1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Nature of operations and basis of presentation

We were incorporated in the state of Delaware on June 14, 1996. We are engaged in the discovery and development of novel, targeted drug candidates in the therapeutic areas of immunology, oncology and immuno-oncology.

Use of estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates and assumptions made by management include those relating to our sublease agreement including the determination of discount rate used, stock-based compensation, impairment issues, estimated useful life of assets, estimated research term on our collaboration agreement with BMS, and estimated accruals, particularly research and development accruals. We believe that the estimates and judgments upon which we rely are reasonable based upon information available to us at the time that these estimates and judgments are made, however actual results could differ from these estimates. To the extent there are material differences between these estimates and actual results, our financial statements will be affected.

Stock award plans

We have three stock option plans, our 2011 Equity Incentive Plan (2011 Plan), 2000 Equity Incentive Plan (2000 Plan) and 2000 Non‑Employee Directors Stock Option Plan (Directors’ Plan), that provide for granting to our officers, directors and all other employees and consultants options to purchase shares of our common stock. We also have our Employee Stock Purchase Plan (Purchase Plan), where eligible employees can purchase shares of our common stock at a price per share equal to the lesser of 85% of the fair market value on the first day of the offering period or 85% of the fair market value on the purchase date. The fair value of each option award is estimated on the date of grant using the Black‑Scholes option pricing model which considered our stock price, as well as assumptions regarding a number of complex and subjective variables. These variables include, but are not limited to, volatility, expected term, risk‑free interest rate and dividends. We estimate volatility over the expected term of the option using historical share price performance. For expected term, we take into consideration our historical data of options exercised, cancelled and expired. The risk‑free rate is based on the U.S. Treasury constant maturity rate. We have not paid and do not expect to pay dividends in the foreseeable future. In order to calculate stock‑ based compensation expense, we also estimate the forfeiture rate using our historical experience with options that cancel before they vest. We review our forfeiture rates each quarter and make any necessary changes to our estimates. We use the straight‑line attribution method over the requisite employee service period for the entire award in recognizing stock‑based compensation expense.

We granted performance-based stock options to purchase shares of our common stock which will vest upon the achievement of certain corporate performance-based milestones. We determined the fair values of these performance-based stock options using the Black-Scholes option pricing model at the date of grant. For the portion of the performance-based stock options of which the performance condition is considered probable of achievement, we recognized stock-based compensation expense on the related estimated fair value of such options on a straight-line basis from the date of grant up to the date when we expect the performance condition will be achieved. For the performance conditions that are not considered probable of achievement at the grant date or upon quarterly re-evaluation, prior to the event actually occurring, we will recognize the related stock-based compensation expense when the event occurs or when we can determine that the performance condition is probable of achievement. In those cases, we will recognize the change in estimate at the time we determine the condition is probable of achievement (by recognizing stock-based compensation expense as cumulative catch-up adjustment as if we had estimated at the grant date that the performance condition would have been achieved) and recognize the remaining compensation cost up to the date when we expect the performance condition will be achieved, if any.

Cash, cash equivalents and short-term investments

We consider all highly liquid investments in debt securities with maturity from the date of purchase of 90 days or less to be cash equivalents. Cash equivalents consist of money market funds, U.S. treasury bills, corporate bonds and commercial paper and investments in government‑sponsored enterprises. Our short-term investments include U.S. treasury bills, obligations of government‑ sponsored enterprises and corporate bonds and commercial paper. By policy, we limit the concentration of credit risk by diversifying our investments among a variety of high credit‑quality issuers.

All cash equivalents and short‑term investments are classified as available‑for‑sale securities. Available‑for‑sale securities are carried at fair value at December 31, 2015 and 2014. Unrealized gains (losses) are reported in the statements of stockholders’ equity and comprehensive loss. Fair value is estimated based on available market information or valuation methodologies. The cost of securities sold is based on the specific identification method. See Note 5 for a summary of available-for-sale securities at December 31, 2015 and 2014.

Fair value of financial instruments

The carrying values of cash, accounts receivable, accounts payable and accrued liabilities approximate fair value due to the short-term maturity of those instruments. Cash equivalents and short-term investments are carried at fair value at December 31, 2015 and 2014.

