2. Summary of Significant Accounting Policies

Unaudited Interim Financial Information

The interim condensed consolidated balance sheet as of September 30, 2018, the statements of operations and comprehensive loss for the three and nine months ended September 30, 2018 and 2017, and the statements of cash flows for the nine months ended September 30, 2018 and 2017 are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s condensed consolidated financial statements included in this report. The financial data and the other information disclosed in these notes to the condensed consolidated financial statements related to the nine-month periods are also unaudited. The results of operations for the nine months ended September 30, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any other future annual or interim period. The balance sheet as of December 31, 2017 included herein was derived from the audited consolidated financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements included in the Company’s Form 10-K as filed with the Securities and Exchange Commission (“SEC”).

Use of Estimates

The accompanying condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accrued liabilities, revenue recognition, fair value of marketable securities, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. Cash equivalents, which consist primarily of amounts invested in money market accounts, are stated at fair value.

Investments

All investments have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its investments at the time of purchase and reevaluates such designation as of each balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest income, net. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest income, net.

Restricted Cash

Restricted cash consists of money market funds held by the Company’s financial institution as collateral for the Company’s obligations under its facility lease for the Company’s corporate headquarters in South San Francisco, California.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents, investments and restricted cash. The Company invests in a variety of financial instruments and, by its policy, limits these financial instruments to high credit quality securities issued by the U.S. government, U.S. government-sponsored agencies and highly rated banks and corporations, subject to certain concentration limits. The Company’s cash, cash equivalents, investments and restricted cash are held by financial institutions in the United States that management believes are of high credit quality. Amounts on deposit may at times exceed federally insured limits.

All of the Company’s collaboration revenue and the majority of the Company’s receivables from collaborations are derived from its collaboration and license agreement with Incyte Corporation, or Incyte, as described in Note 9, Collaboration and Licensing Agreements - Incyte Collaboration and License Agreement.

Revenue Recognition

Effective January 1, 2018, the Company adopted Accounting Standards Codification, or ASC No. 2014-09, Revenue from Contracts with Customers (Topic 606), or ASC 606, using the modified retrospective approach. Under this approach, the Company recorded a cumulative adjustment to decrease accumulated deficit and deferred revenue by $8.8 million. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

The Company has a collaboration and license agreement with Incyte, or the Incyte Collaboration Agreement, that is within the scope of ASC 606, under which it licenses certain rights to one of its product candidates to Incyte Corporation. The terms of this arrangement include payment to the Company of a non-refundable, upfront license fee, and potential development, regulatory and sales milestones, and sales royalties. Each of these payments results in collaboration revenues, except for revenues from royalties on net sales of licensed products, which would be classified as royalty revenues.

In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreement, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract.

Licenses of Intellectual Property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promised goods or services, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, upfront fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Milestone Payments: At the inception of each arrangement that includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received or the underlying activity has been completed. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenue in the period of adjustment.

Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements.

The following table summarizes the impact of adopting ASC 606 on select unaudited condensed statement of operations line items for the nine months ended September 30, 2018 (in thousands, except per share data):

						Balances
						Without the
						Adoption of
Nine Months Ended September 30, 2018	As Reported			Adjustments		ASC 606
Collaboration revenue	$	22,254		$	8,791	$	31,045
Total revenue		22,254			8,791		31,045
Loss from operations		(37,057	)		8,791		(28,266	)
Net loss		(35,130	)		8,791		(26,339	)

Contract Balances

Upfront payments and fees are recorded as deferred revenue upon receipt or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional.

The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less.

The following table presents changes in the Company’s contract assets and liabilities for the nine months ended September 30, 2018 (in thousands):

	Balance at		Balance at
	Beginning of		End of
Nine Months Ended September 30, 2018	Period		Period
Contract liabilities:
Deferred revenue	$	29,017	$	—
Deferred revenue, less current portion		2,028		—

Deferred revenue related to the Incyte Collaboration Agreement, which was comprised of the $57 million transaction price including a $45 million upfront license payment and a $12 million development milestone achieved, less the collaboration revenue recognized from the effective date of the contract, was recognized as the combined performance obligation was satisfied.

The Company had no contract assets as of September 30, 2018. During the nine months ended September 30, 2018, the Company’s contract liabilities, which consisted of deferred revenue, decreased $31.0 million for the nine months ended September 30, 2018, related to revenue recognized in the period related to amounts included in the contract liability at the beginning of the period. In addition, the Company recorded a cumulative adjustment to decrease accumulated deficit and deferred revenue by $8.8 million upon the adoption of ASC 606 on January 1, 2018, using the modified retrospective approach. For the three and nine months ended September 30, 2018, the Company did not recognize any revenue from performance obligations satisfied in previous periods.

