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Document And Entity Information - shares	9 Months Ended
Document And Entity Information - shares	Sep. 30, 2014	Nov. 01, 2014
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q3
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		36,475,420

Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 74,350	$ 109,976
Short-term investments, available-for-sale	114,072
Accounts receivable	902	248
Prepaid and other current assets	3,540	2,765
Deferred financing costs, current portion	15	20
Total current assets	192,879	113,009
Property and equipment, net of accumulated depreciation	1,095	338
Deposits	30	30
Deferred financing costs, less current portion	5	10
Total assets	194,009	113,387
Current liabilities:
Accounts payable	5,846	2,214
Accrued liabilities	5,346	2,420
Loan payable, current portion	5,329	5,573
Total current liabilities	16,521	10,207
Other long-term liabilities	509	347
Loan payable, less current portion	366	4,294
Total liabilities	17,396	14,848
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized at September 30, 2014 and December 31, 2013; no shares issued and outstanding as of September 30, 2014 and December 31, 2013
Common stock, $0.001 par value, 200,000,000 shares authorized at September 30, 2014 and December 31, 2013; 36,412,538 and 26,664,972 shares issued and outstanding as of September 30, 2014 and December 31, 2013, respectively	35	26
Additional paid-in capital	378,436	261,243
Accumulated other comprehensive loss	(63)
Accumulated deficit	(201,795)	(162,730)
Total stockholders' equity	176,613	98,539
Total liabilities and stockholders' equity	$ 194,009	$ 113,387

Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2014	Dec. 31, 2013
Balance Sheets [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	36,412,538	26,664,972
Common stock, shares outstanding	36,412,538	26,664,972

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues:
Contract revenue	$ 1,185	$ 912	$ 2,884	$ 3,491
Total revenues	1,185	912	2,884	3,491
Operating expenses:
Research and development	13,328	5,319	29,712	18,379
General and administrative	4,717	2,029	11,812	5,753
Loss from operations	(16,860)	(6,436)	(38,640)	(20,641)
Other expense:
Interest expense, net	(91)	(270)	(425)	(1,041)
Fair value adjustments to warrant liability				(6,590)
Net loss	(16,951)	(6,706)	(39,065)	(28,272)
Other comprehensive loss:
Unrealized (loss) gain on securities available-for-sale	(43)	1	(63)	3
Comprehensive loss	(16,994)	(6,705)	(39,128)	(28,269)
Net loss	(16,951)	(6,706)	(39,065)	(28,272)
Accretion of redeemable convertible preferred stock				(34,108)
Net loss attributable to common shareholders	$ (16,951)	$ (6,706)	$ (39,065)	$ (62,380)
Per share information:
Net loss per common share, basic and diluted	$ (0.47)	$ (0.26)	$ (1.26)	$ (3.69)
Weighted-average shares outstanding, basic and diluted	35,845,792	25,866,109	30,939,752	16,911,592

Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Sep. 30, 2014	Sep. 30, 2013
Operating activities
Net loss	$ (39,065)	$ (28,272)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	183	197
Non-cash interest expense	118	46
Amortization/accretion of premium/discount on investments	734	416
Share-based compensation costs	2,777	2,853
Fair value measurement of redeemable convertible preferred stock warrant liability		6,590
Changes in operating assets and liabilities:
Accounts receivable	(654)	593
Prepaid expenses and other current assets and deposits	(780)	(1,698)
Accounts payable and accrued liabilities	6,483	501
Net cash used in operating activities	(30,204)	(18,774)
Investing activities:
Purchase of property and equipment	(703)	(125)
Purchase of short-term investments	(138,058)	(1,852)
Sales of short-term investments	2,499	750
Maturities of short-term investments	20,690	9,758
Net cash (used in) provided by investing activities	(115,572)	8,531
Financing activities:
Proceeds from exercise of stock options	2,148	582
Proceeds from employee stock purchase plan issuance	426
Proceeds from exercise of warrant	6	1,537
Proceeds from public offering, net of offering costs	111,845	107,634
Repayment of loan payable	(4,275)	(3,525)
Net cash provided by financing activities	110,150	106,228
(Decrease) increase in cash and cash equivalents	(35,626)	95,985
Cash and cash equivalents, beginning of period	109,976	19,906
Cash and cash equivalents, end of period	74,350	115,891
Supplemental cash flow information:
Interest payments	$ 552	$ 862