Concentration of credit risk

Financial instruments that potentially subject us to concentrations of credit risk are primarily cash and cash equivalents, short-term investments and accounts receivable. Cash equivalents and short-term investments primarily consist of money market funds, U. S. treasury bills, government-sponsored enterprise securities, and corporate bonds and commercial paper. Due to the short-term nature of these investments, we believe we do not have a material exposure to credit risk arising from our investments. All cash and cash equivalents and short-term investments are maintained with financial institutions that management believes are creditworthy.  As of December 31, 2015 and 2014, our accounts receivable primarily consisted of $203,000 from BMS relating to the performance of research activities and $5.8 million time-based non-refundable fee from AZ, respectively.  To date, we have not experienced significant losses with respect to the collection of our accounts receivable and we believe that we do not have a material exposure to credit risk arising from our accounts receivable.

Property and equipment

Property and equipment are stated at cost. Depreciation is calculated using the straight‑line method over the estimated useful lives of the assets, which range from three to seven years.

Revenue recognition

We present revenue from our collaboration arrangements under the FASB ASC 808, Collaboration Arrangements. The terms of these agreements generally contain multiple elements, or deliverables, which may include (i) granting of license rights to our program, (ii) participation in a joint research committee, (iii) performance of research activities, and (iv) clinical supply and materials. The payments we receive under these arrangements typically include one or more of the following: non-refundable, up-front fees; funding of research and/or development efforts; contingent fees due upon the achievement of specified triggering events; and/or royalties on future product sales. We recognize revenue for the performance of services or the delivery of products when each of the following four criteria is met: (i) persuasive evidence of an arrangement exists; (ii) products are delivered or as services are rendered; (iii) the sales price is fixed or determinable; and (iv) collectability is reasonably assured.

Our revenue arrangements with multiple elements are evaluated under FASB ASC 605‑25, Multiple Element Arrangements, and are divided into separate units of accounting if certain criteria are met, including whether the deliverables have stand-alone value, based on the relevant facts and circumstances for each arrangement. The consideration we receive under collaboration arrangements is allocated among the separate units of accounting based on the selling price hierarchy, and the applicable revenue recognition criteria is applied to each of the separate units. We make significant judgments and estimates in the allocation of the consideration among the deliverables under the agreement, as well as the determination of the periods the units will be delivered to our collaborators. If there are deliverables in an arrangement that are not separable from other aspects of the contractual relationship, they are treated as a combined unit of accounting, with the allocated revenue for the combined unit recognized in a manner consistent with the revenue recognition applicable to the final deliverable in the combined unit. Payments received prior to satisfying the relevant revenue recognition criteria are recorded as deferred revenue in the accompanying balance sheets and recognized as revenue when the revenue recognition criteria are met.

We typically receive non-refundable, up-front payments when licensing our intellectual property, which often occurs in conjunction with a research and development agreement. If we believe that the license to our intellectual property has stand-alone value, we generally recognize revenue attributed to the license upon delivery provided that there are no future performance requirements for use of the license. When we believe that the license to our intellectual property does not have stand-alone value, we would recognize revenue attributed to the license ratably from the effective date of the agreement or the delivery of the license up to the estimated completion date of the undelivered performance obligation. Revenues related to the research services with our corporate collaborators are recognized as research services are performed over the related research period. Under these agreements, we are required to perform research activities as specified in the agreement. The payments received are not refundable and are based on a contractual cost per full-time equivalent employee working on the project. Our research and development expenses under the collaborative research agreements approximate the revenue recognized under such agreements over the research period.

Revenues associated with substantive, at-risk milestones pursuant to collaborative agreements are recognized upon achievement of the milestones. We consider a milestone to be substantive at the inception of the arrangement if it is commensurate with either our performance to achieve the milestone or the enhancement of the value of the delivered item as a result of a specific outcome resulting from our performance to achieve the milestone, it relates solely to past performance and it is reasonable relative to all of the deliverables and payment terms within the arrangement. Non-refundable contingent future amounts receivable in connection with future events specified in collaboration agreements that are not considered milestones such as payments contingent solely upon the passage of time or the result of our collaborator's performance will be recognized as revenue when the recognition criteria discussed above are met.

Research and development expenses

Research and development expenses include costs for scientific personnel, supplies, equipment, consultants, research sponsored by us, allocated facility costs, costs related to pre‑clinical and clinical trials, including raw materials, and stock‑based compensation expense. All such costs are charged to research and development expense as incurred and at the time raw materials are purchased.

Research and development accruals

We have various contracts with third parties related to our research and development activities. Costs that are incurred for services rendered, but not billed to us, as of the end of the period are estimated and accrued. We make estimates of the amounts incurred in each period based on the information available to us and our knowledge of the nature of the contractual activities generating such costs. Expenses related to other research and development contracts, such as research contracts, toxicology study contracts and manufacturing contracts are estimated to be incurred generally on a straight‑line basis over the duration of the contracts. Raw materials and study materials purchased for us by third parties are expensed at the time of purchase.

