			6,088			3,764
	Total	$	4,621		$	2,640		$	12,605		$	5,142

The_Company_Details1

The Company (Details1) (USD $)	0 Months Ended
In Thousands, unless otherwise specified	Aug. 04, 2014	Sep. 30, 2014	Dec. 31, 2013
	state
The Company	'	'	'
Accumulated deficit	'	$395,282	$328,798
Minimum age of ambulatory patient	'5 years	'	'
Number of member states of the European Union	28	'	'

Summary_of_significant_account2

Summary of significant accounting policies (Details) (Common stock)	0 Months Ended
	Mar. 07, 2013
Common stock	'
Reverse stock split	'
Reverse stock split ratio	0.0083

Fair_value_of_financial_instru2

Fair value of financial instruments and marketable securities (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financial assets and liabilities measured at fair value on recurring basis	'	'
Marketable securities	$156,516	$127,053
Recurring basis | Total	'	'
Financial assets and liabilities measured at fair value on recurring basis	'	'
Marketable securities	156,516	127,053
Warrant liability	136	58
Recurring basis | Significant other observable inputs (level 2)	'	'
Financial assets and liabilities measured at fair value on recurring basis	'	'
Marketable securities	156,516	127,053
Recurring basis | Significant unobservable inputs (level 3)	'	'
Financial assets and liabilities measured at fair value on recurring basis	'	'
Warrant liability	$136	$58

Fair_value_of_financial_instru3

Fair value of financial instruments and marketable securities (Details 2) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Marketable securities accounted for as available-for-sale securities	'	'
Amortized Cost	$156,585	$126,982
Gross Unrealized Gains	120	102
Gross Unrealized Losses	-189	-31
Fair Value	156,516	127,053
Commercial paper	'	'
Marketable securities accounted for as available-for-sale securities	'	'
Amortized Cost	'	14,993
Gross Unrealized Gains	'	5
Fair Value	'	14,998
Corporate Debt Securities [Member]	'	'
Marketable securities accounted for as available-for-sale securities	'	'
Amortized Cost	122,561	111,989
Gross Unrealized Gains	112	97
Gross Unrealized Losses	-156	-31
Fair Value	122,517	112,055
Government Agencies Debt Securities [Member]	'	'
Marketable securities accounted for as available-for-sale securities	'	'
Amortized Cost	34,024	'
Gross Unrealized Gains	8	'
Gross Unrealized Losses	-33	'
Fair Value	$33,999	'

Fair_value_of_financial_instru4

Fair value of financial instruments and marketable securities (Details 3) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Marketable securities on the balance sheet	'	'
Total Marketable securities, Less Than 12 Months	$65,860	$69,157
Total Marketable securities, More Than 12 Months	90,656	57,896
Commercial paper	'	'
Marketable securities on the balance sheet	'	'
Total Marketable securities, Less Than 12 Months	'	14,998
Corporate Debt Securities [Member]	'	'
Marketable securities on the balance sheet	'	'
Total Marketable securities, Less Than 12 Months	65,860	54,159
Total Marketable securities, More Than 12 Months	56,657	57,896
Government Agencies Debt Securities [Member]	'	'
Marketable securities on the balance sheet	'	'
Total Marketable securities, More Than 12 Months	$33,999	'

Fair_value_of_financial_instru5

Fair value of financial instruments and marketable securities (Details 4) (USD $)	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Per Share data, unless otherwise specified	Common stock	Warrant	Warrant	Warrant	Warrant	Warrant	Warrant	Warrant
			Minimum	Minimum	Maximum	Maximum	Common stock	Common stock
Changes in the fair value of warrant liability	'	'	'	'	'	'	'	'
Beginning balance	'	$58	'	'	'	'	'	'
Change in fair value of warrant liability	'	78	'	'	'	'	'	'
Ending balance	'	$136	'	'	'	'	'	'
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model	'	'	'	'	'	'	'	'
Volatility (as a percent)	'	'	64.00%	61.00%	72.00%	89.00%	'	'
Risk-free interest rate (as a percent)	'	'	0.83%	0.07%	1.78%	2.10%	'	'
Strike price (in dollars per share)	'	'	$128	$128	$2,520	$2,520	'	'
Fair value of shares (in dollars per share)	$15	'	'	'	'	'	$44.01	$16.97
Expected life	'	'	'2 years 8 months 16 days	'3 months 18 days	'4 years 11 months 23 days	'5 years 8 months 12 days	'	'

