Cytokinetics (CYTK) 10-Q 6 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 25, 2013
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'CYTK	'
Entity Registrant Name	'CYTOKINETICS INC	'
Entity Central Index Key	'0001061983	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	29,503,123

Condensed_Balance_Sheets

Condensed Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$19,258	$14,907
Short-term investments	62,384	59,093
Related party accounts receivable	'	4
Prepaid and other current assets	1,679	2,423
Total current assets	83,321	76,427
Property and equipment, net	804	997
Long-term investments	3,754	'
Other assets	127	127
Total assets	88,006	77,551
Current liabilities:	'	'
Accounts payable	1,789	2,002
Accrued liabilities	9,886	4,877
Deferred revenue, current	33,322	'
Related party payables and accrued liabilities	'	150
Short-term portion of deferred rent	14	76
Total current liabilities	45,011	7,105
Deferred revenue, non-current	2,696	'
Long-term portion of deferred rent	548	361
Total liabilities	48,255	7,466
Commitments and contingencies	'	'
Stockholders' equity:	'	'
Common stock, $0.001 par value: Authorized: 81,500,000 shares; Issued and outstanding: 29,503,123 shares at September 30, 2013 and 23,742,911 shares at December 31, 2012	29	24
Additional paid-in capital	528,831	518,923
Accumulated other comprehensive income	19	18
Deficit accumulated during the development stage	-489,128	-448,880
Total stockholders' equity	39,751	70,085
Total liabilities and stockholders' equity	88,006	77,551
Series B convertible preferred stock [Member]	'	'
Stockholders' equity:	'	'
Preferred stock, $0.001 par value: Authorized: 10,000,000 shares; Issued and outstanding: Series B convertible preferred stock - 0 shares at September 30, 2013 and 23,026 shares at December 31, 2012	'	'

Condensed_Balance_Sheets_Paren

Condensed Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	10,000,000	10,000,000
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	81,500,000	81,500,000
Common stock, shares issued	29,503,123	23,742,911
Common stock, shares outstanding	29,503,123	23,742,911
Series B convertible preferred stock [Member]	'	'
Convertible Preferred stock, issued shares	0	23,026
Convertible Preferred stock, outstanding shares	0	23,026

Condensed_Statements_of_Compre

Condensed Statements of Comprehensive Loss (USD $)	3 Months Ended		9 Months Ended		194 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Revenues:	'	'	'	'	'
Research and development revenues from related parties	$564	$963	$1,455	$3,234	$56,783
Research and development, grant and other revenues	2,495	751	3,434	2,141	12,806
License revenues from related parties	'	'	'	'	112,935
License revenues	1,410	'	1,410	'	1,410
Total revenues	4,469	1,714	6,299	5,375	183,934
Operating expenses:	'	'	'	'	'
Research and development	13,445	8,798	35,626	25,785	523,741
General and administrative	3,635	2,991	10,999	8,614	167,380
Restructuring charges (reversals)	'	-2	'	-56	3,586
Total operating expenses	17,080	11,787	46,625	34,343	694,707
Operating loss	-12,611	-10,073	-40,326	-28,968	-510,773
Interest and other, net	23	29	78	54	21,619
Loss before income taxes	-12,588	-10,044	-40,248	-28,914	-489,154
Income tax benefit	'	'	'	'	-26
Net loss	-12,588	-10,044	-40,248	-28,914	-489,128
Deemed dividend related to beneficial conversion feature of convertible preferred stock	'	'	'	-1,307	-4,164
Net loss allocable to common stockholders	-12,588	-10,044	-40,248	-30,221	-493,292
Net loss per share allocable to common stockholders - basic and diluted	($0.43)	($0.45)	($1.52)	($1.86)	'
Weighted-average number of shares used in computing net loss per share allocable to common stockholders - basic and diluted	29,395	22,360	26,413	16,215	'
Comprehensive loss	($12,569)	($10,030)	($40,247)	($28,904)	($489,109)

Condensed_Statements_of_Cash_F

Condensed Statements of Cash Flows (USD $)	9 Months Ended		194 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Cash flows from operating activities:	'	'	'
Net loss	($40,248)	($28,914)	($489,128)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'
Depreciation and amortization of property and equipment	345	462	29,599
Loss on disposal of equipment	-2	-2	297
Non-cash impairment charges	'	'	103
Non-cash restructuring expenses, net of reversals	'	-56	636
Non-cash interest expense	'	'	504
Non-cash forgiveness of loans to officers	'	'	434
Stock-based compensation	2,941	2,876	39,069
Non-cash warrant expense	'	'	1,626
Other non-cash expenses	'	'	141
Changes in operating assets and liabilities:	'	'	'
Related party accounts receivable	4	14	-351
Prepaid and other assets	744	-1,056	-1,834
Accounts payable	-103	334	1,935
Accrued and other liabilities	5,162	-89	10,166
Related party payables and accrued liabilities	-150	-12	'
Deferred revenue	36,018	129	36,018
Net cash provided by (used in) operating activities	4,711	-26,314	-370,785
Cash flows from investing activities:	'	'	'
Purchases of investments	-68,286	-81,513	-1,120,529
Proceeds from sales and maturities of investments	61,241	45,950	1,034,468
Proceeds from sales of auction rate securities	'	'	20,025
Purchases of property and equipment	-290	-66	-31,451
Proceeds from sales of property and equipment	3	2	146
Decrease in restricted cash	'	196	'
Issuance of related party notes receivable	'	'	-1,146
Proceeds from repayments of notes receivable	'	'	859
Net cash used in investing activities	-7,332	-35,431	-97,628
Cash flows from financing activities:	'	'	'
Proceeds from initial public offering, sale of common stock to related party, and public offerings, net of issuance costs	7,450	43,678	257,998
Proceeds from draw down of committed equity financing facilities and at-the-market facility, net of commission and issuance costs	'	2,819	58,095
Proceeds from other issuances of common stock and warrants, net	-478	-361	17,301
Proceeds from issuance of preferred stock, net of issuance costs	'	12,318	154,819
Repurchase of common stock	'	'	-68
Proceeds from loan with UBS	'	'	12,441
Repayment of loan with UBS	'	'	-12,441
Proceeds from equipment financing lines	'	'	23,696
Repayment of equipment financing lines	'	-152	-24,170
Net cash provided by financing activities	6,972	58,302	487,671
Net increase (decrease) in cash and cash equivalents	4,351	-3,443	19,258
Cash and cash equivalents, beginning of period	14,907	18,833	'
Cash and cash equivalents, end of period	$19,258	$15,390	$19,258

