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Document And Entity Information - shares	3 Months Ended
Document And Entity Information - shares	Mar. 31, 2013	May 07, 2013
Document Document And Entity Information [Abstract]
Document Type	10-Q/A
Amendment Flag	true
Amendment Description	The sole purpose of this Amendment No. 1 to Chimerix, Inc.'s Quarterly Report on Form 10-Q (the "Form 10-Q") for the period ended March 31, 2013, as filed with the Securities and Exchange Commission on May 13, 2013, is to furnish Exhibit 101 to the Form 10-Q in accordance with Rule 405 of Regulation S-T. Exhibit 101 provides the financial statements and related notes from the Form 10-Q formatted in XBRL (eXtensible Business Reporting Language). No other changes have been made to the Form 10-Q. This Amendment No. 1 to the Form 10-Q does not reflect events that may have occurred subsequent to the original filing date, and does not modify or update in any way disclosures made in the original Form 10-Q. In accordance with Rule 406T of Regulation S-T, the XBRL related information in Exhibit 101 to this Amendment No. 1 to the Form 10-Q is furnished and shall not be deemed to be "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to the liability of the section, and shall not be part of any registration statement or other document filed under the Securities Act of 1933, as amended (the "Securities Act"), or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.
Document Period End Date	Mar. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Entity Registrant Name	CHIMERIX INC
Entity Central Index Key	0001117480
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		25,722,451

Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 12,039	$ 19,906
Short-term investments, available-for-sale	10,877	9,849
Accounts receivable	1,228	783
Prepaid and other current assets	1,705	983
Deferred financing costs, current portion	31	33
Total current assets	25,880	31,554
Property and equipment, net of accumulated depreciation	391	407
Deposits	22	22
Deferred financing costs, less current portion	40	48
Total assets	26,333	32,031
Current liabilities:
Accounts payable	2,711	1,964
Accrued liabilities	1,713	906
Loan payable, current portion	5,519	4,753
Total current liabilities	9,943	7,623
Other long-term liabilities	338	337
Loan payable, less current portion	8,480	9,867
Redeemable convertible preferred stock warrant liability	9,715	7,512
Total liabilities	28,476	25,339
Redeemable convertible preferred stock	133,248	107,723
Common Stock:
Common stock, $0.001 par value, 89,700,000 shares authorized at March 31, 2013 and December 31, 2012; 1,536,577 and 1,533,996 shares issued and outstanding as of March 31, 2013 and December 31, 2012, respectively	3	3
Additional paid-in capital
Accumulated other comprehensive loss	(3)	(2)
Accumulated deficit	(135,391)	(101,032)
Total stockholders' deficit	(135,391)	(101,031)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	$ 26,333	$ 32,031

Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2013	Dec. 31, 2012
Balance Sheets [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	89,700,000	89,700,000
Common stock, shares issued	1,536,577	1,533,996
Common stock, shares outstanding	1,536,577	1,533,996

Statements Of Operations And Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues:
Contract and grant revenue	$ 1,771	$ 3,078
Total revenues	1,771	3,078
Operating expenses:
Research and development	6,498	6,642
General and administrative	1,821	1,926
Total operating expenses	8,319	8,568
Loss from operations	(6,548)	(5,490)
Interest expense, net	(356)	(109)
Fair value adjustments to warrant liability	(2,203)	(1,299)
Net loss	(9,107)	(6,898)
Other comprehensive loss:
Unrealized gain (loss) on securities available-for-sale	(1)	4
Comprehensive loss	(9,108)	(6,894)
Net loss	(9,107)	(6,898)
Accretion of redeemable convertible preferred stock	(25,525)	(900)
Net loss attributable to common stockholders	$ (34,632)	$ (7,798)
Per share information:
Net loss per common share, basic and diluted	$ (22.58)	$ (5.14)
Weighted-average shares outstanding, basic and diluted	1,534,016	1,517,465

Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
Statements Of Cash Flows - USD ($) $ in Thousands	Mar. 31, 2013	Mar. 31, 2012
Operating activities
Net loss	$ (9,107)	$ (6,898)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	68	73
Non-cash interest expense	65	22
Amortization/accretion of premium/discount on investments	74	29
Share-based compensation costs	265	286
Fair value measurement of redeemable convertible preferred stock warrant liability	2,203	1,299
Net change in:
Accounts receivable	(445)	1,926
Prepaid expenses and other current assets and deposits	(722)	619
Accounts payable and accrued liabilities	1,554	(2,263)
Net cash used in operating activities	(6,045)	(4,907)
Investing activities
Purchase of property and equipment	(52)	(5)
Purchase of short-term investments	(1,853)
Maturities of short-term investments	750	5,893
Net cash provided by (used in) investing activities	(1,155)	5,888
Financing activities
Proceeds from exercise of stock options	8
Proceeds from loan payable		3,000
Debt discount		(15)
Repayment of loan payable	(675)	(2,601)
Stock offering and deferred financing costs		(23)
Net cash provided by (used in) financing activities	(667)	361
Increase (decrease) in cash and cash equivalents	(7,867)	1,342
Cash and cash equivalents at beginning of period	19,906	13,607
Cash and cash equivalents at end of period	12,039	14,949
Supplemental schedule of cash flow information
Interest payments	$ 308	$ 44

The Business And Summary Of Significant Accounting Policies

3 Months Ended

Mar. 31, 2013

The Business And Summary Of Significant Accounting Policies [Abstract]

The Business And Summary Of Significant Accounting Policies

CHIMERIX, INC.

NOTES TO THE FINANCIAL STATEMENTS

(unaudited)

1. The Business and Summary of Significant Accounting Policies

Description of Business

Chimerix, Inc. (the Company) is a biopharmaceutical company committed to the discovery, development and commercialization of novel, oral antiviral therapeutics that are designed to transform patient care in areas of high unmet medical need. The Company’s proprietary lipid technology has given rise to two clinical-stage compounds, CMX001 and CMX157, which have demonstrated the potential for enhanced antiviral activity and safety in convenient, orally administered dosing regimens. CMX001 has shown broad-spectrum activity against double-stranded DNA viruses, including herpesviruses, adenoviruses and polyomaviruses. Chimerix anticipates beginning the Phase 3 SUPPRESS trial in 2013 for the prevention of cytomegalovirus infection in hematopoietic stem cell transplant recipients. The Company’s second clinical-stage compound, CMX157, is a Phase 1 product candidate for the treatment of HIV and was licensed to Merck, Sharp & Dohme Corp. (Merck) in 2012.

On March 25, 2013, the Company’s board of directors approved and implemented a 3.55-for-1 reverse stock split of the Company’s outstanding common stock. The reverse stock split resulted in an adjustment to the preferred stock conversion price to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to the financial statements give retroactive effect to the reverse stock split for all periods presented.

On April 10, 2013, the Company completed the initial public offering (IPO) of its common stock pursuant to a registration statement on Form S-1. In the IPO, the Company sold an aggregate of 7,320,000 shares of common stock under the registration statement at a public offering price $14.00 per share. Net proceeds were approximately $93.2 million, after deducting underwriting discounts and commissions of $7.2 million and offering expenses of $2.1 million. Upon the completion of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock and dividends accrued on Series F redeemable convertible preferred stock were converted into 15,556,091 shares of common stock and all outstanding warrants to purchase redeemable convertible preferred stock were converted into warrants to purchase 1,613,395 shares of common stock. On April 16, 2013, the Company was notified by the underwriters of their intent to exercise the full over-allotment option pursuant to which the Company sold an additional 1,098,000 shares at $14.00 per share. Net proceeds from the over-allotment shares were approximately $14.3 million after deducting underwriting discounts and commissions of $1.1 million.

The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). The preparation of the Company’s financial statements requires estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and the disclosure of contingent assets and liabilities in the financial statements and accompanying notes. Although these estimates are based on knowledge of current events and actions the Company may undertake in the future, actual results may ultimately differ from these estimates and assumptions.

The accompanying interim financial statements are unaudited. The unaudited interim financial statements have been prepared in accordance with GAAP on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the Company’s financial position, results of operations and cash flows for the dates and periods presented herein. These financial statements should be read in conjunction with the financial statements and notes set forth in the Company’s final prospectus dated April 10, 2013 filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended, with the Securities and Exchange Commission on April 11, 2013. Interim operating results are not necessarily indicative of operating results for the full year.

Cash and Cash Equivalents

The Company considers any highly liquid instrument with an original maturity of three months or less at acquisition to be a cash equivalent. Cash equivalents consist of money market accounts.

Investments

Investments consist primarily of corporate bonds and commercial paper. The Company invests in high-credit quality investments in accordance with its investment policy which minimizes the probability of loss.

Available-for-sale securities are carried at fair value as determined by quoted market prices, with the unrealized gains and losses, net of tax, reported as a separate component of stockholders deficit. Realized gains and losses are determined using the specific identification method and transactions are recorded on a settlement date basis in interest income or expense, net. Investments with original maturities beyond three months at the date of purchase and which mature on, or less than twelve months from, the balance sheet date are classified as long-term. The Company periodically reviews available-for-sale securities for other-than-temporary declines in fair value below the cost basis and whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Any such declines in value judged to be other-than-temporary on available-for-sale securities are reported in interest income or expense, net. There were no such declines in value for the three months ended March 31, 2013 and the year ended December 31, 2012.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash, cash equivalents, short-term investments and accounts receivable. The Company is exposed to credit risk, subject to federal deposit insurance, in the event of default by the financial institutions holding its cash and cash equivalents to the extent of amounts recorded on the balance sheets. Accounts receivable represent amounts due from an agency of the federal government.

