Chimerix (CMRX) 10-Q 11 May 15 2015 Q1 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 27, 2015
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Entity Registrant Name	CHIMERIX INC
Entity Central Index Key	1117480
Current Fiscal Year End Date	-19
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		41,316,704

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$55,605	$128,462
Short-term investments, available-for-sale	118,898	106,114
Accounts receivable	977	106
Prepaid expenses and other current assets	1,780	2,775
Total current assets	177,260	237,457
Long-term investments	95,239	52,973
Property and equipment, net of accumulated depreciation	1,329	1,310
Other long-term assets	297	138
Total assets	274,125	291,878
Current liabilities:
Accounts payable	6,920	5,938
Accrued liabilities	6,630	6,833
Loan payable, net	2,892	4,296
Total current liabilities	16,442	17,067
Long-term liabilities	161	175
Total liabilities	16,603	17,242
Other long-term liabilities
Commitments and contingencies	0	0
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized at March 31, 2015 and December 31, 2014; no shares issued and outstanding as of March 31, 2015 and December 31, 2014	0	0
Common stock, $0.001 par value, 200,000,000 shares authorized at March 31, 2015 and December 31, 2014; 41,310,063 and 41,031,770 shares issued and outstanding as of March 31, 2015 and December 31, 2014, respectively	41	41
Additional paid-in capital	501,130	496,602
Accumulated other comprehensive gain, net	659	35
Accumulated deficit	-244,308	-222,042
Total stockholders’ equity	257,522	274,636
Total liabilities and stockholders’ equity	$274,125	$291,878

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, par value	$0.00	$0.00
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	$0.00	$0.00
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	41,310,063	41,031,770

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Loss (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Marketable Securities, Unrealized Gain (Loss)	$625	($32)
Revenues [Abstract]
Contract revenue	1,238	780
Total revenues	1,238	780
Operating expenses:
Research and development	17,444	8,292
General and administrative	6,123	2,672
Loss from operations	-22,329	-10,184
Interest income (expense), net	63	-196
Net loss	-22,266	-10,380
Other comprehensive loss:
Net loss	-22,266	-10,380
Comprehensive loss	($21,641)	($10,412)
Per share information:
Net loss per common share, basic and diluted	($0.54)	($0.39)
Weighted-average shares outstanding, basic and diluted	41,220,989	26,762,264

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Cash Flows [Abstract]
Repayments of Debt	$1,425	$1,425
Cash flows from operating activities:
Net loss	-22,266	-10,380
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of property and equipment	114	50
Amortization of debt costs	26	42
Amortization of premium/discount on investments	425	108
Share-based compensation	2,402	772
Amortization of deferred lease obligation	-12	3
Changes in operating assets and liabilities:
Accounts receivable	-871	159
Prepaid expenses and other assets	832	1,064
Accounts payable and accrued liabilities	511	-934
Net cash used in operating activities	-18,839	-9,116
Cash flows from investing activities:
Purchase of property and equipment	-133	-99
Purchase of short-term investments	-26,709	-62,640
Purchase of long-term investments	-65,232	0
Sales of short-term investments	1,003	0
Maturities of short-term investments	36,352	0
Net cash used in investing activities	-54,719	-62,739
Cash flows from financing activities:
Proceeds from exercise of stock options	665	496
Proceeds from employee stock purchase plan stock purchases	461	229
Proceeds from exercise of warrants	1,000	0
Net cash provided by (used in) financing activities	701	-700
Net decrease in cash and cash equivalents	-72,857	-72,555
Cash and cash equivalents, beginning of period	128,462	109,976
Cash and cash equivalents, end of period	55,605	37,421
Supplemental disclosure cash flow information:
Cash paid for interest	$70	$198

