Immune Design 10-K 14 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 12, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	IMDZ
Entity Registrant Name	Immune Design Corp.
Entity Central Index Key	1,437,786
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		48,125,008
Entity Public Float			$ 209.3

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 72,454	$ 45,214
Short-term investments	68,653	62,041
Accounts receivable	647	517
Inventory	684	607
Prepaid expenses	1,571	2,546
Restricted cash	6,000	0
Other receivables	3,134	3,156
Total current assets	153,143	114,081
Property and equipment, net	491	414
Security deposit	200	0
Total assets	153,834	114,495
Current liabilities:
Accounts payable	2,334	4,559
Accrued liabilities	6,186	4,935
Accrued litigation-related settlement	6,000	7,250
Deferred revenue	0	2,519
Total current liabilities	14,520	19,263
Other noncurrent liabilities	102	56
Commitments and contingencies (Note 9)
Stockholders’ equity:
Common stock, $0.001 par value per share; 100,000,000 authorized at December 31, 2017 and 2016; 48,068,650 and 25,413,055 shares issued and outstanding at December 31, 2017 and 2016, respectively	48	25
Preferred stock, $0.001 par value; 10,000,000 shares authorized at December 31, 2017 and 2016; no shares issued or outstanding	0	0
Additional paid-in capital	374,970	278,913
Accumulated deficit	(235,757)	(183,738)
Accumulated other comprehensive loss	(49)	(24)
Total stockholders’ equity	139,212	95,176
Total liabilities and stockholders’ equity	$ 153,834	$ 114,495

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Common stock
Par value per share (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	100,000,000	100,000,000
Shares issued (in shares)	48,068,650	25,413,055
Shares outstanding (in shares)	48,068,650	25,413,055
Preferred stock
Par value per share (in dollars per share)	$ 0.001	$ 0.001
Shares issued (in shares)	0	0
Shares outstanding (in shares)	0	0
Shares authorized (in shares)	10,000,000	10,000,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Collaborative revenue	$ 6,880	$ 4,633	$ 4,157
Licensing revenue	0	7,000	3,500
Product sales	315	1,627	1,853
Total revenues	7,195	13,260	9,510
Operating expenses:
Cost of product sales	84	481	774
Research and development	43,670	45,134	33,087
General and administrative	16,253	21,859	15,134
Total operating expenses	60,007	67,474	48,995
Loss from operations	(52,812)	(54,214)	(39,485)
Interest and other income	950	684	40
Net loss	(51,862)	(53,530)	(39,445)
Unrealized loss on investments	(25)	(24)	0
Comprehensive loss	$ (51,887)	$ (53,554)	$ (39,445)
Basic and diluted net loss per share (in dollars per share)	$ (1.75)	$ (2.47)	$ (2.06)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	29,626,941	21,638,468	19,155,918

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED DEFICIT	ACCUMULATED OTHER COMPREHENSIVE LOSS
Beginning balance at Dec. 31, 2014	$ 66,346	$ 17	$ 157,092	$ (90,763)	$ 0
Beginning balance (in shares) at Dec. 31, 2014		16,878,817
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon completion of public offering, net of offering costs	75,359	$ 3	75,356
Issuance of common stock upon completion of public offering, net of offering costs (in shares)		3,047,409
Issuance of common stock under stock-based compensation plans	436	$ 0	436
Issuance of common stock under stock-based compensation plans (in shares)		226,976
Stock-based compensation	6,297		6,297
Net loss	(39,445)			(39,445)	0
Unrealized loss on investments	0
Ending balance at Dec. 31, 2015	108,993	$ 20	239,181	(130,208)	0
Ending balance (in shares) at Dec. 31, 2015		20,153,202
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon completion of public offering, net of offering costs	30,310	$ 5	30,305
Issuance of common stock upon completion of public offering, net of offering costs (in shares)		5,226,369
Issuance of common stock under stock-based compensation plans	144	$ 0	144
Issuance of common stock under stock-based compensation plans (in shares)		33,484
Stock-based compensation	9,283		9,283
Net loss	(53,530)			(53,530)	0
Unrealized loss on investments	(24)				(24)
Ending balance at Dec. 31, 2016	$ 95,176	$ 25	278,913	(183,738)	(24)
Ending balance (in shares) at Dec. 31, 2016	25,413,055	25,413,055
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment from adoption of accounting standard on stock-based compensation	$ 0		157	(157)
Issuance of common stock upon completion of public offering, net of offering costs	86,576	$ 23	86,553
Issuance of common stock upon completion of public offering, net of offering costs (in shares)		22,425,000
Issuance of common stock under stock-based compensation plans	714	$ 0	714
Issuance of common stock under stock-based compensation plans (in shares)		230,595
Stock-based compensation	8,633		8,633
Net loss	(51,862)			(51,862)	0
Unrealized loss on investments	(25)				(25)
Ending balance at Dec. 31, 2017	$ 139,212	$ 48	$ 374,970	$ (235,757)	$ (49)
Ending balance (in shares) at Dec. 31, 2017	48,068,650	48,068,650

Consolidated Statements of Sto6

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common stock
Share price (in dollars per share)	$ 4.10	$ 6.25	$ 26.5
Stock issuance costs	$ 5,367	$ 2,355	$ 5,397

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (51,862)	$ (53,530)	$ (39,445)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	351	304	243
Amortization of premium/discount on investments	(26)	126	0
Stock-based compensation	8,633	9,283	6,297
Changes in operating assets and liabilities:
Accounts receivable	(130)	455	998
Inventory	(77)	(594)	12
Prepaid expenses	975	(892)	(1,021)
Restricted cash	(6,000)	0	0
Other receivables	22	(3,059)	0
Security deposit	(200)	0	0
Accounts payable	(2,225)	1,485	(3,829)
Accrued liabilities	1,203	976	(519)
Accrued litigation-related settlement	(1,250)	7,250	0
Deferred revenue	(2,545)	2,496	(510)
Deferred rent and other noncurrent liabilities	72	(40)	(27)
Net cash used in operating activities	(53,059)	(35,740)	(37,801)
Investing activities
Purchases of property and equipment	(428)	(133)	(427)
Purchases of short-term investments	(71,611)	(102,288)	0
Maturities of short-term investments	65,000	40,000	0
Net cash used in investing activities	(7,039)	(62,421)	(427)
Financing activities
Issuance of common stock in public offering, net of offering costs	86,624	30,310	75,359
Proceeds from issuances of common stock under stock-based compensation plans	714	144	436
Net cash provided by financing activities	87,338	30,454	75,795
Net (decrease) increase in cash and cash equivalents	27,240	(67,707)	37,567
Cash and cash equivalents, beginning of year	45,214	112,921	75,354
Cash and cash equivalents, end of year	72,454	45,214	112,921
Supplemental cash flow information
Unpaid stock offering costs	$ 48	$ 0	$ 0