Other_comprehensive_income_los2

Other comprehensive income (loss) and accumulated other comprehensive items (Details) (USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014
Other comprehensive income and accumulated other comprehensive items	'	'
Balance at the beginning of the period	$90	$70
Other comprehensive income/(losses) before reclassifications	-159	-139
Other comprehensive income/(loss)	-159	-139
Balance at the end of the period	-69	-69
Unrealized Gains/(Losses) On Marketable Securities	'	'
Other comprehensive income and accumulated other comprehensive items	'	'
Balance at the beginning of the period	90	70
Other comprehensive income/(losses) before reclassifications	-159	-139
Other comprehensive income/(loss)	-159	-139
Balance at the end of the period	($69)	($69)

Accounts_payable_and_accrued_e2

Accounts payable and accrued expenses (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts payable and accrued expenses	'	'
Employee compensation, benefits, and related accruals	$5,729	$5,103
Consulting and contracted research	5,709	4,006
Professional fees	3,592	1,294
Accounts payable	518	1,124
Other	945	680
Accounts payable and accrued expenses	$16,493	$12,207

Capital_structure_Details

Capital structure (Details) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

3 Months Ended

0 Months Ended

Mar. 31, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Mar. 07, 2013

Feb. 28, 2013

Mar. 07, 2013

Mar. 07, 2013

Mar. 07, 2013

Feb. 12, 2014

Mar. 07, 2013

Jun. 30, 2013

Feb. 12, 2014

Jun. 30, 2013

Mar. 31, 2013

Feb. 28, 2013

Mar. 07, 2013

Series One and Series Two

Series One and Series Two

Series Four convertible preferred stock

Series Five convertible preferred stock

Series Five convertible preferred stock

Common stock

Common stock

Common stock

Common stock

Series Four and Series Five Convertible Preferred Stock

Convertible promissory notes

Convertible promissory notes

Convertible promissory notes

Warrant

Warrant

Warrant

Maximum

Series Four convertible preferred stock

Capital structure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal amount of convertible promissory notes issued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$6,000,000

'

Warrants issued to purchase shares

'

'

'

'

'

2,527,675

'

'

'

'

'

'

'

'

'

'

'

Exercise price (in dollars per share)

'

'

'

'

'

$0.01

'

'

'

'

'

'

'

'

'

'

'

Debt discount recorded to interest expense

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,000,000

'

'

Shares issued and sold

'

'

'

'

2,527,675

'

4,497,035

'

'

5,163,265

'

9,627,800

'

'

'

'

'

Aggregate gross proceeds

'

'

'

'

'

'

54,000,000

'

'

'

'

'

'

'

'

'

'

Amount raised in bridge financing

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,000,000

'

'

Gross proceeds raised

60,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares issued upon conversion of convertible promissory notes

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

502,919

Reverse stock split ratio

'

'

'

'

'

'

'

'

'

'

0.0083

'

'

'

'

'

'

Number of shares issued upon conversion

'

'

'

'

'

'

'

6,700,487

2,095,515

'

'

'

'

14,170,956

'

'

'

Gain on extinguishment of shares of Series One, Two and Three stock

'

'

3,391,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Share price (in dollars per share)

'

'

'

'

'

'

'

'

'

'

'

$15

'

'

'

'

'

Public offering price (in dollars per share)

'

'

'

'

'

'

'

'

'

$24.50

'

'

'

'

'

'

'

Common stock shares issuable pursuant to the exercise by the underwriters of an over-allotment option

'

'

'

'

'

'

'

'

'

'

'

1,255,800

673,469

'

'

'

'

Net proceeds from initial public offering

'

'

'

'

'

'

'

'

'

'

'

131,600,000

'

'

'

'

'

Net proceeds from public offerings

'

$118,383,000

$131,650,000

'

'

'

'

'

'

$118,400,000

'

'

'

'

'

'

'

Common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, authorized shares

'