Organization_and_Summary_of_Si

Organization and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Organization and Summary of Significant Accounting Policies	'
	Note 1. Organization and Summary of Significant Accounting Policies
	Overview
	Cytokinetics, Incorporated (the “Company”, “we” or “our”) was incorporated under the laws of the state of Delaware on August 5, 1997. The Company is a clinical-stage biopharmaceutical company focused on the discovery and development of novel small molecule therapeutics that modulate muscle function for the potential treatment of serious diseases and medical conditions. The Company is a development stage enterprise and has been primarily engaged in conducting research, developing drug candidates and technologies, and raising capital.
	The Company’s financial statements contemplate the conduct of the Company’s operations in the normal course of business. The Company has incurred an accumulated deficit of $489.1 million since inception and there can be no assurance that the Company will attain profitability. The Company had a net loss of $40.2 million for the nine months ended September 30, 2013. Cash, cash equivalents and investments increased to $85.4 million at September 30, 2013 from $74.0 million at December 31, 2012 due principally to cash receipts from licensing transactions and sales of common stock. The Company anticipates that it will continue to have operating losses and net cash outflows in future periods.
	The Company is subject to risks common to development stage companies including, but not limited to, development of new drug candidates, dependence on key personnel, and the ability to obtain additional capital as needed to fund its future plans. The Company’s liquidity will be impaired if sufficient additional capital is not available on terms acceptable to the Company. To date, the Company has funded its operations primarily through sales of its common stock and convertible preferred stock, licensing of its patents and know-how, contract payments under its collaboration agreements, debt financing arrangements, government grants and interest income. Until it achieves profitable operations, the Company intends to continue to fund operations through payments from strategic collaborations, additional sales of equity securities, government grants and debt financings. The Company has never generated revenues from commercial sales of its drugs and may not have drugs to market for at least several years, if ever. The Company’s success is dependent on its ability to enter into new strategic collaborations and/or raise additional capital and to successfully develop and market one or more of its drug candidates. As a result, the Company may choose to raise additional capital through equity or debt financings to continue to fund its operations in the future. The Company cannot be certain that sufficient funds will be available from such a financing or through a collaborator when required or on satisfactory terms. Additionally, there can be no assurance that the Company’s drug candidates will be accepted in the marketplace or that any future products can be developed or manufactured at an acceptable cost. These factors could have a material adverse effect on the Company’s future financial results, financial position and cash flows.
	Based on the current status of its research and development plans, the Company believes that its existing cash, cash equivalents and investments at September 30, 2013 will be sufficient to fund its cash requirements for at least the next 12 months. If, at any time, the Company’s prospects for financing its research and development programs decline, the Company may decide to reduce research and development expenses by delaying, discontinuing or reducing its funding of one or more of its research or development programs. Alternatively, the Company might raise funds through strategic collaborations, public or private financings or other arrangements. Such funding, if needed, may not be available on favorable terms, or at all.
	The financial statements do not include any adjustments that might result from the outcome of this uncertainty.
	Basis of Presentation
	The accompanying unaudited condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. The financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for the fair statement of the balances and results for the periods presented. These interim financial statement results are not necessarily indicative of results to be expected for the full fiscal year or any future interim period.
	The balance sheet at December 31, 2012 has been derived from the audited financial statements at that date. The financial statements and related disclosures have been prepared with the presumption that users of the interim financial statements have read or have access to the audited financial statements for the preceding fiscal year. Accordingly, these financial statements should be read in conjunction with the audited financial statements and notes thereto contained in the Company’s Form 10-K for the year ended December 31, 2012, as filed with the SEC on March 15, 2013.
	Significant Accounting Policies
	The Company’s significant accounting policies are disclosed in its annual report on Form 10-K for the year ended December 31, 2012, as filed with the SEC on March 15, 2013, and have not changed as of September 30, 2013, except as noted below.
	Reverse Stock Split
	On June 24, 2013, the Company effected a one-for-six reverse stock split of its common stock through an amendment to its amended and restated certificate of incorporation (the “COI Amendment”). As of the effective time of the reverse stock split, every six shares of the Company’s issued and outstanding common stock were converted into one issued and outstanding share of common stock, without any change in par value per share. The reverse stock split affected all shares of the Company’s common stock outstanding immediately prior to the effective time of the reverse stock split, as well as the number of shares of common stock available for issuance under the Company’s equity incentive plans. In addition, the reverse stock split effected a reduction in the number of shares of common stock issuable upon the conversion of shares of preferred stock or upon the exercise of stock options or warrants outstanding immediately prior to the effectiveness of the reverse stock split. No fractional shares were issued as a result of the reverse stock split. Stockholders who would otherwise have been entitled to receive a fractional share received cash payments in lieu thereof. In addition, the COI Amendment reduced the number of authorized shares of common stock to 81.5 million.
	As the par value per share of the Company’s common stock remained unchanged at $0.001 per share, a total of $139,000 was reclassified from common stock to additional paid-in capital. All references to shares of common stock and per share data for all periods presented in the accompanying condensed financial statements and notes thereto have been adjusted to reflect the reverse stock split on a retroactive basis.
	Recently Adopted Accounting Pronouncements
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Statement Update (“ASU”) 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. This update requires entities to disclose items reclassified out of accumulated other comprehensive income and into net income in a single location within the financial statements. On January 1, 2013, the Company adopted this new accounting guidance and discloses reclassifications out of accumulated other comprehensive income and into net income in the footnotes to the financial statements.
	Accounting Pronouncements Not Yet Adopted
	In July 2013, the FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. ASU 2013-11 amends accounting guidance on the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or tax credit carryforward exists. This new guidance requires entities, if certain criteria are met, to present an unrecognized tax benefit, or portion of an unrecognized tax benefit, in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward when such items exist in the same taxing jurisdiction. The provisions of ASU 2013-11 are effective for fiscal years and interim periods beginning after December 15, 2013, which corresponds to the Company’s first quarter of fiscal year 2014. This update can be applied prospectively to all unrecognized tax benefits that exist at the effective date. Retrospective application is permitted. The Company is evaluating when to adopt ASU 2013-11 and the effect the adoption will have on its financial statements.

Net_Loss_Per_Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Net Loss Per Share	'
	Note 2. Net Loss Per Share
	Basic net loss per share allocable to common stockholders is computed by dividing net loss allocable to common stockholders by the weighted average number of vested common shares outstanding during the period. Diluted net loss per share allocable to common stockholders is computed by giving effect to all potentially dilutive common shares, including outstanding stock options, unvested restricted stock units, warrants, convertible preferred stock and shares issuable under the Company’s Employee Stock Purchase Plan (“ESPP”), by applying the treasury stock method. The following is the calculation of basic and diluted net loss per share allocable to common stockholders (in thousands, except per share data):
		Three Months Ended						Nine Months Ended
		September 30,			September 30,			September 30,			September 30,
		2013			2012			2013			2012
	Net loss	$	(12,588	)	$	(10,044	)	$	(40,248	)	$	(28.914	)
	Deemed dividend related to beneficial conversion feature of convertible preferred stock		—			—			—			(1,307	)
	Net loss allocable to common stockholders	$	(12,588	)	$	(10,044	)	$	(40,248	)	$	(30,221	)
	Weighted-average common shares outstanding (weighted average number of shares used in computing net loss per share allocable to common stockholders) — basic and diluted		29,395			22,360			26,413			16,215
	Net loss per share allocable to common stockholders — basic and diluted	$	(0.43	)	$	(0.45	)	$	(1.52	)	$	(1.86	)
	The following instruments were excluded from the computation of diluted net loss per share for the periods presented because their effect would have been antidilutive (in thousands):
		Three and Nine Months Ended
		September 30,			September 30,
		2013			2012
	Options to purchase common stock		2,452			1,819
	Warrants to purchase common stock		7,692			9,009
	Series A convertible preferred stock (as converted to common stock)		—			—
	Series B convertible preferred stock (as converted to common stock)		—			3,838
	Restricted stock units		42			226
	Shares issuable related to the ESPP		31			20
	Total shares		10,217			14,912

Supplemental_Cash_Flow_Data

Supplemental Cash Flow Data	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Data	'
	Note 3. Supplemental Cash Flow Data
	Supplemental cash flow data was as follows (in thousands):
		Nine Months Ended				Period from
		September 30,		September 30,		August 5, 1997
		2013		2012		(date of inception)
						to September 30,
						2013
	Significant non-cash investing and financing activities:
	Deferred stock-based compensation	$	—	$	—	$	6,940
	Purchases of property and equipment through accounts payable		110		—		110
	Purchases of property and equipment through accrued liabilities		29		5		29
	Purchases of property and equipment through trade in value of disposed property and equipment		—		—		258
	Penalty on restructuring of equipment financing lines		—		—		475
	Conversion of convertible preferred stock to common stock		13,626		—		146,798
	Warrants issued in equity financing		—		—		1,585

Related_Party_Research_and_Dev

Related Party Research and Development Arrangements	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]	'
Related Party Research and Development Arrangements	'
	Note 4. Related Party Research and Development Arrangements
	Amgen Inc. (“Amgen”)
	In 2006, the Company entered into a collaboration and option agreement with Amgen to discover, develop and commercialize novel small molecule therapeutics, including omecamtiv mecarbil, that activate cardiac muscle contractility for potential applications in the treatment of heart failure (the “Amgen Agreement”). The agreement granted Amgen an option to obtain an exclusive license worldwide, except Japan, to develop and commercialize omecamtiv mecarbil and other drug candidates arising from the collaboration. In 2009, Amgen exercised its option.
	In June 2013, the Company and Amgen amended the Amgen Agreement to expand Amgen’s exclusive license to include Japan, resulting in a worldwide collaboration (the “Amgen Agreement Amendment”). Under the Amgen Agreement Amendment, the Company received a non-refundable upfront license fee of $15 million. As of September 30, 2013, the Company determined that all conditions necessary for revenue recognition under Accounting Standards Codification (“ASC”) 605-10 had not been met and accordingly, deferred the revenue attributable to the Amgen Agreement Amendment until the criteria of ASC 605-10 have been satisfied. In October 2013, the Company determined that all conditions necessary for revenue recognition under ASC 605-10 had been satisfied and accordingly, will begin recognizing revenue attributable to the Amgen Agreement Amendment in the fourth quarter of 2013.
	In conjunction with the Amgen Agreement Amendment, the Company also entered into a common stock purchase agreement with Amgen, which provided for the sale of 1,404,100 shares of the Company’s common stock at a price per share of $7.12 and an aggregate purchase price of $10.0 million which was received in June 2013. Under the terms of this agreement, Amgen has agreed to certain trading and other restrictions with respect to the Company’s common stock. The Company determined the fair value of the stock issued to Amgen to be $7.5 million. The excess of cash received over fair value of $2.5 million was deferred and will be allocated between the license and services based on their relative selling prices using best estimate of selling price. Allocated consideration will be recognized as revenue as revenue criteria is satisfied, or as services are performed over approximately 12 months.
	At September 30, 2013, the Company had $17.5 million of deferred revenue under the Amgen Agreement Amendment.
	Under the Amgen Agreement Amendment, the Company plans to conduct a Phase I pharmacokinetic study intended to support inclusion of Japan in a potential Phase III clinical development program and potential global registration dossier for omecamtiv mecarbil. Amgen will reimburse the Company for the costs of this study. In addition, the Company is eligible to receive additional pre-commercialization milestone payments relating to the development of omecamtiv mecarbil in Japan of up to $50 million, and royalties on net sales of omecamtiv mecarbil in Japan. Such royalty rates will range from the high single digits to the low teens. The Company has determined that the additional milestones are not substantive, as they are primarily the result of Amgen’s performance and therefore revenue will be recognized as the Company completes any performance obligations, or if all performance obligations have been delivered at the point the milestone is reached, the revenue from the milestone would be recognized at that time.
	Pursuant to the Amgen Agreement, the Company has recognized research and development revenue from Amgen for reimbursements of its costs of certain full-time employee equivalents (“FTEs”) supporting a collaborative research program directed to the discovery of next-generation cardiac sarcomere activator compounds and of other costs related to that research program. These reimbursements were recorded as research and development revenues from related parties. Revenue from Amgen was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	FTE reimbursements	$	564	$	963	$	1,455	$	3,231
	Reimbursements of other costs		—		—		—		3
	Total revenue from Amgen	$	564	$	963	$	1,455	$	3,234
	At both December 31, 2012 and September 30, 2013, there were no related party receivables under the Amgen Agreement.