Accounts Receivable

Accounts receivable at March 31, 2013 and December 31, 2012 consisted of amounts billed and unbilled under the Company’s contract with the Biomedical Advanced Research and Development Authority (BARDA). Receivables under the BARDA contract are recorded as qualifying research activities as conducted and invoices from the Company’s vendors are received. The Company carries its accounts receivable at cost less an allowance for doubtful accounts. On a periodic basis, the Company evaluates its accounts receivable and establishes an allowance based on its history of collections and write-offs and the current status of all receivables. The Company does not accrue interest on trade receivables. If accounts become uncollectible, they will be written off through a charge to the allowance for doubtful accounts. The Company has not recorded a charge to allowance for doubtful accounts as management believes all receivables are fully collectible.

Fair Value of Financial Instruments

The carrying amounts of certain financial instruments, including accounts receivable, notes receivable, accounts payable and accrued expenses approximate their fair values due to the short-term nature of such instruments. The carrying amount of borrowings under loans payable approximates its fair value based on the determination that the stated rate on such loans payable is consistent with current interest rates for similar borrowing arrangements available to the Company.

For assets and liabilities recorded at fair value, it is the Company’s policy to maximize the use of observable inputs and minimize the use of unobservable inputs when developing fair value measurements, in accordance with the fair value hierarchy. Fair value measurements for assets and liabilities where there exists limited or no observable market data are based primarily upon estimates and are often calculated based on the economic and competitive environment, the characteristics of the asset or liability and other factors. Therefore, fair value measurements cannot be determined with precision and may not be realized in an actual sale or immediate settlement of the asset or liability. Additionally, there may be inherent weaknesses in any calculation technique and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the calculated current or future fair values. The Company utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures.

The Company groups assets and liabilities at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. An adjustment to the pricing method used within either Level 1 or Level 2 inputs could generate a fair value measurement that effectively falls in a lower level in the hierarchy. These levels are:



Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access.



Level 2 — Valuations based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and models for which all significant inputs are observable, either directly or indirectly.



Level 3 — Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

The determination of where an asset or liability falls in the hierarchy requires significant judgment. The Company evaluates hierarchy disclosures and, based on various factors, it is possible that an asset or liability may be classified differently from period to period. However, the Company expects that changes in classification between levels will be rare.

The warrants issued for Series F redeemable convertible preferred stock are categorized as Level 3 as there are significant unobservable inputs. The valuation of the warrants reflects a two stage process. Using a contingent claims model in combination with the Company’s Series F financing, which occurred in February 2011, the fair value of total equity and all components of the Company’s capital structure, including the warrants, is determined as of the time of the financing event. Using this value as a starting point, a series of equity values and associated probabilities are calculated using simulation methodologies that incorporate both Monte Carlo and risk neutral frameworks. Based on assessments of expected returns and volatilities consistent with market practice, a distribution of equity values was produced which covered the range of values that an informed market participant might expect. These outcomes were organized into ranges and a probability calculated based on the percent of the total falling into each range. This process created a range of equity values. Using a contingent claims framework, each equity value is allocated to the various components of the capital structure including the warrants. Each warrant value is weighted by its respective probability to determine the final fair value of the warrants as of March 31, 2013 and December 31, 2012. The key unobservable inputs used in the determination of the March 31, 2013 fair value are (i) volatility – 76%, (ii) range of implied fair value of the Series F redeemable convertible preferred stock – $8.02 to $13.42, (iii) time to liquidity – 8 months to 5 years, and (iv) range of probabilities of liquidity event outcomes – 3% to 33%.

There was no material re-measurement to fair value of financial assets and liabilities that are not measured at fair value on a recurring basis.

Below is a table that presents information about certain assets and liabilities measured at fair value on a recurring basis:

			Fair Value Measurements at March 31, 2013
	March 31, 2013		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	10,703	$	10,703	$	—	$	—
Short-term investments		10,877		—		10,877		—
Redeemable convertible preferred stock warrant liability		9,715		—		—		9,715

			Fair Value Measurements at December 31, 2012
	December 31, 2012		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	17,687	$	16,381	$	1,306	$	—
Short-term investments		9,849		—		9,849		—
Redeemable convertible preferred stock warrant liability		7,512		—		—		7,512

Below is a table that presents a reconciliation of the beginning and ending balances of liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3):


	Fair Value Measurements (Level 3)
	(in thousands)
Redeemable Convertible Preferred Stock Warrant Liability
Balance at January 1, 2012	$	6,491
Issuance		174
Fair value increase recorded in other expense		847
Fair value at December 31, 2012		7,512
Fair value increase recorded in other expense		2,203
Fair value at March 31, 2013	$	9,715

Prepaid and Other Current Assets

Prepaid and other current assets consist of the following:

	March 31, 2013		December 31, 2012
	(in thousands)
Prepaid development expenses	$	43	$	486
Deferred public offering costs		1,477		273
Other prepaid and other current assets		185		224
	$	1,705	$	983

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation. Depreciation is determined on a straight-line basis over the estimated useful lives of the assets, which generally range from three to five years. Leasehold improvements are amortized over the shorter of the useful life of the asset or the term of the related lease. Maintenance and repairs are charged against expense as incurred.

Impairment of Long-Lived Assets

The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. If the estimated future cash flows (undiscounted and without interest charges) from the use of an asset are less than the carrying value, a write-down would be recorded to reduce the related asset to its estimated fair value. To date, no such write-downs have occurred.

Deferred Public Offering Costs

Deferred public offering costs totaling $1.5 million at March 31, 2013 and $0.3 million at December 31, 2012 are included in prepaid and other current assets. These costs represent legal and accounting costs related to the Company’s efforts to raise capital through an IPO. IPO costs were deferred until completion of the Company’s IPO in April 2013 and such costs will be reclassified to additional paid-in capital as a reduction of the IPO proceeds.

Deferred Rent

The Company recognizes rent expense on a straight-line basis over the non-cancelable term of its operating lease and records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. The Company also records landlord-funded lease incentives, such as reimbursable leasehold improvements, as a deferred rent liability, which is amortized as a reduction of rent expense over the non-cancelable term of its operating lease.

Accrued Liabilities

Accrued liabilities consist of the following:


	March 31, 2013		December 31, 2012
	(in thousands)
Accrued compensation	$	508	$	560
Accrued development expenses		652		98
Other accrued liabilities		553		248
	$	1,713	$	906

Revenue Recognition

The Company’s revenues generally consist of (i) contract and grant revenues – revenues generated under federal contracts and other awarded grants, and (ii) collaboration and licensing revenues – revenues related to non-refundable upfront fees, royalties and milestone payments earned under license agreements. Revenues are recognized when the following criteria are met: (1) persuasive evidence that an arrangement exists; (2) delivery of the products and/or services has occurred; (3) the selling price is fixed or determinable; and (4) collectability is reasonably assured.

For arrangements that involve the delivery of more than one element, each product, service and/or right to use assets is evaluated to determine whether it qualifies as a separate unit of accounting. This determination is based on whether the deliverable has “stand-alone value” to the customer. The consideration that is fixed or determinable is then allocated to each separate unit of accounting based on the relative selling prices of each deliverable. The consideration allocated to each unit of accounting is recognized as the related goods and services are delivered, limited to the consideration that is not contingent upon future deliverables. If the arrangement constitutes a single unit of accounting, the revenue recognition policy must be determined for the entire arrangement and the consideration received is recognized over the period of inception through the date the last deliverable within the single unit of accounting is expected to be delivered. Revisions to the estimated period of recognition are reflected in revenue prospectively.

Non-refundable upfront fees are recorded as deferred revenue and recognized into revenue as license fees from collaborations on a straight-line basis over the estimated period of the Company’s substantive performance obligations. If the Company does not have substantive performance obligations, the Company recognizes non-refundable upfront fees into revenue through the date the deliverable is satisfied. Analyzing the arrangement to identify deliverables requires the use of judgment and each deliverable may be an obligation to deliver services, a right or license to use an asset, or another performance obligation.

Research and Development

Major components of research and development costs include cash compensation, stock based compensation, pre-clinical studies, clinical trial and related clinical manufacturing, drug development, materials and supplies, and fees paid to consultants and other entities that conduct certain research and development activities of the Company’s behalf. Research and development costs, including upfront fees and milestones paid to contract research organizations, are expensed as goods as received or services rendered. Costs incurred in connection with clinical trial activities for which the underlying nature of the activities themselves do not directly relate to active research and development, such as costs incurred for market research and focus groups linked to clinical strategy as well as costs to build the Company’s brand, are not included in research and development costs but are reflected as general and administrative costs.

Interest Expense, Net

Interest expense, net includes interest earned on short-term investments, interest incurred on loans payable, the amortization of deferred financing costs related to fees paid to attorneys and other non-lender entities in order to acquire debt, and the amortization of debt discount related to fees paid to the lender in order to acquire debt.

Income Taxes

Deferred tax assets and liabilities are determined based on differences between the financial and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Valuation allowances are established when the Company determines that it is more likely than not that some portion of a deferred tax asset will not be realized. The Company has incurred operating losses from April 7, 2000 (inception) through March 31, 2013, and therefore has not recorded any current provision for income taxes.