The_Business_and_Summary_of_Si

The Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
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 conjugate technology to unlock the potential of some of the most potent broad-spectrum antivirals by enhancing their antiviral activity and safety profiles in convenient, orally administered dosing regimens. Based on the Company’s proprietary lipid conjugate technology, its lead compound, brincidofovir (BCV or CMX001), is in Phase 3 clinical development; in addition, the Company has an active discovery program focusing on viral targets for which limited or no therapies are currently available or where current therapies have significant liabilities.
	Basis of Presentation
	The accompanying unaudited consolidated financial statements include the accounts of the Company and its wholly owned subsidiary and have been prepared in accordance with U.S. generally accepted accounting principles (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, 2014.  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 months ended March 31, 2015 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.
	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.
	At March 31, 2015 and December 31, 2014, the Company had cash equivalents, consisting of money market accounts, and short-term and long-term investments consisting of U.S. Treasury securities, whose value is based on using quoted market prices. Accordingly, these securities are classified as Level 1.
	At March 31, 2015 and December 31, 2014, the Company had cash equivalents, short-term investments and long-term investments comprised of corporate bonds, commercial paper and brokered certificates of deposit for which quoted prices are not available that are valued using independent pricing models or other model-based valuation techniques such as the present value of future cash flows, adjusted for the security’s credit rating, prepayment assumptions and other factors such as credit loss assumptions. Accordingly, these securities are classified as Level 2.
	The Company’s preferred stock investment in ContraVir Pharmaceuticals (NASDAQ: CTRV) (ContraVir) is categorized as Level 3 as there are significant unobservable inputs. The valuation of the investment at March 31, 2015 and December 31, 2014 was calculated on an as if converted to common share basis with a discount for lack of marketability applied due to the 18 month restriction from the date of the investment on selling the converted common shares. An option pricing model was used to determine the discount for lack of marketability of 24% and 25% at March 31, 2015 and December 31, 2014, respectively. The key unobservable inputs used in the option pricing model at March 31, 2015 were (i) exercise price - $3.08, (ii) dividend yield - 0%, (iii) expected holding period - 1.22 years, (iv) risk-free rate - 0.26%, and (v) volatility - 65%. The key unobservable inputs used in the option pricing model at December 31, 2014 were (i) exercise price - $2.22, (ii) dividend yield - 0%, (iii) expected holding period - 1.5 years, (iv) risk-free rate - 0.44%, and (v) volatility - 65%. The increase in valuation of the preferred stock for the quarter ended March 31, 2015 was recorded as an unrealized gain in investment, net of tax in the Consolidated Statements of Operations and Comprehensive Loss.
	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 (in thousands):
		Fair Value Measurements
		March 31, 2015
		Total		Quoted Prices in		Significant Other		Significant
				Active Markets		Observable Inputs		Unobservable Inputs
				for Identical Assets		(Level 2)		(Level 3)
				(Level 1)
	Cash equivalents
	Money market funds	$	41,867	$	41,867	$	—	$	—
	Certificates of deposit	240		—		240		—
	Commercial paper	9,997		—		9,997		—
	Total cash equivalents	52,104		41,867		10,237		—
	Short-term investments
	Certificates of deposit	18,434		—		18,434		—
	Corporate bonds	41,109		$	—	$	41,109	$	—
	Commercial paper	6,246		—		6,246		—
	U.S. Treasury securities	53,109		53,109		—		—
	Total short-term investments	118,898		53,109		65,789		—
	Long-term investments
	Certificates of deposit	12,973		—		12,973		—
	U.S. Treasury securities	79,758		79,758		—		—
	Preferred stock of U.S. corporation	2,508		—		—		2,508
	Total long-term investments	95,239		79,758		12,973		2,508
	Total assets	$	266,241	$	174,734	$	88,999	$	2,508
		Fair Value Measurements
		December 31, 2014
		Total		Quoted Prices in		Significant Other		Significant
				Active Markets		Observable Inputs		Unobservable Inputs
				for Identical Assets		(Level 2)		(Level 3)
				(Level 1)
	Cash equivalents
	Money market funds	$	125,606	$	125,606	$	—	$	—
	Certificates of deposit	480		—		480		—
	Total cash equivalents	126,086		125,606		480		—
	Short-term investments
	Certificates of deposit	16,982		—		16,982		—
	Corporate bonds	69,892		—		69,892		—
	Commercial paper	11,240		—		11,240		—
	U.S. Treasury securities	8,000		8,000		—		—
	Total short-term investments	106,114		8,000		98,114		—
	Long-term investments
	Certificates of deposit	10,996		—		10,996		—
	U.S. Treasury securities	40,196		40,196		—		—
	Preferred stock of U.S. corporation	1,781		—		—		1,781
	Total long-term investments	52,973		40,196		10,996		1,781
	Total assets	$	285,173	$	173,802	$	109,590	$	1,781
	Below is a table that presents a reconciliation of the beginning and ending balances of assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):
	Fair Value Measurements
	(Level 3)
Preferred stock of U.S. corporation:
Fair value at December 31, 2014	$	1,781
Fair value increase recorded in other comprehensive gain, net	727
Fair value at March 31, 2015	$	2,508
Revenue Recognition
The Company’s revenues generally consist of (i) contract and grant revenue – revenue generated under federal contracts and other awarded grants, and (ii) collaboration and licensing revenue – revenue 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.
Milestone payments are recognized when earned, provided that (i) the milestone event is substantive; (ii) there is no ongoing performance obligation related to the achievement of the milestone earned; and (iii) it would result in additional payments. Milestone payments are considered substantive if all of the following conditions are met: the milestone payment is non-refundable; achievement of the milestone was not reasonably assured at the inception of the arrangement; substantive effort is involved to achieve the milestone; the amount of the milestone appears reasonable in relation to the effort expended, the other milestones in the arrangement; and the related risk associated with the achievement of the milestone. Contingent based event payments the Company may receive under a license or collaboration agreement will be recognized when received.
Research and Development Prepaids and Accruals
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 March 31, 2015, 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 and employee stock purchase plan rights. 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 March 31, 2015 and 2014.
The calculation of weighted-average diluted shares outstanding excludes the dilutive effect of warrants and options to purchase common stock and employee stock purchase plan rights, as the impact of such items are anti-dilutive during periods of net loss. Potential common shares excluded from the calculations were 1,408,852 and 2,645,620 for the three months ended March 31, 2015 and 2014, 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.
In May 2014, the FASB issued ASU No. 2014-09: Revenue from Contracts with Customers (Topic 606). The ASU establishes a principles-based approach for accounting for revenue arising from contracts with customers and supersedes existing revenue recognition guidance. The ASU provides that an entity should apply a five-step approach for recognizing revenue, including (1) identify the contract with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when, or as, the entity satisfies a performance obligation. Also, the entity must provide various disclosures concerning the nature, amount and timing of revenue and cash flows arising from contracts with customers. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016 and early application is not permitted. The Company is currently analyzing the impact of this new accounting guidance.
In April 2015, the FASB issued ASU No. 2015-03, “Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs,” which requires debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the associated debt liability, and amortization of those costs should be reported as interest expense. This ASU is effective for financial statements issued for annual and interim periods beginning after December 15, 2015, and early adoption is permitted for financial statements that have not been previously issued. The new guidance should be applied on a retrospective basis for each period presented in the balance sheet. The Company does not expect the adoption of ASU 2015-03 to have a material impact on its consolidated financial statements.