The Business and Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2014

The Business and Summary of Significant Accounting Policies [Abstract]

The Business and Summary of Significant Accounting Policies

1. The Business and Summary of Significant Accounting Policies

Description of Business

Chimerix, Inc. (the Company) is a biopharmaceutical company dedicated to discovering, developing and commercializing novel, oral antivirals to address unmet medical needs. The Company was founded in 2000 based on the promise of its proprietary lipid technology to unlock the potential of some of the most potent antivirals by enhancing their antiviral activity and safety profiles in convenient, orally administered dosing regimens. Based on the Company’s proprietary lipid technology, its lead compound, brincidofovir (brincidofovir, CMX001), is in Phase 3 clinical development; in addition, the Company has an active discovery program focusing on viral targets for which no therapies are currently available.

On March 25, 2013, the Company’s board of directors approved and implemented a 3.55-for-1 reverse split of the Company’s outstanding common stock. 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 of $14.00 per share. Net proceeds were approximately $93.3 million, after deducting underwriting discounts and commissions of $7.1 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 underwriters exercised the full over-allotment option pursuant to which the Company sold an additional 1,098,000 shares of common stock 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.

On October 23, 2013, the Company completed an underwritten secondary public offering of 2,476,995 shares of common stock held by certain of the Company’s existing stockholders at a price to the public of $16.50 per share. The Company did not issue any shares of common stock and received no proceeds in connection with such offering. The principal purposes of the offering were to facilitate an orderly distribution of shares and to increase the Company’s public float.

On May 27, 2014, the Company completed an underwritten public offering of 8,395,000 shares of common stock, including 1,095,000 shares sold pursuant to the full exercise of an over-allotment option previously granted to the underwriters. All of the shares were offered by the Company at a price to the public of $14.22 per share. Net proceeds to the Company from this offering, after deducting underwriting discounts and commissions and other offering expenses payable by the Company, were approximately $111.8 million. The securities described above were offered by the Company pursuant to a shelf registration statement declared effective by the Securities and Exchange Commission (the SEC) on May 16, 2014.

The accompanying unaudited financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Company’s audited financial statements and notes thereto included in its Annual Report on Form 10-K for the year ended December 31, 2013. In the opinion of the Company’s management, all adjustments, consisting of normal recurring adjustments, necessary for a fair presentation of its financial position, operating results and cash flows for the periods presented have been included. Operating results for the three and nine months ended September 30, 2014 are not necessarily indicative of the results that may be expected for the full year, for any other interim period or for any future year.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts of assets, liabilities, revenues and expenses reported in the financial statements and accompanying notes. Actual results could differ from these estimates.

Fair Value of Financial Instruments

The carrying amounts of certain financial instruments, including accounts 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.

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 September 30, 2014
	September 30, 2014		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	$	73,054	$	73,054	$	—	$	—
Short-term investments		114,072		—		114,072		—


			Fair Value Measurements at December 31, 2013
	December 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	$	107,349	$	107,349	$	—	$	—

Short-term investments consist of corporate bonds, commercial paper and certificates of deposit and are valued based on various observable inputs such as benchmark yields, reported trades, broker/dealer quotes, benchmark securities and bids.

Revenue Recognition

The Company’s revenues generally consist of revenue generated under federal contracts. 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.