Other_Research_and_Development

Other Research and Development Revenue Arrangements	9 Months Ended
	Sep. 30, 2013
Research And Development [Abstract]	'
Other Research and Development Revenue Arrangements	'
	Note 5. Other Research and Development Revenue Arrangements
	Grants
	In 2010, the National Institute of Neurological Disorders and Stroke (“NINDS”) awarded the Company a $2.8 million grant to support research and development of tirasemtiv, a fast skeletal troponin activator currently in Phase II clinical trials, directed to the potential treatment of myasthenia gravis for a period of up to three years. In September 2012, the NINDS awarded the Company an additional $0.5 million for this program under a separate grant. Management determined that the Company was the principal participant in the grant arrangement, and, accordingly, the Company recorded amounts earned under the arrangement as revenue. The project period for both of these grants ended June 30, 2013 and no further funds are available to us under these grants.
	The Company recognized grant revenue under this grant arrangement as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	NINDS myasthenia gravis	$	—	$	264	$	69	$	896
	Other Research and Development Arrangements
	Astellas Pharma Inc. (“Astellas”)
	In June 2013, the Company entered into a collaboration and license agreement (the “Astellas Agreement”) with Astellas. The primary objective of the collaboration to be conducted under the Astellas Agreement is to advance novel therapies for diseases and medical conditions associated with muscle weakness.
	Under the Astellas Agreement, the Company granted Astellas an exclusive license to co-develop and jointly commercialize CK-2127107, a fast skeletal troponin activator, for potential application in non-neuromuscular indications worldwide. CK-2127107, which is currently in Phase I clinical development, will be developed jointly by the Company and Astellas. The Company will be primarily responsible for the conduct of Phase I clinical trials and certain Phase II readiness activities for CK-2127107 and Astellas will be primarily responsible for the conduct of subsequent development and commercialization activities for CK-2127107.
	The parties will jointly conduct research to identify next-generation skeletal muscle activators to be nominated as potential drug candidates, at Astellas’ expense. Astellas has the exclusive rights to develop and commercialize fast skeletal troponin activators from this research program in non-neuromuscular indications and to develop and commercialize other novel mechanism skeletal muscle activators from this research program in all indications, subject to certain co-development and co-promotion rights of the Company under the Astellas Agreement. Astellas will be responsible for the costs associated with the development of all collaboration products, including CK-2127107.
	The Company retains an option to conduct early-stage development for certain agreed upon indications at its initial expense, subject to reimbursement if development continues under the collaboration. The Company also retains an option to co-promote collaboration products in the United States and Canada. Astellas will reimburse the Company for certain expenses associated with its co-promotion activities.
	In July 2013, the Company received an upfront payment of $16 million in connection with the execution of the Astellas Agreement, and is eligible to potentially receive over $24 million in reimbursement of sponsored research and development activities during the initial two years of the collaboration. Based on the achievement of pre-specified criteria, the Company may receive over $250 million in milestone payments relating to the development and commercial launch of collaboration products, including up to $112 million in development and commercial launch milestones for CK-2127107. The Company may also receive up to $200 million in payments for achievement of pre-specified sales milestones related to net sales of all collaboration products under the Astellas Agreement. In the event Astellas commercializes any collaboration products, the Company will also receive royalties on sales of such collaboration products, including royalties ranging from the high single digits to the high teens on sales of products containing CK-2127107. In addition to the foregoing development, commercial launch and sales milestones, the Company may also receive payments for the achievement of pre-specified milestones relating to the joint research program.
	The Company retains the exclusive right to develop and commercialize tirasemtiv for the potential treatment of amyotrophic lateral sclerosis and other neuromuscular disorders independently from the Astellas Agreement.
	As of June 30, 2013, the Company deferred revenue related to the Astellas Agreement in accordance with ASC 605-25. The Company evaluated whether the delivered elements under the arrangement have value on a stand-alone basis. Upfront, non-refundable licensing payments are assessed to determine whether or not the licensee is able to obtain stand-alone value from the license. Where this is not the case, the Company does not consider the license deliverable to be a separate unit of accounting, and the revenue is deferred with revenue recognition for the license fee being recognized in conjunction with the other deliverables that constitute the combined unit of accounting.
	The Company determined that the license and the research and development services are a single unit of accounting as the license was determined to not have stand-alone value. Accordingly, the Company is recognizing this revenue using the proportional performance model. As of September 30, 2013, the Company has recognized $1.4 million of the $16 million upfront license fee as license revenue and deferred the remaining $14.6 million.
	The Company recognizes milestone payments utilizing the milestone method of revenue recognition. The Company believes the milestones related to research and early development are substantive as there is uncertainty that the milestones will be met, the milestone can only be achieved with the Company’s past and current performance and the achievement of the milestone will result in additional payment to the Company. The Company believes that the milestones related to later development and commercialization are not substantive as they are primarily the result of the collaborative partner’s performance and therefore will be recognized as the Company completes its performance obligations under the agreement, if any. To date, the Company has not recognized any milestone revenue from its collaboration with Astellas.
	Research and development revenue from Astellas was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	License revenues	$	1,410	$	—	$	1,410	$	—
	FTE reimbursements		1,191		—		1,191		—
	Reimbursements of other costs		1,118		—		1,118		—
	Total revenue from Astellas	$	3,719		—	$	3,719		—
	At September 30, 2013, the Company had $18.4 million of deferred revenue under the Astellas Agreement as the Company has received prepayment on expenses expected to be incurred in the fourth quarter of 2013.
	As part of an initiative to seek certain more focused collaborations intended to offset certain research costs, the Company entered into agreements with two early-stage biopharmaceutical companies during 2011 and 2012.
	Global Blood Therapeutics, Inc. (“Global Blood”)
	In October 2011, the Company entered into a collaboration agreement with Global Blood. Under an agreed research plan, scientists from Global Blood and our FTEs conducted research focused on small molecule therapeutics that target the blood. The Company provided Global Blood access to certain research facilities, FTEs and other resources at agreed reimbursement rates that approximated our costs. In April 2012, the Company extended this agreement through December 2012. The Company was the primary obligor in the collaboration arrangement, and accordingly, the Company recorded expense reimbursements from Global Blood as research and development revenue.
	Research and development revenue from Global Blood was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	Expense reimbursements from Global Blood Therapeutics	$	7	$	358	$	7	$	1,116
	MyoKardia, Inc.
	In August 2012, the Company entered into a collaboration agreement with MyoKardia, Inc. Under an agreed research plan, scientists from MyoKardia and our FTEs conducted research focused on small molecule therapeutics that inhibit cardiac sarcomere proteins. The Company provided to MyoKardia access to certain research facilities, and continues to provide FTEs and other resources at agreed reimbursement rates that approximate our costs. The Company was the primary obligor in the collaboration arrangement, and accordingly, the Company recorded expense reimbursements from MyoKardia as research and development revenue.
	Research and development revenue from MyoKardia was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	Expense reimbursements from MyoKardia	$	179	$	129	$	1,024	$	129