Investments

Investments	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Investments	2. Investments
	The following table summarizes the Company's short-term and long-term investments:
			March 31, 2015
			Amortized Cost		Gross  Unrealized Gains		Gross  Unrealized Losses			Estimated Fair Value
			(in thousands)
	Corporate bonds		$	41,127	$	—	$	(18	)	$	41,109
	Certificates of deposit		31,399		17		(10		)	31,406
	U.S. Treasury securities		132,897		17		(46		)	132,868
	Commercial paper		6,246		—		—			6,246
	Preferred stock of U.S. corporation		1,545		963		—			2,508
	Total investments		$	213,214	$	997	$	(74	)	$	214,137
			31-Dec-14
			Amortized Cost		Gross  Unrealized Gains		Gross  Unrealized Losses			Estimated Fair Value
			(in thousands)
	Corporate bonds		$	69,947	$	—	$	(56	)	$	69,891
	Certificates of deposit		28,039		1		(62		)	27,978
	U.S. Treasury securities		48,279		—		(82		)	48,197
	Commercial paper		11,242		—		(2		)	11,240
	Preferred stock of U.S. corporation		1,545		236		—			1,781
	Total investments		$	159,052	$	237	$	(202	)	$	159,087
	The following table summarizes the scheduled maturity for the Company's investments at March 31, 2015 (in thousands):
		March 31, 2015
	Maturing in one year or less	$	118,898
	Maturing after one year through two years	95,239
	Total investments	$	214,137

Loan_Payable

Loan Payable	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [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. 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 has an interest-only period of twelve months followed by a 30 months principal and interest amortization period with interest being charged at 8.25% per year for the full period of the LSA. The second tranche has a 6 months interest-only period followed by a 32 months 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 short-term liabilities depending on the nature of the fees and are being accreted through interest expense over the life of the loans.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [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 $0.2 million and $0.1 million for the three months ended March 31, 2015 and 2014, 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 BARDA agreement and certain costs may be questioned as appropriate under the BARDA agreement. Management believes that such amounts in the current year, if any, are not significant. Accordingly, no provision for refundable amounts under the BARDA agreement has been made as of March 31, 2015 and December 31, 2014.