Accrued Research and Development Costs

The Company records accrued liabilities for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced, and includes these costs in accrued liabilities in the consolidated balance sheets and within research and development expense in the consolidated statements of operations. These costs are a significant component of the Company’s research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers under the service agreements. The Company makes significant judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued costs and actual costs incurred. However, the status and timing of actual services performed, number of patients enrolled, and the rate of patient enrollments may vary from the Company’s estimates, resulting in adjustments to expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect the Company’s results of operations.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding during the period without consideration of common stock equivalents. Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (“FASB”) issued a comprehensive new standard on revenue from contracts with customers, ASC 606. The standard’s core principle is that a reporting entity will 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. Entities have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. In 2016, the FASB updated the guidance for reporting revenue gross versus net to improve the implementation guidance on principal versus agent considerations, and for identifying performance obligations and the accounting of intellectual property licenses. In addition, the FASB introduced practical expedients and made narrow scope improvements to the new accounting guidance.

The Company adopted the accounting standard update on January 1, 2018 using the modified retrospective approach for its collaboration and license agreement with Incyte. Therefore, comparative information was not adjusted and the impact of the transition is reflected in opening accumulated deficit. The consideration the Company is eligible to receive under this agreement includes upfront payments, research and development funding, milestone payments, and sales-based royalties. The new revenue recognition standard differs from the previous accounting in many respects, such as in the accounting for variable consideration and the measurement of progress toward completion of performance obligations. The most significant impact of the standard relates to the Company’s method of revenue recognition for performance obligations that are delivered over time. Under the new standard, milestone payments are included in the transaction price as variable consideration, subject to a constraint, and are allocated to the performance obligations in the contract. Therefore, the milestone payments are recognized over the performance period rather than when achieved. In addition, legacy guidance permitted straight-line recognition of revenue for performance obligations that are delivered over time. The new standard requires an entity to recognize revenue based on the pattern of transfer of the services. The impact of adoption resulted in the Company recording an adjustment to decrease the accumulated deficit and deferred revenue by $8.8 million at January 1, 2018 to reflect revenue being recognized based on a measurement of progress toward completion of the combined performance obligation, rather than on a straight-line basis.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which is aimed at making leasing activities more transparent, and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. The ASU is effective for all interim and annual reporting periods beginning after December 15, 2018 with early adoption permitted and was previously required to be applied with a modified retrospective approach to each prior reporting period presented. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, or ASU No. 2018-11. In issuing ASU No. 2018-11, the FASB is permitting another transition method for ASU 2016-02, which allows the transition to the new lease standard by recognizing a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company is finalizing its assessment of the impact of adoption and anticipates electing this new transition method when it adopts the new standard effective January 1, 2019.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash Payments, or ASC 230, to clarify how entities should present restricted cash and restricted cash equivalents in their statements of cash flows. Under this update, entities are required to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in their statements of cash flows. The Company adopted this standard on January 1, 2018 retrospectively. The adoption of this standard did not impact the Company’s unaudited condensed consolidated balance sheets, statements of operations, or statements of comprehensive loss. The following table summarizes the impact of adopting ASC 230 on select unaudited condensed statement of cash flows line items (in thousands) for the nine months ended September 30, 2017:

						Balances
						With the
	As Originally					Adoption of
	Reported			Adjustments		ASC 230
Change in restricted cash	$	(394	)	$	394	$	—
Net cash provided by (used in) investing activities		(117,484	)		394		(117,090	)
Net increase in cash, cash equivalents and restricted cash^*		28,810			394		29,204
Cash, cash equivalents and restricted cash at beginning of period^*		10,601			46		10,647
Cash, cash equivalents and restricted cash at end of period^*		39,411			440		39,851

*	For the nine months ended September 30, 2017, this line item, as originally reported, excluded restricted cash.

The Tax Cuts and Jobs Act, or Tax Act, was enacted on December 22, 2017 and provides for significant changes to U.S. tax law. Among other provisions, the Act reduces the U.S. corporate income tax rate to 21%, effective in 2018. As a result, the Company remeasured its U.S. deferred tax assets and liabilities as of December 31, 2017 based on the reduction of the U.S. federal corporate tax rate from 35% to 21% and assessed the realizability of its deferred tax assets based on its understanding of the provisions of the new law. The remeasurement resulted in an estimated one-time reduction in deferred tax assets of $17.8 million as of December 31, 2017, which was fully offset by a corresponding change to the Company’s valuation allowance.

In March 2018, the FASB issued ASU No. 2018-05 – Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118, or SAB 118, which provides guidance on accounting for the Tax Act, and provides a measurement period should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting. In accordance with this guidance, the Company considers its accounting for the impacts of the new tax law to be provisional. During the three and nine months ended September 30, 2018, no additional measurement-period adjustments were made by the Company related to the Tax Act. The Company continues to assess the impact of the recently enacted tax law and associated guidance on its business and consolidated financial statements and plans to complete its accounting for the income tax effects of the Tax Act within the one-year measurement period in 2018.

In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. The ASU expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The ASU also clarifies that Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under Revenue from Contracts with Customers (Topic 606). The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted. The Company is currently assessing the effect that the ASU will have on its financial position, results of operations, and disclosures.