Additionally, the Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities based on the technical merits of the position. The tax benefit recognized in the financial statements for a particular tax position is based on the largest benefit that is more likely than not to be realized upon settlement. Accordingly, the Company establishes reserves for uncertain tax positions.

Share-Based Compensation

The Company measures and recognizes compensation expense for all share-based payment awards made to employees and directors, including employee stock options, based on estimated fair values. The fair value of share-based awards is estimated on the grant date using the Black-Scholes valuation model. The value of the portion of the award that is ultimately expected to vest is recorded as expense over the requisite service periods.

The Company also accounts for equity instruments issued to non-employees using a fair value approach. The Company values equity instruments, stock options and warrants granted to lenders and consultants using the Black-Scholes valuation model. The measurement of non-employee share-based compensation is subject to periodic adjustments as the underlying equity instruments vest and is recognized as an expense over the term of the related financing or the period over which services are received.

Basic and Dilutive Net Loss Per Share of Common Stock

Basic net loss per share of common stock is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period, excluding the dilutive effects converting redeemable convertible preferred stock, warrants to purchase redeemable convertible preferred stock, restricted stock and options. Diluted net loss per share of common stock is computed by dividing the net loss by the sum of the weighted-average number of shares of common stock outstanding during the period plus the potential dilutive effects of redeemable convertible preferred stock and warrants to purchase redeemable convertible preferred stock, and options outstanding during the period calculated in accordance with the treasury stock method, but are excluded if their effect is anti-dilutive. Because the impact of these items is anti-dilutive during the periods of net loss, there was no difference between basic and diluted loss per share of common stock for the three months ended March 31, 2013 and 2012.

The calculation of weighted-average diluted shares outstanding excludes the dilutive effect of converting redeemable convertible preferred stock, warrants to purchase convertible preferred stock and options to purchase common stock, as the impact of such items are anti-dilutive during periods of net loss. Shares excluded from the calculations were 11,511,182 and 11,313,242 for the three months ended March 31, 2013 and 2012, respectively.

Segments

The Company operates in only one segment. The chief operating decision-maker and management use cash flows as the primary measure to manage the business and do not segment the business for internal reporting or decision making.

Impact of Recently Issued Accounting Standards

On February 5, 2013, the Financial Accounting Standards Board issued an amendment ASU 2013-2, “Comprehensive Income (Topic 220)” (“ASU 2013-02”) to the disclosure requirements for reporting reclassifications out of accumulated other comprehensive income (“AOCI”). ASU 2013-02 was effective for the first interim or annual period beginning after December 15, 2012. The amendment requires companies to present information about reclassification adjustments from accumulated other comprehensive income to the income statement, including the income statement line items affected by the reclassification. The information must be presented in the financial statements in a single note or on the face of the financial statements. The new accounting guidance also requires the disclosure to be cross referenced to other financial statement disclosures for reclassification items that are not reclassified directly to net income in their entirety in the same reporting period. The Company adopted ASU 2013-02 in the first quarter of 2013. There was no material impact to the Company’s consolidated financial position, results of operations or cash flows upon adoption of this guidance.

Investments

3 Months Ended

Mar. 31, 2013

Investments [Abstract]

Investments

2. Investments

The following table summarizes available-for-sale securities:

	March 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Corporate bonds	$	10,131	$	—	$	(3	)	$	10,128
Commercial paper		749		—		—			749
Total	$	10,880	$	—	$	(3	)	$	10,877

	December 31, 2012
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Corporate bonds	$	8,353	$	—	$	(2	)	$	8,351
Commercial paper		1,498		—		—			1,498
Total	$	9,851	$	—	$	(2	)	$	9,849

All of the Company’s investments as of March 31, 2013 and December 31, 2012 had maturities of one year or less.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-Glossary Debt Security
-URI http://asc.fasb.org/extlink&oid=6509901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-Glossary Equity Security
-URI http://asc.fasb.org/extlink&oid=6511694

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27232-111563

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27405-111563

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 3, 19, 20, 21, 22, 137
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Property And Equipment

3 Months Ended

Mar. 31, 2013

Property And Equipment [Abstract]

Property And Equipment

3. Property and Equipment

Property and equipment consist of the following:

	March 31, 2013			December 31, 2012
	(in thousands)
Lab equipment	$	1,005		$	958
Leasehold improvements		78			78
Computer equipment		398			393
Office furniture and equipment		212			212
		1,693			1,641
Less accumulated depreciation		(1,302	)		(1,234	)
	$	391		$	407

- Definition

The entire disclosure for long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software. This disclosure may include property plant and equipment accounting policies and methodology, a schedule of property, plant and equipment gross, additions, deletions, transfers and other changes, depreciation, depletion and amortization expense, net, accumulated depreciation, depletion and amortization expense and useful lives, income statement disclosures, assets held for sale and public utility disclosures.

+ References + Details

Loan Payable	3 Months Ended
Loan Payable	Mar. 31, 2013
Loan Payable [Abstract]
Loan Payable	4. Loan Payable On January 27, 2012, the Company entered into a Loan and Security Agreement (LSA) with Silicon Valley Bank (SVB) and MidCap Financial SBIC, LP (MidCap) allowing for borrowings up to $15.0 million, split between a first tranche of $3.0 million borrowed at the time of the agreement, and a second tranche of up to $12.0 million that would be available to be drawn by December 31, 2012 upon meeting one of three stated financial and/or operational goals. The first tranche was used to repay the remaining principal balance outstanding of $2.6 million under a previous loan. This repayment was deemed a modification of debt and therefore the remaining related deferred financing costs totaling $0.1 million remained in deferred financing costs and are being amortized over the term of the LSA through interest expense. The first tranche has an interest-only period of twelve months followed by a thirty-month principal and interest amortization period with interest being charged at 8.25% per year for the full period of the LSA. The Company met one of the financial and/or operational goals mentioned above and, in September 2012, the remaining $12.0 million was borrowed in the second tranche. The second tranche has a six-month interest-only period followed by a thirty-two month principal and interest amortization period with interest being charged at the same rate as the first tranche. There are certain fees in accordance with the LSA which are being recorded as discounts or other long and short-term liabilities depending on the nature of the fees. The fees are being accreted through interest expense. Approximately $38,000 was recorded in interest expense for the three months ended March 31, 2013 and 2012. Concurrently with entering into the LSA, the Company also granted SVB a warrant to purchase shares of Series F preferred stock at a price of $2.045 per share equal to 2% of the aggregate amount of the advances made to the Company pursuant to the LSA, divided by the exercise price. In relation to the first tranche, 29,340 warrants became exercisable, and in relation to the second tranche, an additional 117,360 warrants became exercisable. As discussed in Note 1, the warrants are classified as a liability and are required to be measured at fair value. Therefore, the warrants were recorded as a debt discount at their fair value at the time of grant and accreted over the life of the LSA using the effective interest method. The subsequent re-valuation of the warrants (at fair value) resulted in other expense of $57,000 and $34,000 for the three months ended March 31, 2013 and 2012, respectively. Upon the completion of the IPO, these warrants were converted into warrants to purchase 41,323 shares of common stock.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References + Details

Commitments And Contingencies	3 Months Ended
Commitments And Contingencies	Mar. 31, 2013
Commitments And Contingencies [Abstract]
Commitments And Contingencies	5. Commitments and Contingencies Leases The Company leases its facilities and certain office equipment under long-term non-cancelable operating leases that expire at various dates through 2018. Rent expense under non-cancelable operating leases and other month-to-month equipment rental agreements, including common area maintenance fees, totaled approximately $0.1 million and $0.1 million for the three months ended March 31, 2013 and 2012, respectively. Significance of Revenue Source The Company is the recipient of federal research contract funds from BARDA. Periodic audits are required under the grant and contract agreements and certain costs may be questioned as appropriate under the agreements. Management believes that such amounts in the current year, if any, are not significant. Accordingly, no provision for refundable amounts under the agreements has been made as of March 31, 2013 and December 31, 2012.

- Definition

The entire disclosure for commitments and contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 20
-Section 50
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25287-109308

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 14
-Paragraph 3
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 5
-Paragraph 9, 10, 11, 12
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Redeemable Convertible Preferred Stock

3 Months Ended

Mar. 31, 2013

Redeemable Convertible Preferred Stock [Abstract]

Redeemable Convertible Preferred Stock

6. Redeemable Convertible Preferred Stock

In February 2011, the Company issued 22,004,895 shares of $0.001 par value Series F redeemable convertible preferred stock at $2.045 per share and warrants to purchase an aggregate of 5,501,215 shares of Series F redeemable convertible preferred stock at an exercise price of $2.045 per share for proceeds of $45.0 million, less issuance costs of $0.2 million. The warrants are exercisable at any time and expire on February 4, 2018.

In January 2012, the Company issued a warrant to SVB to purchase a number of shares of Series F redeemable convertible preferred stock at an exercise price of $2.045 per share equal to 2% of the aggregate amount of the advances made to the Company pursuant to the LSA, divided by the exercise price. Following the first and second tranches of the LSA, the warrant was exercisable to purchase an aggregate of 146,700 shares of Series F redeemable convertible preferred stock. The warrant issued to SVB is exercisable until January 22, 2022.