Cash_Equivalents_and_Investmen

Cash Equivalents and Investments	9 Months Ended
	Sep. 30, 2013
Investments Debt And Equity Securities [Abstract]	'
Cash Equivalents and Investments	'
	Note 6. Cash Equivalents and Investments
	The amortized cost and fair value of cash equivalents and available for sale investments at September 30, 2013 and December 31, 2012 were as follows (in thousands):
		September 30, 2013
		Amortized		Unrealized		Unrealized		Fair		Maturity
		Cost		Gains		Losses		Value		Dates
	Cash equivalents — money market funds	$	17,201	$	—	$	—	$	17,201
	Short-term investments — U.S. Treasury securities	$	62,367	$	17	$	—	$	62,384	10/2013-9/2014
	Long-term investments — U.S. Treasury securities	$	3,752	$	2	$	—	$	3,754	Nov-14
		December 31, 2012
		Amortized		Unrealized		Unrealized		Fair		Maturity
		Cost		Gains		Losses		Value		Dates
	Cash equivalents — money market funds	$	10,655	$	—	$	—	$	10,655
	Short-term investments — U.S. Treasury securities	$	59,075	$	18	$	—	$	59,093	1/2013-11/2013
	As of both September 30, 2013 and December 31, 2012, the Company’s U.S. Treasury securities classified as short-term investments had unrealized losses of zero. The Company collected the contractual cash flows on its U.S. Treasury securities that matured from January 1, 2013 through October 25, 2013, and expects to be able to collect all contractual cash flows on the remaining maturities of its U.S. Treasury securities.
	Interest income was as follows (in thousands):
		Three Months Ended				Nine Months Ended				Period from
										August 5, 1997(date
		September 30,		September 30,		September 30,		September 30,		of inception) to
		2013		2012		2013		2012		September 30,2013
	Interest income	$	23	$	30	$	74	$	52	$	28,683

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Note 7. Fair Value Measurements
	The Company follows the fair value accounting guidance to value its financial assets and liabilities. Fair value is defined as the price that would be received for assets when sold or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). The Company utilizes market data or assumptions that the Company believes market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs can be readily observable, market corroborated or generally unobservable.
	The Company primarily applies the market approach for recurring fair value measurements and endeavors to utilize the best information reasonably available. Accordingly, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible, and considers the security issuers’ and the third-party insurers’ credit risk in its assessment of fair value.
	The Company classifies the determined fair value based on the observability of those inputs. Fair value accounting guidance establishes a fair value hierarchy that prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). The three defined levels of the fair value hierarchy are as follows:
	Level 1 — Observable inputs such as quoted prices in active markets for identical assets or liabilities;
	Level 2 — Inputs, other than the quoted prices in active markets, that are observable either directly or through corroboration with observable market data; and
	Level 3 — Unobservable inputs for which there is little or no market data for the assets or liabilities, such as internally-developed valuation models.
	Financial assets measured at fair value on a recurring basis as of September 30, 2013 and December 31, 2012 were classified in one of the three categories described above as follows (in thousands):
		September 30, 2013
		Fair Value Measurements Using						Assets
		Level 1		Level 2		Level 3		At Fair Value
	Money market funds	$	17,201	$	—	$	—	$	17,201
	U.S. Treasury securities		66,138		—		—		66,138
	Total	$	83,339	$	—	$	—	$	83,339
	Amounts included in:
	Cash and cash equivalents	$	17,201	$	—	$	—	$	17,201
	Short-term investments		62,384		—		—		62,384
	Long-term investments		3,754		—		—		3,754
	Total	$	83,339	$	—	$	—	$	83,339
		December 31, 2012
		Fair Value Measurements Using						Assets
		Level 1		Level 2		Level 3		At Fair Value
	Money market funds	$	10,655	$	—	$	—	$	10,655
	U.S. Treasury securities		59,093		—		—		59,093
	Total	$	69,748	$	—	$	—	$	69,748
	Amounts included in:
	Cash and cash equivalents	$	10,655	$	—	$	—	$	10,655
	Short-term investments		59,093		—		—		59,093
	Total	$	69,748	$	—	$	—	$	69,748
	The valuation technique used to measure fair value for the Company’s Level 1 assets is a market approach, using prices and other relevant information generated by market transactions involving identical assets. As of September 30, 2013 and December 31, 2012, the Company had no financial assets measured at fair value on a recurring basis using significant Level 2 or Level 3 inputs.
	The carrying amount of the Company’s accounts receivable and accounts payable approximates fair value due to the short-term nature of these instruments.

Stockholders_Equity_Deficit

Stockholders' Equity (Deficit)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Stockholders' Equity (Deficit)	'
	Note 8. Stockholders’ Equity (Deficit)
	Accumulated Other Comprehensive Income
	In the first nine months of 2013, the Company reclassified insignificant amounts of unrealized gains (losses) on investments out of accumulated other comprehensive income into net loss.
	Common stock
	In conjunction with the Amgen Agreement Amendment (see Note 4), in June 2013, Amgen purchased 1,404,100 shares of the Company’s common stock at a price per share of $7.12. The Company determined the fair value of the stock issued to Amgen to be $7.5 million. The excess of cash received over fair value of $2.5 million was deferred and will be recognized as revenue as services are performed over approximately 12 months.
	Convertible Preferred Stock
	Each share of Series B convertible preferred stock is convertible into common stock at any time at the holder’s option. As a result of the one-for-six reverse stock split effected in June 2013, the conversion ratio for Series B convertible preferred stock changed from 1,000 shares of common stock per share of Series B convertible preferred stock to 166.67 shares of common stock per share of Series B convertible preferred stock.
	In the first quarter of 2013, 4,000 shares of Series B convertible preferred stock were converted into 666,667 shares of common stock. In the second quarter of 2013, 15,026 shares of Series B convertible preferred stock were converted into 2,504,334 shares of common stock. On July 2, 2013, 4,000 shares of Series B convertible preferred stock, which represented all remaining shares of Series B convertible preferred stock, were converted into 666,667 shares of common stock. The conversions were in accordance with the terms of the original agreement under which the Series B convertible preferred stock was issued in 2012.
	Warrants
	In February 2013, warrants to purchase 1,000 shares of the Company’s common stock at an exercise price of $5.28 per share were cash exercised in accordance with the June 20, 2012 underwriting agreements the Company entered into in connection with two separate, concurrent offerings for our securities (the “June 2012 Public Offerings”).
	In the second quarter of 2013, the Company issued 358,460 shares of common stock related to cashless exercise of warrants in accordance with the June 2012 Public Offerings. There were no exercises of warrants in the third quarter of 2013.
	MLV
	On June 10, 2011, the Company entered into an At-The-Market Issuance Sales Agreement (the “MLV Agreement”) with McNicoll, Lewis & Vlak LLC (“MLV”), pursuant to which the Company may issue and sell shares of common stock having an aggregate offering price of up to $20.0 million or 2,397,279 shares, whichever occurs first, from time to time through MLV as the sales agent. The issuance and sale of shares by the Company under the MLV Agreement, if any, are subject to the continued effectiveness of the Company’s registration statement on Form S-3, which was declared effective by the SEC on June 23, 2011 (File No. 333-174869) and the terms and conditions of the MLV Agreement. As of December 31, 2012, the Company had issued a total of 862,592 shares through MLV for total net proceeds of approximately $5.3 million. As of October 25, 2013, there have been no further issuances of shares through MLV.
	Stock Option Plans
	Stock option activity for the nine months ended September 30, 2013 under the Company’s 2004 Equity Incentive Plan, as amended, and the Company’s 1997 Stock Option/Stock Issuance Plan was as follows:
		Shares			Stock Options			Weighted
		Available for			Outstanding			Average Exercise
		Grant of						Price per Share of
		Options						Stock Options
		or Awards
	Balance at December 31, 2012		878,711			1,790,527		$	18.96
	Options granted		(769,979	)		769,979			5.93
	Options exercised		—			(21,397	)		5.32
	Options forfeited		19,382			(19,382	)		4.88
	Options expired		68,205			(68,205	)		16.17
	Restricted stock units granted		(41,661	)		—			—
	Restricted stock units forfeited		5,014			—			—
	Balance at September 30, 2013		159,672			2,451,522		$	15.18
	Restricted stock unit activity for the nine months ended September 30, 2013 was as follows:
		Number of			Weighted
		Shares			Average Award
					Date Fair Value per
					Share
	Restricted stock units outstanding at December 31, 2012		216,913		$	6.78
	Restricted stock units granted		41,661			6
	Restricted stock units vested		(211,897	)		6.78
	Restricted stock units forfeited		(5,014	)		6.78
	Unvested restricted stock units outstanding at September 30, 2013		41,663		$	6