Stockbased_Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation	5. Share-based Compensation
	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. The number of shares of common stock reserved for future issuance automatically increases on January 1 of each calendar year by 4% 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. On January 1, 2015, the common stock reserved for issuance under the 2013 Plan was automatically increased by 1,641,271 shares. As of March 31, 2015, there was a total of 2,011,058 shares reserved for future issuance under the 2013 Plan.
	Employee Stock Purchase Plan
	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, 2015, the common stock reserved for issuance under the ESPP was automatically increased by an additional 410,317 shares bringing the total number of shares of common stock that may be purchased under the ESPP to 1,329,277.
	The Company has reserved a total of 1,381,191 shares of common stock to be purchased under the ESPP, of which 1,329,277 shares remained available for purchase as of March 31, 2015. 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 ESPP also provides for an automatic reset feature to start participants on a new twenty-four month participation period in the event that the common stock market value on a purchase date is less than the common stock value on the first day of the twenty-four month offering period. The Company issued 25,639 and 14,184 shares of common stock pursuant to the ESPP for the three months ended March 31, 2015 and 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.
	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. For the three months ended March 31, 2015 and 2014, there was no non-employee share-based compensation expense. Employee-related compensation expense recognized related to stock options, RSUs and the ESPP is as follows (in thousands):
		Three Months Ended March 31,
		2015		2014
	Research and development expense	$	1,025	$	376
	General and administrative expense	1,377		396
	Total share-based compensation expense	$	2,402	$	772

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes
	The Company estimates an annual effective tax rate of 0% for the year ending December 31, 2015 as the Company incurred losses for the three month period ended March 31, 2015 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, 2015. 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.
	As of March 31, 2015, the Company had no unrecognized tax benefits that would reduce the Company’s effective tax rate if recognized.

Significant_Agreements

Significant Agreements	3 Months Ended
	Mar. 31, 2015
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.
	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 months ended March 31, 2015 or 2014.
	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. On August 28, 2014, the second option segment of the contract to provide approximately $17.0 million through November 30, 2015 was executed.
	Under the contract, BARDA will reimburse the Company, plus pay a fixed fee, for the research and development of brincidofovir as a treatment for 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 months ended March 31, 2015 and 2014, the Company recognized revenue of $1.2 million and $0.8 million, respectively, under this contract.
	ContraVir Pharmaceuticals
	On December 17, 2014, the Company entered into a license agreement with ContraVir Pharmaceuticals (NASDAQ: CTRV) for the development and commercialization of CMX157, our clinical stage nucleotide analog, for certain antiviral indications. Under the terms of the agreement, ContraVir has sole responsibility with respect to the control of the development and commercialization of CMX157.
	In exchange for the license to CMX157 rights, the Company received an upfront payment consisting of 120,000 shares of ContraVir Series B Convertible Preferred Stock with a stated value of $1.2 million. In addition, the Company is eligible to receive up to approximately $20.0 million in clinical, regulatory and initial commercial milestones in the United States and Europe, as well as royalties and additional milestones based on commercial sales in those territories. Either party may terminate the license agreement upon the occurrence of a material breach by the other party (subject to standard cure periods), or upon certain events involving the bankruptcy or insolvency of the other party. ContraVir may also terminate the license agreement without cause on a country-by-country basis upon sixty (60) days’ prior written notice.
	The upfront payment of 120,000 shares of ContraVir Series B Convertible Preferred Stock was valued at $1.5 million at the time of the agreement. The Company recorded this amount as a long-term investment and deferred revenue, which is included in accrued liabilities in the Consolidated Balance Sheets. Upon completion of the transfer of the IND and technical know-how related to CMX157, the Company will recognize the upfront payment as revenue. As of March 31, 2015, this transfer had not been completed. As of March 31, 2015 and December 31, 2014, the fair value of the investment was $2.5 million and $1.8 million, respectively.

Subsequent_Event

Subsequent Event	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	8. Subsequent Events
	The Company has evaluated subsequent events through the issuance date of these financial statements to ensure that this filing includes appropriate disclosure of events both recognized in the financial statements as of March 31, 2015, and events which occurred subsequently but were not recognized in the financial statements.