The following table summarizes the authorized, issued and outstanding shares of redeemable convertible preferred stock as of March 31, 2013 and December 31, 2012:


	Authorized Shares		Issued and Outstanding Shares
Series A		800,000		800,000
Series B		2,233,879		2,233,879
Series B-1		2,054,333		2,033,333
Series C		5,141,690		5,141,690
Series D		11,354,526		11,295,846
Series E		7,894,871		7,894,871
Series F		40,200,000		22,004,895
Total Shares		69,679,299		51,404,514

All preferred stock was convertible into common stock based on the relationship of the original issue price and the then effective conversion price for each series of stock, subject to adjustments for anti-dilution. Upon the completion of the IPO, the Company’s outstanding shares of redeemable convertible preferred stock and dividends accrued on Series F redeemable convertible preferred stock were automatically converted into an aggregate of 15,556,091 shares of common stock.

Warrants

The following warrants for the purchase of preferred stock on a one-to-one basis were issued, outstanding and exercisable at March 31, 2013 and December 31, 2012:

Class	Date	Shares		Price Per Share		Expiration
Series B-1	November 5, 2003		21,000	$	1.500	November 2013
Series D	November 24, 2008		58,680	$	2.045	November 2018
Series F	February 7, 2011		5,501,215	$	2.045	February 2018
Series F	January 27, 2012		146,700	$	2.045	January 2022

As discussed in Note 1, the warrants exercisable for the Company’s Series F preferred stock are classified as a liability and are required to be measured at fair value. Therefore, such warrants were recorded at the full fair value with the Company’s Series F preferred stock being recorded at the residual value at the time of issuance. At each reporting date, the warrants exercisable for the Company’s Series F preferred stock are recorded to fair value which is charged to other income. The fair valuation of such warrants resulted in other expense of $2.1 million and $1.3 million for the three months ended March 31, 2013 and 2012, respectively.

Upon the completion of the IPO, all outstanding warrants to purchase redeemable convertible preferred stock were converted into warrants to purchase 1,613,395 shares of common stock. On April 16, 2013, a warrant was exercised to purchase 211,783 shares of our common stock. The Company received proceeds of $1.5 million in connection with such exercise.

Stockholders' Deficit

3 Months Ended

Mar. 31, 2013

Stockholders' Deficit [Abstract]

Stockholders' Deficit

7. Stockholders’ Deficit

Common Stock

The Company’s common stock consists of 89.7 million authorized shares at March 31, 2013 and December 31, 2012 and 1.5 million shares issued and outstanding at March 31, 2013 and December 31, 2012, respectively.

Shares Reserved for Future Issuance

The following shares of common stock reserved for future issuances are as follows:



	March 31, 2013		December 31, 2012
Conversion of preferred stock and preferred stock warrants		16,093,483		16,093,483
Stock options issued and outstanding		2,774,058		2,593,423
Restricted Stock units outstanding		102,547		43,199
Authorized for future grants under the 2012 Equity Incentive Plan		185,369		427,933
		19,155,457		19,158,038

Stock Options

The Company has stock option plans under which incentive or nonqualified stock options may be awarded to employees, directors and consultants. The Company’s 2012 Equity Incentive Plan (the 2012 Plan), which became effective in February 2012, is a continuation of and successor to the Company’s 2002 Equity Incentive Plan (the 2002 Plan). The Company’s board of directors has authorized the grant of options for the purchase of up to 3,567,835 shares of the Company’s common stock as of March 31, 2013 and December 31, 2012.

Under the 2012 Plan, the Company’s board of directors determines the terms and conditions of options granted. The exercise price for stock options shall not be less than the fair market value at the date of grant, and the options expire no later than ten years from the date of grant. Options issued to employees generally vest one-fourth on the first anniversary date following the date of grant and ratably each month for the next three years. Any outstanding options that are cancelled are automatically returned to the option pool.

The 2012 Plan has an “early exercise” provision under which options to purchase common stock may be exercised prior to being fully vested; however, the shares issued for options exercised under the “early exercise” provision continue to vest under the same terms as the underlying exercised option. Upon termination of an employee prior to the vesting of such shares, the Company can either repurchase the unvested shares or let the repurchase right expire.

In connection with the IPO, the company adopted the 2013 Equity Incentive Plan (the 2013 Plan). The 2013 Plan provides for the grant of incentive stock options (ISOs), nonstatutory stock options (NSOs), stock appreciation rights, restricted stock awards, restricted stock unit (RSU) awards, performance-based stock awards, and other forms of equity compensation (collectively, stock awards), all of which may be granted to employees, including officers, non-employee directors and consultants of the Company and its affiliates. Additionally, the 2013 Plan provides for the grant of performance cash awards. ISOs may be granted only to employees. All other awards may be granted to employees, including officers, and to non-employee directors and consultants. Initially, the aggregate number of shares of common stock that may be issued pursuant to stock awards under the 2013 Plan is the sum of (i) 1,408,450 shares, plus (ii) the number of shares reserved for issuance under the 2012 Plan at the time the 2013 Plan becomes effective, plus (iii) any shares subject to outstanding stock options or other stock awards that would have otherwise returned to the 2012 Plan (such as upon the expiration or termination of a stock award prior to vesting). Additionally, the number of shares of common stock reserved for issuance under the 2013 Plan will automatically increase on January 1 of each year, beginning on January 1, 2014 (assuming the 2013 Plan becomes effective before such date) and continuing through and including January 1, 2023, by 2.5% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the Company’s board of directors. The maximum number of shares that may be issued upon the exercise of ISOs under the 2013 Plan is 2,816,901 shares. Following the effectiveness of the 2013 Plan in April 2013, no further grants will be made under the 2012 Plan.

In February 2013 the Company’s board of directors adopted the 2013 Employee Stock Purchase Plan (ESPP) which was subsequently ratified by our stockholders and became effective in April 2013. The purpose of the ESPP is to retain the services of new employees and secure the services of new and existing employees while providing incentives for such individuals to exert maximum efforts toward the Company’s success and that of its affiliates. The ESPP authorizes the issuance of 704,225 shares of common stock pursuant to purchase rights granted to the Company’s employees or to employees of any of its designated affiliates. The number of shares of common stock reserved for issuance will automatically increase on January 1 of each calendar year, from January 1, 2014 (assuming the ESPP becomes effective before such date) through January 1, 2023 by the least of (a) 1% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, (b) 422,535 shares, or (c) a number determined by the Company’s board of directors that is less than (a) and (b). The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the Code. As of the date hereof, no shares of common stock have been purchased under the ESPP.

A summary of activity related to the Company’s stock options is as follows:

	Number of Options Outstanding			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in Years)
Balance, December 31, 2012		2,593,423		$	2.45		7.36
Granted		184,506			6.39		—
Exercised		(2,581	)		3.16		—
Forfeited		(1,290	)		2.60		—
Balance, March 31, 2013		2,774,058		$	2.71		7.30
Exercisable at March 31, 2013		1,717,710		$	2.28		6.48
Vested or expected to vest at March 31, 2013		2,580,766		$	2.71		7.25

For awards with only service conditions and graded-vesting features, the Company recognizes compensation expense on a straight-line basis over the requisite service period. The fair value of options vested and share-based compensation expense recognized are as follows:

	Three Months Ended March 31,
	2013		2012
	(in thousands)
Research and development:
Employee	$	107	$	100
Non-employee		16		10
General and administrative:
Employee		110		167
Non-employee		32		9
	$	265	$	286

Restricted Stock Units

In 2012 and 2013, the Company issued RSUs to certain employees which vest based on specific performance criteria. By their terms, the RSUs become immediately vested upon the earlier of (i) a change of control and (ii) the effective date of a registration statement for the Company’s common stock, subject to the continuous service with the Company at the applicable vesting event. When vested, the RSU represents the right to be issued the number of shares of the Company’s common stock that is equal to the number of RSUs granted.

A summary of activity related to the Company’s RSUs is as follows:

	Number of Restricted Stock Units Outstanding
Balance, December 31, 2012		43,199
Granted		59,348
Balance, March 31, 2013		102,547

As of March 31, 2013, no compensation had been recorded as it was not considered probable that the performance criteria would be met.

Upon the effective date of the registration statement for the IPO, 102,547 RSUs that had been previously granted to Company employees vested. The RSUs will convert into common stock 180 days after the date of the IPO.