Clinical Trial Accruals/Prepaids

As part of the process of preparing financial statements, the Company is required to estimate its expenses resulting from its obligation under contracts with vendors and consultants and clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations which vary contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company’s objective is to reflect the appropriate clinical trial expenses in its financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. Depending on amounts paid to the contract research organization and other third-party vendors as compared to actual expenses incurred, there might be a prepaid balance recorded as a prepaid asset. The Company determines accrual estimates through discussion with applicable personnel and outside service providers as to the progress or state of completion of trials, or the services completed. During the course of a clinical trial, the Company adjusts its rate of clinical trial expense recognition if actual results differ from its estimates. The Company makes estimates of its accrued expenses as of each balance sheet date in its financial statements based on facts and circumstances known at that time. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of status and timing of services performed relative to the actual status and timing of services performed may vary and may result in the Company reporting amounts that are too high or too low for any particular period. Through September 30, 2014, there had been no material adjustments to the Company’s prior period estimates of accrued expenses for clinical trials. The Company’s clinical trial accrual is dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors.

Basic and Diluted Net Loss Per Common Share

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 of warrants and options to purchase common stock. Diluted net loss per common share is computed by dividing 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 warrants and options to purchase common stock 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 or the nine months ended September 30, 2014 and 2013.

The calculation of weighted-average diluted shares outstanding excludes the dilutive effect of warrants 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 2,757,883 and 3,253,638 for the three months ended September 30, 2014 and 2013, respectively and 2,802,829 and 6,153,403 for the nine months ended September 30, 2014 and 2013, respectively.

Impact of Recently Issued Accounting Standards

In June 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-12, “Compensation — Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period.” The amendments in this update require that a performance target that affects vesting and that could be achieved after the requisite service period should be treated as a performance condition. A reporting entity should apply existing guidance in Topic 718 as it relates to awards with performance conditions that affect vesting to account for such awards. As such, the performance target should not be reflected in estimating the grant-date fair value of the award. ASU 2014-12 is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Earlier adoption is permitted. The adoption of this standard is not expected to have an impact on the Company’s financial position or results of operations.

Investments

9 Months Ended

Sep. 30, 2014

Investments [Abstract]

Investments

2. Investments

The following table summarizes available-for-sale securities:


	September 30, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Corporate bonds	$	87,525	$	2	$	(56	)	$	87,471
Commercial paper		18,730		3		(5	)		18,728
Certificates of deposit		7,880		—		(7	)		7,873
Total	$	114,135	$	5	$	(68	)	$	114,072

The Company had no short or long-term investments at December 31, 2013. All of the Company’s investments as of September 30, 2014 had maturities of one year or less at the time of purchase.

- Definition

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

+ References + Details

Equity Transactions and Share-based Compensation

9 Months Ended

Sep. 30, 2014

Equity and Share-based Compensation [Abstract]

Equity and Share-based Compensation

5. Equity Transactions and Share-based Compensation

Warrants

Upon the completion of the Company’s IPO, all outstanding warrants to purchase redeemable convertible preferred stock were marked to market resulting in a $6.4 million fair value adjustment for the nine months ended September 30, 2013. There was no expense related to the valuation of the warrants for the three months ended September 30, 2014. Upon completion of the IPO, the warrants were converted into warrants to purchase 1,613,395 shares of common stock and were no longer required to be measured at fair value.

The following warrants for the purchase of common stock were issued, outstanding and exercisable at September 30, 2014:

Class

Date

Price Per Share

Expiration

Common

February 7, 2011

726,601

7.26

February 2018

Stock Options

In connection with the Company’s 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. On January 1, 2014, the common stock reserved for issuance under the 2013 Plan was automatically increased by 666,624 shares. As of September 30, 2014, there was a total of 1,256,376 shares reserved for future issuance under the 2013 Plan. At the Company’s annual meeting, held on June 20, 2014, shareholders approved a change to the annual automatic increase in the number of common shares to be reserved for issuance under the 2013 Plan by changing the percentage increase from 2.5% to 4.0% 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.

In February 2013, the Company’s board of directors adopted the 2013 Employee Stock Purchase Plan (ESPP), which was subsequently ratified by stockholders and became effective in April 2013. Initially, the ESPP authorized 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 automatically increases on January 1 of each calendar year, from January 1, 2014 through January 1, 2023 by the lesser 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). On January 1, 2014, the common stock reserved for issuance under the ESPP was automatically increased by an additional 266,649 shares bringing the total number of shares of common stock that may be purchased under the ESPP to 970,874.