Interest_and_Other_Net

Interest and Other, Net	9 Months Ended
	Sep. 30, 2013
Other Income And Expenses [Abstract]	'
Interest and Other, Net	'
	Note 9. Interest and Other, Net
	Components of Interest and other, net were as follows (in thousands):
		Three Months Ended						Nine Months Ended					Period from
													August 5, 1997
		September 30,			September 30,			September 30,		September 30,			(date of inception)
		2013			2012			2013		2012			to September 30, 2013
	Interest income and other income	$	24		$	30		$	76	$	56		$	29,176
	Interest expense and other expense		(1	)		(1	)		2		(2	)		(5,972	)
	Warrant expense		—			—			—		—			(1,585	)
	Interest and other, net	$	23		$	29		$	78	$	54		$	21,619
	Interest income and other income primarily consisted of interest income generated from the Company’s cash, cash equivalents and investments.
	Warrant expense for the period from inception to September 30, 2013 was related to the change in the fair value of the warrant liability that was recorded in connection with the Company’s registered direct equity offering in May 2009.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Note 10. Income Taxes
	The Company follows the accounting guidance established by the FASB which defines the threshold for recognizing the benefits of tax return positions in the financial statements as “more-likely-than-not” to be sustained by the taxing authorities based solely on the technical merits of the position. If the recognition threshold is met, the tax benefit is measured and recognized as the largest amount of tax benefit that, in the Company’s judgment, is greater than 50% likely to be realized.
	The Company files income tax returns with the United States Internal Revenue Service (“IRS”) and the state of California. For jurisdictions in which tax filings are made, the Company is subject to income tax examination for all fiscal years since inception. The Company believes that it maintains adequate reserves for uncertain tax positions.
	In general, under section 382 of the Internal Revenue Code (“Section 382”), a corporation that undergoes an ‘ownership change’ is subject to limitations on its ability to utilize its pre-change net operating losses (“NOLs”) and tax credits to offset future taxable income. The Company has performed a Section 382 analysis and does not believe that it has experienced an ownership change since 2006. A portion of the Company’s existing NOLs and tax credits are subject to limitations arising from previous ownership changes. Future changes in the Company’s stock ownership, some of which are outside of our control, could result in an ownership change under Section 382 and result in additional limitations.

Organization_and_Summary_of_Si1

Organization and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Overview	'
	Overview
	Cytokinetics, Incorporated (the “Company”, “we” or “our”) was incorporated under the laws of the state of Delaware on August 5, 1997. The Company is a clinical-stage biopharmaceutical company focused on the discovery and development of novel small molecule therapeutics that modulate muscle function for the potential treatment of serious diseases and medical conditions. The Company is a development stage enterprise and has been primarily engaged in conducting research, developing drug candidates and technologies, and raising capital.
	The Company’s financial statements contemplate the conduct of the Company’s operations in the normal course of business. The Company has incurred an accumulated deficit of $489.1 million since inception and there can be no assurance that the Company will attain profitability. The Company had a net loss of $40.2 million for the nine months ended September 30, 2013. Cash, cash equivalents and investments increased to $85.4 million at September 30, 2013 from $74.0 million at December 31, 2012 due principally to cash receipts from licensing transactions and sales of common stock. The Company anticipates that it will continue to have operating losses and net cash outflows in future periods.
	The Company is subject to risks common to development stage companies including, but not limited to, development of new drug candidates, dependence on key personnel, and the ability to obtain additional capital as needed to fund its future plans. The Company’s liquidity will be impaired if sufficient additional capital is not available on terms acceptable to the Company. To date, the Company has funded its operations primarily through sales of its common stock and convertible preferred stock, licensing of its patents and know-how, contract payments under its collaboration agreements, debt financing arrangements, government grants and interest income. Until it achieves profitable operations, the Company intends to continue to fund operations through payments from strategic collaborations, additional sales of equity securities, government grants and debt financings. The Company has never generated revenues from commercial sales of its drugs and may not have drugs to market for at least several years, if ever. The Company’s success is dependent on its ability to enter into new strategic collaborations and/or raise additional capital and to successfully develop and market one or more of its drug candidates. As a result, the Company may choose to raise additional capital through equity or debt financings to continue to fund its operations in the future. The Company cannot be certain that sufficient funds will be available from such a financing or through a collaborator when required or on satisfactory terms. Additionally, there can be no assurance that the Company’s drug candidates will be accepted in the marketplace or that any future products can be developed or manufactured at an acceptable cost. These factors could have a material adverse effect on the Company’s future financial results, financial position and cash flows.
	Based on the current status of its research and development plans, the Company believes that its existing cash, cash equivalents and investments at September 30, 2013 will be sufficient to fund its cash requirements for at least the next 12 months. If, at any time, the Company’s prospects for financing its research and development programs decline, the Company may decide to reduce research and development expenses by delaying, discontinuing or reducing its funding of one or more of its research or development programs. Alternatively, the Company might raise funds through strategic collaborations, public or private financings or other arrangements. Such funding, if needed, may not be available on favorable terms, or at all.
	The financial statements do not include any adjustments that might result from the outcome of this uncertainty.
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. The financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for the fair statement of the balances and results for the periods presented. These interim financial statement results are not necessarily indicative of results to be expected for the full fiscal year or any future interim period.
	The balance sheet at December 31, 2012 has been derived from the audited financial statements at that date. The financial statements and related disclosures have been prepared with the presumption that users of the interim financial statements have read or have access to the audited financial statements for the preceding fiscal year. Accordingly, these financial statements should be read in conjunction with the audited financial statements and notes thereto contained in the Company’s Form 10-K for the year ended December 31, 2012, as filed with the SEC on March 15, 2013.
Significant Accounting Policies	'
	Significant Accounting Policies
	The Company’s significant accounting policies are disclosed in its annual report on Form 10-K for the year ended December 31, 2012, as filed with the SEC on March 15, 2013, and have not changed as of September 30, 2013, except as noted below.
Reverse Stock Split	'
	Reverse Stock Split
	On June 24, 2013, the Company effected a one-for-six reverse stock split of its common stock through an amendment to its amended and restated certificate of incorporation (the “COI Amendment”). As of the effective time of the reverse stock split, every six shares of the Company’s issued and outstanding common stock were converted into one issued and outstanding share of common stock, without any change in par value per share. The reverse stock split affected all shares of the Company’s common stock outstanding immediately prior to the effective time of the reverse stock split, as well as the number of shares of common stock available for issuance under the Company’s equity incentive plans. In addition, the reverse stock split effected a reduction in the number of shares of common stock issuable upon the conversion of shares of preferred stock or upon the exercise of stock options or warrants outstanding immediately prior to the effectiveness of the reverse stock split. No fractional shares were issued as a result of the reverse stock split. Stockholders who would otherwise have been entitled to receive a fractional share received cash payments in lieu thereof. In addition, the COI Amendment reduced the number of authorized shares of common stock to 81.5 million.
	As the par value per share of the Company’s common stock remained unchanged at $0.001 per share, a total of $139,000 was reclassified from common stock to additional paid-in capital. All references to shares of common stock and per share data for all periods presented in the accompanying condensed financial statements and notes thereto have been adjusted to reflect the reverse stock split on a retroactive basis.
Recently Adopted Accounting Pronouncements	'
	Recently Adopted Accounting Pronouncements
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Statement Update (“ASU”) 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. This update requires entities to disclose items reclassified out of accumulated other comprehensive income and into net income in a single location within the financial statements. On January 1, 2013, the Company adopted this new accounting guidance and discloses reclassifications out of accumulated other comprehensive income and into net income in the footnotes to the financial statements.
Accounting Pronouncements Not Yet Adopted	'
	Accounting Pronouncements Not Yet Adopted
	In July 2013, the FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. ASU 2013-11 amends accounting guidance on the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or tax credit carryforward exists. This new guidance requires entities, if certain criteria are met, to present an unrecognized tax benefit, or portion of an unrecognized tax benefit, in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward when such items exist in the same taxing jurisdiction. The provisions of ASU 2013-11 are effective for fiscal years and interim periods beginning after December 15, 2013, which corresponds to the Company’s first quarter of fiscal year 2014. This update can be applied prospectively to all unrecognized tax benefits that exist at the effective date. Retrospective application is permitted. The Company is evaluating when to adopt ASU 2013-11 and the effect the adoption will have on its financial statements.