The_Business_and_Summary_of_Si1

The Business and Summary of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Description of Business	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 conjugate technology to unlock the potential of some of the most potent broad-spectrum antivirals by enhancing their antiviral activity and safety profiles in convenient, orally administered dosing regimens. Based on the Company’s proprietary lipid conjugate technology, its lead compound, brincidofovir (BCV or CMX001), is in Phase 3 clinical development; in addition, the Company has an active discovery program focusing on viral targets for which limited or no therapies are currently available or where current therapies have significant liabilities.
	Basis of Presentation
	The accompanying unaudited consolidated financial statements include the accounts of the Company and its wholly owned subsidiary and have been prepared in accordance with U.S. generally accepted accounting principles (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, 2014.  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 months ended March 31, 2015 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.
Fair Value of Financial Instruments	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.
	At March 31, 2015 and December 31, 2014, the Company had cash equivalents, consisting of money market accounts, and short-term and long-term investments consisting of U.S. Treasury securities, whose value is based on using quoted market prices. Accordingly, these securities are classified as Level 1.
	At March 31, 2015 and December 31, 2014, the Company had cash equivalents, short-term investments and long-term investments comprised of corporate bonds, commercial paper and brokered certificates of deposit for which quoted prices are not available that are valued using independent pricing models or other model-based valuation techniques such as the present value of future cash flows, adjusted for the security’s credit rating, prepayment assumptions and other factors such as credit loss assumptions. Accordingly, these securities are classified as Level 2.
	The Company’s preferred stock investment in ContraVir Pharmaceuticals (NASDAQ: CTRV) (ContraVir) is categorized as Level 3 as there are significant unobservable inputs. The valuation of the investment at March 31, 2015 and December 31, 2014 was calculated on an as if converted to common share basis with a discount for lack of marketability applied due to the 18 month restriction from the date of the investment on selling the converted common shares. An option pricing model was used to determine the discount for lack of marketability of 24% and 25% at March 31, 2015 and December 31, 2014, respectively. The key unobservable inputs used in the option pricing model at March 31, 2015 were (i) exercise price - $3.08, (ii) dividend yield - 0%, (iii) expected holding period - 1.22 years, (iv) risk-free rate - 0.26%, and (v) volatility - 65%. The key unobservable inputs used in the option pricing model at December 31, 2014 were (i) exercise price - $2.22, (ii) dividend yield - 0%, (iii) expected holding period - 1.5 years, (iv) risk-free rate - 0.44%, and (v) volatility - 65%. The increase in valuation of the preferred stock for the quarter ended March 31, 2015 was recorded as an unrealized gain in investment, net of tax in the Consolidated Statements of Operations and Comprehensive Loss.
	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 (in thousands):
		Fair Value Measurements
		March 31, 2015
		Total		Quoted Prices in		Significant Other		Significant
				Active Markets		Observable Inputs		Unobservable Inputs
				for Identical Assets		(Level 2)		(Level 3)
				(Level 1)
	Cash equivalents
	Money market funds	$	41,867	$	41,867	$	—	$	—
	Certificates of deposit	240		—		240		—
	Commercial paper	9,997		—		9,997		—
	Total cash equivalents	52,104		41,867		10,237		—
	Short-term investments
	Certificates of deposit	18,434		—		18,434		—
	Corporate bonds	41,109		$	—	$	41,109	$	—
	Commercial paper	6,246		—		6,246		—
	U.S. Treasury securities	53,109		53,109		—		—
	Total short-term investments	118,898		53,109		65,789		—
	Long-term investments
	Certificates of deposit	12,973		—		12,973		—
	U.S. Treasury securities	79,758		79,758		—		—
	Preferred stock of U.S. corporation	2,508		—		—		2,508
	Total long-term investments	95,239		79,758		12,973		2,508
	Total assets	$	266,241	$	174,734	$	88,999	$	2,508
		Fair Value Measurements
		December 31, 2014
		Total		Quoted Prices in		Significant Other		Significant
				Active Markets		Observable Inputs		Unobservable Inputs
				for Identical Assets		(Level 2)		(Level 3)
				(Level 1)
	Cash equivalents
	Money market funds	$	125,606	$	125,606	$	—	$	—
	Certificates of deposit	480		—		480		—
	Total cash equivalents	126,086		125,606		480		—
	Short-term investments
	Certificates of deposit	16,982		—		16,982		—
	Corporate bonds	69,892		—		69,892		—
	Commercial paper	11,240		—		11,240		—
	U.S. Treasury securities	8,000		8,000		—		—
	Total short-term investments	106,114		8,000		98,114		—
	Long-term investments
	Certificates of deposit	10,996		—		10,996		—
	U.S. Treasury securities	40,196		40,196		—		—
	Preferred stock of U.S. corporation	1,781		—		—		1,781
	Total long-term investments	52,973		40,196		10,996		1,781
	Total assets	$	285,173	$	173,802	$	109,590	$	1,781
	Below is a table that presents a reconciliation of the beginning and ending balances of assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):
		Fair Value Measurements
		(Level 3)
	Preferred stock of U.S. corporation:
	Fair value at December 31, 2014	$	1,781
	Fair value increase recorded in other comprehensive gain, net	727
Fair value at March 31, 2015	$	2,508
Revenue Recognition	Revenue Recognition
	The Company’s revenues generally consist of (i) contract and grant revenue – revenue generated under federal contracts and other awarded grants, and (ii) collaboration and licensing revenue – revenue 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.
Clinical Trial Accruals/Prepaids	Research and Development Prepaids and Accruals
	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 March 31, 2015, 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 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 and employee stock purchase plan rights. 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 March 31, 2015 and 2014.
	The calculation of weighted-average diluted shares outstanding excludes the dilutive effect of warrants and options to purchase common stock and employee stock purchase plan rights, as the impact of such items are anti-dilutive during periods of net loss. Potential common shares excluded from the calculations were 1,408,852 and 2,645,620 for the three months ended March 31, 2015 and 2014, respectively.