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. Compensation expense recognized related to stock options, RSUs and the ESPP is as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
	(in thousands)				(in thousands)
Research and development:
Employee	$	524	$	109	$	428	$	422
Non-employee		—		7		—		28
General and administrative:
Employee		838		100		2,349		350
Non-employee		—		48		—		125
	$	1,362	$	264	$	2,777	$	925

During the three months ended June 30, 2014, the Company recorded an immaterial out of period adjustment of $1.4 million to properly state additional paid-in-capital with a resulting decrease in compensation expense related to restricted stock awards that vested in 2013 in connection with the IPO. On April 9, 2014, Kenneth I. Moch, the Company’s then President and Chief Executive Officer, resigned. The Company entered into a severance agreement with Mr. Moch that provides for severance benefits to him in connection with his resignation. Among other benefits, Mr. Moch received accelerated vesting of all of his outstanding stock options as if he had continued service for an additional 15 month period. In addition, Mr. Moch’s vested options were modified to extend his exercise period to December 31, 2014. The Company recorded a charge of $1.0 million to compensation expense on the date of his resignation related to the acceleration of vesting and the modification.

On September 19, 2014, the Company accelerated the vesting of all outstanding stock options granted to a former member of the Company’s board of directors. The Company recorded a charge of $0.3 million to compensation expense on that date related to the acceleration of vesting.

Employee Stock Purchase Plan

The Company has reserved a total of 970,874 shares of common stock to be purchased under the ESPP, of which 944,599 shares remain available for purchase at September 30, 2014. Eligible employees may authorize up to 15% of their salary to purchase common stock at the lower of 85% of the beginning price or 85% of the ending price during each six-month purchase interval. The Company issued 12,091 and 26,275 shares of common stock pursuant to the ESPP for the three and nine months ended September 30, 2014, respectively. Compensation expense for shares purchased under the ESPP related to the purchase discount and the “look-back” option were determined using a Black-Scholes option pricing model. The Company recorded compensation expense of $70,000 for the three months ended September 30, 2014 and $219,000 for the nine months ended September 30, 2014. The compensation expense related to the three and nine months ended September 30, 2013 was immaterial.

Significant Agreements	9 Months Ended
Significant Agreements	Sep. 30, 2014
Significant Agreements [Abstract]
Significant Agreements	7. 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 brincidofovir. 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. 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 connection with the development and commercialization of brincidofovir, 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. In addition, upon commercialization of any product utilizing the UC Patent Rights (which would include the commercialization of brincidofovir), 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 brincidofovir) the Company is obligated to pay to UC a fee, which amount will vary depending upon the amount of any payments 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. With respect to brincidofovir, the fee payable to UC will not exceed 5% of the sublicense fee. 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. The Company did not recognize expenses under this agreement for the three or nine months ended September 30, 2014 or the year ended December 31, 2013. Biomedical Advanced Research and Development Authority (BARDA) In February 2011, the Company entered into a contract with BARDA for the development of brincidofovir as a medical countermeasure in the event of a smallpox release. The contract has been amended several times, most recently on August 28, 2014, to execute the second option segment of the contract to provide approximately $17.0 million through November 30, 2015. Under the contract, BARDA will reimburse the Company, plus pay a fixed fee, for the research and development of brincidofovir as a 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. 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 if all remaining option segments are exercised. The Company is currently performing under the first and second option segments of the contract during which the Company may receive up to a total of $5.3 million under the first option segment and $17.0 million under the second option segment in expense reimbursement and fees. For the three and nine months ended September 30, 2014, the Company recognized revenue of $1.2 million and $2.9 million, respectively, under this contract.