Net_Loss_Per_Share_Tables

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]	'
Calculation of Basic and Diluted Net Loss Per Share Allocable to Common Stockholders	'
	The following is the calculation of basic and diluted net loss per share allocable to common stockholders (in thousands, except per share data):
		Three Months Ended						Nine Months Ended
		September 30,			September 30,			September 30,			September 30,
		2013			2012			2013			2012
	Net loss	$	(12,588	)	$	(10,044	)	$	(40,248	)	$	(28.914	)
	Deemed dividend related to beneficial conversion feature of convertible preferred stock		—			—			—			(1,307	)
	Net loss allocable to common stockholders	$	(12,588	)	$	(10,044	)	$	(40,248	)	$	(30,221	)
	Weighted-average common shares outstanding (weighted average number of shares used in computing net loss per share allocable to common stockholders) — basic and diluted		29,395			22,360			26,413			16,215
	Net loss per share allocable to common stockholders — basic and diluted	$	(0.43	)	$	(0.45	)	$	(1.52	)	$	(1.86	)
Instruments Excluded from the Computation of Diluted Net Loss Per Share	'
	The following instruments were excluded from the computation of diluted net loss per share for the periods presented because their effect would have been antidilutive (in thousands):
		Three and Nine Months Ended
		September 30,			September 30,
		2013			2012
	Options to purchase common stock		2,452			1,819
	Warrants to purchase common stock		7,692			9,009
	Series A convertible preferred stock (as converted to common stock)		—			—
	Series B convertible preferred stock (as converted to common stock)		—			3,838
	Restricted stock units		42			226
	Shares issuable related to the ESPP		31			20
	Total shares		10,217			14,912

Supplemental_Cash_Flow_Data_Ta

Supplemental Cash Flow Data (Tables)	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Data	'
	Supplemental cash flow data was as follows (in thousands):
		Nine Months Ended				Period from
		September 30,		September 30,		August 5, 1997
		2013		2012		(date of inception)
						to September 30,
						2013
	Significant non-cash investing and financing activities:
	Deferred stock-based compensation	$	—	$	—	$	6,940
	Purchases of property and equipment through accounts payable		110		—		110
	Purchases of property and equipment through accrued liabilities		29		5		29
	Purchases of property and equipment through trade in value of disposed property and equipment		—		—		258
	Penalty on restructuring of equipment financing lines		—		—		475
	Conversion of convertible preferred stock to common stock		13,626		—		146,798
	Warrants issued in equity financing		—		—		1,585

Related_Party_Research_and_Dev1

Related Party Research and Development Arrangements (Tables)	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]	'
Revenue from Amgen	'
	Revenue from Amgen was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	FTE reimbursements	$	564	$	963	$	1,455	$	3,231
	Reimbursements of other costs		—		—		—		3
	Total revenue from Amgen	$	564	$	963	$	1,455	$	3,234

Other_Research_and_Development1

Other Research and Development Revenue Arrangements (Tables)	9 Months Ended
	Sep. 30, 2013
Summary of Total Grant Revenue	'
	The Company recognized grant revenue under this grant arrangement as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	NINDS myasthenia gravis	$	—	$	264	$	69	$	896
Global Blood [Member]	'
Summary of Reimbursed Expenses	'
	Research and development revenue from Global Blood was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	Expense reimbursements from Global Blood Therapeutics	$	7	$	358	$	7	$	1,116
MyoKardia [Member]	'
Summary of Reimbursed Expenses	'
	Research and development revenue from MyoKardia was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	Expense reimbursements from MyoKardia	$	179	$	129	$	1,024	$	129
Astellas [Member]	'
Summary of Reimbursed Expenses	'
	Research and development revenue from Astellas was as follows (in thousands):
		Three Months Ended				Nine Months Ended
		September 30,		September 30,		September 30,		September 30,
		2013		2012		2013		2012
	License revenues	$	1,410	$	—	$	1,410	$	—
	FTE reimbursements		1,191		—		1,191		—
	Reimbursements of other costs		1,118		—		1,118		—
	Total revenue from Astellas	$	3,719		—	$	3,719		—

Cash_Equivalents_and_Investmen1

Cash Equivalents and Investments (Tables)	9 Months Ended
	Sep. 30, 2013
Investments Debt And Equity Securities [Abstract]	'
Amortized Cost and Fair Value of Cash Equivalents and Available for Sale Investments	'
	The amortized cost and fair value of cash equivalents and available for sale investments at September 30, 2013 and December 31, 2012 were as follows (in thousands):
		September 30, 2013
		Amortized		Unrealized		Unrealized		Fair		Maturity
		Cost		Gains		Losses		Value		Dates
	Cash equivalents — money market funds	$	17,201	$	—	$	—	$	17,201
	Short-term investments — U.S. Treasury securities	$	62,367	$	17	$	—	$	62,384	10/2013-9/2014
	Long-term investments — U.S. Treasury securities	$	3,752	$	2	$	—	$	3,754	Nov-14
		December 31, 2012
		Amortized		Unrealized		Unrealized		Fair		Maturity
		Cost		Gains		Losses		Value		Dates
	Cash equivalents — money market funds	$	10,655	$	—	$	—	$	10,655
	Short-term investments — U.S. Treasury securities	$	59,075	$	18	$	—	$	59,093	1/2013-11/2013
Summary of Interest Income	'
	Interest income was as follows (in thousands):
		Three Months Ended				Nine Months Ended				Period from
										August 5, 1997(date
		September 30,		September 30,		September 30,		September 30,		of inception) to
		2013		2012		2013		2012		September 30,2013
	Interest income	$	23	$	30	$	74	$	52	$	28,683

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Summary of Financial Assets Measured at Fair Value on a Recurring Basis	'
	Financial assets measured at fair value on a recurring basis as of September 30, 2013 and December 31, 2012 were classified in one of the three categories described above as follows (in thousands):
		September 30, 2013
		Fair Value Measurements Using						Assets
		Level 1		Level 2		Level 3		At Fair Value
	Money market funds	$	17,201	$	—	$	—	$	17,201
	U.S. Treasury securities		66,138		—		—		66,138
	Total	$	83,339	$	—	$	—	$	83,339
	Amounts included in:
	Cash and cash equivalents	$	17,201	$	—	$	—	$	17,201
	Short-term investments		62,384		—		—		62,384
	Long-term investments		3,754		—		—		3,754
	Total	$	83,339	$	—	$	—	$	83,339
		December 31, 2012
		Fair Value Measurements Using						Assets
		Level 1		Level 2		Level 3		At Fair Value
	Money market funds	$	10,655	$	—	$	—	$	10,655
	U.S. Treasury securities		59,093		—		—		59,093
	Total	$	69,748	$	—	$	—	$	69,748
	Amounts included in:
	Cash and cash equivalents	$	10,655	$	—	$	—	$	10,655
	Short-term investments		59,093		—		—		59,093
	Total	$	69,748	$	—	$	—	$	69,748

Stockholders_Equity_Deficit_Ta

Stockholders' Equity (Deficit) (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]	'
Summary of Stock Option Activity	'
	Stock option activity for the nine months ended September 30, 2013 under the Company’s 2004 Equity Incentive Plan, as amended, and the Company’s 1997 Stock Option/Stock Issuance Plan was as follows:
		Shares			Stock Options			Weighted
		Available for			Outstanding			Average Exercise
		Grant of						Price per Share of
		Options						Stock Options
		or Awards
	Balance at December 31, 2012		878,711			1,790,527		$	18.96
	Options granted		(769,979	)		769,979			5.93
	Options exercised		—			(21,397	)		5.32
	Options forfeited		19,382			(19,382	)		4.88
	Options expired		68,205			(68,205	)		16.17
	Restricted stock units granted		(41,661	)		—			—
	Restricted stock units forfeited		5,014			—			—
	Balance at September 30, 2013		159,672			2,451,522		$	15.18
Summary of Restricted Stock Unit Activity	'
	Restricted stock unit activity for the nine months ended September 30, 2013 was as follows:
		Number of			Weighted
		Shares			Average Award
					Date Fair Value per
					Share
	Restricted stock units outstanding at December 31, 2012		216,913		$	6.78
	Restricted stock units granted		41,661			6
	Restricted stock units vested		(211,897	)		6.78
	Restricted stock units forfeited		(5,014	)		6.78
	Unvested restricted stock units outstanding at September 30, 2013		41,663		$	6

Interest_and_Other_Net_Tables

Interest and Other, Net (Tables)	9 Months Ended
	Sep. 30, 2013
Other Income And Expenses [Abstract]	'
Components of Interest and Other, Net	'
	Components of Interest and other, net were as follows (in thousands):
		Three Months Ended						Nine Months Ended					Period from
													August 5, 1997
		September 30,			September 30,			September 30,		September 30,			(date of inception)
		2013			2012			2013		2012			to September 30, 2013
	Interest income and other income	$	24		$	30		$	76	$	56		$	29,176
	Interest expense and other expense		(1	)		(1	)		2		(2	)		(5,972	)
	Warrant expense		—			—			—		—			(1,585	)
	Interest and other, net	$	23		$	29		$	78	$	54		$	21,619