125,000,000

'

125,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital_structure_Details_2

Capital structure (Details 2) (Warrant, Common stock, USD $)	Sep. 30, 2014	Dec. 31, 2013
2014	'	'
Warrants	'	'
Warrant shares	'	1,428
Exercise price (in dollars per share)	'	$128
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	'
Exercise price (in dollars per share)	$2,520	'
2014	'	'
Warrants	'	'
Warrant shares	'	452
Exercise price (in dollars per share)	'	$2,520

Net_loss_per_share_Details

Net loss per share (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator	'	'	'	'
Net loss	($27,282)	($4,416)	($66,484)	($33,688)
Deemed dividend	'	'	'	-18,249
Gain on exchange of convertible preferred stock in connection with recapitalization	'	'	'	3,391
Net loss attributable to common stockholders	($27,282)	($4,416)	($66,484)	($48,546)
Denominator	'	'	'	'
Denominator for basic and diluted net loss per share (in shares)	29,351,693	23,803,282	28,441,827	8,995,167
Net loss per share:	'	'	'	'
Basic and diluted (in dollars per share)	($0.93)	($0.19)	($2.34)	($5.40)

Net_loss_per_share_Details_2

Net loss per share (Details 2)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Net loss per share	'	'
Total shares excluded from calculation	4,173,098	3,101,667
Stock Options	'	'
Net loss per share	'	'
Total shares excluded from calculation	3,443,778	1,987,860
Restricted stock	'	'
Net loss per share	'	'
Total shares excluded from calculation	729,320	1,113,807

Stock_option_plan_Details

Stock option plan (Details) (USD $)	9 Months Ended				0 Months Ended			1 Months Ended		1 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Mar. 05, 2013	Mar. 05, 2013	Mar. 05, 2013	Mar. 05, 2013	31-May-13	31-May-13	31-May-13	31-May-13
	Stock option	Stock option	Stock option	2013 Stock Incentive Plan	2013 Stock Incentive Plan	2013 Stock Incentive Plan	2013 Stock Incentive Plan	2009 Equity and Long-Term Incentive Plan	2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan	2013 Long Term Incentive Plan	2013 Long Term Incentive Plan
		Minimum	Maximum		Stock option	Restricted stock	Common stock		Common stock	Minimum	Common stock
											Maximum
Stock award plan	'	'	'	'	'	'	'	'	'	'	'
Number of shares authorized	'	'	'	'	'	'	739,937	'	'	'	'
Number of shares of restricted stock granted	'	'	'	'	4,613	735,324	'	'	'	'	'
Number of shares available for issuance	'	'	'	0	'	'	'	'	122,296	'	'
Number of additional shares authorized	'	'	'	'	'	'	'	2,500,000	'	'	'
Number of shares subject to outstanding awards	'	'	'	'	'	'	'	'	'	'	3,040,444
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%	'
Number of options	'	'	'	'	'	'	'	'	'	'	'
Outstanding at the beginning of the period (in shares)	2,095,592	'	'	'	'	'	'	'	'	'	'
Granted (in shares)	1,469,496	'	'	'	'	'	'	'	'	'	'
Forfeited (in shares)	-85,775	'	'	'	'	'	'	'	'	'	'
Expired (in shares)	-35	'	'	'	'	'	'	'	'	'	'
Outstanding at the end of the period (in shares)	3,443,778	'	'	'	'	'	'	'	'	'	'
Vested or expected to vest at the end of the period (in shares)	3,217,812	'	'	'	'	'	'	'	'	'	'
Exercisable at the end of the period (in shares)	722,835	'	'	'	'	'	'	'	'	'	'
Exercised (in shares)	-35,500	'	'	'	'	'	'	'	'	'	'
Weighted-average exercise price	'	'	'	'	'	'	'	'	'	'	'
Outstanding at the beginning of the period (in dollars per share)	$20.24	'	'	'	'	'	'	'	'	'	'
Granted (in dollars per share)	$29.57	'	'	'	'	'	'	'	'	'	'
Forfeited (in dollars per share)	$11.78	'	'	'	'	'	'	'	'	'	'
Expired (in dollars per share)	$646.66	'	'	'	'	'	'	'	'	'	'
Outstanding at the end of the period (in dollars per share)	$24.52	'	'	'	'	'	'	'	'	'	'
Vested or expected to vest at the end of the period (in dollars per share)	$23.01	'	'	'	'	'	'	'	'	'	'
Exercisable at the end of the period (in dollars per share)	$36.23	'	'	'	'	'	'	'	'	'	'
Exercised (in dollars per share)	$10.96	'	'	'	'	'	'	'	'	'	'
Weighted-average remaining contractual term	'	'	'	'	'	'	'	'	'	'	'
Outstanding at the end of the period	'8 years 10 months 24 days	'	'	'	'	'	'	'	'	'	'
Vested or expected to vest at the end of the period	'9 years	'	'	'	'	'	'	'	'	'	'
Exercisable at the end of the period	'8 years 3 months 18 days	'	'	'	'	'	'	'	'	'	'
Aggregate intrinsic value	'	'	'	'	'	'	'	'	'	'	'
Outstanding at the end of the period (in dollars)	$84,456	'	'	'	'	'	'	'	'	'	'
Vested or expected to vest at the end of the period (in dollars)	79,675	'	'	'	'	'	'	'	'	'	'
Exercisable at the end of the period (in dollars)	$22,463	'	'	'	'	'	'	'	'	'	'
Valuation assumptions	'	'	'	'	'	'	'	'	'	'	'
Risk-free interest rate (as a percent)	'	0.11%	2.04%	'	'	'	'	'	'	'	'
Expected volatility (as a percent)	'	79.00%	91.00%	'	'	'	'	'	'	'	'
Expected term	'	'5 years 6 months	'6 years 3 months	'	'	'	'	'	'	'	'
Weighted average grant date fair value (in dollars per share)	$21.70	'	'	'	'	'	'	'	'	'	'
Inducement grants for non-statutory stock options.	448,800	'	'	'	'	'	'	'	'	'	'