The Business and Summary of Significant Accounting Policies (Policy)

9 Months Ended

Sep. 30, 2014

The Business and Summary of Significant Accounting Policies [Abstract]

Description of Business

Use of Estimates

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 September 30, 2014
	September 30, 2014		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	$	73,054	$	73,054	$	—	$	—
Short-term investments		114,072		—		114,072		—


			Fair Value Measurements at December 31, 2013
	December 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	$	107,349	$	107,349	$	—	$	—

Revenue Recognition

Clinical Trial Accruals/Prepaids

Basic and Diluted Net Loss Per Common Share

- Definition

Disclosure of accounting policy for revenue recognition. If the entity has different policies for different types of revenue transactions, the policy for each material type of transaction is generally disclosed. If a sales transaction has multiple element arrangements (for example, delivery of multiple products, services or the rights to use assets) the disclosure may indicate the accounting policy for each unit of accounting as well as how units of accounting are determined and valued. The disclosure may encompass important judgment as to appropriateness of principles related to recognition of revenue. The disclosure also may indicate the entity's treatment of any unearned or deferred revenue that arises from the transaction.

+ References + Details

The Business and Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2014

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 September 30, 2014
	September 30, 2014		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	$	73,054	$	73,054	$	—	$	—
Short-term investments		114,072		—		114,072		—


			Fair Value Measurements at December 31, 2013
	December 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	$	107,349	$	107,349	$	—	$	—

Investments (Tables)

9 Months Ended

Sep. 30, 2014

Investments [Abstract]

Summary of Available-for-Sale Securities

The following table summarizes available-for-sale securities:


	September 30, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Corporate bonds	$	87,525	$	2	$	(56	)	$	87,471
Commercial paper		18,730		3		(5	)		18,728
Certificates of deposit		7,880		—		(7	)		7,873
Total	$	114,135	$	5	$	(68	)	$	114,072

- 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 + Details

Equity Transactions and Share-based Compensation (Tables)

9 Months Ended

Sep. 30, 2014

Equity and Share-based Compensation [Abstract]

Schedule of Warrants Issued, Outstanding and Exercisable

The following warrants for the purchase of common stock were issued, outstanding and exercisable at September 30, 2014:

Class

Date

Price Per Share

Expiration

Common

February 7, 2011

726,601

7.26

February 2018

Schedule of Share-Based Compensation Expense

Compensation expense recognized related to stock options, RSUs and the ESPP is as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
	(in thousands)				(in thousands)
Research and development:
Employee	$	524	$	109	$	428	$	422
Non-employee		—		7		—		28
General and administrative:
Employee		838		100		2,349		350
Non-employee		—		48		—		125
	$	1,362	$	264	$	2,777	$	925

- 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

The Business and Summary of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Millions						3 Months Ended		9 Months Ended
	May 27, 2014 USD ($) $ / shares shares	Oct. 23, 2013 $ / shares shares	Apr. 16, 2013 USD ($) $ / shares shares	Apr. 10, 2013 USD ($) $ / shares shares	Mar. 25, 2013	Sep. 30, 2014 shares	Sep. 30, 2013 shares	Sep. 30, 2014 shares	Sep. 30, 2013 shares
Description Of Business
Stock split, reverse description					the Company's board of directors approved and implemented a 3.55-for-1 reverse split of the Company's outstanding common stock
Reverse stock split, conversion ratio					3.55
Stock issued during the period, shares \| shares	8,395,000	2,476,995		7,320,000
Shares issued, price per share \| $ / shares		$ 16.50
Stock price, public offering \| $ / shares	$ 14.22			$ 14.00
Proceeds from public offering \| $	$ 111.8			$ 93.3
Public offering underwriting discounts and commissions \| $				7.1
Offering expenses \| $				$ 2.1
Per share information:
Anti-dilutive securities excluded from the calculation loss per share \| shares						2,757,883	3,253,638	2,802,829	6,153,403
Over Allotment Options [Member]
Description Of Business
Stock issued during the period, shares \| shares	1,095,000		1,098,000
Stock issued during the period, value \| $			$ 14.3
Stock price, public offering \| $ / shares			$ 14.00
Public offering underwriting discounts and commissions \| $			$ 1.1
Series F [Member]
Description Of Business
Conversion of stock, shares converted \| shares				15,556,091
Warrant [Member]
Description Of Business
Conversion of stock, shares converted \| shares				1,613,395