- Definition

The entire disclosure for shareholders' equity, comprised of portions attributable to the parent entity and noncontrolling interest, if any, including other comprehensive income (as applicable). Including, but not limited to: (1) balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings; (2) accumulated balance for each classification of other comprehensive income and total amount of comprehensive income; (3) amount and nature of changes in separate accounts, including the number of shares authorized and outstanding, number of shares issued upon exercise and conversion, and for other comprehensive income, the adjustments for reclassifications to net income; (4) rights and privileges of each class of stock authorized; (5) basis of treasury stock, if other than cost, and amounts paid and accounting treatment for treasury stock purchased significantly in excess of market; (6) dividends paid or payable per share and in the aggregate for each class of stock for each period presented; (7) dividend restrictions and accumulated preferred dividends in arrears (in aggregate and per share amount); (8) retained earnings appropriations or restrictions, such as dividend restrictions; (9) impact of change in accounting principle, initial adoption of new accounting principle and correction of an error in previously issued financial statements; (10) shares held in trust for Employee Stock Ownership Plan (ESOP); (11) deferred compensation related to issuance of capital stock; (12) note received for issuance of stock; (13) unamortized discount on shares; (14) description, terms, and number of warrants or rights outstanding; (15) shares under subscription and subscription receivables, effective date of new retained earnings after quasi-reorganization and deficit eliminated by quasi-reorganization and, for a period of at least ten years after the effective date, the point in time from which the new retained dates; and (16) retroactive effective of subsequent change in capital structure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Section B
-Paragraph 7, 11A
-Chapter 1
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
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-Paragraph d
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Reference 18: http://www.xbrl.org/2003/role/presentationRef
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-Number 210
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
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Reference 20: http://www.xbrl.org/2003/role/presentationRef
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Reference 23: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2013
Income Taxes [Abstract]
Income Taxes	8. Income Taxes The Company estimates an annual effective tax rate of 0% for the year ending December 31, 2013 as the Company incurred losses for the three month period ended March 31, 2013 and is forecasting additional losses through the 4th quarter, resulting in an estimated net loss for both financial statement and tax purposes for the year ending December 31, 2013. Therefore, no federal or state income taxes are expected and none have been recorded at this time. Income taxes have been accounted for using the liability method in accordance with FASB ASC 740. Due to the Company's history of losses since inception, there is not enough evidence at this time to support that the Company will generate future income of a sufficient amount and nature to utilize the benefits of its net deferred tax assets. Accordingly, the deferred tax assets have been reduced by a valuation allowance, since it has been determined that it is more likely than not that all of the deferred tax assets will not be realized. At March 31, 2013, the Company had no unrecognized tax benefits that would reduce the Company’s effective tax rate if recognized.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

+ Details

Significant Agreements	3 Months Ended
Significant Agreements	Mar. 31, 2013
Significant Agreements [Abstract]
Significant Agreements	9. Significant Agreements The Regents of the University of California In May 2002, the Company entered into a license agreement with The Regents of the University of California (UC) under which the Company obtained an exclusive, worldwide license to UC’s patent rights in certain inventions (the UC Patent Rights) related to lipid-conjugated antiviral compounds and their use, including certain patents relating to CMX001 and CMX157. The license agreement was amended in September 2002 in order to expand the scope of the license and again in December 2010 in order to modify certain financial terms. The agreement was amended a third time in September 2011 to add additional patents related to certain metabolically stable lipid-conjugate compounds. A fourth amendment was executed in July 2012 to alter the rights and obligations of the parties in light of the Company’s current business plans. As partial consideration for the rights granted to the Company under the license agreement, the Company is required to pay certain cash milestone payments in connection with the development and commercialization of compounds that are covered by the UC Patent Rights. In connection with the development and commercialization of CMX001 and CMX157, the Company could be required to pay UC up to an aggregate of $3.4 million in milestone payments, assuming the achievement of all applicable milestone events under the license agreement. Under the license agreement, the Company is permitted to research, develop, manufacture and commercialize products utilizing the UC Patent Rights for all human and veterinary uses, and to sublicense such rights. UC retained the right, on behalf of itself and other non-profit institutions, to use the UC Patent Rights for educational and research purposes and to publish information about the UC Patent Rights. In consideration for the rights granted under the license agreement, the Company has issued UC an aggregate of 64,788 shares of common stock. As additional consideration, the Company is required to pay certain cash milestone payments in connection with the development and commercialization of compounds that are covered by the UC Patent Rights, plus certain annual fees to maintain such patents until the Company commercializes a product utilizing UC Patent Rights. In addition, upon commercialization of any product utilizing the UC Patent Rights (which would include the commercialization of CMX001 or CMX157), the Company will be required to pay low single digit royalties on net sales of such product. In the event the Company sublicenses a UC Patent Right (including UC Patent Rights relating to CMX001 or CMX157), the Company is obligated to pay to UC a fee, which amount will vary depending upon the size of any upfront payment the Company receives and the clinical development stage of the compound being sublicensed, but which could be up to approximately 50% of the sublicense fee in certain circumstances. In addition, the Company will also be required to pay to UC a low single digit sublicense royalty on net sales of products that use the sublicensed UC Patent Rights, but in no event will the Company be required to pay more than 50% of the royalties it receives in connection with the relevant sublicense. Any such royalty payment will be reduced by other payments the Company is required to make to third parties until a minimum royalty has been reached. As a result of meeting certain milestones and sublicense fees related to the license agreement, the Company recognized expenses of $0.9 million for the year ended December 31, 2012. The Company did not recognize expenses for the three months ended March 31, 2013. Biomedical Advanced Research and Development Authority In February 2011, the Company entered into a contract with BARDA for the advanced development of CMX001 as a medical countermeasure in the event of a smallpox release. The contract has been amended several times, most recently on February 21, 2013, to extend the period of performance of the base performance segment through May 31, 2013. Under the contract, BARDA will reimburse the Company, plus pay us a fixed fee, for the research and development of CMX001 as a broad-spectrum therapeutic antiviral for the treatment of smallpox infections. The contract consists of an initial performance period, referred to as the base performance segment, plus up to four extension periods of approximately one year each, referred to as option segments, each of which may be exercised at BARDA’s sole discretion. The Company must complete the agreed upon milestones and deliverables in each discrete work segment before the next option segment is eligible to be exercised. Under the contract as currently in effect, the Company may receive up to $75.8 million in expense reimbursement and $5.3 million in fees. The Company is currently completing the base performance segment of the contract under which the Company may receive up to a total of $31.0 million in expense reimbursement and fees. The term of the base performance segment ends on May 31, 2013. Currently, the Company is in discussions with BARDA regarding subsequent segments of the contract. Merck, Sharp & Dohme Corp. In July 2012, the Company entered into a collaboration and license agreement granting Merck exclusive worldwide rights to CMX157, the Company’s lipid acyclic nucleoside phosphonate currently being evaluated to treat HIV infection. Under the terms of the agreement, Merck received an exclusive worldwide license for any human use of CMX157 and has agreed to use commercially reasonable efforts to develop and commercialize CMX157 in the United States and at least three major European markets. Following execution of the agreement, the Company received a $17.5 million upfront payment from Merck. As additional consideration, the Company is eligible to receive up to a total of $151.0 million in milestone payments if certain development and regulatory milestones are achieved by Merck for products utilizing CMX157, as well as tiered royalties on net sales ranging from high single digits to low double digits, depending upon the volume of sales of each applicable product, if CMX157 is successfully commercialized. Milestone payments are triggered upon the completion of various stages of the regulatory approval process for each of the first two indications for CMX157, with the final milestones reached upon approval in the United States and three major European markets. Royalties for any given product will continue on a country-by-country basis through the later of the expiration of the Company’s patent rights applicable to such product or ten years from the first commercial sale of such product. The Company’s participation in the collaboration with Merck, including its involvement in the joint steering committee to monitor the development of CMX157, represents a right and an observation role only, rather than a substantive performance obligation. As such, the Company’s performance in this collaboration relates to the specific transfers in connection with the license which was completed during the same quarter the agreement was entered into. Therefore, the Company recognized the upfront payment during the year ended December 31, 2012. The contingent event-based payments that the Company may receive pursuant to the agreement do not meet the definition of a milestone as achievement of the triggering event for such payments is based on the performance of Merck and not Chimerix. Therefore, the milestone method will not be applied to those payments.

Subsequent Events

3 Months Ended

Mar. 31, 2013

Subsequent Events [Abstract]

Subsequent Events

10. Subsequent Events

Authorized Share Capital

Effective April 16, 2013, the Company’s certificate of incorporation was amended and restated to provide for 200,000,000 authorized shares of common stock with a par value of $0.001 per share, and 10,000,000 authorized shares of undesignated preferred stock with a par value of $0.001 per share.

Initial Public Offering

On April 16, 2013, the Company announced completion of its IPO, whereby the Company sold a total of 8,418,000 shares of common stock at $14.00 per share for net proceeds of $107.5 million (after underwriting discounts, commissions and estimated offering costs as of March 31, 2013). This amount includes the full exercise of the over-allotment option to purchase 1,098,000 shares of common stock by the Company’s underwriters. Upon completion of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock and dividends accrued on Series F redeemable convertible preferred stock were converted into 15,556,091 shares of common stock and all outstanding warrants to purchase redeemable convertible preferred stock converted into warrants to purchase 1,613,395 shares of common stock.

The financial statements as of March 31, 2013 and 2012, including share and per share amounts, do not include the effects of the IPO.

Restricted Stock Units

Warrant Exercise

On April 16, 2013, a warrant was exercised with respect to 211,783 shares of common stock. The Company received proceeds of $1.5 million in connection with such exercise.

Pro Forma Balance Sheet

The balance sheet data below show, on a pro forma basis, the impact on certain balance sheet items of significant equity transactions which occurred since March 31, 2013. Specifically, the pro forma balance sheet data give effect to the following in connection with the completion of the IPO on April 16, 2013: (i) the conversion of all of the Company’s outstanding shares of redeemable convertible preferred stock and accrued dividends in Series F redeemable convertible preferred stock into an aggregate of 15,556,091 shares of common stock, (ii) the sale of 8,418,000 shares of common stock at a price to the public of $14.00 per share in the IPO, net of underwriting discounts and unpaid offering costs, (iii) the reclassification of $1.5 million of offering costs attributable to the IPO from prepaid and other current assets to additional paid in capital, and (iv) the issuance of 211,783 shares of common stock pursuant to the exercise of a warrant for the purchase of common shares.