Description of the Business

Description of the Business	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business	Description of the Business Immune Design Corp. (we, us or our) is a clinical-stage immunotherapy company focused on cancer with next-generation in vivo approaches designed to enable the body’s immune system to fight disease. We have engineered our technologies to activate the immune system’s natural ability to create tumor-specific cytotoxic T cells (CTLs) to fight cancer. We are developing multiple product candidates from our two discovery platforms, ZVex ® and GLAAS ® . Our primary product candidates, CMB305 and G100, utilize multiple immuno-oncology approaches and are being evaluated in multiple Phase 1 and Phase 2 trials. We are planning to begin a Phase 3 clinical trial of CMB305 in patients with synovial sarcoma in mid 2018. In addition, we have licensed to third parties the right to use the GLAAS platform in select infectious disease and allergy indications. We were incorporated in February 2008 in the State of Delaware. Our operations are headquartered in Seattle, Washington and we have an additional facility in South San Francisco, California.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). To conform with GAAP, the preparation of our financial statements requires management to make judgments, assumptions, and estimates that affect the amounts reported in our financial statements and accompanying notes. Estimates are used for, but not limited to, accruals for clinical trial activity, other accrued liabilities, and assumptions used in determining stock-based compensation expense. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable. Actual results could differ materially from those estimates. Principles of Consolidation Our consolidated financial statements include the financial position and results of operations of Immune Design Corp. and Immune Design Ltd., our wholly owned subsidiary. Immune Design Ltd. was incorporated in the United Kingdom in February 2016 and to date there have been no financial transactions or balances related to this entity. Segments We operate in one segment and use cash flow as the primary measure to manage our business and do not segment the business for internal reporting or decision-making purposes. Offering Costs Offering costs represent legal, accounting and other direct costs related to our efforts to raise capital through our follow-on public offerings in October 2017, September 2016 and April 2015 and for our initial public offering (IPO) in July 2014. These costs were deferred until completion of the follow-on public offerings and IPO, respectively, at which time they were reclassified to additional paid-in capital as a reduction of the proceeds. Cash and Cash Equivalents Cash equivalents are highly liquid investments with a maturity of 90 days or less at the date of purchase and primarily consist of investments in money market funds. In addition, we maintain cash balances with financial institutions in excess of insured limits and do not anticipate any losses on such cash balances. Concentration of Risk We limit our credit risk associated with cash and cash equivalents by placing our deposits with banks we believe are highly creditworthy and our investments with highly rated money market funds. Short-Term Investments Our short-term investments include funds invested in U.S. Treasury securities with a final maturity of each security of less than one year. All investments are classified as available-for-sale securities and are recorded at fair value based on quoted prices in active markets, with unrealized gains and losses excluded from earnings and reported in other comprehensive income (loss). Purchase premiums and discounts are recognized in interest income using the interest method over the terms of the securities. Realized gains and losses and declines in fair value that are deemed to be other than temporary are reflected in the consolidated statements of operations and comprehensive income (loss) using the specific-identification method. Accounts Receivable Accounts receivable are amounts due from other companies related primarily to licensing fees, product sales and research and development services. We considered the need for an allowance for doubtful accounts and have concluded that no allowance was needed as of December 31, 2017 or 2016 , as the estimated risk of loss on our accounts receivable was determined to be minimal. Inventory Inventory is recorded at the lower of cost or market. Cost includes amounts related to materials and labor, and is determined on a specific identification basis in a manner which approximates the first-in, first-out method. We record adjustments to inventory for potentially excess, obsolete, expired, or impaired items. Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation. Depreciation is computed using the straight-line method over an estimated useful life that is generally three years , while leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to operations. Maintenance and repairs are expensed as incurred. Asset improvements are capitalized. Impairment of Long-Lived Assets Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Conditions that would necessitate an impairment assessment include a significant decline in the observable market value of an asset, a significant change in the extent or manner in which an asset is used, or any other significant adverse change that would indicate that the carrying amount of an asset is not recoverable. Accrued Liabilities Accrued liabilities represent accrued compensation including vacation accruals, unearned revenue and accrued expenses. As part of the process of preparing our consolidated financial statements, we are required to estimate our accrued professional services and research and development expenses. This process involves reviewing contracts and vendor agreements, communicating with our applicable personnel to identify services that have been performed on our behalf. We estimate the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual cost. We make estimates of our accrued expenses as of each balance sheet date in our consolidated financial statements based on facts and circumstances known to us. We base our expenses related to contract manufacturing and clinical trials on our estimates of the services received and efforts expended pursuant to contracts with multiple contract manufacturing organizations and clinical research organizations that conduct and manage supply and clinical trials on our behalf. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period. To date, we have not experienced any significant adjustments to our estimates. Leases and Deferred Rent We have entered into lease agreements for laboratory and office facilities. These leases are classified as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease. Incentives granted under our facilities leases, including allowances to fund leasehold improvements and rent escalations are accrued as deferred rent. Leasehold improvements funded by the lessor are capitalized and are recognized as reductions to rental expense on a straight-line basis over the term of the lease. Revenue Recognition We derive our revenue from collaboration and licensing agreements and the sale of products associated with material transfer, collaboration and supply agreements. Licensing fees, are recognized when the amounts are earned and determinable during the applicable period. We recognize up-front nonrefundable license fees when due under contractual agreements and when we do not have a continuing obligation to provide services related to the agreement. Revenue associated with nonrefundable up-front license fees under arrangements where the license fees and research and development activities cannot be accounted for as separate units of accounting is deferred and recognized as revenue on a straight-line basis over the expected term of our continued involvement in the research and development process. Revenues from the achievement of research and development milestones, if deemed substantive, are recognized as revenue when the milestones are achieved, and the milestone payments are due and collectible. If not deemed substantive, we recognize such milestones as revenue on a straight-line basis over the remaining expected term of continued involvement in the research and development process. Milestones are considered substantive if all of the following conditions are met: (1) the milestone is nonrefundable, (2) achievement of the milestone was not reasonably assured at the inception of the arrangement, (3) substantive effort is involved to achieve the milestone and (4) 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 and any ongoing research and development or other services are priced at fair value. Payments received in advance of work performed are recorded as unearned revenue. Certain agreements from which we derive our revenue include multiple deliverables. We recognize the revenue for each deliverable at fair value determined to be the estimated selling price in cases when neither vendor specific objective evidence nor third-party evidence is available. Revenues derived from funding of development costs are recognized when the related costs are incurred and when collectability is reasonably assured. Revenue is recognized when all of the following criteria are met: (1) persuasive evidence of an arrangement exists, (2) delivery has occurred or services have been rendered, (3) the price to the customer is fixed or determinable and (4) collectability is reasonably assured. The evaluation of these revenue recognition criteria requires significant management judgment. For instance, we use judgment to assess collectability based on factors such as the customer’s creditworthiness and past collection history, if applicable. If we determine that collection of a payment is not reasonably assured, revenue recognition is deferred until receipt of payment. We also use judgment to assess whether a price is fixed or determinable including, but not limited to, reviewing contractual terms and conditions related to payment terms. Revenue from product sales of glucopyranosyl lipid A (GLA), a product from our GLAAS platforms, is recognized when the risk of loss has passed to the customer or deferred until such time that risk of loss has passed. All revenues associated from the sale of GLA products supplied by us are reported under product sales with the applicable costs reported under cost of product sales. Product sales consist of the direct costs associated with the manufacture and formulation of GLA, including costs to purchase raw materials, third-party contract manufacturing costs, assay testing and ongoing product stability testing. We consider significant revenue concentrations to be customers who account for 10% or more of total revenues generated by us during the periods presented. We had one collaboration partner that accounted for 96% of revenue for the year ended December 31, 2017 , two collaboration partners at 64% and 35% of revenue for the year ended December 31, 2016 , and three collaboration partners at 44% , 36% and 20% of revenue for the year ended December 31, 2015 . The collaboration partners accounted for 100% of accounts receivable as of December 31, 2017 and 2016 . We do not believe the loss of such customers would have a material adverse effect on us. Stock-Based Compensation We account for stock-based compensation under the fair value method. Stock-based compensation costs related to employees and directors is measured at the grant date, based on the fair-value-based measurement of the award estimated using the Black-Scholes option-pricing model, and is recognized as expense over the requisite service period on a straight-line basis. Options granted to non-employee service providers are accounted for at estimated fair value using the Black-Scholes option-pricing model and are remeasured over the vesting term as earned. Prior to the Financial Accounting Standards Board (FASB) adoption of Accounting Standards Update (ASU) No. 2016-09 on January 1, 2017, stock-based compensation expense recognized was calculated based on awards ultimately expected to vest and was reduced for estimated forfeitures. Upon the FASB adoption of ASU No. 2016-09, effective January 1, 2017, we have elected to account for forfeitures as they occur. As of January 1, 2017, we had unrecorded forfeitures of $157,000 . Upon adoption, we recognized this expense as an adjustment to retained earnings with a corresponding increase to additional paid-in-capital. In addition, under this guidance, on a prospective basis, companies will no longer record excess tax benefits and certain tax deficiencies in additional paid-in-capital. Instead, they will record all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement and eliminates the requirement that excess tax benefits be realized before companies can recognize them. As of January 1, 2017, we had an unrecognized excess tax benefit of $1.2 million and upon adoption, we recognized this excess tax benefit as a deferred tax asset with a corresponding increase to our deferred tax asset valuation allowance. Research and Development Research and development costs are expensed as incurred. Research and development costs primarily include personnel costs, materials and manufacturing to support clinical trials, fees paid to consultants and outside service providers, costs to conduct clinical trials and allocated overhead. Amounts incurred in connection with collaboration agreements are also included in research and development expense. Payments made prior to the receipt of goods or services to be used in research and development are deferred until the goods or services are received. Income Taxes Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and the operating loss and tax credit carry forwards. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Deferred tax assets and liabilities are measured at the balance sheet date using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period such tax rate changes are enacted. Our net deferred tax asset has been fully offset by a valuation allowance because of our history of losses. Any potential accrued interest and penalties related to unrecognized tax benefits within operations would be recorded as income tax expense. To date, there have been no interest or penalties charged to us related to the underpayment of income taxes. Comprehensive Loss Comprehensive loss is composed of net loss and other comprehensive income or loss that are excluded from net loss. For the years ended December 31, 2017 and 2016 , other comprehensive loss consists of unrealized losses on our available-for-sale securities. For the year ended December 31, 2015 , there was no difference between comprehensive loss and net loss. Subsequent Events We consider events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. Recent Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09 amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, the FASB deferred the effective date of the revenue recognition guidance to reporting periods beginning after December 15, 2017. The new standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We currently anticipate adopting the new standard effective January 1, 2018, using the modified retrospective method. We will continue to monitor additional modifications, clarifications or interpretations undertaken by the FASB that may impact our current conclusions. We primarily derive our revenue from license and collaboration agreements. The consideration we are eligible to receive under these agreements includes upfront payments, research and development funding, milestone payments and royalties. Each license and collaboration agreement is unique and will be assessed separately under the five-step process under the new standard. The new revenue recognition standard differs from the current accounting standard in many respects, such as in the accounting for variable considerations and the measurement of progress toward completion of performance obligations. We performed a review of all of our ongoing license and collaboration agreements and based upon our assessment and given the nature of our arrangements and the related performance obligations, we determined there will be no impact on our financial position and results of operations as a result of the adoption of the standard on January 1, 2018, the date of adoption. In February 2016, FASB issued ASU 2016-02 related to lease accounting. This standard will require organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases that are greater than 12 months in duration. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from previous GAAP. There continues to be a differentiation between finance leases and operating leases, however, the principal difference from previous guidance is that the lease assets and lease liabilities arising from operating leases will be recognized on the balance sheets. For capital or finance leases, lessees will recognize amortization of the right-of-use asset separately from interest on the lease liability. For operating leases, lessees will recognize a single total lease expense. The standard is effective for public companies for the fiscal years and interim reporting periods beginning after December 15, 2018. We plan to adopt this new standard prospectively on January 1, 2019. We are evaluating the impact of the adoption of this standard on our consolidated financial statements. We expect that it will increase our lease assets and correspondingly increase our lease liabilities. In August 2016, the FASB issued ASU No. 2016-15 which provides new guidance on the classification of certain cash receipts and payments in the statement of cash flows. The new guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. We will be required to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. We are currently assessing the impact that the new guidance will have on its consolidated statements of cash flows. In November 2016, the FASB issued ASU No. 2016-18 that relates to restricted cash. The new guidance requires amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. We will be required to revise our consolidated statements of cash flows to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. Adoption of the new guidance will not have a significant impact on our financial position and results of operations. In May 2017, the FASB issued ASU No. 2017-09 to provide clarity and reduce both diversity in practice and cost and complexity when applying the guidance in Topic 718 about a change to the terms and conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The amendments in this update are effective for annual periods, including interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted, and applied prospectively to modifications that occur on or after the adoption date. We are currently reviewing and evaluating this recent update and plan to adopt on the required adoption date. For the year ended December 31, 2017, there were no modifications to the terms or conditions of a share-based payment award. In September 2017, the FASB issued ASU No. 2017-13 to amend revenue recognition (Topic 605), revenue from contracts with customers (Topic 606), leases (Topic 840), and leases (Topic 842) adding Securities and Exchange Commission (SEC) paragraphs pursuant to an SEC Staff Announcement made at the July 20, 2017 Emerging Issues Task Force (EITF) meeting. We are currently reviewing and evaluating this recent update and plan to adopt as required. For the year ended December 31, 2017, there were no modifications or changes incorporated with respect to this recently issued update.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Because of net losses recognized in each period, potential common shares issuable upon the exercise of outstanding stock options and warrants and the conversion of preferred shares in the IPO into common shares have not been reflected in the calculation of diluted net loss per share due to the anti-dilutive effect. Diluted net loss per share, therefore, does not differ from basic net loss per share. The common stock equivalents issuable upon the conversion or exercise of the following dilutive securities have been excluded from the computation of diluted net loss per share attributable to common stockholders calculation because their effect would have been anti-dilutive for the periods presented: DECEMBER 31, 2017 2016 2015 Outstanding stock option grants 4,094,532 3,590,393 2,832,467 Unvested restricted stock awards 195,172 107,250 — Total 4,289,704 3,697,643 2,832,467

Cash Equivalents and Short-Term

Cash Equivalents and Short-Term Investments	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Cash Equivalents and Short-Term Investments	Cash Equivalents and Short-Term Investments The amortized cost and fair value of our cash equivalents and short-term investments are as follows (in thousands): December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Money market funds $ 70,502 $ — $ — $ 70,502 U.S. Treasury securities 68,702 — (49 ) 68,653 Total $ 139,204 $ — $ (49 ) $ 139,155 Classified as: Cash equivalents $ 70,502 Short-term investments 68,653 Total $ 139,155 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Money market funds $ 36,412 $ 2 $ — $ 36,414 U.S. Treasury securities 62,066 2 (28 ) 62,040 Total $ 98,478 $ 4 $ (28 ) $ 98,454 Classified as: Cash equivalents $ 36,414 Short-term investments 62,040 Total $ 98,454 All U.S. Treasury securities held as of December 31, 2017 and 2016 were classified as available-for-sale securities and had contractual maturities of less than one year. There were no realized gains or losses on these securities for the period presented.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments We measure and record cash and cash equivalents and convertible preferred stock warrant liabilities at fair value in the accompanying financial statements. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value, is as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 : Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 1 securities consist of highly liquid money market funds. The fair value of Level 1 assets has been determined using quoted prices in active markets for identical assets. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. The following tables summarize our financial assets and liabilities measured at fair value on a recurring basis (in thousands): December 31, 2017 LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Money market funds $ 70,502 $ — $ — $ 70,502 U.S. Treasury securities 68,653 — — 68,653 Total $ 139,155 $ — $ — $ 139,155 December 31, 2016 LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Money market funds $ 36,414 $ — $ — $ 36,414 U.S. Treasury securities 62,040 — — $ 62,040 Total $ 98,454 $ — $ — $ 98,454

Inventory

Inventory	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventory	Inventory Inventory consists of the following (in thousands): DECEMBER 31, 2017 2016 Work in process $ 541 $ 567 Finished goods 143 40 Total inventory $ 684 $ 607

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consists of the following (in thousands): DECEMBER 31, 2017 2016 Laboratory equipment $ 2,624 $ 2,330 Leasehold improvements 183 156 Computer equipment and software 584 483 Office equipment, furniture, and fixtures 178 174 Total 3,569 3,143 Less: accumulated depreciation and amortization (3,078 ) (2,729 ) Total property and equipment, net $ 491 $ 414 Depreciation and amortization expense was $351,000 , $304,000 and $243,000 for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities Accrued liabilities consist of the following (in thousands): DECEMBER 31, 2017 2016 Research and development services $ 3,352 $ 3,027 Legal and professional services 48 28 Employee compensation 2,777 1,880 Other 9 — Total accrued liabilities $ 6,186 $ 4,935