The_Business_and_Summary_of_Si2

The Business and Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2015
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 (in thousands):
		Fair Value Measurements
		March 31, 2015
		Total		Quoted Prices in		Significant Other		Significant
				Active Markets		Observable Inputs		Unobservable Inputs
				for Identical Assets		(Level 2)		(Level 3)
				(Level 1)
	Cash equivalents
	Money market funds	$	41,867	$	41,867	$	—	$	—
	Certificates of deposit	240		—		240		—
	Commercial paper	9,997		—		9,997		—
	Total cash equivalents	52,104		41,867		10,237		—
	Short-term investments
	Certificates of deposit	18,434		—		18,434		—
	Corporate bonds	41,109		$	—	$	41,109	$	—
	Commercial paper	6,246		—		6,246		—
	U.S. Treasury securities	53,109		53,109		—		—
	Total short-term investments	118,898		53,109		65,789		—
	Long-term investments
	Certificates of deposit	12,973		—		12,973		—
	U.S. Treasury securities	79,758		79,758		—		—
	Preferred stock of U.S. corporation	2,508		—		—		2,508
	Total long-term investments	95,239		79,758		12,973		2,508
	Total assets	$	266,241	$	174,734	$	88,999	$	2,508
		Fair Value Measurements
		December 31, 2014
		Total		Quoted Prices in		Significant Other		Significant
				Active Markets		Observable Inputs		Unobservable Inputs
				for Identical Assets		(Level 2)		(Level 3)
				(Level 1)
	Cash equivalents
	Money market funds	$	125,606	$	125,606	$	—	$	—
	Certificates of deposit	480		—		480		—
	Total cash equivalents	126,086		125,606		480		—
	Short-term investments
	Certificates of deposit	16,982		—		16,982		—
	Corporate bonds	69,892		—		69,892		—
	Commercial paper	11,240		—		11,240		—
	U.S. Treasury securities	8,000		8,000		—		—
	Total short-term investments	106,114		8,000		98,114		—
	Long-term investments
	Certificates of deposit	10,996		—		10,996		—
	U.S. Treasury securities	40,196		40,196		—		—
	Preferred stock of U.S. corporation	1,781		—		—		1,781
	Total long-term investments	52,973		40,196		10,996		1,781
	Total assets	$	285,173	$	173,802	$	109,590	$	1,781
	Below is a table that presents a reconciliation of the beginning and ending balances of assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) (in thousands):
		Fair Value Measurements
		(Level 3)
	Preferred stock of U.S. corporation:
	Fair value at December 31, 2014	$	1,781
	Fair value increase recorded in other comprehensive gain, net	727
	Fair value at March 31, 2015	$	2,508

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Securities	The following table summarizes the Company's short-term and long-term investments:
			March 31, 2015
			Amortized Cost		Gross  Unrealized Gains		Gross  Unrealized Losses			Estimated Fair Value
			(in thousands)
	Corporate bonds		$	41,127	$	—	$	(18	)	$	41,109
	Certificates of deposit		31,399		17		(10		)	31,406
	U.S. Treasury securities		132,897		17		(46		)	132,868
	Commercial paper		6,246		—		—			6,246
	Preferred stock of U.S. corporation		1,545		963		—			2,508
	Total investments		$	213,214	$	997	$	(74	)	$	214,137
			31-Dec-14
			Amortized Cost		Gross  Unrealized Gains		Gross  Unrealized Losses			Estimated Fair Value
			(in thousands)
	Corporate bonds		$	69,947	$	—	$	(56	)	$	69,891
	Certificates of deposit		28,039		1		(62		)	27,978
	U.S. Treasury securities		48,279		—		(82		)	48,197
	Commercial paper		11,242		—		(2		)	11,240
	Preferred stock of U.S. corporation		1,545		236		—			1,781
	Total investments		$	159,052	$	237	$	(202	)	$	159,087
Investments Classified by Contractual Maturity Date	The following table summarizes the scheduled maturity for the Company's investments at March 31, 2015 (in thousands):
		March 31, 2015
	Maturing in one year or less	$	118,898
	Maturing after one year through two years	95,239
	Total investments	$	214,137

Stockbased_Compensation_Tables

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-Based Compensation Expense	Employee-related compensation expense recognized related to stock options, RSUs and the ESPP is as follows (in thousands):
		Three Months Ended March 31,
		2015		2014
	Research and development expense	$	1,025	$	376
	General and administrative expense	1,377		396
	Total share-based compensation expense	$	2,402	$	772