Organization_and_Summary_of_Si2

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended		194 Months Ended
	Jun. 24, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012
Accounting Policies [Abstract]	'	'	'	'	'	'	'
Accumulated deficit incurred	'	($489,128,000)	'	($489,128,000)	'	($489,128,000)	($448,880,000)
Net loss	'	-12,588,000	-10,044,000	-40,248,000	-28,914,000	-489,128,000	'
Cash, cash equivalents and investments	'	85,400,000	'	85,400,000	'	85,400,000	74,000,000
Cash requirements term	'	'	'	'12 months	'	'	'
Reverse stock split, description	'As of the effective time of the reverse stock split, every six shares of the Company's issued and outstanding common stock were converted into one issued and outstanding share of common stock, without any change in par value per share.	'	'	'	'	'	'
Reverse stock split, conversion ratio	0.1667	'	'	'	'	'	'
Number of authorized shares of common stock	'	81,500,000	'	81,500,000	'	81,500,000	81,500,000
Common stock par value	'	$0.00	'	$0.00	'	$0.00	$0.00
Reclassification from common stock to additional paid-in capital	'	'	'	$139,000	'	'	'

Net_Loss_Per_Share_Calculation

Net Loss Per Share - Calculation of Basic and Diluted Net Loss Per Share Allocable to Common Stockholders (Detail) (USD $)	3 Months Ended		9 Months Ended		194 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'	'
Net loss	($12,588)	($10,044)	($40,248)	($28,914)	($489,128)
Deemed dividend related to beneficial conversion feature of convertible preferred stock	'	'	'	-1,307	-4,164
Net loss allocable to common stockholders	($12,588)	($10,044)	($40,248)	($30,221)	($493,292)
Weighted-average common shares outstanding (weighted average number of shares used in computing net loss per share allocable to common stockholders) - basic and diluted	29,395	22,360	26,413	16,215	'
Net loss per share allocable to common stockholders - basic and diluted	($0.43)	($0.45)	($1.52)	($1.86)	'

Net_Loss_Per_Share_Instruments

Net Loss Per Share - Instruments Excluded from the Computation of Diluted Net Loss Per Share (Detail)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Total shares	10,217	14,912
Options to purchase common stock [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Total shares	2,452	1,819
Warrants to purchase common stock [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Total shares	7,692	9,009
Series A convertible preferred stock [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Total shares	'	'
Series B convertible preferred stock [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Total shares	'	3,838
Restricted stock units [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Total shares	42	226
Shares issuable related to the ESPP [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Total shares	31	20

Supplemental_Cash_Flow_Data_Su

Supplemental Cash Flow Data - Supplemental Cash Flow Data (Detail) (USD $)	9 Months Ended		194 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Significant non-cash investing and financing activities:	'	'	'
Deferred stock-based compensation	'	'	$6,940
Purchases of property and equipment through accounts payable	110	'	110
Purchases of property and equipment through accrued liabilities	29	5	29
Purchases of property and equipment through trade in value of disposed property and equipment	'	'	258
Penalty on restructuring of equipment financing lines	'	'	475
Conversion of convertible preferred stock to common stock	$13,626	'	$146,798
Warrants issued in equity financing	'	'	1,585

Related_Party_Research_and_Dev2

Related Party Research and Development Arrangements - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended	194 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Jun. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Jun. 30, 2013
					Amgen [Member]	Amgen [Member]	Amgen [Member]	Amgen [Member]	Amgen [Member]
								License and services [Member]	License and services [Member]
Related Party Transaction [Line Items]	'	'	'	'	'	'	'	'	'
Non-refundable license fee	'	'	'	'	$15,000,000	'	'	'	'
Common stock, shares issued	29,503,123	29,503,123	29,503,123	23,742,911	1,404,100	'	'	'	'
Per share price of common stock	'	'	'	'	$7.12	'	'	'	'
Aggregate purchase price	'	'	'	'	10,000,000	'	'	'	'
Common stock fair value	'	'	'	'	7,500,000	7,500,000	'	'	'
Deferred revenue	'	'	'	'	'	17,500,000	'	2,500,000	2,500,000
Maximum Pre-commercialization milestone payments received	1,410,000	1,410,000	1,410,000	'	'	50,000,000	'	'	'
Related party accounts receivable - Amgen	'	'	'	$4,000	'	$0	$0	'	'

Related_Party_Research_and_Dev3

Related Party Research and Development Arrangements - Revenue from Amgen (Detail) (USD $)	3 Months Ended		9 Months Ended		194 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Related Party Transaction [Line Items]	'	'	'	'	'
Total revenue from Amgen	$564	$963	$1,455	$3,234	$56,783
Amgen [Member]	'	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'	'
FTE reimbursements	564	963	1,455	3,231	'
Reimbursements of other costs	'	'	'	3	'
Total revenue from Amgen	$564	$963	$1,455	$3,234	'

Other_Research_and_Development2

Other Research and Development Revenue Arrangements - Additional information (Detail) (USD $)	1 Months Ended		9 Months Ended	12 Months Ended				1 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2010	Sep. 30, 2013	Sep. 30, 2013	Jun. 30, 2013	Jul. 31, 2013	Jul. 31, 2013	Jul. 31, 2013	Jul. 31, 2013
					Astellas [Member]	Astellas [Member]	Astellas [Member]	Minimum [Member]	Minimum [Member]	Maximum [Member]	Maximum [Member]
						License fee [Member]	License fee [Member]		Development and commercial products [Member]		Achievement of sales milestones [Member]
Research and Development Expenses [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Grant to support research and development	'	'	'	$2.80	'	'	'	'	'	'	'
Potential treatment of myasthenia gravis term	'	'	'	'3 years	'	'	'	'	'	'	'
Additional grant awarded	'	0.5	'	'	'	'	'	'	'	'	'
Upfront payment received	16	'	'	'	'	'	'	'	'	'	'
Potential amount receivable under collaboration agreement	'	'	'	'	'	'	'	24	'	'	'
Milestone payments received	'	'	'	'	'	'	'	'	112	250	200
Deferred revenue	'	'	'	'	18.4	14.6	16	'	'	'	'
Revenue recognized	'	'	$1.40	'	'	'	'	'	'	'	'

Other_Research_and_Development3

Other Research and Development Revenue Arrangements - Summary of Total Grant Revenue (Detail) (NINDS myasthenia gravis [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
NINDS myasthenia gravis [Member]	'	'	'	'
Research and Development Arrangement, Contract to Perform for Others [Line Items]	'	'	'	'
Total grant revenue	'	$264	$69	$896

Other_Research_and_Development4

Other Research and Development Revenue Arrangements - Summary of Reimbursed Expenses (Detail) (USD $)	3 Months Ended		9 Months Ended		194 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Research and Development Arrangement, Contract to Perform for Others [Line Items]	'	'	'	'	'
License revenues	$1,410	'	$1,410	'	$1,410
Total revenues	4,469	1,714	6,299	5,375	183,934
Astellas [Member]	'	'	'	'	'
Research and Development Arrangement, Contract to Perform for Others [Line Items]	'	'	'	'	'
License revenues	1,410	'	1,410	'	'
FTE reimbursements	1,191	'	1,191	'	'
Expense reimbursements	1,118	'	1,118	'	'
Total revenues	3,719	'	3,719	'	'
Global Blood [Member]	'	'	'	'	'
Research and Development Arrangement, Contract to Perform for Others [Line Items]	'	'	'	'	'
Expense reimbursements	7	358	7	1,116	'
MyoKardia [Member]	'	'	'	'	'
Research and Development Arrangement, Contract to Perform for Others [Line Items]	'	'	'	'	'
Expense reimbursements	$179	$129	$1,024	$129	'

Cash_Equivalents_and_Investmen2

Cash Equivalents and Investments - Amortized Cost and Fair Value of Cash Equivalents and Available for Sale Investments (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Cash equivalents [Member] | Money market funds [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Amortized Cost	17,201	10,655
Unrealized Gains	'	'
Unrealized Losses	'	'
Fair Value	17,201	10,655
Short-term investments [Member] | U.S. Treasury securities [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Amortized Cost	62,367	59,075
Unrealized Gains	17	18
Unrealized Losses	'	'
Fair Value	62,384	59,093
Long-term investments [Member] | U.S. Treasury securities [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Amortized Cost	3,752	'
Unrealized Gains	2	'
Unrealized Losses	'	'
Fair Value	3,754	'
Maturity Date	'2014-11	'
Minimum [Member] | Short-term investments [Member] | U.S. Treasury securities [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Maturity Date	'2013-10	'2013-01
Maximum [Member] | Short-term investments [Member] | U.S. Treasury securities [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Maturity Date	'2014-09	'2013-11