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases We lease laboratory and office space under an operating lease in Seattle, Washington. Our previous lease commenced February 2013 and ended December 31, 2016. In January 2016 , we entered into a new lease agreement for approximately 20,133 square feet of office and laboratory space, which includes and expands on the space previously subleased. The lease commenced on January 1, 2017 with a term of five years and an option to extend the term for an additional three years . The annual base rent is $1.1 million for the first year and increases by 2.5% each year thereafter. We recognize rent expense on a straight-line basis over the lease period and accrue for rent expense incurred but not paid. The lease also requires us to pay for operating and maintenance expenses. Through December 31, 2017 and 2016 , we incurred $183,000 and $156,000 , respectively, in leasehold improvements and accumulated amortization of $147,000 and $123,000 , respectively. Also under the terms of the lease, in January 2017 we provided a $200,000 letter of credit as a security deposit. We also lease 9,640 square feet of office space under an operating lease in South San Francisco, California. The lease commenced in January 2015 and continues through January 2020 , with an option to extend for an additional five years . The terms of the office lease provide for rental payments on a monthly basis and on a graduated scale. We recognize rent expense on a straight-line basis over the lease period and accrue for rent expense incurred but not paid. The lease also requires us to pay additional amounts for operating and maintenance expenses beginning January 2016. In connection with the lease, we were required to provide a $121,000 letter of credit as a security deposit. As of December 31, 2017 , no funds had been drawn down on the letter of credit. As of December 31, 2017 , future minimum lease payments are as follows (in thousands): 2018 $ 1,486 2019 1,525 2020 1,203 2021 1,200 2022 — Total future minimum lease payments $ 5,414 Rent expense under operating leases was approximately $1.5 million , $713,000 and $849,000 , for the years ended December 31, 2017 , 2016 and 2015 , respectively. In May 2017 , we entered into a sublease agreement with a third party subtenant, pursuant to which we are subleasing 5,048 square feet of our Seattle laboratory and office space for a period of three years . The annual base rent payable under this sublease is $273,000 for the first year and will increase by 2.5% each year thereafter. Rent under this sublease agreement is reflected in other income. Contingencies In June 2015, we entered into a clinical supply agreement with NanoPass Technologies LTD (NanoPass) for the use of their intradermal delivery device in certain of our clinical trials. In July 2015, in connection with the execution of the agreement, we paid an upfront fee of $600,000 for access and rights to use their device. In December 2015, we initiated a Phase 2 clinical trial using the device which triggered a milestone payment of $500,000 . Both the upfront fee and milestone payments were capitalized to prepaid expenses on the accompanying balance sheet and are being amortized to research and development expense over the related milestone periods. As of December 31, 2017 , the upfront and milestone payments have been fully amortized to research and development expense. In October 2016, we entered into a letter agreement with NanoPass which amended our clinical supply agreement to expand the field of use to include all oncology immunotherapy applications, which provided for additional milestone payments to NanoPass upon achievement of future clinical milestones. Per the terms of the letter agreement, we paid NanoPass an additional one-time non-refundable payment of $150,000 . In addition, we agreed to pay certain future milestone fees up to an aggregate of $8.8 million upon the achievement of certain clinical milestones. However, pursuant to our current clinical protocol, we do not plan to use the NanoPass intradermal delivery device in our Phase 3 clinical trial studying CMB305 in patients with synovial sarcoma. Under our license agreements with the Infectious Disease Research Institute (IDRI), we are contingently obligated to pay any potential future milestone payments, which could total up to $2.3 million and $1.3 million , respectively, for the first and each subsequent exclusive licensed product we develop, and $1.3 million and $625,000 , respectively, for the first and each subsequent non-exclusive licensed product we develop. We are also contingently obligated to pay potential future milestone payments to third parties as part of certain collaboration and licensing agreements, which could total up to $7.7 million in aggregate payments for the ZVex products we develop. We also have potential future royalty payments we may be required to make under our licensing agreements as described in Note 10. Payments under these agreements are uncertain due to the occurrence of the events requiring payment under these agreements, including our share of potential future milestone and royalty payments. These payments generally become due and payable only upon achievement of certain clinical development, regulatory or commercial milestones.