The_Business_and_Summary_of_Si3

The Business and Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	0 Months Ended		3 Months Ended		6 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2014	Dec. 31, 2014
Accounting Policies [Abstract]
Fair value, investments, redemption restriction period					18 months
Fair value inputs, discount for lack of marketability	24.00%	25.00%
Per share information:
Anti-dilutive securities excluded from the calculation loss per share			1,408,852	2,645,620
Fair value assumptions, exercise price			$3.08			$2.22
Fair value assumptions, expected divided rate	0.00%	0.00%
Fair value assumptions, expected term		1 year 6 months	1 year 2 months 19 days
Fair value assumptions, risk free interest rate			0.26%			0.44%
Fair value assumptions, expected volatility rate			65.00%			65.00%

The_Business_and_Summary_of_Si4

The Business and Summary of Significant Accounting Policies (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	$118,898		$106,114
Available-for-sale Securities	214,137		159,087
Available-for-sale Securities, Gross Realized Gain (Loss)	625	-32
Fair value, measurements, recurring
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	52,104		126,086
Short-term investments, available-for-sale	118,898		106,114
Available-for-sale Securities, Noncurrent	95,239		52,973
Assets, fair value	266,241		285,173
Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	41,867		125,606
Short-term investments, available-for-sale	53,109		8,000
Assets, fair value	174,734		173,802
Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	10,237		480
Short-term investments, available-for-sale	65,789		98,114
Assets, fair value	88,999		109,590
Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Short-term investments, available-for-sale	0		0
Available-for-sale Securities, Noncurrent	0		1,781
Assets, fair value	2,508		1,781
Money market funds | Fair value, measurements, recurring
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	41,867		125,606
Money market funds | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	41,867		125,606
Money market funds | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Money market funds | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Certificates of deposit
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities	31,406		27,978
Certificates of deposit | Fair value, measurements, recurring
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	240		480
Short-term investments, available-for-sale	18,434		16,982
Available-for-sale Securities, Noncurrent	12,973		10,996
Certificates of deposit | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Short-term investments, available-for-sale	0		0
Available-for-sale Securities, Noncurrent	0		0
Certificates of deposit | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	240		480
Short-term investments, available-for-sale	18,434		16,982
Available-for-sale Securities, Noncurrent	12,973		10,996
Certificates of deposit | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0		0
Short-term investments, available-for-sale	0		0
Available-for-sale Securities, Noncurrent			0
Corporate bonds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities	41,109		69,891
Corporate bonds | Fair value, measurements, recurring
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	41,109		69,892
Corporate bonds | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	0		0
Corporate bonds | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	41,109		69,892
Corporate bonds | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	0		0
Commercial paper
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities	6,246		11,240
Commercial paper | Fair value, measurements, recurring
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	9,997
Short-term investments, available-for-sale	6,246		11,240
Commercial paper | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0
Short-term investments, available-for-sale	0		0
Commercial paper | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	9,997
Short-term investments, available-for-sale	6,246		11,240
Commercial paper | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0
Short-term investments, available-for-sale	0		0
U.S. Treasury securities
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities	132,868		48,197
U.S. Treasury securities | Fair value, measurements, recurring
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	53,109		8,000
Available-for-sale Securities, Noncurrent	79,758		40,196
U.S. Treasury securities | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	53,109		8,000
Available-for-sale Securities, Noncurrent	79,758		40,196
U.S. Treasury securities | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	0		0
Available-for-sale Securities, Noncurrent	0		0
U.S. Treasury securities | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Short-term investments, available-for-sale	0		0
Available-for-sale Securities, Noncurrent	0		0
Preferred stock of U.S. corporation
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	2,508		1,781
Available-for-sale Securities	2,508		1,781
Available-for-sale Securities, Gross Realized Gain (Loss)	727
Preferred stock of U.S. corporation | Fair value, measurements, recurring
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	2,508		1,781
Preferred stock of U.S. corporation | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	0		0
Preferred stock of U.S. corporation | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	0		0
Preferred stock of U.S. corporation | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	2,508		1,781
Debt securities | Fair value, measurements, recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	79,758		40,196
Debt securities | Fair value, measurements, recurring | Significant Other Observable Inputs (Level 2)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	12,973		10,996
Debt securities | Fair value, measurements, recurring | Significant Unobservable Inputs (Level 3)
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Available-for-sale Securities, Noncurrent	$2,508