	Actual as of March 31, 2013			Pro Forma as of March 31, 2013
	(in thousands)
Selected Balance Sheet Data
Cash, cash equivalents and short-term investments	$	22,916		$	134,056
Total current assets		25,880			135,543
Total assets		26,333			135,996
Total current liabilities		9,943			9,943
Total liabilities		28,476			18,761
Redeemable convertible preferred stock		133,248			—
Common stock		3			27
Additional paid-in capital		—			252,602
Accumulated deficit		(135,391	)		(135,391	)
Total stockholders' (deficit) equity		(135,391	)		117,235
Total liabilities, redeemable convertible preferred stock and stockholders' (deficit) equity	$	26,333		$	135,996

The Business And Summary Of Significant Accounting Policies (Policy)

3 Months Ended

Mar. 31, 2013

The Business And Summary Of Significant Accounting Policies [Abstract]

Description Of Business

Description of Business

Cash And Cash Equivalents

Cash and Cash Equivalents

The Company considers any highly liquid instrument with an original maturity of three months or less at acquisition to be a cash equivalent. Cash equivalents consist of money market accounts.

Investments

Concentration Of Credit Risk

Concentration of Credit Risk

Accounts Receivable

Fair Value Of Financial Instruments

Fair Value of Financial Instruments



Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access.



Level 3 — Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

There was no material re-measurement to fair value of financial assets and liabilities that are not measured at fair value on a recurring basis.

Below is a table that presents information about certain assets and liabilities measured at fair value on a recurring basis:

			Fair Value Measurements at March 31, 2013
	March 31, 2013		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	10,703	$	10,703	$	—	$	—
Short-term investments		10,877		—		10,877		—
Redeemable convertible preferred stock warrant liability		9,715		—		—		9,715

			Fair Value Measurements at December 31, 2012
	December 31, 2012		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	17,687	$	16,381	$	1,306	$	—
Short-term investments		9,849		—		9,849		—
Redeemable convertible preferred stock warrant liability		7,512		—		—		7,512

Below is a table that presents a reconciliation of the beginning and ending balances of liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3):


	Fair Value Measurements (Level 3)
	(in thousands)
Redeemable Convertible Preferred Stock Warrant Liability
Balance at January 1, 2012	$	6,491
Issuance		174
Fair value increase recorded in other expense		847
Fair value at December 31, 2012		7,512
Fair value increase recorded in other expense		2,203
Fair value at March 31, 2013	$	9,715

Property And Equipment

Property and Equipment

Impairment Of Long-Lived Assets

Impairment of Long-Lived Assets

Deferred Public Offering Costs

Deferred Rent

Revenue Recognition

Research and Development

Interest Expense, Net

Income Taxes

Share-Based Compensation

Basic And Dilutive Net Loss Per Share Of Common Stock

Basic and Dilutive Net Loss Per Share of Common Stock

Segments

The Business And Summary Of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2013

The Business And Summary Of Significant Accounting Policies [Abstract]

Assets And Liabilities Measured At Fair Value On A Recurring Basis

Below is a table that presents information about certain assets and liabilities measured at fair value on a recurring basis:

			Fair Value Measurements at March 31, 2013
	March 31, 2013		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	10,703	$	10,703	$	—	$	—
Short-term investments		10,877		—		10,877		—
Redeemable convertible preferred stock warrant liability		9,715		—		—		9,715

			Fair Value Measurements at December 31, 2012
	December 31, 2012		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents	$	17,687	$	16,381	$	1,306	$	—
Short-term investments		9,849		—		9,849		—
Redeemable convertible preferred stock warrant liability		7,512		—		—		7,512

Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis

Below is a table that presents a reconciliation of the beginning and ending balances of liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3):


	Fair Value Measurements (Level 3)
	(in thousands)
Redeemable Convertible Preferred Stock Warrant Liability
Balance at January 1, 2012	$	6,491
Issuance		174
Fair value increase recorded in other expense		847
Fair value at December 31, 2012		7,512
Fair value increase recorded in other expense		2,203
Fair value at March 31, 2013	$	9,715

Schedule Of Prepaid And Other Current Assets

Prepaid and other current assets consist of the following:

	March 31, 2013		December 31, 2012
	(in thousands)
Prepaid development expenses	$	43	$	486
Deferred public offering costs		1,477		273
Other prepaid and other current assets		185		224
	$	1,705	$	983

Schedule Of Accrued Liabilities

Accrued liabilities consist of the following:


	March 31, 2013		December 31, 2012
	(in thousands)
Accrued compensation	$	508	$	560
Accrued development expenses		652		98
Other accrued liabilities		553		248
	$	1,713	$	906

- Definition

Tabular disclosure of the fair value measurement of liabilities using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and gains or losses recognized in other comprehensive income (loss) and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs) by class of liability.

+ References + Details

Investments (Tables)

3 Months Ended

Mar. 31, 2013

Investments [Abstract]

Summary Of Available-For-Sale Securities

The following table summarizes available-for-sale securities:

	March 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Corporate bonds	$	10,131	$	—	$	(3	)	$	10,128
Commercial paper		749		—		—			749
Total	$	10,880	$	—	$	(3	)	$	10,877

	December 31, 2012
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Corporate bonds	$	8,353	$	—	$	(2	)	$	8,351
Commercial paper		1,498		—		—			1,498
Total	$	9,851	$	—	$	(2	)	$	9,849

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27337-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27198-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 19, 20, 21
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 17
-Subparagraph a, b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 03-1
-Paragraph 21
-Subparagraph a, b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Property And Equipment (Tables)

3 Months Ended

Mar. 31, 2013

Property And Equipment [Abstract]

Property And Equipment

Property and equipment consist of the following:

	March 31, 2013			December 31, 2012
	(in thousands)
Lab equipment	$	1,005		$	958
Leasehold improvements		78			78
Computer equipment		398			393
Office furniture and equipment		212			212
		1,693			1,641
Less accumulated depreciation		(1,302	)		(1,234	)
	$	391		$	407

Redeemable Convertible Preferred Stock (Tables)

3 Months Ended

Mar. 31, 2013

Redeemable Convertible Preferred Stock [Abstract]

Summary Of Authorized, Issued And Outstanding Shares Of Redeemable Convertible Preferred Stock

The following table summarizes the authorized, issued and outstanding shares of redeemable convertible preferred stock as of March 31, 2013 and December 31, 2012:


	Authorized Shares		Issued and Outstanding Shares
Series A		800,000		800,000
Series B		2,233,879		2,233,879
Series B-1		2,054,333		2,033,333
Series C		5,141,690		5,141,690
Series D		11,354,526		11,295,846
Series E		7,894,871		7,894,871
Series F		40,200,000		22,004,895
Total Shares		69,679,299		51,404,514

Schedule Of Warrants Issued, Outstanding And Exercisable

The following warrants for the purchase of preferred stock on a one-to-one basis were issued, outstanding and exercisable at March 31, 2013 and December 31, 2012:

Class	Date	Shares		Price Per Share		Expiration
Series B-1	November 5, 2003		21,000	$	1.500	November 2013
Series D	November 24, 2008		58,680	$	2.045	November 2018
Series F	February 7, 2011		5,501,215	$	2.045	February 2018
Series F	January 27, 2012		146,700	$	2.045	January 2022

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

- Definition

Tabular disclosure of temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

+ References + Details

Stockholders' Deficit (Tables)

3 Months Ended

Mar. 31, 2013

Stockholders' Deficit [Abstract]

Schedule Of Shares Reserved For Future Issuance

The following shares of common stock reserved for future issuances are as follows:



	March 31, 2013		December 31, 2012
Conversion of preferred stock and preferred stock warrants		16,093,483		16,093,483
Stock options issued and outstanding		2,774,058		2,593,423
Restricted Stock units outstanding		102,547		43,199
Authorized for future grants under the 2012 Equity Incentive Plan		185,369		427,933
		19,155,457		19,158,038

Summary Of Activity Related To Stock Options

A summary of activity related to the Company’s stock options is as follows:

	Number of Options Outstanding			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in Years)
Balance, December 31, 2012		2,593,423		$	2.45		7.36
Granted		184,506			6.39		—
Exercised		(2,581	)		3.16		—
Forfeited		(1,290	)		2.60		—
Balance, March 31, 2013		2,774,058		$	2.71		7.30
Exercisable at March 31, 2013		1,717,710		$	2.28		6.48
Vested or expected to vest at March 31, 2013		2,580,766		$	2.71		7.25

Fair Value Of Option Vested And Share-Based Compensation Expense

The fair value of options vested and share-based compensation expense recognized are as follows:

	Three Months Ended March 31,
	2013		2012
	(in thousands)
Research and development:
Employee	$	107	$	100
Non-employee		16		10
General and administrative:
Employee		110		167
Non-employee		32		9
	$	265	$	286

Summary Of Activity Related To Restricted Stock Units

A summary of activity related to the Company’s RSUs is as follows:

	Number of Restricted Stock Units Outstanding
Balance, December 31, 2012		43,199
Granted		59,348
Balance, March 31, 2013		102,547

Subsequent Events (Tables)

3 Months Ended

Mar. 31, 2013

Subsequent Events [Abstract]