License and Collaboration Agree

License and Collaboration Agreements	12 Months Ended
	Dec. 31, 2017
Research and Development [Abstract]
License and Collaboration Agreements	License and Collaboration Agreements Licenses Granted In August 2014, we entered into an agreement with Sanofi under which we granted Sanofi an exclusive license for use of our GLAAS platform to discover, develop and commercialize products to treat peanut allergy. Sanofi may terminate the agreement at any time upon six months’ written notice. We recognized no milestone revenue under this agreement for the year ended December 31, 2017 , and $7.0 million and $1.0 million in milestone revenue under this agreement for the years ended December 31, 2016 and 2015 , respectively. The agreement provides for additional payments of up to $160.0 million based upon the attainment of certain development and commercialization milestones and tiered royalties on sales of approved products. We currently have two separate license agreements with MedImmune, LLC (MedImmune), entered into October 2010, pursuant to which we granted MedImmune a worldwide, sublicensable, exclusive license to use GLA to develop and sell vaccines in two different infectious disease indications. Under the license agreements, MedImmune is obligated to use commercially reasonable efforts to develop and obtain regulatory approval for a licensed product in certain markets and to market and sell licensed products in any country where it obtains regulatory approval. In 2010, MedImmune paid us upfront payments under the license agreements. Under each license agreement, MedImmune is obligated to make additional payments based on achievement of certain development, regulatory, and commercial milestones for the licensed indication. MedImmune is also obligated to pay us a low double-digit percentage share of non-royalty payments that it receives from sublicensees and a mid single-digit percentage royalty payment on net sales of licensed products, which royalty is subject to reduction under certain circumstances. Under each license agreement, MedImmune is obligated to make additional aggregate payments of $62.9 million to $72.5 million , depending on the infectious disease indication and the achievement of certain development, regulatory and commercial milestones for the licensed indication. We recognized no revenue for the achievement of development milestones under these license agreements for the years ended December 31, 2017 and 2016 , and $2.5 million in milestone revenue for the year ended December 31, 2015 . Licenses Acquired In July 2008, we licensed certain patent rights, know-how and technology related to our GLAAS platform from the Infectious Disease Research Institute (IDRI), specifically products and formulations containing GLA and another synthetic TLR 4 agonist referred to as SLA. This license was amended and restated in 2010. In November 2015, we entered into a separate agreement with IDRI to license a patent related to our GLAAS technology in the field of cancer. Under this agreement, we paid IDRI an upfront license fee in the amount of $250,000 , which was recognized as research and development expense. Upon the achievement of certain developmental and regulatory milestones, we will be obligated to pay IDRI up to $250,000 and $125,000 , respectively, for the first and each subsequent licensed product we develop. In December 2015, we entered into a Second Amended and Restated License Agreement with IDRI, in which we obtained additional rights under the licensed technology, which rights vary by disease indication, and we returned to IDRI certain previously licensed GLA rights in select, primarily developing-world infectious disease indications. W e received an exclusive license for SLA products in oncology, human allergy and addiction, as well as an option to obtain additional exclusive licenses in select infectious disease indications. In December 2015, in connection with the execution of the second restated agreement, we paid an upfront fee of $2.3 million , whic h was recorded as research and development expense. We are obligated to pay IDRI up to $2.3 million and $1.3 million , respectively, in additional payments for the first and each subsequent exclusive licensed product we develop, and $1.3 million and $625,000 , respectively, for the first and each subsequent non-exclusive licensed product we develop, based on the achievement of certain developmental and regulatory milestones. In addition, we will be obligated to pay certain commercialization milestones and royalty payments of single-digit percentage of net sales, if and when a licensed product is commercialized. We are also obligated to share with IDRI a percentage of payments received from any third-party sublicensees. Additionally, if we exercise our option for additional infectious disease indications, we will be required to make upfront, milestone and royalty payments for such additional indications, which payments are subject to similar terms and conditions as are applicable to other milestone and royalty payments. We recognized no IDRI license-related milestone fees for the year ended December 31, 2017 , and $925,000 and $2.9 million in IDRI license-related milestone fees, which were expensed in research and development expenses, for the years ended December 31, 2016 and 2015 , respectively. In 2009, we licensed certain patent rights directed to the production of dendritic cell-targeted therapeutic and prophylactic immunization strategies from the California Institute of Technology (Caltech) in exchange for shares of our common stock valued at $25,000 . We made annual minimum royalty payments of $25,000 under the license until we recognized $100,000 in license-related milestone fees, which we expensed in research and development expenses for the year ended December 31, 2017. No license-related milestone fees were recognized or paid for the years ended December 31, 2016 and 2015. In addition, we agreed to pay certain fees in the future, including milestone payments upon achievement of certain development and commercialization milestones and royalty payments on net sales in the low single-digit percentage. We are required to pay Caltech up to an aggregate of $1.5 million in additional payments upon the achievement of certain regulatory and sales milestones. In June 2015, we entered into a clinical supply agreement with NanoPass for the use of their intradermal delivery device in certain of our clinical trials. See Note 9 for additional information. In October 2016, we entered into a license agreement with TheraVectys SA (TVS), pursuant to which we received a field limited, non-exclusive, sublicensable license for oncology uses to certain current and future intellectual property rights owned, controlled and licensed by TVS relating to lentiviral vector technologies. We will owe TVS milestone payments based on the achievement of certain development and regulatory milestones for each licensed product, in the aggregate amount of up to $5.8 million , except that the first two milestones payments are waived for CMB305/LV305. In addition, we will be obligated to pay a single commercial milestone payment for each product that achieves a specified net sales amount. We will owe royalties to TVS on product sales that are made directly by us or our affiliates, subject to certain royalty-offset provisions. For the first four products, including LV305/CMB305, royalties will be based on a low-single digit percentage of net sales, and for subsequent products, tiered royalties will be based on low-to-mid-single digit percentages of net sales. TVS will also receive a mid-single digit percentage of revenues that we receive for sublicensing the licensed intellectual property. Collaborations In October 2014, we entered into a collaboration with Sanofi Pasteur for the development of a Herpes Simplex Virus (HSV) immune therapy. Sanofi Pasteur and Immune Design are each contributing product candidates to the collaboration: Sanofi Pasteur is contributing HSV-529, a clinical-stage replication-defective HSV vaccine product candidate, and we contribute G103, our preclinical trivalent vaccine product candidate. The collaboration will explore the potential of various combinations of agents, including leveraging our GLAAS platform, with the goal to select the best potential immune therapy for patients. Each company will develop the products jointly through Phase 2 clinical trials, at which point Sanofi Pasteur intends to continue development of the most promising candidate and be responsible for commercialization. Sanofi Pasteur will bear the costs of all preclinical and clinical development, with Immune Design providing a specific formulation of GLA from the GLAAS platform at its cost through Phase 2 studies. Immune Design will be eligible to receive future milestone and royalty payments on any licensed product developed from the collaboration. We recognize funding from collaborative research and development efforts as revenue as we perform or deliver the related services in accordance with contract terms as long as we will receive payment for such services upon standard payment terms. The costs of the related services performed are recorded as research and development expenses on the consolidated statement of operations. For the years ended December 31, 2017 , 2016 and 2015 , we recognized $6.9 million , $4.6 million and $4.2 million , respectively, in revenue under this collaboration arrangement. As of December 31, 2017 and 2016 , we had an outstanding unbilled receivable of $605,000 and zero , respectively, and unearned revenue of zero and $2.5 million , respectively, under this collaboration arrangement. The unbilled receivable represents collaboration research services earned, but not yet billed to Sanofi Pasteur as of December 31, 2017.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock Our board of directors has the authority to fix and determine and to amend the number of shares of any series of preferred stock that is wholly unissued or to be established and to fix and determine and to amend the designation, preferences, voting powers and limitations, and the relative, participating, optional or other rights, of any series of shares of preferred stock that is wholly unissued or to be established. There was no preferred stock issued and outstanding as of December 31, 2017 and December 31, 2016 . Public Offerings In April 2015, we closed an underwritten public offering of 3,000,000 shares of our common stock at a price of $26.50 per share. In May 2015, we sold an additional 47,409 shares directly to our underwriters when they exercised a portion of their option to purchase additional shares at $26.50 per share. We received net proceeds of $75.4 million (inclusive of the exercise of a portion of the underwriters’ option to purchase additional shares), after underwriting discounts and commissions and offering expenses totaling $5.4 million . In September 2016, we closed an underwritten public offering of 5,226,369 shares of common stock at a price of $6.25 per share. We received net proceeds of $30.3 million (inclusive of the exercise of a portion of the underwriters’ option to purchase additional shares), after underwriting discounts and commissions, and offering expenses totaling $2.4 million . In October 2017, we closed an underwritten public offering of 22,425,000 shares of common stock at a price of $4.10 per share. We received net proceeds of $86.6 million (inclusive of the exercise of a portion of the underwriters’ option to purchase additional shares), after underwriting discounts and commissions, and offering expenses totaling $5.4 million . Common Stock We had 48,068,650 and 25,413,055 shares of common stock outstanding as of December 31, 2017 and 2016 , respectively. Shares of common stock reserved for future issuance were as follows: AS OF DECEMBER 31, 2017 2016 Shares available for issuance under the employee stock purchase plan 475,010 503,620 Options granted and outstanding 4,094,532 3,590,393 Unvested restricted stock units 195,172 107,250 Shares available for future option grants and restricted stock awards 947,199 724,723 Shares reserved for future issuance under equity incentive plans 5,711,913 4,925,986 Equity Incentive Plans 2014 Employee Stock Purchase Plan In April 2014, our board of directors adopted, and in July 2014 our stockholders approved, the 2014 Employee Stock Purchase Plan (2014 ESPP). The total number of shares of common stock available for issuance under the 2014 ESPP may increase annually on January 1 by (i) the lesser of 1% of the total number of shares issued and outstanding as of December 31 of the immediately preceding year or (ii) 200,000 shares, or less as deemed appropriate by the Board of Directors. For 2017, the Board of Directors determined the current shares available to be issued under the 2014 ESPP was sufficient and did not increase the amount of authorized shares. 2008 Equity Incentive Plan and 2014 Omnibus Incentive Plan In 2008, we adopted the 2008 Equity Incentive Plan (2008 Plan) for eligible employees, officers, directors, and consultants, which provided for the grant of incentive and non-statutory stock options, restricted stock awards, restructured stock unit awards grant, and stock appreciation rights. The terms of the stock awards, including vesting requirements, were determined by the board of directors, subject to the provisions of the 2008 Plan. In April 2014, our board of directors adopted, and in July 2014 our stockholders approved, the 2014 Omnibus Incentive Plan (2014 Plan) which provides for the granting of certain awards to eligible employees, officers, directors, and consultants. Upon approval of the 2014 Plan by the stockholders in July 2014, 1,400,000 shares of our common stock were reserved for issuance under the 2014 Plan, and we ceased granting stock awards under the 2008 Plan. All shares of common stock subject to awards under the 2008 Plan that expire, terminate, or are otherwise surrendered, canceled, forfeited or repurchased without having been fully exercised or resulting in the issuance of common stock become available for issuance under the 2014 Plan. Stock options granted under the 2008 and 2014 Plans generally vest within four years, and vested options are exercisable until ten years after the date of grant. Vesting of certain employee options may be accelerated in the event of a change in control of our company. We grant stock options to employees with exercise prices equal to the fair value of our common stock on the date of grant. There were a total of 3,927,135 shares of common stock authorized under the 2014 Plan as of December 31, 2017 . The total number of shares of common stock available for issuance under the 2014 Plan will automatically increase annually on January 1 by 4% of the total number of shares issued and outstanding as of December 31 of the immediately preceding year. On January 1, 2017, in accordance with the 2014 Plan annual increase provisions, the authorized shares increased by 1,016,522 shares. Restricted Stock Units In 2016, we began issuing restricted stock units (RSUs) to employees under the 2014 Plan. The fair value of the RSUs is determined on the date of grant based on the market price of our common stock. RSUs are recognized as an expense ratably over the vesting period and our RSUs generally vest over four years with 25% of the total award vesting on each anniversary of the vesting commencement date. Summary RSU information is as follows: Shares Weighted Average Grant Date Fair Value Outstanding at January 1, 2016 — $ — Granted 118,000 $ 19.39 Vested — $ — Canceled/Forfeited (10,750 ) $ 19.39 Outstanding at December 31, 2016 107,250 $ 19.39 Granted 224,540 $ 5.60 Vested (26,802 ) $ 19.39 Canceled/Forfeited (109,816 ) $ 6.13 Outstanding at December 31, 2017 195,172 $ 10.99 During the year ended December 31, 2017, the total estimated grant date fair value for RSUs granted was $1.3 million . The total fair value of RSUs vested was $150,000 . In 2017, the Company recognized stock-based compensation expenses of $719,000 related to RSUs. As of December 31, 2017, total unrecognized stock-based compensation expenses related to unvested RSUs was $1.5 million , which is expected to be recognized on a straight-line basis over a weighted-average period of approximately 2.35 years. Stock Option Activity Summary stock option information is as follows: OPTIONS OUTSTANDING WEIGHTED- AVERAGE EXERCISE PRICE WEIGHTED- AVERAGE REMAINING CONTRACT TERM (IN YEARS) AGGREGATE INTRINSIC VALUE (IN THOUSANDS) Outstanding at January 1, 2016 2,832,467 $ 11.48 Granted 991,110 $ 15.49 Exercised (20,782 ) $ 3.12 Forfeited (182,605 ) $ 19.01 Expired (29,797 ) $ 25.65 Outstanding at December 31, 2016 3,590,393 $ 12.13 7.33 $ 5,062 Granted 954,301 $ 6.46 Exercised (175,183 ) $ 2.56 Forfeited (117,124 ) $ 14.35 Expired (157,855 ) $ 17.19 Outstanding at December 31, 2017 4,094,532 $ 10.96 7.21 $ 2,771 Vested and expected to vest after December 31, 2017 4,094,532 $ 10.96 7.21 $ 2,771 Exercisable at December 31, 2017 2,464,086 $ 10.98 6.29 $ 2,771 As of December 31, 2017 , there was $10.8 million of total unrecognized stock-based compensation expense related to nonvested stock options that is expected to be recognized over a weighted-average period of 2.1 years. The total intrinsic value of options exercised during the years ended December 31, 2017 , 2016 and 2015 was $868,000 , $124,000 and $5.0 million , respectively. Stock-Based Compensation Expense Total stock-based compensation expense recognized in our statements of operations is as follows (in thousands): YEARS ENDED DECEMBER 31, 2017 2016 2015 Employee: Research and development $ 3,613 $ 3,923 $ 2,034 General and administrative 4,879 5,029 3,810 Non-Employee: Research and development 85 268 205 General and administrative 56 63 248 Total stock-based compensation expense $ 8,633 $ 9,283 $ 6,297 We use the Black-Scholes option pricing model to estimate the fair value of stock options at the grant date. The Black-Scholes option pricing model requires us to make certain estimates and assumptions, including assumptions related to the expected price volatility of our stock, the period during which the options will be outstanding, the rate of return on risk-free investments, and the expected dividend yield of our stock. The fair values of stock options granted to employees were calculated using the following assumptions: YEARS ENDED DECEMBER 31, 2017 2016 2015 Weighted-average estimated fair value $ 4.41 $ 10.07 $ 15.65 Risk-free interest rate (1) 1.9% - 2.2% 1.1% - 2.4% 1.5% - 1.9% Expected term of options (in years) (2) 5.50 - 6.08 5.50 - 9.46 5.50 - 6.08 Expected stock price volatility (3) 80% - 91% 77% - 93% 77% - 91% Expected dividend yield (4) —% —% —% (1) The risk-free interest rate assumption was based on zero-coupon U.S. Treasury instruments that had terms consistent with the expected term of our stock option grants. (2) We used the “simplified method” for options to determine the expected term of our stock option grants. Under this approach, the weighted-average expected life is presumed to be the average of the vesting term and the contractual term of the option. (3) Volatility is a measure of the amount by which a financial variable, such as share price, has fluctuated or is expected to fluctuate during a period. We analyzed the stock price volatility of companies at a similar stage of development to estimate expected volatility of our stock price. (4) We have never declared or paid cash dividends and do not presently plan to pay cash dividends in the foreseeable future.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes No provision for income taxes has been recorded for the years ended December 31, 2017 and 2016 due to the operating losses incurred since inception for which no benefit has been recorded. The reconciliation of the U.S. income tax rate to the effective income tax rate for continuing operations is as follows: AS OF DECEMBER 31, 2017 2016 Statutory tax rate 35.0 % 35.0 % Effect of: Permanent differences (6.4 ) (1.5 ) Other (0.5 ) (0.4 ) General business credits 15.1 2.4 Change in valuation allowance 15.6 (35.5 ) Tax Reform - tax rate change (58.8 ) — Effective tax rate — % — % Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred taxes are as follows (in thousands): AS OF DECEMBER 31, 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 39,971 $ 52,154 Research and development credit 13,392 5,582 Depreciation and amortization 1,241 2,023 Other temporary differences 4,477 6,154 Gross deferred tax assets 59,081 65,913 Deferred tax asset valuation allowance (59,081 ) (65,913 ) Net deferred tax assets $ — $ — Accounting Standards Codification (ASC) 740, Income Taxes, requires companies to recognize the effect of the tax law changes in the period of enactment. However, the SEC staff issued Staff Accounting Bulletin 118 which will allow companies to record provisional amounts during a measurement period that is similar to the measurement period used when accounting for business combinations. On December 22, 2017, the Tax Cuts and Jobs Act of 2017, or the Tax Act, was signed into law. Although the Tax Act is generally effective January 1, 2018, GAAP requires recognition of the tax effects of new legislation during the reporting period that includes the enactment date, which was December 22, 2017. The Company has adjusted its deferred tax assets and liabilities based on the reduction of the U.S. federal corporate tax rate from 35% to 21% and assessed the realizability of our deferred tax assets based on our current understanding of the provisions of the Tax Act. The primary impact of the Tax Act resulted from the re-measurement of deferred tax assets and liabilities due to the change in the corporate tax rate, reducing our deferred tax assets by $30.5 million with a corresponding reduction in our valuation allowance. Overall, this had a net zero effect on our effective tax rate for the year as the Company has a full valuation allowance against its deferred tax assets and is currently in a taxable loss. We consider our accounting for the impacts of the Tax Act to be incomplete and the Company will continue to assess the impact of the Tax Act (and expected further guidance from federal and state tax authorities as well as further guidance for the associated income tax accounting) on our business and consolidated financial statements over the next 12 months. Additional work will be necessary for a more detailed analysis of our deferred tax assets and liabilities as well as potential correlative adjustments. We do not expect any material subsequent adjustments to these amounts. Adjustments, if any, are not expected to have any impact to our results of operations due to our loss position and valuation allowance. Realization of deferred tax assets is dependent on future earnings, if any, the timing and amount of which are uncertain. Accordingly, the deferred tax assets have been offset by a valuation allowance. The valuation allowance relates primarily to net deferred tax assets from operating losses and research and development credits. The net deferred tax asset has been fully offset by a valuation allowance. The valuation allowance (decreased) increased by $(6.8) million and $18.9 million during 2017 and 2016 , respectively. As of December 31, 2017 and 2016 , we had approximately $190.3 million and $152.5 million in federal net operating loss carryforwards and approximately $13.4 million and $5.6 million in federal research and development tax credit carryforwards, respectively. The net operating losses and federal research and development credits will begin to expire in varying amounts between 2028 and 2037 if not utilized. The Tax Reform Act of 1986, or the Tax Reform Act, provides for a limitation on the annual use of net operating loss and research and development tax credit carryforwards following certain ownership changes (as defined by the Act) that could limit our ability to utilize these carryforwards. We may have experienced an ownership change, as defined by the Act, as a result of past financings. Accordingly, our ability to utilize the aforementioned carryforwards may be limited. Additionally, U.S. tax laws limit the time during which these carryforwards may be applied against future taxes; therefore, we may not be able to take full advantage of these carryforwards for federal income tax purposes. As of January 1, 2017, the Company had unrecognized excess tax benefits of $1.2 million related to prior stock option exercises. Upon adoption of ASU 2016-09, the Company recognized this excess tax benefit as a deferred tax asset with a corresponding increase to the deferred tax asset valuation allowance. We file income tax returns in the U.S. federal jurisdiction as well as the state of California. We are not currently under audit in any tax jurisdiction. Tax years from 2008 through 2017 are currently open for audit by federal and state taxing authorities. We recognize interest and penalties accrued on any unrecognized tax benefits as a component of income tax expense. During the years ended December 31, 2017 and 2016 , we did not recognize any accrued interest or penalties associated with unrecognized benefits. Additionally, we did not record any unrecognized tax benefits at December 31, 2017 and 2016 .