Investments (Details) - USD ($) $ in Thousands	9 Months Ended
Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Amortized cost	$ 114,135
Gross unrealized gains	5
Gross unrealized losses	(68)
Estimated fair value	$ 114,072
Short-term investments		$ 0
Long-term investments		$ 0
Investments maturity period, maximum	1 year
Corporate Bonds [Member]
Schedule of Investments [Line Items]
Amortized cost	$ 87,525
Gross unrealized gains	2
Gross unrealized losses	(56)
Estimated fair value	87,471
Commercial Paper [Member]
Schedule of Investments [Line Items]
Amortized cost	18,730
Gross unrealized gains	3
Gross unrealized losses	(5)
Estimated fair value	18,728
Certificates of Deposit [Member]
Schedule of Investments [Line Items]
Amortized cost	7,880
Gross unrealized losses	(7)
Estimated fair value	$ 7,873

Loan Payable (Details) - USD ($)	3 Months Ended			9 Months Ended
Loan Payable (Details) - USD ($)	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2013	Jan. 27, 2012
Line of Credit Facility [Line Items]
Loan and security agreement, maximum capacity							$ 15,000,000
Interest expense	$ 91,000	$ 270,000		$ 425,000	$ 1,041,000
Warrants to purchase common stock						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
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%
Loan and Security Agreement [Member]
Line of Credit Facility [Line Items]
Interest expense	$ 21,000	$ 34,000		$ 73,000	$ 109,000

Equity Transactions and Share-based Compensation (Narrative) (Details) - USD ($)				1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 19, 2014	Jun. 20, 2014	Jan. 02, 2014	Feb. 28, 2013	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Sep. 30, 2014	Dec. 31, 2013	Mar. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares authorized					200,000,000				200,000,000	200,000,000
Common stock, shares issued					36,412,538				36,412,538	26,664,972
Common stock, shares outstanding					36,412,538				36,412,538	26,664,972
Redeemable convertible preferred stock, warrants issued								1,613,395
Fair value adjustment of warrants								$ 6,400,000
Warrants to purchase common stock											41,323
Decrease to compensation expense, restricted stock						$ 1,400,000
Former Chief Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accelerated shares period of vesting						15 months
Allocated share-based compensation expense						$ 1,000,000
Board of Directors Chairman [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated share-based compensation expense	$ 300,000
2013 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized to be granted				704,225
Number of shares outstanding under the plan								422,535
Percentage of total number of shares of capital stock outstanding				1.00%
ESPP shares available to plan					970,874				970,874
Shares remaining available for purchase					944,599				944,599
Increase in shares under the plan			266,649
Percentage of pay that employee can contribute, maximum					15.00%
Percentage of fair value employees pay					85.00%
Shares issued					12,091				26,275
Compensation expense					$ 70,000				$ 219,000
The 2013 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares authorized			666,624
Shares available for issuance					1,256,376				1,256,376
Percentage of total number of shares of capital stock outstanding		4.00%					2.50%

Significant Agreements (Details) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
Significant Agreements (Details) $ in Thousands	Feb. 28, 2011 USD ($) item	May 31, 2002 USD ($) shares	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)
Long-term Purchase Commitment [Line Items]
Contract revenue			$ 1,185	$ 912	$ 2,884	$ 3,491
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%
Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Contract revenue			$ 1,200		2,900
Number of extension periods \| item	4
Other segments, period	1 year
Research and Development Arrangement First Option [Member]
Long-term Purchase Commitment [Line Items]
Contract revenue					5,300
Research and Development Arrangement Second Option [Member]
Long-term Purchase Commitment [Line Items]
Contract revenue					$ 17,000
Maximum [Member] \| Brincidofovir [Member]
Long-term Purchase Commitment [Line Items]
Sublicense fee amount, payable fee percentage					5.00%
Maximum [Member] \| Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Reimbursement revenue	$ 75,800
Maximum [Member] \| Research and Development Arrangement [Member] \| Scenario, Plan [Member]
Long-term Purchase Commitment [Line Items]
Contract revenue	$ 5,300