Investments_Summary_of_Availab

Investments - Summary of Available-for-Sale securities (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of Investments [Line Items]
Amortized Cost	$213,214	$159,052
Gross Unrealized Gains	997	237
Gross Unrealized Losses	-74	-202
Available-for-sale Securities	214,137	159,087
Long-term investments	95,239	52,973
Corporate bonds
Schedule of Investments [Line Items]
Amortized Cost	41,127	69,947
Gross Unrealized Gains	0	0
Gross Unrealized Losses	-18	-56
Available-for-sale Securities	41,109	69,891
Certificates of deposit
Schedule of Investments [Line Items]
Amortized Cost	31,399	28,039
Gross Unrealized Gains	17	1
Gross Unrealized Losses	-10	-62
Available-for-sale Securities	31,406	27,978
U.S. Treasury securities
Schedule of Investments [Line Items]
Amortized Cost	132,897	48,279
Gross Unrealized Gains	17	0
Gross Unrealized Losses	-46	-82
Available-for-sale Securities	132,868	48,197
Commercial paper
Schedule of Investments [Line Items]
Amortized Cost	6,246	11,242
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	-2
Available-for-sale Securities	6,246	11,240
Preferred stock of U.S. corporation
Schedule of Investments [Line Items]
Amortized Cost	1,545	1,545
Gross Unrealized Gains	963	236
Gross Unrealized Losses	0	0
Available-for-sale Securities	$2,508	$1,781

Investments_Schedule_of_Invest

Investments - Schedule of Investment Maturity (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Investments, Debt and Equity Securities [Abstract]
Maturing in one year or less	$118,898
Maturing after one year through two years	95,239
Total investments	$214,137	$159,087

Loan_Payable_Details

Loan Payable (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2012	Jan. 27, 2012
Line of Credit Facility [Line Items]
Loan and security agreement, maximum capacity		$15
Second tranche
Line of Credit Facility [Line Items]
Loan and security agreement, remaining capacity		12
Interest only period	6 months
Principal and interest amortization period	32 months
First tranche
Line of Credit Facility [Line Items]
Loan and security agreement, outstanding		$3
Interest only period	12 months
Principal and interest amortization period	30 months
Loan and security agreement, interest rate	8.25%

Commitments_and_Contingencies_

Commitments and Contingencies (Narrative) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Operating leases, rent expense	$0.20	$0.10

Stockbased_Compensation_Narrat

Stock-based Compensation (Narrative) (Details) (USD $)	3 Months Ended		0 Months Ended	1 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Jan. 01, 2015	Feb. 28, 2013	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized	200,000,000				200,000,000
Allocated share-based compensation expense	$2,402	$772
2013 employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation, Evergreen Option Provision, Equity Increase				1.00%
Shares available for issuance	1,329,277			1,381,191
Percentage of pay that employee can contribute, maximum	15.00%
Number of shares authorized to be granted				704,225
Number of shares outstanding under the plan				422,535
Additional shares authorized			410,317
Percentage of fair value employees pay	85.00%
Shares issued	25,639	14,184
The 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation, Evergreen Option Provision, Equity Increase	4.00%
Shares available for issuance	2,011,058
Additional shares authorized			1,641,271

Stockbased_Compensation_Schedu

Stock-based Compensation (Schedule of Stock-based Compensation Expense) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense	$2,402	$772
Employee | Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense	1,025	376
Employee | General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share-based compensation expense	$1,377	$396

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details)	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Estimated annual effective tax rate	0.00%

Significant_Agreements_Details

Significant Agreements (Details) (USD $)	3 Months Ended		1 Months Ended	58 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	31-May-02	Nov. 30, 2015	Dec. 17, 2014	Dec. 31, 2014
Long-term Purchase Commitment [Line Items]
Contract revenue	$1,238,000	$780,000
Available-for-sale Securities	214,137,000					159,087,000
Regents of University of California
Long-term Purchase Commitment [Line Items]
Milestone payments			3,400,000
Number of options outstanding, Granted			64,788
Sublicense fee percentage			50.00%
Royalties percentage			50.00%
Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Contract revenue	1,200,000	800,000
Number of extension periods	4
Other segments, period	1 year
Research and development arrangement second option | Forecast
Long-term Purchase Commitment [Line Items]
Contract revenue				17,000,000
Preferred Stock, ContraVir Series B | ContraVir Pharmaceuticals
Long-term Purchase Commitment [Line Items]
Other Significant Noncash Transaction, Shares Received as Consideration					120,000
Preferred Stock, Value, Issued					1,200,000
Deferred Revenue					20,000,000
Other Significant Noncash Transaction, Value of Consideration Received					1,500,000
Maximum | Brincidofovir
Long-term Purchase Commitment [Line Items]
Sublicense fee amount, payable fee percentage	5.00%
Maximum | Research and Development Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Reimbursement revenue	75,800,000
Maximum | Research and Development Arrangement [Member] | Forecast
Long-term Purchase Commitment [Line Items]
Contract revenue				5,300,000
Preferred stock of U.S. corporation
Long-term Purchase Commitment [Line Items]
Available-for-sale Securities	$2,508,000					$1,781,000