Legal Proceedings

Legal Proceedings	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings	Legal Proceedings TheraVectys SA v. Immune Design Corp. On October 17, 2016, we entered into a Settlement Agreement and a License Agreement with TheraVectys SA (TVS) obtaining certain present and future intellectual property rights and resolving the litigation that TVS initiated against us in the Chancery Court of the State of Delaware in July 2014, as well as related claims and counterclaims. In the proceeding, TVS had alleged that it had entered into a contractual relationship with Henogen SA (Henogen) in 2010 with respect to the production of lentiviral vector vaccines for TVS. Henogen is a contract manufacturing organization with which we contracted for the manufacture of our LV305 product candidate. TVS alleged that its contractual relationship with Henogen contained an exclusivity provision limiting Henogen’s ability to participate in the manufacturing process of a vaccine based on lentiviral DNA vectors for third parties, as well as a provision preventing Henogen from sharing or using certain TVS confidential technology for manufacturing processes developed by TVS with or for the benefit of others. TVS alleged that we entered into a contractual relationship with Henogen in 2012 to manufacture lentiviral vectors for vaccines, which TVS contends interfered with its contract with Henogen and resulted in the use of certain TVS confidential information and trade secrets. In addition, the complaint alleged that we obtained shipments of lentiviral vectors for vaccines from Henogen and conducted clinical trials with these lentiviral vectors. The complaint asserted four counts for relief: tortious interference with contractual relationship, unfair competition, misappropriation of trade secrets, and unjust enrichment. Claimed damages were not specified. Under the Settlement Agreement, TVS agreed to dismiss all pending litigation brought by TVS against us and to withdraw patent opposition proceedings (EPO Proceeding) brought by TVS against our European Patent No EP 2 456 786 (EU Patent). Also under the Settlement Agreement, both parties agreed to a broad release of claims against one another based on acts or omissions arising out of the litigation, or the facts and circumstances giving rise to the litigation. Neither party made any admission of liability or wrongdoing under the Settlement Agreement. As a non-contingent fee for a license to certain present and future intellectual property of TVS, and in consideration for the settlement of all claims and disputes between the parties, we paid $6.0 million into an escrow account (Escrowed Payment), and we also agreed to pay $1.25 million to TVS when we next raised $25.0 million , in the aggregate, through equity sales, debt or licensing revenue. The Escrowed Payment was to be disbursed to TVS as follows: (a) fifty percent ( 50% ) when (i) Institut Pasteur consented to the granting by TVS to us of a sublicense to certain patents licensed by TVS (or to be licensed by TVS) from Institut Pasteur and (ii) the litigation in the United States and Belgium had been dismissed; and (b) fifty percent ( 50% ) upon the final resolution of the EPO Proceeding if the scope of the EU Patent remained unchanged (Escrow Conditions); provided, that delays in satisfying the Escrow Conditions would potentially result in a reduction of the amount of the Escrowed Payment that would be disbursed to TVS. In November 2017, we paid $1.25 million to TVS upon completion of an underwritten public offering in which we raised estimated net proceeds of approximately $86.6 million , after deducting underwriting discounts, commissions and offering expenses. In February 2018, the parties came to an agreement on the timing and satisfaction of the Escrow Conditions, and the escrow agent disbursed $5.25 million of the Escrowed Payment to TVS and $750,000 of the Escrowed Payment to Immune Design. No additional payments are expected to be made under the terms of the Settlement Agreement (see Note 15). In addition, the License Agreement provides us with a field limited, non-exclusive, sublicensable license for oncology uses to certain current and future intellectual property rights owned, controlled and licensed by TVS. For licensed products developed under the License Agreement, we would be obligated to pay certain development and commercial milestones and royalties. We determined that the aggregate payment amount expected to be paid to TVS is $7.3 million and as such, the aggregate payment amount should be allocated between (1) dismissal of the litigation; and (2) license to current and future TVS intellectual property (IP). As we are not able to reliably estimate the fair value of the litigation dismissal, we assigned a fair value to the aggregate amount of the license to current and future TVS IP through the use of a benchmarking approach and determined the fair value of the license to current and future IP obtained from TVS by benchmarking this deal against similar recent (within the last 5 years) deals within our industry. The metrics we used in our benchmarking approach included similarities in industry, product type, therapeutic area, stage of product development and exclusivity. Based upon the results of our benchmark approach, we determined that the fair value assigned to the license to current and future TVS IP to be $1.4 million with the remaining residual amount of $5.9 million allocated to the dismissal of the litigation. For the year ended December 31, 2016, the $5.9 million allocated to the dismissal of litigation is recorded as a general and administrative expense and the $1.4 million allocated to the license acquired for current and future TVS IP granted to us is recorded as a research and development expense on the consolidated statements of operations. European Patent Opposition In February 2013, a third party filed an opposition at the European Patent Office (EPO) requesting revocation of European Patent No. 2068918 directed to GLA formulations and uses. This patent is owned by Infectious Disease Research Institute (IDRI), and we hold an exclusive license to this patent in certain fields. The oral proceedings for this opposition were held in September 2016. At the oral proceedings, the EPO maintained the patent in an amended form, which continues to cover the GLAAS products being developed by us and our licensees. We and the opponent have appealed this decision. However, the outcome of an appeal to this proceeding will not be known for several years.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plan	Employee Benefit Plan We sponsor a 401(k) defined contribution plan for our employees. Employee contributions are voluntary. We may match employee contributions in amounts to be determined at our sole discretion. Currently, we have elected to satisfy the safe-harbor rules by matching contributions equal to 100% of employee salary deferrals that do not exceed 3% of the employee’s compensation, plus 50% matching employee salary deferrals between 3% and 5% of the employee’s compensation. Employer contributions have totaled approximately $300,000 , $243,000 , and $214,000 for the years ended December 31, 2017 , 2016 and 2015 respectively.

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event In February 2018, in accordance with the terms of the Settlement Agreement entered into on October 17, 2016, between the Company and TVS (see Note 13), the parties came to an agreement on the timing and satisfaction of the Escrow Conditions, and the escrow agent disbursed $5.25 million of the Escrowed Payment to TVS and $750,000 of the Escrowed Payment to the Company. The $750,000 recoupment of the Escrowed Payment by the Company is considered a nonrecognized subsequent event and will be recognized in the quarter ended March 31, 2018 as a reduction to general and administrative expenses.

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information (Unaudited)	Selected Quarterly Financial Information (Unaudited) The following amounts are in thousands, except per share amounts: Quarter Ended March 31, June 30, September 30, December 31, (unaudited) Total revenues $ 5,465 $ 729 $ 516 $ 485 Net loss $ (12,620 ) $ (13,846 ) $ (13,416 ) $ (11,980 ) Basic and diluted net loss per share $ (0.50 ) $ (0.54 ) $ (0.52 ) $ (0.29 ) Quarter Ended March 31, June 30, September 30, December 31, (unaudited) Total revenues $ 1,863 $ 1,133 $ 8,206 $ 2,058 Net loss $ (12,294 ) $ (14,347 ) $ (12,443 ) $ (14,446 ) Basic and diluted net loss per share $ (0.61 ) $ (0.71 ) $ (0.60 ) $ (0.57 )