Schedule Of Selected Balance Sheet Data Since IPO


	Actual as of March 31, 2013			Pro Forma as of March 31, 2013
	(in thousands)
Selected Balance Sheet Data
Cash, cash equivalents and short-term investments	$	22,916		$	134,056
Total current assets		25,880			135,543
Total assets		26,333			135,996
Total current liabilities		9,943			9,943
Total liabilities		28,476			18,761
Redeemable convertible preferred stock		133,248			—
Common stock		3			27
Additional paid-in capital		—			252,602
Accumulated deficit		(135,391	)		(135,391	)
Total stockholders' (deficit) equity		(135,391	)		117,235
Total liabilities, redeemable convertible preferred stock and stockholders' (deficit) equity	$	26,333		$	135,996

The Business And Summary Of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Thousands				3 Months Ended
	Apr. 16, 2013 USD ($) $ / shares shares	Apr. 10, 2013 USD ($) $ / shares shares	Mar. 25, 2013 item	Mar. 31, 2013 USD ($) $ / shares shares	Mar. 31, 2012 shares	Dec. 31, 2012 USD ($)
Description Of Business
Stock split, reverse description			the Company's board of directors approved and implemented a 3.55-for-1 reverse stock split of the Company's outstanding common stock
Reverse stock split, coversion ratio \| item			3.55
Deferred Public Offering Costs
Deferred public offering costs \| $				$ 1,477		$ 273
Per share information:
Anti-dilutive securities excluded from the calculation loss per share \| shares				11,511,182	11,313,242
Over Allotment Options [Member]
Description Of Business
Stock issued during the period, shares \| shares	1,098,000
Public offering underwriting discounts and commissions \| $		$ 1,100
Subsequent Event [Member]
Description Of Business
Stock issued during the period, shares \| shares	8,418,000	7,320,000
Stock price, initial public offering \| $ / shares	$ 14.00	$ 14.00
Proceeds from initial public offering \| $	$ 107,500	$ 93,200
Public offering underwriting discounts and commissions \| $		7,200
Offering expenses \| $		$ 2,100
Subsequent Event [Member] \| Over Allotment Options [Member]
Description Of Business
Stock issued during the period, shares \| shares		1,098,000
Stock issued during the period, value \| $		$ 14,300
Stock price, initial public offering \| $ / shares		$ 14.00
Series F [Member] \| Subsequent Event [Member]
Description Of Business
Conversion of stock, shares converted \| shares	15,556,091	15,556,091
Warrant [Member]
Fair Value Of Financial Instruments
Volatility				76.00%
Warrant [Member] \| Subsequent Event [Member]
Description Of Business
Conversion of stock, shares converted \| shares		1,613,395
Maximum [Member]
Property And Equipment
Property and equipment, useful life				5 years
Maximum [Member] \| Series F [Member]
Fair Value Of Financial Instruments
Fair value \| $ / shares				$ 13.42
Maximum [Member] \| Warrant [Member]
Fair Value Of Financial Instruments
Expected term				5 years
Expected liquidity				33.00%
Minimum [Member]
Property And Equipment
Property and equipment, useful life				3 years
Minimum [Member] \| Series F [Member]
Fair Value Of Financial Instruments
Fair value \| $ / shares				$ 8.02
Minimum [Member] \| Warrant [Member]
Fair Value Of Financial Instruments
Expected term				8 months
Expected liquidity				3.00%

The Business And Summary Of Significant Accounting Policies (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Liabilities, fair value	$ 9,715	$ 7,512	$ 6,491
Significant Unobservable Inputs (Level 3) [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Liabilities, fair value	9,715	7,512
Cash and Cash Equivalents [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value	10,703	17,687
Cash and Cash Equivalents [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value	10,703	16,381
Cash and Cash Equivalents [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value		1,306
Short-term Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value	10,877	9,849
Short-term Investments [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value	$ 10,877	$ 9,849

The Business And Summary Of Significant Accounting Policies (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
The Business And Summary Of Significant Accounting Policies [Abstract]
Beginning of period	$ 7,512	$ 6,491
Issuance		174
Fair value increase recorded in other expense	2,203	847
Ending period	$ 9,715	$ 7,512

The Business And Summary Of Significant Accounting Policies (Schedule Of Prepaid And Other Current Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012
The Business And Summary Of Significant Accounting Policies [Abstract]
Prepaid development expenses	$ 43	$ 486
Deferred public offering costs	1,477	273
Other prepaid and other current assets	185	224
Prepaid and other current assets, total	$ 1,705	$ 983

The Business And Summary Of Significant Accounting Policies (Schedule Of Accrued Liabilties) (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012
The Business And Summary Of Significant Accounting Policies [Abstract]
Accrued compensation	$ 508	$ 560
Accrued development expenses	652	98
Other accrued liabilities	553	248
Accrued liabilities, current, total	$ 1,713	$ 906

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable arising from transactions not otherwise specified in the taxonomy. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References + Details

Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Amortized cost	$ 10,880	$ 9,851
Gross unrealized gains
Gross unrealized losses	(3)	(2)
Estimated fair value	$ 10,877	$ 9,849
Investments maturity period, maximum	1 year	1 year
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Amortized cost	$ 10,131	$ 8,353
Gross unrealized gains
Gross unrealized losses	(3)	(2)
Estimated fair value	10,128	8,351
Commercial Paper [Member]
Schedule of Investments [Line Items]
Amortized cost	749	1,498
Gross unrealized gains
Estimated fair value	$ 749	$ 1,498

- Definition

Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13, 17
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15C
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Section A
-Paragraph 4, 5
-Chapter 3
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 16
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15D
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Property And Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,693	$ 1,641
Less accumulated depreciation	(1,302)	(1,234)
Property and equipment, net	391	407
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,005	958
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	78	78
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	398	393
Office Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 212	$ 212

- Definition

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

+ References + Details

Loan Payable (Details)	3 Months Ended
Loan Payable (Details)	Mar. 31, 2013 USD ($) $ / item shares	Mar. 31, 2012 USD ($)	Jan. 27, 2012 USD ($)
Line of Credit Facility [Line Items]
Loan and security agreement, maximum capacity			$ 15,000,000
Interest expense	$ 356,000	$ 109,000
Preferred stock, strike price \| $ / item	2.045
Aggregate amount of advances, percentage	2.00%
Other expenses	$ 57,000	$ 34,000
Warrants to purchase common stock \| shares	41,323
Second Tranche [Member]
Line of Credit Facility [Line Items]
Loan and security agreement, remaining capacity			12,000,000
Interest only period		6 months
Principal and interest amortization period		32 months
Warrants to purchase common stock \| shares	117,360
First Tranche [Member]
Line of Credit Facility [Line Items]
Loan and security agreement, outstanding			$ 3,000,000
Loan payment		$ 2,600,000
Deferred financing costs		$ 100,000
Interest only period		12 months
Principal and interest amortization period		30 months
Loan and security agreement, interest rate		8.25%
Warrants to purchase common stock \| shares	29,340
Loan And Security Agreement [Member]
Line of Credit Facility [Line Items]
Interest expense	$ 38,000	$ 38,000

Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Commitments And Contingencies [Abstract]
Operating leases, rent expense	$ 0.1	$ 0.1

Redeemable Convertible Preferred Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended
	Apr. 16, 2013	Apr. 10, 2013	Jan. 27, 2012	Feb. 07, 2011	Mar. 31, 2013	Mar. 31, 2012
Redeemable convertible preferred stock issued					51,404,514
Aggregate number of common shares converted from redeemable convertible preferred stock					15,556,091
Series F [Member]
Redeemable convertible preferred stock issued				22,004,895	22,004,895
Redeemable convertible preferred stock issued, par value per share				$ 0.001
Redeemable convertible preferred stock issued, redemption price per share			$ 2.045	$ 2.045
Redeemable convertible preferred stock, warrants issued			146,700	5,501,215
Redeemable convertible preferred stock, warrants issued, issuance costs				$ 0.2
Proceeds from issuance of redeemable preferred stock				$ 45.0
Warrants expiration date			Jan. 22, 2022	Feb. 04, 2018
Percentage of the aggregate amount of advances made			2.00%
Warrant [Member]
Other expense as a result of fair valuation of warrants					$ 2.1	$ 1.3
Subsequent Event [Member] \| Warrant [Member]
Redeemable convertible preferred stock, warrants issued		1,613,395
Class of warrant or rights exercised	211,783
Proceeds from exercise of warrants	$ 1.5

Redeemable Convertible Preferred Stock (Summary Of Authorized, Issued And Outstanding Shares Of Redeemable Convertible Preferred Stock) (Details) - shares	Mar. 31, 2013	Feb. 07, 2011
Authorized shares	69,679,299
Issued and outstanding shares	51,404,514
Series A [Member]
Authorized shares	800,000
Issued and outstanding shares	800,000
Series B [Member]
Authorized shares	2,233,879
Issued and outstanding shares	2,233,879
Series B-1 [Member]
Authorized shares	2,054,333
Issued and outstanding shares	2,033,333
Series C [Member]
Authorized shares	5,141,690
Issued and outstanding shares	5,141,690
Series D [Member]
Authorized shares	11,354,526
Issued and outstanding shares	11,295,846
Series E [Member]
Authorized shares	7,894,871
Issued and outstanding shares	7,894,871
Series F [Member]
Authorized shares	40,200,000
Issued and outstanding shares	22,004,895	22,004,895