Leases

We currently lease our research and office space under a noncancelable lease agreement with our landlord through January 2018. In December 2014, we entered into a sublease agreement with an unrelated third party to occupy a portion of our research and office space. In connection with this sublease, we recognized a loss on the sublease of $9.3 million during the fourth quarter of 2014. We record rent expense on a straight‑line basis for our lease, net of sublease income, wherein such arrangements contain scheduled rent increases over the term of the lease and sublease, respectively. For our sublease arrangement which we classified as an operating lease, our loss on the sublease is comprised of the present value of our future payments to our landlord less the present value of our future rent payments expected from our subtenant over the term of the sublease. The present value factor, which also affects the level of accreted interest expense that we will recognize as additional charges over the term of the lease, is based on our estimate of our credit‑risk adjusted borrowing rate at the time the initial sublease liability is calculated. Our estimate of our credit‑risk adjusted borrowing rate was based on our comparison of the rates used by other companies of our size, our financial condition at the time we entered into such sublease agreement, as well as other factors that would affect our credit worthiness.

Contingencies

We are subject to claims related to the patent protection of certain of our technologies, as well as a purported securities class action lawsuit and other litigation. We are required to assess the likelihood of any adverse judgments or outcomes to these matters as well as potential ranges of probable losses. A determination of the amount of reserves required, if any, for these contingencies is made after careful analysis of each individual issue.

Income taxes

We use the asset and liability method to account for income taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using 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 from a change in tax rates is recognized in income in the period the change is enacted. A valuation allowance is established to reduce deferred tax assets to an amount whose realization is more likely than not.

Net loss per share

Basic net loss per share is computed by dividing net loss by the weighted‑average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted‑average number of shares of common stock outstanding during the period and the number of additional shares of common stock that would have been outstanding if potentially dilutive securities had been issued. Potentially dilutive securities include warrant and stock options and shares issuable under our Purchase Plan. The dilutive effect of these potentially dilutive securities is reflected in diluted earnings per share by application of the treasury stock method. Under the treasury stock method, an increase in the fair market value of our common stock can result in a greater dilutive effect from potentially dilutive securities.

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except per share amounts):

 

 

During the periods presented, we had securities which could potentially dilute basic loss per share, but were excluded from the computation of diluted net loss per share for all periods presented, as their effect would have been antidilutive. These securities consist of the following (in thousands except per share data):

 

 

Recent accounting pronouncements

In August 2014, the FASB issued ASU No. 2014-15—Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern under ASC Subtopic 205-40, Presentation of Financial Statements—Going Concern. ASU No. 2014-15 provides guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. Management’s evaluation should be based on relevant conditions and events that are known and reasonably knowable at the date that the financial statements are issued (or at the date that the financial statements are available to be issued when applicable). Substantial doubt about an entity’s ability to continue as a going concern exists when relevant conditions and events, considered in the aggregate, indicate that it is probable that the entity will be unable to meet its obligations as they become due within one year after the date that the financial statements are issued (or available to be issued). ASU No. 2014-15 is effective for the annual period ending after December 15, 2016 and early adoption is permitted. We will continue to evaluate the guidance under ASU No. 2014-15 and present the required disclosures within our financial statements at the time of adoption. We plan to adopt this new standard in our annual financial statements for the year ending December 31, 2016 and we believe that the adoption of ASU No. 2014-15 will have no material effect on our financial statement disclosures.

In May 2014, the FASB issued ASU No. 2014-09—Revenue from Contracts with Customers, which supersedes the revenue recognition requirements under ASC Topic 605, Revenue Recognition, and most industry-specific guidance under the ASC. The core principle of ASU No. 2014-09 is that an entity should recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 defines a five step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than required under existing U.S. GAAP including identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU No. 2014-09 also requires additional disclosures to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. ASU No. 2014-09 allows for either full retrospective or modified retrospective adoption, and we have not yet determined which approach we will apply. In July 2015, the FASB deferred by one year the effective date of ASU No. 2014-09 with the new effective date beginning after December 15, 2017, and the interim periods within that year and will allow early adoption for all entities as of the original effective date for public business entities, which was annual reporting periods beginning after December 15, 2016. We plan to adopt this new standard on  January 1, 2018. We are currently evaluating the potential impact of the adoption of ASU No. 2014-09 on our financial statements and cannot estimate the impact of adoption at this time.