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). To conform with GAAP, the preparation of our financial statements requires management to make judgments, assumptions, and estimates that affect the amounts reported in our financial statements and accompanying notes. Estimates are used for, but not limited to, accruals for clinical trial activity, other accrued liabilities, and assumptions used in determining stock-based compensation expense. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable. Actual results could differ materially from those estimates.
Principles of Consolidation	Our consolidated financial statements include the financial position and results of operations of Immune Design Corp. and Immune Design Ltd., our wholly owned subsidiary. Immune Design Ltd. was incorporated in the United Kingdom in February 2016 and to date there have been no financial transactions or balances related to this entity.
Segments	We operate in one segment and use cash flow as the primary measure to manage our business and do not segment the business for internal reporting or decision-making purposes.
Offering Costs	Offering costs represent legal, accounting and other direct costs related to our efforts to raise capital through our follow-on public offerings in October 2017, September 2016 and April 2015 and for our initial public offering (IPO) in July 2014. These costs were deferred until completion of the follow-on public offerings and IPO, respectively, at which time they were reclassified to additional paid-in capital as a reduction of the proceeds.
Cash and Cash Equivalents	Cash equivalents are highly liquid investments with a maturity of 90 days or less at the date of purchase and primarily consist of investments in money market funds. In addition, we maintain cash balances with financial institutions in excess of insured limits and do not anticipate any losses on such cash balances.
Concentration of Risk	We limit our credit risk associated with cash and cash equivalents by placing our deposits with banks we believe are highly creditworthy and our investments with highly rated money market funds.
Short-term investments	Our short-term investments include funds invested in U.S. Treasury securities with a final maturity of each security of less than one year. All investments are classified as available-for-sale securities and are recorded at fair value based on quoted prices in active markets, with unrealized gains and losses excluded from earnings and reported in other comprehensive income (loss). Purchase premiums and discounts are recognized in interest income using the interest method over the terms of the securities. Realized gains and losses and declines in fair value that are deemed to be other than temporary are reflected in the consolidated statements of operations and comprehensive income (loss) using the specific-identification method.
Accounts Receivable	Accounts receivable are amounts due from other companies related primarily to licensing fees, product sales and research and development services.
Inventory	Inventory is recorded at the lower of cost or market. Cost includes amounts related to materials and labor, and is determined on a specific identification basis in a manner which approximates the first-in, first-out method. We record adjustments to inventory for potentially excess, obsolete, expired, or impaired items.
Property and Equipment	Property and equipment are stated at cost, net of accumulated depreciation. Depreciation is computed using the straight-line method over an estimated useful life that is generally three years , while leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to operations. Maintenance and repairs are expensed as incurred. Asset improvements are capitalized.
Impairment of Long-Lived Assets	Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Conditions that would necessitate an impairment assessment include a significant decline in the observable market value of an asset, a significant change in the extent or manner in which an asset is used, or any other significant adverse change that would indicate that the carrying amount of an asset is not recoverable.
Accrued Liabilities	Accrued liabilities represent accrued compensation including vacation accruals, unearned revenue and accrued expenses. As part of the process of preparing our consolidated financial statements, we are required to estimate our accrued professional services and research and development expenses. This process involves reviewing contracts and vendor agreements, communicating with our applicable personnel to identify services that have been performed on our behalf. We estimate the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual cost. We make estimates of our accrued expenses as of each balance sheet date in our consolidated financial statements based on facts and circumstances known to us. We base our expenses related to contract manufacturing and clinical trials on our estimates of the services received and efforts expended pursuant to contracts with multiple contract manufacturing organizations and clinical research organizations that conduct and manage supply and clinical trials on our behalf. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period. To date, we have not experienced any significant adjustments to our estimates.
Leases and Deferred Rent	We have entered into lease agreements for laboratory and office facilities. These leases are classified as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease. Incentives granted under our facilities leases, including allowances to fund leasehold improvements and rent escalations are accrued as deferred rent. Leasehold improvements funded by the lessor are capitalized and are recognized as reductions to rental expense on a straight-line basis over the term of the lease.
Revenue Recognition	We derive our revenue from collaboration and licensing agreements and the sale of products associated with material transfer, collaboration and supply agreements. Licensing fees, are recognized when the amounts are earned and determinable during the applicable period. We recognize up-front nonrefundable license fees when due under contractual agreements and when we do not have a continuing obligation to provide services related to the agreement. Revenue associated with nonrefundable up-front license fees under arrangements where the license fees and research and development activities cannot be accounted for as separate units of accounting is deferred and recognized as revenue on a straight-line basis over the expected term of our continued involvement in the research and development process. Revenues from the achievement of research and development milestones, if deemed substantive, are recognized as revenue when the milestones are achieved, and the milestone payments are due and collectible. If not deemed substantive, we recognize such milestones as revenue on a straight-line basis over the remaining expected term of continued involvement in the research and development process. Milestones are considered substantive if all of the following conditions are met: (1) the milestone is nonrefundable, (2) achievement of the milestone was not reasonably assured at the inception of the arrangement, (3) substantive effort is involved to achieve the milestone and (4) 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 and any ongoing research and development or other services are priced at fair value. Payments received in advance of work performed are recorded as unearned revenue. Certain agreements from which we derive our revenue include multiple deliverables. We recognize the revenue for each deliverable at fair value determined to be the estimated selling price in cases when neither vendor specific objective evidence nor third-party evidence is available. Revenues derived from funding of development costs are recognized when the related costs are incurred and when collectability is reasonably assured. Revenue is recognized when all of the following criteria are met: (1) persuasive evidence of an arrangement exists, (2) delivery has occurred or services have been rendered, (3) the price to the customer is fixed or determinable and (4) collectability is reasonably assured. The evaluation of these revenue recognition criteria requires significant management judgment. For instance, we use judgment to assess collectability based on factors such as the customer’s creditworthiness and past collection history, if applicable. If we determine that collection of a payment is not reasonably assured, revenue recognition is deferred until receipt of payment. We also use judgment to assess whether a price is fixed or determinable including, but not limited to, reviewing contractual terms and conditions related to payment terms. Revenue from product sales of glucopyranosyl lipid A (GLA), a product from our GLAAS platforms, is recognized when the risk of loss has passed to the customer or deferred until such time that risk of loss has passed. All revenues associated from the sale of GLA products supplied by us are reported under product sales with the applicable costs reported under cost of product sales. Product sales consist of the direct costs associated with the manufacture and formulation of GLA, including costs to purchase raw materials, third-party contract manufacturing costs, assay testing and ongoing product stability testing. We consider significant revenue concentrations to be customers who account for 10% or more of total revenues generated by us during the periods presented.
Stock-Based Compensation	We account for stock-based compensation under the fair value method. Stock-based compensation costs related to employees and directors is measured at the grant date, based on the fair-value-based measurement of the award estimated using the Black-Scholes option-pricing model, and is recognized as expense over the requisite service period on a straight-line basis. Options granted to non-employee service providers are accounted for at estimated fair value using the Black-Scholes option-pricing model and are remeasured over the vesting term as earned. Prior to the Financial Accounting Standards Board (FASB) adoption of Accounting Standards Update (ASU) No. 2016-09 on January 1, 2017, stock-based compensation expense recognized was calculated based on awards ultimately expected to vest and was reduced for estimated forfeitures. Upon the FASB adoption of ASU No. 2016-09, effective January 1, 2017, we have elected to account for forfeitures as they occur. As of January 1, 2017, we had unrecorded forfeitures of $157,000 . Upon adoption, we recognized this expense as an adjustment to retained earnings with a corresponding increase to additional paid-in-capital. In addition, under this guidance, on a prospective basis, companies will no longer record excess tax benefits and certain tax deficiencies in additional paid-in-capital. Instead, they will record all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement and eliminates the requirement that excess tax benefits be realized before companies can recognize them. As of January 1, 2017, we had an unrecognized excess tax benefit of $1.2 million and upon adoption, we recognized this excess tax benefit as a deferred tax asset with a corresponding increase to our deferred tax asset valuation allowance.
Research and Development	Research and development costs are expensed as incurred. Research and development costs primarily include personnel costs, materials and manufacturing to support clinical trials, fees paid to consultants and outside service providers, costs to conduct clinical trials and allocated overhead. Amounts incurred in connection with collaboration agreements are also included in research and development expense. Payments made prior to the receipt of goods or services to be used in research and development are deferred until the goods or services are received.
Income Taxes	Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and the operating loss and tax credit carry forwards. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Deferred tax assets and liabilities are measured at the balance sheet date using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period such tax rate changes are enacted. Our net deferred tax asset has been fully offset by a valuation allowance because of our history of losses. Any potential accrued interest and penalties related to unrecognized tax benefits within operations would be recorded as income tax expense. To date, there have been no interest or penalties charged to us related to the underpayment of income taxes.
Comprehensive Loss	Comprehensive loss is composed of net loss and other comprehensive income or loss that are excluded from net loss.
Subsequent Events	We consider events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.
Recent Accounting Pronouncements	In May 2014, the FASB issued ASU No. 2014-09 amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, the FASB deferred the effective date of the revenue recognition guidance to reporting periods beginning after December 15, 2017. The new standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We currently anticipate adopting the new standard effective January 1, 2018, using the modified retrospective method. We will continue to monitor additional modifications, clarifications or interpretations undertaken by the FASB that may impact our current conclusions. We primarily derive our revenue from license and collaboration agreements. The consideration we are eligible to receive under these agreements includes upfront payments, research and development funding, milestone payments and royalties. Each license and collaboration agreement is unique and will be assessed separately under the five-step process under the new standard. The new revenue recognition standard differs from the current accounting standard in many respects, such as in the accounting for variable considerations and the measurement of progress toward completion of performance obligations. We performed a review of all of our ongoing license and collaboration agreements and based upon our assessment and given the nature of our arrangements and the related performance obligations, we determined there will be no impact on our financial position and results of operations as a result of the adoption of the standard on January 1, 2018, the date of adoption. In February 2016, FASB issued ASU 2016-02 related to lease accounting. This standard will require organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases that are greater than 12 months in duration. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from previous GAAP. There continues to be a differentiation between finance leases and operating leases, however, the principal difference from previous guidance is that the lease assets and lease liabilities arising from operating leases will be recognized on the balance sheets. For capital or finance leases, lessees will recognize amortization of the right-of-use asset separately from interest on the lease liability. For operating leases, lessees will recognize a single total lease expense. The standard is effective for public companies for the fiscal years and interim reporting periods beginning after December 15, 2018. We plan to adopt this new standard prospectively on January 1, 2019. We are evaluating the impact of the adoption of this standard on our consolidated financial statements. We expect that it will increase our lease assets and correspondingly increase our lease liabilities. In August 2016, the FASB issued ASU No. 2016-15 which provides new guidance on the classification of certain cash receipts and payments in the statement of cash flows. The new guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. We will be required to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. We are currently assessing the impact that the new guidance will have on its consolidated statements of cash flows. In November 2016, the FASB issued ASU No. 2016-18 that relates to restricted cash. The new guidance requires amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. We will be required to revise our consolidated statements of cash flows to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. Adoption of the new guidance will not have a significant impact on our financial position and results of operations. In May 2017, the FASB issued ASU No. 2017-09 to provide clarity and reduce both diversity in practice and cost and complexity when applying the guidance in Topic 718 about a change to the terms and conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The amendments in this update are effective for annual periods, including interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted, and applied prospectively to modifications that occur on or after the adoption date. We are currently reviewing and evaluating this recent update and plan to adopt on the required adoption date. For the year ended December 31, 2017, there were no modifications to the terms or conditions of a share-based payment award. In September 2017, the FASB issued ASU No. 2017-13 to amend revenue recognition (Topic 605), revenue from contracts with customers (Topic 606), leases (Topic 840), and leases (Topic 842) adding Securities and Exchange Commission (SEC) paragraphs pursuant to an SEC Staff Announcement made at the July 20, 2017 Emerging Issues Task Force (EITF) meeting. We are currently reviewing and evaluating this recent update and plan to adopt as required. For the year ended December 31, 2017, there were no modifications or changes incorporated with respect to this recently issued update.
Net Loss Per Share	Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Because of net losses recognized in each period, potential common shares issuable upon the exercise of outstanding stock options and warrants and the conversion of preferred shares in the IPO into common shares have not been reflected in the calculation of diluted net loss per share due to the anti-dilutive effect. Diluted net loss per share, therefore, does not differ from basic net loss per share.
Fair Value Measurement	We measure and record cash and cash equivalents and convertible preferred stock warrant liabilities at fair value in the accompanying financial statements. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value, is as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 : Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 1 securities consist of highly liquid money market funds. The fair value of Level 1 assets has been determined using quoted prices in active markets for identical assets. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy.

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The common stock equivalents issuable upon the conversion or exercise of the following dilutive securities have been excluded from the computation of diluted net loss per share attributable to common stockholders calculation because their effect would have been anti-dilutive for the periods presented: DECEMBER 31, 2017 2016 2015 Outstanding stock option grants 4,094,532 3,590,393 2,832,467 Unvested restricted stock awards 195,172 107,250 — Total 4,289,704 3,697,643 2,832,467

Cash Equivalents and Short-Te26

Cash Equivalents and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Cash, Cash Equivalents and Investments	The amortized cost and fair value of our cash equivalents and short-term investments are as follows (in thousands): December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Money market funds $ 70,502 $ — $ — $ 70,502 U.S. Treasury securities 68,702 — (49 ) 68,653 Total $ 139,204 $ — $ (49 ) $ 139,155 Classified as: Cash equivalents $ 70,502 Short-term investments 68,653 Total $ 139,155 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Money market funds $ 36,412 $ 2 $ — $ 36,414 U.S. Treasury securities 62,066 2 (28 ) 62,040 Total $ 98,478 $ 4 $ (28 ) $ 98,454 Classified as: Cash equivalents $ 36,414 Short-term investments 62,040 Total $ 98,454

Fair Value of Financial Instr27

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables summarize our financial assets and liabilities measured at fair value on a recurring basis (in thousands): December 31, 2017 LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Money market funds $ 70,502 $ — $ — $ 70,502 U.S. Treasury securities 68,653 — — 68,653 Total $ 139,155 $ — $ — $ 139,155 December 31, 2016 LEVEL 1 LEVEL 2 LEVEL 3 TOTAL Assets: Money market funds $ 36,414 $ — $ — $ 36,414 U.S. Treasury securities 62,040 — — $ 62,040 Total $ 98,454 $ — $ — $ 98,454

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventory	Inventory consists of the following (in thousands): DECEMBER 31, 2017 2016 Work in process $ 541 $ 567 Finished goods 143 40 Total inventory $ 684 $ 607

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and equipment consists of the following (in thousands): DECEMBER 31, 2017 2016 Laboratory equipment $ 2,624 $ 2,330 Leasehold improvements 183 156 Computer equipment and software 584 483 Office equipment, furniture, and fixtures 178 174 Total 3,569 3,143 Less: accumulated depreciation and amortization (3,078 ) (2,729 ) Total property and equipment, net $ 491 $ 414

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): DECEMBER 31, 2017 2016 Research and development services $ 3,352 $ 3,027 Legal and professional services 48 28 Employee compensation 2,777 1,880 Other 9 — Total accrued liabilities $ 6,186 $ 4,935

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Future minimum lease payments	As of December 31, 2017 , future minimum lease payments are as follows (in thousands): 2018 $ 1,486 2019 1,525 2020 1,203 2021 1,200 2022 — Total future minimum lease payments $ 5,414