- Definition

The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

+ References + Details

Redeemable Convertible Preferred Stock (Schedule Of Warrants Issued, Outstanding And Exercisable) (Details) - $ / shares	Jan. 27, 2012	Feb. 07, 2011	Nov. 24, 2008	Nov. 05, 2003
Series B-1 [Member]
Redeemable convertible preferred stock, warrants issued				21,000
Redeemable convertible preferred stock issued, redemption price per share				$ 1.500
Warrants expiration date				Nov. 01, 2013
Series D [Member]
Redeemable convertible preferred stock, warrants issued			58,680
Redeemable convertible preferred stock issued, redemption price per share			$ 2.045
Warrants expiration date			Nov. 01, 2018
Series F [Member]
Redeemable convertible preferred stock, warrants issued	146,700	5,501,215
Redeemable convertible preferred stock issued, redemption price per share	$ 2.045	$ 2.045
Warrants expiration date	Jan. 22, 2022	Feb. 04, 2018

- Definition

Amount to be paid per share that is classified as temporary equity by entity upon redemption. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

+ References + Details

Stockholders' Deficit (Narrative) (Details) - shares		1 Months Ended	3 Months Ended
Stockholders' Deficit (Narrative) (Details) - shares	Apr. 10, 2013	Feb. 28, 2013	Jun. 30, 2013	Mar. 31, 2013	Apr. 16, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued				1,536,577		1,533,996
Common stock, shares outstanding				1,536,577		1,533,996
Common stock, shares authorized				89,700,000		89,700,000
Number of shares outstanding under the plan				2,774,058		2,593,423
Number of shares authorized to be granted				185,369		427,933
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Conversion period from date of initial public offering			180 days
Restricted stock units previously granted and vested				102,547
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized to be granted				3,567,835		3,567,835
The 2012 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period, description				Options issued to employees generally vest one-fourth on the first anniversary date following the date of grant and ratably each month for the next three years.
The 2013 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares authorized				1,408,450
Number of shares authorized to be granted				1,408,450
Percentage of total number of shares of capital stock outstanding				2.50%
2013 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding under the plan				422,535
Number of shares authorized to be granted		704,225
Percentage of total number of shares of capital stock outstanding		1.00%
Maximum [Member] \| The 2012 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options expiration period				10 years
Maximum [Member] \| The 2013 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized to be granted				2,816,901
Authorized Share Capital [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares authorized					200,000,000
Subsequent Event [Member] \| Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Conversion period from date of initial public offering	180 days
Restricted stock units previously granted and vested	102,547

Stockholders' Deficit (Schedule Of Shares Reserved For Future Issuance) (Details) - shares	Mar. 31, 2013	Dec. 31, 2012
Stockholders' Deficit [Abstract]
Conversion of preferred stock and preferred stock warrants	16,093,483	16,093,483
Stock options issued and outstanding	2,774,058	2,593,423
Restricted Stock units outstanding	102,547	43,199
Authorized for future grants under the 2012 Equity Incentive Plan	185,369	427,933
Shares of common stock reserved for future issuance	19,155,457	19,158,038

Stockholders' Deficit (Summary Of Activity Related To Stock Options) (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Stockholders' Deficit [Abstract]
Number of options outstanding, Beginning balance	2,593,423
Number of options outstanding, Granted	184,506
Number of options outstanding, Exercised	(2,581)
Number of options outstanding, Forfeited	(1,290)
Number of options outstanding, Ending balance	2,774,058	2,593,423
Number of options outstanding, Exercisable	1,717,710
Number of options outstanding, Vested and expected to vest	2,580,766
Weighted-average exercise price, beginning balance	$ 2.45
Weighted-average exercise price, Granted	6.39
Weighted-average exercise price, Exercised	3.16
Weighted-average exercise price, Forfeited	2.60
Weighted-average exercise price, Ending balance	2.71	$ 2.45
Weighted-average exercise price, Exercisable	2.28
Weighted-average exercise price, Vested or expected to vest	$ 2.71
Weighted-average remaining contractual life (in years)	7 years 3 months 18 days	7 years 4 months 10 days
Weighted-average remaining contractual life (in years), Exercisable	6 years 5 months 23 days
Weighted-average remaining contractual life (in years), Vested or expected to vest	7 years 3 months

Stockholders' Deficit (Fair Value Of Option Vested And Share-Based Compensation Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Fair value of option vested and allocated share-based compensation expense	$ 265	$ 286
Research and Development Expense [Member] \| Employee [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Fair value of option vested and allocated share-based compensation expense	107	100
Research and Development Expense [Member] \| Non-Employee [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Fair value of option vested and allocated share-based compensation expense	16	10
General and Administrative Expense [Member] \| Employee [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Fair value of option vested and allocated share-based compensation expense	110	167
General and Administrative Expense [Member] \| Non-Employee [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Fair value of option vested and allocated share-based compensation expense	$ 32	$ 9

Stockholders' Deficit (Summary Of Activity Related To Restricted Stock Units) (Details)	3 Months Ended
	Mar. 31, 2013 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance, December 31, 2012	43,199
Balance, March 31, 2013	102,547
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance, December 31, 2012	43,199
Granted	59,348
Balance, March 31, 2013	102,547

Income Taxes (Narrative) (Details)	12 Months Ended
Income Taxes (Narrative) (Details)	Dec. 31, 2013
Income Taxes [Abstract]
Estimated annual effective tax rate	0.00%

Significant Agreements (Details) $ in Thousands	1 Months Ended			3 Months Ended		12 Months Ended
Significant Agreements (Details) $ in Thousands	Jul. 31, 2012 USD ($)	Feb. 28, 2011 USD ($) item	May 31, 2002 USD ($) shares	Mar. 31, 2013 USD ($) shares	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)
Long-term Purchase Commitment [Line Items]
Number of options outstanding, Granted \| shares				184,506
Contract and grant revenue				$ 1,771	$ 3,078
Merck, Sharp and Dohme Corp. [Member]
Long-term Purchase Commitment [Line Items]
Upfront payment, receivable	$ 17,500
Product royalty period	10 years
Regents Of University Of California [Member]
Long-term Purchase Commitment [Line Items]
Milestone payments			$ 3,400
Number of options outstanding, Granted \| shares			64,788
Sublicense fee percentage			50.00%
Royalties percentage			50.00%
Other expenses						$ 900
Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Contract and grant revenue		$ 5,300
Number of extension periods \| item		4
Other segments, period		1 year
Maximum [Member] \| Merck, Sharp and Dohme Corp. [Member]
Long-term Purchase Commitment [Line Items]
Milestone payments				151,000
Maximum [Member] \| Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Contract and grant revenue				$ 31,000
Reimbursement revenue		$ 75,800

Subsequent Events (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Apr. 16, 2013	Apr. 10, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Subsequent Event [Line Items]
Common stock, shares authorized				89,700,000	89,700,000
Common stock, par value				$ 0.001	$ 0.001
Restricted Stock Units (RSUs) [Member]
Subsequent Event [Line Items]
Restricted stock units previously granted and vested				102,547
Conversion period from date of initial public offering			180 days
Authorized Share Capital [Member]
Subsequent Event [Line Items]
Common stock, shares authorized	200,000,000
Common stock, par value	$ 0.001
Preferred stock, shares authorized	10,000,000
Preferred stock, par value	$ 0.001
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock issued during the period, shares	8,418,000	7,320,000
Stock price, initial public offering	$ 14.00	$ 14.00
Proceeds from initial public offering	$ 107.5	$ 93.2
Subsequent Event [Member] \| Restricted Stock Units (RSUs) [Member]
Subsequent Event [Line Items]
Restricted stock units previously granted and vested		102,547
Conversion period from date of initial public offering		180 days
Shares exercised	211,783
Proceeds from exercise of warrants	$ 1.5
Subsequent Event [Member] \| Warrant [Member]
Subsequent Event [Line Items]
Conversion of stock, shares converted	1,613,395
Subsequent Event [Member] \| Series F [Member]
Subsequent Event [Line Items]
Conversion of stock, shares converted	15,556,091	15,556,091
Over Allotment Options [Member]
Subsequent Event [Line Items]
Stock issued during the period, shares	1,098,000
Over Allotment Options [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Stock issued during the period, shares		1,098,000
Stock price, initial public offering		$ 14.00

Subsequent Events (Schedule Of Selected Balance Sheet Data Since IPO) (Details) - USD ($) $ in Thousands	Mar. 31, 2013	Dec. 31, 2012
Cash, cash equivalents and short-term investments	$ 22,916
Total current assets	25,880	$ 31,554
Total assets	26,333	32,031
Total current liabilities	9,943	7,623
Total liabilities	28,476	25,339
Redeemable convertible preferred stock	133,248	107,723
Common stock	3	3
Additional paid-in capital
Accumulated deficit	(135,391)	(101,032)
Total stockholders' (deficit) equity	(135,391)	(101,031)
Total liabilities, redeemable convertible preferred stock and stockholders' (deficit) equity	26,333	$ 32,031
Pro Forma [Member]
Cash, cash equivalents and short-term investments	134,056
Total current assets	135,543
Total assets	135,996
Total current liabilities	9,943
Total liabilities	18,761
Common stock	27
Additional paid-in capital	252,602
Accumulated deficit	(135,391)
Total stockholders' (deficit) equity	117,235
Total liabilities, redeemable convertible preferred stock and stockholders' (deficit) equity	$ 135,996