Cash_Equivalents_and_Investmen3

Cash Equivalents and Investments - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Short-term investments [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Unrealized Gain (loss)	$0	$0
U.S. Treasury securities [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
U.S. Treasury securities maturity start date	1-Jan-13	'
U.S. Treasury securities maturity end date	25-Oct-13	'

Cash_Equivalents_and_Investmen4

Cash Equivalents and Investments - Summary of Interest Income (Detail) (USD $)	3 Months Ended		9 Months Ended		194 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Cash Equivalents And Investments [Abstract]	'	'	'	'	'
Interest income	$23	$30	$74	$52	$28,683

Fair_Value_Measurements_Summar

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	$83,339	$69,748
Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	17,201	10,655
U.S. Treasury securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	66,138	59,093
Fair Value Measurements Using Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	83,339	69,748
Fair Value Measurements Using Level 1 [Member] | Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	17,201	10,655
Fair Value Measurements Using Level 1 [Member] | U.S. Treasury securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	66,138	59,093
Fair Value Measurements Using Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Fair Value Measurements Using Level 2 [Member] | Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Fair Value Measurements Using Level 2 [Member] | U.S. Treasury securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Fair Value Measurements Using Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Fair Value Measurements Using Level 3 [Member] | Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Fair Value Measurements Using Level 3 [Member] | U.S. Treasury securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Amounts included in: Cash and cash equivalents [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	17,201	10,655
Amounts included in: Cash and cash equivalents [Member] | Fair Value Measurements Using Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	17,201	10,655
Amounts included in: Cash and cash equivalents [Member] | Fair Value Measurements Using Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Amounts included in: Cash and cash equivalents [Member] | Fair Value Measurements Using Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Short-term investments [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	62,384	59,093
Short-term investments [Member] | Fair Value Measurements Using Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	62,384	59,093
Short-term investments [Member] | Fair Value Measurements Using Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Short-term investments [Member] | Fair Value Measurements Using Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Long-term investments [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	3,754	'
Long-term investments [Member] | Fair Value Measurements Using Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	3,754	'
Long-term investments [Member] | Fair Value Measurements Using Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'
Long-term investments [Member] | Fair Value Measurements Using Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Assets at fair value	'	'

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Fair Value Measurements Using Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial assets measured at fair value on a recurring basis	$0	$0
Fair Value Measurements Using Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Financial assets measured at fair value on a recurring basis	$0	$0

Stockholders_Equity_Deficit_Ad

Stockholders' Equity (Deficit) - Additional Information (Detail) (USD $)

1 Months Ended

6 Months Ended

6 Months Ended

9 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

1 Months Ended

0 Months Ended

In Millions, except Share data, unless otherwise specified

Jun. 24, 2013

Jun. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Feb. 28, 2013

Jun. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Jun. 30, 2013

Jun. 10, 2011

Dec. 31, 2012

Jun. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Jun. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Oct. 25, 2013

Jul. 02, 2013

Jul. 02, 2013

Warrants to purchase common stock [Member]

Amgen [Member]

Amgen [Member]

Amgen [Member]

Amgen [Member]

At-The-Market Issuance Sales Agreement [Member]

MLV Agreement [Member]

Series B convertible preferred stock [Member]

Series B convertible preferred stock [Member]

Series B convertible preferred stock [Member]

Series B convertible preferred stock [Member]

Common Stock [Member]

Common Stock [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

License and services [Member]

License and services [Member]

MLV Agreement [Member]

Series B convertible preferred stock [Member]

Common Stock [Member]

Share Based Compensation [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares issued

'

'

29,503,123

23,742,911

'

1,404,100

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Per share price of common stock

'

'

'

'

'

$7.12

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock fair value

'

'

'

'

'

$7.50

$7.50

'

'

'

'

'

'

'

'

'

'

'

'

'

Deferred revenue

'

'

'

'

'

'

17.5

2.5

2.5

'

'

'

'

'

'

'

'

'

'

'

Deferred revenue recognized term

'

'

'

'

'

'12

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Convertible preferred stock converted into common stock

'

'

'

'

'

'

'

'

'

'

'

'

15,026

4,000

1,000

'

'

'

4,000

'

Common Stock issued pursuant to Series B preferred Stock Conversion

'

'

'

'

'

'

'

'

'

'

'

'

'

'

167

2,504,334

666,667

'

'

666,667

Reverse stock split, conversion basis

'As of the effective time of the reverse stock split, every six shares of the Company's issued and outstanding common stock were converted into one issued and outstanding share of common stock, without any change in par value per share.

'

'

'

'

'

'

'

'

'

'

'One-for-six

'

'

'

'

'

'

'

'

Warrants purchase upon exercise of common stock

'

'

'

'

1,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants purchase upon exercise of common stock, exercise price

'

'

'

'

5.28

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of issued shares of common stock related to cashless exercise of warrants

'

358,460

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum aggregated offer value of saleable and issuable shares

'

'

'

'

'

'

'

'

'

20

'

'

'

'

'

'

'

'

'

'

Maximum saleable and issuable shares

'

'

'

'

'

'

'

'

'

2,397,279

'

'

'

'

'

'

'

'

'

'

Convertible Preferred stock, issued shares

'

'

'

'

'

'

'

'

'

'

862,592

'

'

'

'

'

'

0

'

'

Net proceeds from sales of common stock

'

'

'

'

'

'

'

'

'

'

$5.30

'

'

'

'

'

'

'

'

'

Stockholders_Equity_Deficit_Su

Stockholders' Equity (Deficit) - Summary of Stock Option Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares Available for Grant of Options or Awards, Beginning Balance	878,711
Shares Available for Grant of Options or Awards, Options granted	-769,979
Shares Available for Grant of Options or Awards, Options exercised	'
Shares Available for Grant of Options or Awards, Options Forfeited	19,382
Shares Available for Grant of Options or Awards, Options expired	68,205
Shares Available for Grant of Options or Awards, Ending Balance	159,672
Stock Options Outstanding, Beginning Balance	1,790,527
Stock Options Outstanding, Options granted	769,979
Stock Options Outstanding, Options exercised	-21,397
Stock Options Outstanding, Options Forfeited	-19,382
Stock Options Outstanding, Options expired	-68,205
Stock Options Outstanding, Ending Balance	2,451,522
Weighted Average Exercise Price per Share of Stock Options, Beginning Balance	$18.96
Weighted Average Exercise Price per Share of Stock Options, Options granted	$5.93
Weighted Average Exercise Price per Share of Stock Options, Options exercised	$5.32
Weighted Average Exercise Price per Share of Stock Options, Options Forfeited	$4.88
Weighted Average Exercise Price per Share of Stock Options, Options expired	$16.17
Weighted Average Exercise Price per Share of Stock Options, Ending Balance	$15.18
Restricted stock units [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares Available for Grant of Options or Awards, Options granted	'
Shares Available for Grant of Options or Awards, Restricted stock units granted	-41,661
Shares Available for Grant of Options or Awards, Restricted stock units forfeited	5,014
Stock Options Outstanding, Options Forfeited	'
Weighted Average Exercise Price per Share of Stock Options, Restricted stock units granted	'
Weighted Average Exercise Price per Share of Stock Options, Restricted stock units forfeited	'

Stockholders_Equity_Deficit_Su1

Stockholders' Equity (Deficit) - Summary of Restricted Stock Unit Activity (Detail) (Restricted Stock [Member], USD $)	9 Months Ended
	Sep. 30, 2013
Restricted Stock [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Restricted stock units outstanding, Number of Shares, Beginning Balance	216,913
Restricted stock units granted, Number of Shares	41,661
Restricted stock units vested, Number of Shares	-211,897
Restricted stock units forfeited, Number of Shares	-5,014
Unvested restricted stock units outstanding, Number of shares, Ending Balance	41,663
Restricted stock units outstanding, Weighted Average Award Date Fair Value per Share, Beginning Balance	$6.78
Restricted stock units granted, Weighted Average Award Date Fair Value per Share	$6
Restricted stock units vested, Weighted Average Award Date Fair Value per Share	$6.78
Restricted stock units forfeited, Weighted Average Award Date Fair Value per Share	$6.78
Unvested restricted stock units outstanding, Weighted Average Award Date Fair Value per Share, Ending Balance	$6

Interest_and_Other_Net_Compone

Interest and Other, Net - Components of Interest and Other, Net (Detail) (USD $)	3 Months Ended		9 Months Ended		194 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Other Income And Expenses [Abstract]	'	'	'	'	'
Interest income and other income	$24	$30	$76	$56	$29,176
Interest expense and other expense	-1	-1	2	-2	-5,972
Warrant expense	'	'	'	'	-1,585
Interest and other, net	$23	$29	$78	$54	$21,619

Income_Taxes_Additional_inform

Income Taxes - Additional information (Detail)	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Percentage of income tax likely to be realized	50.00%