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Shares of Common Stock Reserved for Future Issuance	Shares of common stock reserved for future issuance were as follows: AS OF DECEMBER 31, 2017 2016 Shares available for issuance under the employee stock purchase plan 475,010 503,620 Options granted and outstanding 4,094,532 3,590,393 Unvested restricted stock units 195,172 107,250 Shares available for future option grants and restricted stock awards 947,199 724,723 Shares reserved for future issuance under equity incentive plans 5,711,913 4,925,986
Schedule of Restricted Stock Units	Summary RSU information is as follows: Shares Weighted Average Grant Date Fair Value Outstanding at January 1, 2016 — $ — Granted 118,000 $ 19.39 Vested — $ — Canceled/Forfeited (10,750 ) $ 19.39 Outstanding at December 31, 2016 107,250 $ 19.39 Granted 224,540 $ 5.60 Vested (26,802 ) $ 19.39 Canceled/Forfeited (109,816 ) $ 6.13 Outstanding at December 31, 2017 195,172 $ 10.99
Summary of Stock Options	Summary stock option information is as follows: OPTIONS OUTSTANDING WEIGHTED- AVERAGE EXERCISE PRICE WEIGHTED- AVERAGE REMAINING CONTRACT TERM (IN YEARS) AGGREGATE INTRINSIC VALUE (IN THOUSANDS) Outstanding at January 1, 2016 2,832,467 $ 11.48 Granted 991,110 $ 15.49 Exercised (20,782 ) $ 3.12 Forfeited (182,605 ) $ 19.01 Expired (29,797 ) $ 25.65 Outstanding at December 31, 2016 3,590,393 $ 12.13 7.33 $ 5,062 Granted 954,301 $ 6.46 Exercised (175,183 ) $ 2.56 Forfeited (117,124 ) $ 14.35 Expired (157,855 ) $ 17.19 Outstanding at December 31, 2017 4,094,532 $ 10.96 7.21 $ 2,771 Vested and expected to vest after December 31, 2017 4,094,532 $ 10.96 7.21 $ 2,771 Exercisable at December 31, 2017 2,464,086 $ 10.98 6.29 $ 2,771
Schedule of Stock-Based Compensation Expense Recognized	Total stock-based compensation expense recognized in our statements of operations is as follows (in thousands): YEARS ENDED DECEMBER 31, 2017 2016 2015 Employee: Research and development $ 3,613 $ 3,923 $ 2,034 General and administrative 4,879 5,029 3,810 Non-Employee: Research and development 85 268 205 General and administrative 56 63 248 Total stock-based compensation expense $ 8,633 $ 9,283 $ 6,297
Schedule of Fair Value of Stock Options Granted to Employees	The fair values of stock options granted to employees were calculated using the following assumptions: YEARS ENDED DECEMBER 31, 2017 2016 2015 Weighted-average estimated fair value $ 4.41 $ 10.07 $ 15.65 Risk-free interest rate (1) 1.9% - 2.2% 1.1% - 2.4% 1.5% - 1.9% Expected term of options (in years) (2) 5.50 - 6.08 5.50 - 9.46 5.50 - 6.08 Expected stock price volatility (3) 80% - 91% 77% - 93% 77% - 91% Expected dividend yield (4) —% —% —% (1) The risk-free interest rate assumption was based on zero-coupon U.S. Treasury instruments that had terms consistent with the expected term of our stock option grants. (2) We used the “simplified method” for options to determine the expected term of our stock option grants. Under this approach, the weighted-average expected life is presumed to be the average of the vesting term and the contractual term of the option. (3) Volatility is a measure of the amount by which a financial variable, such as share price, has fluctuated or is expected to fluctuate during a period. We analyzed the stock price volatility of companies at a similar stage of development to estimate expected volatility of our stock price. (4) We have never declared or paid cash dividends and do not presently plan to pay cash dividends in the foreseeable future.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The reconciliation of the U.S. income tax rate to the effective income tax rate for continuing operations is as follows: AS OF DECEMBER 31, 2017 2016 Statutory tax rate 35.0 % 35.0 % Effect of: Permanent differences (6.4 ) (1.5 ) Other (0.5 ) (0.4 ) General business credits 15.1 2.4 Change in valuation allowance 15.6 (35.5 ) Tax Reform - tax rate change (58.8 ) — Effective tax rate — % — %
Schedule of Deferred Tax Assets and Liabilities	Significant components of our deferred taxes are as follows (in thousands): AS OF DECEMBER 31, 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 39,971 $ 52,154 Research and development credit 13,392 5,582 Depreciation and amortization 1,241 2,023 Other temporary differences 4,477 6,154 Gross deferred tax assets 59,081 65,913 Deferred tax asset valuation allowance (59,081 ) (65,913 ) Net deferred tax assets $ — $ —

Selected Quarterly Financial 34

Selected Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following amounts are in thousands, except per share amounts: Quarter Ended March 31, June 30, September 30, December 31, (unaudited) Total revenues $ 5,465 $ 729 $ 516 $ 485 Net loss $ (12,620 ) $ (13,846 ) $ (13,416 ) $ (11,980 ) Basic and diluted net loss per share $ (0.50 ) $ (0.54 ) $ (0.52 ) $ (0.29 ) Quarter Ended March 31, June 30, September 30, December 31, (unaudited) Total revenues $ 1,863 $ 1,133 $ 8,206 $ 2,058 Net loss $ (12,294 ) $ (14,347 ) $ (12,443 ) $ (14,446 ) Basic and diluted net loss per share $ (0.61 ) $ (0.71 ) $ (0.60 ) $ (0.57 )

Description of the Business - N

Description of the Business - Narrative (Details)	12 Months Ended
	Dec. 31, 2017platform
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of discovery platforms	2

Summary of Significant Accoun36

Summary of Significant Accounting Policies - Segments (Details)	12 Months Ended
	Dec. 31, 2017segment
Accounting Policies [Abstract]
Number of operating segments	1

Summary of Significant Accoun37

Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Allowance for doubtful accounts receivable	$ 0	$ 0

Summary of Significant Accoun38

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Estimated useful lives	3 years

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Cumulative effect adjustment from adoption of accounting standard on stock-based compensation		$ 0
Unrecognized excess tax benefits	$ 1,200	1,200
ADDITIONAL PAID-IN CAPITAL
Concentration Risk [Line Items]
Cumulative effect adjustment from adoption of accounting standard on stock-based compensation		157
ADDITIONAL PAID-IN CAPITAL | Accounting Standards Update 2016-09
Concentration Risk [Line Items]
Cumulative effect adjustment from adoption of accounting standard on stock-based compensation		157
ACCUMULATED DEFICIT
Concentration Risk [Line Items]
Cumulative effect adjustment from adoption of accounting standard on stock-based compensation		(157)
ACCUMULATED DEFICIT | Accounting Standards Update 2016-09
Concentration Risk [Line Items]
Cumulative effect adjustment from adoption of accounting standard on stock-based compensation		$ (157)
Customer Concentration Risk | Sales Revenue, Net
Concentration Risk [Line Items]
Concentration risk, percentage	96.00%
Customer Concentration Risk | Sales Revenue, Net | Collaboration Partner One
Concentration Risk [Line Items]
Concentration risk, percentage		64.00%	44.00%
Customer Concentration Risk | Sales Revenue, Net | Collaboration Partner Two
Concentration Risk [Line Items]
Concentration risk, percentage		35.00%	36.00%
Customer Concentration Risk | Sales Revenue, Net | Collaboration Partner Three
Concentration Risk [Line Items]
Concentration risk, percentage			20.00%

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,289,704	3,697,643	2,832,467
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,094,532	3,590,393	2,832,467
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	195,172	107,250	0

Cash Equivalents and Short-Te41

Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Money market funds at amortized cost	$ 72,454	$ 45,214	$ 112,921	$ 75,354
Total amortized cost	139,204	98,478
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(49)	(28)
Money market funds, fair value	70,502	36,414
U.S. Treasury securities, fair value	68,653	62,040
Total fair value	139,155	98,454
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Money market funds at amortized cost	70,502	36,412
Money market funds, Gross Unrealized Gains	0	2
Money market funds, fair value	70,502	36,414
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
U.S. Treasury securities, amortized cost	68,702	62,066
U.S. Treasury securities, Gross Unrealized Gains	0	2
Gross Unrealized Losses	(49)	(28)
U.S. Treasury securities, fair value	$ 68,653	$ 62,040

Fair Value of Financial Instr42

Fair Value of Financial Instruments - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 68,653	$ 62,040
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	70,502	36,414
Fair Value	68,653	62,040
Total	139,155	98,454
Recurring | LEVEL 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	70,502	36,414
Fair Value	68,653	62,040
Total	139,155	98,454
Recurring | LEVEL 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Fair Value	0	0
Total	0	0
Recurring | LEVEL 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Fair Value	0	0
Total	$ 0	$ 0

Inventory (Details)

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Work in process	$ 541	$ 567
Finished goods	143	40
Total inventory	$ 684	$ 607

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,569	$ 3,143
Less: accumulated depreciation and amortization	(3,078)	(2,729)
Total property and equipment, net	491	414
Depreciation and amortization	351	304	$ 243
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,624	2,330
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	183	156
Less: accumulated depreciation and amortization	(147)	(123)
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	584	483
Office equipment, furniture, and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 178	$ 174

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Research and development services	$ 3,352	$ 3,027
Legal and professional services	48	28
Employee compensation	2,777	1,880
Other	9	0
Total accrued liabilities	$ 6,186	$ 4,935

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	Jan. 01, 2017USD ($)	May 31, 2017USD ($)ft²	Jan. 31, 2017USD ($)	Oct. 31, 2016USD ($)	Jan. 31, 2016ft²	Dec. 31, 2015USD ($)	Jul. 31, 2015USD ($)	Jan. 31, 2015USD ($)ft²	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Other Commitments [Line Items]
Square footage leased | ft²					20,133			9,640
Term of lease	5 years
Optional lease extension period	3 years							5 years
Annual base rent	$ 1,100,000
Annual increase in base rent, percent	2.50%
Leasehold improvements									$ 183,000	$ 156,000
Accumulated depreciation									3,078,000	2,729,000
Payments for Deposits			$ 200,000
Funds drawn on letter of credit									0
Rent expense									1,500,000	713,000	$ 849,000
Sublease agreement, rentable square feet | ft²		5,048
Sublease agreement term		3 years
Sublease agreement, annual base rent		$ 273,000
Sublease agreement, annual base rent, percent		2.50%
Collaborative Arrangement | ZVex Product | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									7,700,000
Collaborative Arrangement | NanoPass Technologies LTD | Intradermal Delivery Device
Other Commitments [Line Items]
Collaborative arrangement, license fee						$ 500,000	$ 600,000
Collaborative arrangement, non-refundable deposit				$ 150,000
Collaborative Arrangement | NanoPass Technologies LTD | Intradermal Delivery Device | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to				$ 8,800,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA First Exclusive Product | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									2,300,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA Subsequent Exclusive Products | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									1,300,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA First Non-Exclusive Product | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									1,300,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA Subsequent Non-Exclusive Products | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									625,000
Financial Standby Letter of Credit
Other Commitments [Line Items]
Letter of credit provided as security deposit								$ 121,000
Leasehold improvements
Other Commitments [Line Items]
Accumulated depreciation									$ 147,000	$ 123,000

Commitments and Contingencies47

Commitments and Contingencies - Future Minimum Lease Payments (Details)	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 1,486,000
2,019	1,525,000
2,020	1,203,000
2,021	1,200,000
2,022	0
Total future minimum lease payments	$ 5,414,000