Loan Payable	9 Months Ended
Loan Payable	Sep. 30, 2014
Loan Payable [Abstract]
Loan Payable	3. 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 borrowings under the LSA are collateralized by a security interest in all of the Company’s assets, excluding its intellectual property. 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 30-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 32 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 $21,000 and $34,000 was included in interest expense for the three months ended September 30, 2014 and 2013, respectively, and $73,000 and $109,000 for the nine months ended September 30, 2014 and 2013, respectively. Concurrently with entering into the LSA, the Company also granted SVB a warrant to purchase shares of Series F preferred stock. Upon the completion of the Company’s IPO, this warrant was converted into a warrant to purchase 41,323 shares of common stock. In May 2013, SVB exercised the warrant in full and it is no longer outstanding.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2014
Commitments and Contingencies [Abstract]
Commitments and Contingencies	4. 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 September 30, 2014 and 2013, respectively, and approximately $0.4 million and $0.4 million for the nine months ended September 30, 2014 and 2013, respectively. Significance of Revenue Source The Company is the recipient of federal research contract funds from the Biomedical Advanced Research and Development Authority (BARDA). Periodic audits are required under the Company’s contract agreement and certain costs may be questioned as appropriate under the BARDA 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 September 30, 2014 and December 31, 2013.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2014
Income Taxes [Abstract]
Income Taxes	6. Income Taxes The Company estimates an annual effective tax rate of 0% for the year ending December 31, 2014 as the Company incurred losses for the nine month period ended September 30, 2014 and is forecasting additional losses through the fourth quarter, resulting in an estimated net loss for both financial statement and tax purposes for the year ending December 31, 2014. 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 Accounting Standards Codification 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 full valuation allowance, since the Company does not currently believe that realization of its deferred tax assets is more likely than not. At September 30, 2014, the Company had no unrecognized tax benefits that would reduce the Company’s effective tax rate if recognized.

Subsequent Event	9 Months Ended
Subsequent Event	Sep. 30, 2014
Subsequent Event [Abstract]
Subsequent Event	8. Subsequent Event On November 5, 2014, the Company completed an underwritten public offering of 4,197,500 shares of common stock, including 547,500 shares sold pursuant to the full exercise of an option previously granted to the underwriters to purchase additional shares of common stock. All of the shares were offered by the Company at a price to the public of $29.00 per share. The net proceeds from this offering, after deducting underwriting discounts and commissions and other offering expenses payable by the Company, were approximately $114.0 million. The securities described above were offered by the Company pursuant to an automatic shelf registration statement which immediately became effective by rule of the SEC on October 29, 2014.

The Business and Summary of Significant Accounting Policies (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value	$ 73,054	$ 107,349
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	73,054	$ 107,349
Cash and Cash Equivalents [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value
Short-term Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value	114,072
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	$ 114,072
Short-term Investments [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Assets, fair value

Equity Transactions and Share-based Compensation (Schedule of Warrants Issued, Outstanding and Exercisable) (Details) - Common Stock [Member]	9 Months Ended
	Sep. 30, 2014 $ / shares shares
Warrants date exercisable	Feb. 07, 2011
Warrants issued, outstanding and exercisable \| shares	726,601
Warrants exercise price \| $ / shares	$ 7.26
Warrants expiration date	Feb. 01, 2018

Income Taxes (Narrative) (Details)	9 Months Ended
Income Taxes (Narrative) (Details)	Sep. 30, 2014
Scenario, Forecast [Member]
Estimated annual effective tax rate	0.00%

Subsequent Event (Details) - USD ($) $ / shares in Units, $ in Thousands					9 Months Ended
	Nov. 05, 2014	May 27, 2014	Oct. 23, 2013	Apr. 10, 2013	Sep. 30, 2014	Sep. 30, 2013
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues		8,395,000	2,476,995	7,320,000
Shares issued, price per share			$ 16.50
Proceeds from public offering					$ 111,845	$ 107,634
Subsequent Event [Member] \| Underwritten Public Offering [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues	4,197,500
Shares sold pursuant to the full exercise of an option	547,500
Shares issued, price per share	$ 29.00
Proceeds from public offering	$ 114,000