Stock_option_plan_Details_2

Stock option plan (Details 2) (Restricted stock, USD $)	9 Months Ended
	Sep. 30, 2014
Restricted stock	'
Number of Shares	'
Balance at the beginning of the period (in shares)	1,110,226
Vested (in shares)	-371,280
Forfeited (in shares)	-9,626
Balance at the end of the period (in shares)	729,320
Weighted Average Grant Date Fair Value	'
Balance at the beginning of the period (in dollars per share)	$10.68
Vested (in dollars per share)	$10.60
Forfeited (in dollars per share)	$10.66
Balance at the end of the period (in dollars per share)	$10.72

Stock_option_plan_Details_3

Stock option plan (Details 3) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based compensation expense recorded in the statement of operations	'	'	'	'
Share-based compensation expense	$4,621,000	$2,640,000	$12,605,000	$5,142,000
Unrecognized compensation cost	38,700,000	'	38,700,000	'
Weighted average remaining service period for recognition of unrecognized compensation cost	'	'	'2 years 8 months 12 days	'
Research and development	'	'	'	'
Share-based compensation expense recorded in the statement of operations	'	'	'	'
Share-based compensation expense	2,363,000	677,000	6,517,000	1,378,000
General and administrative	'	'	'	'
Share-based compensation expense recorded in the statement of operations	'	'	'	'
Share-based compensation expense	$2,258,000	$1,963,000	$6,088,000	$3,764,000

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

Subsequent_events_Details

Subsequent events (Details) (USD $)	0 Months Ended		1 Months Ended		1 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 07, 2013	Feb. 12, 2014	Jun. 30, 2013	Oct. 31, 2014	Oct. 31, 2014	Oct. 31, 2014	Oct. 31, 2014
	Series Four convertible preferred stock	Common stock	Common stock	Subsequent event	Subsequent event	Subsequent event	Subsequent event
					Scenario, Forecast [Member]	Follow On Public Offering [Member]	Over Allotment Option [Member]
Subsequent events	'	'	'	'	'	'	'
Shares issued	4,497,035	5,163,265	9,627,800	'	'	3,450,000	450,000
Share price (in dollars per share)	'	'	$15	$36.25	'	'	'
Net proceeds	'	'	'	'	$117.50	'	'