License and Collaboration Agr48

License and Collaboration Agreements - Narrative (Details)	1 Months Ended			12 Months Ended
	Oct. 31, 2016USD ($)payment	Dec. 31, 2015USD ($)	Nov. 30, 2015USD ($)	Dec. 31, 2017USD ($)license_agreement	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2009USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development				$ 43,670,000	$ 45,134,000	$ 33,087,000
TheraVectys SA | Collaborative Arrangement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments	$ 5,800,000
Number of milestone payments waived | payment	2
GLAAS Discovery Platform | Sanofi | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized				0	7,000,000	1,000,000
Milestone receivables				160,000,000
GLAAS Discovery Platform | Infectious Disease Research Institute | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development			$ 250,000
GLA | MedImmune LLC | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized				0	0	2,500,000
GLA | MedImmune LLC | Collaborative Arrangement, Product | Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone receivables				62,900,000
GLA | MedImmune LLC | Collaborative Arrangement, Product | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone receivables				72,500,000
GLA | Infectious Disease Research Institute | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized				0	925,000	2,900,000
First GLAAS Discovery Platform Product | Infectious Disease Research Institute | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				250,000
Subsequent GLAAS Discovery Platform Products | Infectious Disease Research Institute | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				125,000
GLA/SLA Product | Infectious Disease Research Institute | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development		$ 2,300,000
GLA/SLA First Exclusive Product | Infectious Disease Research Institute | Collaborative Arrangement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				2,300,000
GLA/SLA Subsequent Exclusive Products | Infectious Disease Research Institute | Collaborative Arrangement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				1,300,000
GLA/SLA First Non-Exclusive Product | Infectious Disease Research Institute | Collaborative Arrangement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				1,300,000
GLA/SLA Subsequent Non-Exclusive Products | Infectious Disease Research Institute | Collaborative Arrangement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				625,000
Dendritic Cell-targeted Theraputic and Prophylactic Immunization Strategies | California Institute of Technology | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized				$ 100,000	0	0
Number of license agreements | license_agreement				2
Annual license fee							$ 25,000
Dendritic Cell-targeted Theraputic and Prophylactic Immunization Strategies | California Institute of Technology | Collaborative Arrangement | Common stock
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Value of common stock issued for license							$ 25,000
Dendritic Cell-targeted Theraputic and Prophylactic Immunization Strategies | California Institute of Technology | Collaborative Arrangement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				$ 1,500,000
Herpes Simplex Virus | Sanofi Pasteur | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Unbilled receivable				605,000	0
Unearned receivable				0	2,500,000
Herpes Simplex Virus | Sanofi Pasteur | Collaborative Arrangement, Product | Collaboration Revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized				$ 6,900,000	$ 4,600,000	$ 4,200,000

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 01, 2017	Nov. 30, 2017	Oct. 31, 2017	Sep. 30, 2016	May 31, 2015	Apr. 30, 2015	Jul. 31, 2014	May 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued (in shares)									0	0
Shares outstanding (in shares)									0	0
Proceeds from issuance of common stock		$ 86,600	$ 86,600	$ 30,300				$ 75,400	$ 86,624	$ 30,310	$ 75,359
Stock issuance costs			$ (5,400)	$ (2,400)				$ (5,400)
Shares outstanding (in shares)									48,068,650	25,413,055
Common stock reserved for future issuance (in shares)									5,711,913	4,925,986
Employee share-based compensation expense									$ 8,633	$ 9,283	6,297
Intrinsic value of stock options exercised									$ 868	$ 124	$ 5,000
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)									4,094,532	3,590,393
Unrecognized stock based compensation expense									$ 10,800
Weighted average recognition period for stock-based compensation expense									2 years 25 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares)									195,172	107,250
Vesting term										4 years
Award vesting percent										25.00%
Total estimated grant date fair value of RSUs granted									$ 1,300
Total fair value of RSUs vested									150
Employee share-based compensation expense									719
Unrecognized stock based compensation expense									$ 1,500
Weighted average recognition period for stock-based compensation expense									2 years 4 months 6 days
2014 Employee Stock Purchase Plan | Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in common stock available for issuance (as a percent)							1.00%
Increase in authorized shares							200,000
Common stock reserved for future issuance (in shares)									475,010	503,620
2014 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in common stock available for issuance (as a percent)							4.00%
Increase in authorized shares	1,016,522
Common stock reserved for future issuance (in shares)							1,400,000
Common stock authorized (in shares)									3,927,135
2008 and 2014 Equity Incentive Plans | Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting term									4 years
Option expiration period									10 years
Public Offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period (in shares)			22,425,000	5,226,369		3,000,000
Share price (in dollars per share)			$ 4.1	$ 6.25		$ 26.50
Underwriters option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period (in shares)					47,409
Share price (in dollars per share)					$ 26.50			$ 26.50

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Shares of Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	5,711,913	4,925,986
Employee Stock Option
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	4,094,532	3,590,393
Restricted stock units
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	195,172	107,250
Future Stock Grants
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	947,199	724,723
2014 Employee Stock Purchase Plan | Employee Stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	475,010	503,620

Stockholders' Equity - Schedu51

Stockholders' Equity - Schedule of RSU's (Details) - Restricted stock units - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, beginning of period (in shares)	107,250	0
Granted (in shares)	224,540	118,000
Vested (in shares)	(26,802)	0
Canceled/Forfeited (in shares)	(109,816)	(10,750)
Outstanding, end of period (in shares)	195,172	107,250
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 19.39
Granted (in dollars per share)	5.60	$ 19.39
Vested (in dollars per share)	19.39	0
Canceled/Forfeited (in dollars per share)	6.13	19.39
Outstanding, end of period (in dollars per share)	$ 10.99	$ 19.39

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, Beginning balance (in shares)	3,590,393	2,832,467
Options granted (in shares)	954,301	991,110
Options exercised (in shares)	(175,183)	(20,782)
Options forfeited (in shares)	(117,124)	(182,605)
Options expired (in shares)	(157,855)	(29,797)
Options outstanding, Ending balance (in shares)	4,094,532	3,590,393	2,832,467
Options vested and expected to vest (in shares)	4,094,532
Exercisable options (in shares)	2,464,086
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (in dollars per share)	$ 12.13	$ 11.48
Options granted (in dollars per share)	6.46	15.49
Options exercised (in dollars per share)	2.56	3.12
Options forfeited (in dollars per share)	14.35	19.01
Options expired (in dollars per share)	17.19	25.65
Ending balance (in dollars per share)	10.96	$ 12.13	$ 11.48
Options vested and expected to vest (in dollars per share)	10.96
Exercisable options (in dollars per share)	$ 10.98
Weighted average remaining contract term for outstanding options	7 years 2 months 15 days	7 years 3 months 29 days
Weighted average remaining contract term for options vested and expected to vest	7 years 2 months 15 days
Weighted average remaining contract term for exercisable options	6 years 3 months 14 days
Aggregate intrinsic value, outstanding	$ 2,771	$ 5,062
Aggregate intrinsic value of options vested and expected to vest	2,771
Aggregate intrinsic value of exercisable options	$ 2,771

Stockholders' Equity - Schedu53

Stockholders' Equity - Schedule of Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Employee share-based compensation expense	$ 8,633	$ 9,283	$ 6,297
Employee | Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Employee share-based compensation expense	3,613	3,923	2,034
Employee | General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Employee share-based compensation expense	4,879	5,029	3,810
Non-Employee | Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Employee share-based compensation expense	85	268	205
Non-Employee | General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Employee share-based compensation expense	$ 56	$ 63	$ 248

Stockholders' Equity - Schedu54

Stockholders' Equity - Schedule of Fair Value of Stock Options Granted to Employees (Details) - Employee Stock Option - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average estimated fair value	$ 4.41	$ 10.07	$ 15.65
Risk-free interest rate min	1.90%	1.10%	1.50%
Risk-free interest rate max	2.20%	2.40%	1.90%
Expected stock price volatility min	80.00%	77.00%	77.00%
Expected stock price volatility max	91.00%	93.00%	91.00%
Expected dividend yield	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time to maturity	5 years 6 months	5 years 6 months	5 years 6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time to maturity	6 years 29 days	9 years 5 months 16 days	6 years 29 days

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory tax rate	35.00%	35.00%
Permanent differences	(6.40%)	(1.50%)
Other	(0.50%)	(0.40%)
General business credits	15.10%	2.40%
Change in valuation allowance	15.60%	(35.50%)
Tax Reform - tax rate change	(58.80%)	0.00%
Effective tax rate	0.00%	0.00%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Asset (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 39,971	$ 52,154
Research and development credit	13,392	5,582
Depreciation and amortization	1,241	2,023
Other temporary differences	4,477	6,154
Gross deferred tax assets	59,081	65,913
Deferred tax asset valuation allowance	(59,081)	(65,913)
Net deferred tax assets	$ 0	$ 0

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Tax Credit Carryforward [Line Items]
Decrease in deferred tax asset due to Tax Act	$ 30.5
Increase in valuation allowance	(6.8)	$ 18.9
Net operating loss carryforwards	190.3	152.5
Unrecognized excess tax benefits	1.2	1.2
Research Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Research and development tax credit carryforwards	$ 13.4	$ 5.6

Legal Proceedings (Details)

Legal Proceedings (Details) - USD ($)	1 Months Ended				2 Months Ended	12 Months Ended
	Feb. 28, 2018	Nov. 30, 2017	Oct. 31, 2017	Sep. 30, 2016	May 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 17, 2016
Loss Contingencies [Line Items]
Proceeds from issuance of common stock		$ 86,600,000	$ 86,600,000	$ 30,300,000	$ 75,400,000	$ 86,624,000	$ 30,310,000	$ 75,359,000
Subsequent Event
Loss Contingencies [Line Items]
Escrow disbursements made during the period	$ 750,000
TheraVectys SA | Subsequent Event
Loss Contingencies [Line Items]
Escrow disbursements made during the period	$ 5,250,000
TheraVectys SA
Loss Contingencies [Line Items]
Payments for underwriting expense		$ 1,250,000
Collaborative Arrangement | TheraVectys SA | Maximum
Loss Contingencies [Line Items]
Obligation							1,400,000		$ 1,400,000
Settled Litigation | TheraVectys SA v. Immune Design Corp.
Loss Contingencies [Line Items]
Settlement agreement, escrow deposit									6,000,000
Settlement agreement, additional amount based on future conditions									1,250,000
Settlement agreement, contingent payout based on capital funding									$ 25,000,000
Payment of legal settlement, milestone one, percent									50.00%
Payment of legal settlement, milestone two, percent									50.00%
Estimate of possible loss									$ 7,300,000
Estimated litigation liability									$ 5,900,000
Loss in period							$ 5,900,000

Employee Benefit Plan - Narrati

Employee Benefit Plan - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Employer contribution	$ 300	$ 243	$ 214
Up to 3% of Employee's Compensation [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer match percentage	100.00%
Percent of employee's salary for employer match	3.00%
Between 3% and 5% of Employee's Compensation [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer match percentage	50.00%
Between 3% and 5% of Employee's Compensation [Member] | Minimum
Defined Contribution Plan Disclosure [Line Items]
Percent of employee's salary for employer match	3.00%
Between 3% and 5% of Employee's Compensation [Member] | Maximum
Defined Contribution Plan Disclosure [Line Items]
Percent of employee's salary for employer match	5.00%

Subsequent Event (Details)

Subsequent Event (Details) - Subsequent Event	1 Months Ended
	Feb. 28, 2018USD ($)
Subsequent Event [Line Items]
Escrow disbursements made during the period	$ 750,000
TheraVectys SA
Subsequent Event [Line Items]
Escrow disbursements made during the period	$ 5,250,000

Selected Quarterly Financial 61

Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 485	$ 516	$ 729	$ 5,465	$ 2,058	$ 8,206	$ 1,133	$ 1,863	$ 7,195	$ 13,260	$ 9,510
Net loss	$ (11,980)	$ (13,416)	$ (13,846)	$ (12,620)	$ (14,446)	$ (12,443)	$ (14,347)	$ (12,294)	$ (51,862)	$ (53,530)	$ (39,445)
Basic and diluted net loss per share (in dollars per share)	$ (0.29)	$ (0.52)	$ (0.54)	$ (0.50)	$ (0.57)	$ (0.60)	$ (0.71)	$ (0.61)	$ (1.75)	$ (2.47)	$ (2.06)