Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. Operating results for the nine months ended September 30, 2018, are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. The consolidated balance sheet at December 31, 2017, has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. For further information, refer to the annual consolidated financial statements and footnotes thereto of the Company. The Company’s significant accounting policies are described in Note 2 of Notes to Consolidated Financial Statements included in its Annual Report on Form 10-K for the year ended December 31, 2017 (2017 Annual Report on Form 10-K). During the first quarter of 2018, the Company adopted Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606). As a result of the adoption of Topic 606, the Company has updated its Revenue Recognition policies. There were no other changes to its significant accounting policies from those disclosed in its 2017 Annual Report on Form 10-K. Revenue Recognition The Company’s revenue to date has been generated primarily from licensing fees received under its collaborative licensing agreements with AbbVie Ltd. (AbbVie) and Kyowa Hakko Kirin Co., Ltd. (KHK) and reimbursements for expenses from KHK. The terms of the agreements include non-refundable upfront fees, funding of research and development activities, payments based upon achievement of milestones, and royalties on net product sales. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which 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 Topic 606, the entity performs the following five steps: (i) identify the promised goods or services in the contract with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including the constraint on variable consideration; (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. At contract inception, the Company assesses the goods or services promised within each contract, 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. Licenses of intellectual property: If a 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, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, 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, up-front 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 milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price, which is then allocated to each performance obligation. Milestone payments that are not within the control of the Company, such as approvals from regulators, are not considered probable of being achieved until those approvals are received. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones 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 license, collaboration, and other revenues and earnings in the period of adjustment and in future periods through the end of the performance obligation period. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) 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. Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the licensee and, if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the customer exercises these options, any additional payments are recorded when the customer obtains control of the goods, which is upon delivery. For a complete discussion of accounting for collaborative licensing agreements, see Note 3, Collaboration Agreements. The Recent Accounting Pronouncements The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012 (the JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected not to avail itself of this exemption from new or revised accounting standards, and, therefore, will be subject to the same new or revised accounting standards as public companies that are not emerging growth companies. In May 2014, the Financial Accounting Standards Board (FASB) issued Topic 606, which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition (Topic 605). The FASB has subsequently issued a number of amendments to Topic 606. The Company adopted this new standard on January 1, 2018 using the modified retrospective transition method. As of January 1, 2018, upon adoption of Topic 606, the Company recorded a cumulative adjustment of $2,634,000 to increase accumulated deficit and increase deferred revenue. This adjustment was the remainder of the transaction price related to the $15,000,000 received milestones that were recognized under the prior milestone recognition methodology when the milestones were achieved in 2010 and 2012. For a complete discussion of accounting for collaborative licensing agreements, see Note 3, Collaboration Agreements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02), which supersedes ASC 840, Leases. ASU 2016-02 requires the recognition of lease assets and lease liabilities by lessees for those leases previously classified as operating leases. The standard is effective for public companies for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted. The Company has not yet completed its final evaluation of the impact of this guidance, but it believes the primary change to the financial statements will relate to the recognition of right-of-use assets and offsetting lease liabilities in the consolidated balance sheet for operating leases. The Company will adopt ASU 2016–02 as of January 1, 2019 and will apply certain practical expedients offered in the guidance, such as those that state that the Company need not reassess whether expired or existing contracts contain leases, reevaluate the classification of expired or existing leases, or reassess initial direct costs for existing leases.

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. Operating results for the nine months ended September 30, 2018, are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. The consolidated balance sheet at December 31, 2017, has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. For further information, refer to the annual consolidated financial statements and footnotes thereto of the Company.

The Company’s significant accounting policies are described in Note 2 of Notes to Consolidated Financial Statements included in its Annual Report on Form 10-K for the year ended December 31, 2017 (2017 Annual Report on Form 10-K). During the first quarter of 2018, the Company adopted Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606). As a result of the adoption of Topic 606, the Company has updated its Revenue Recognition policies. There were no other changes to its significant accounting policies from those disclosed in its 2017 Annual Report on Form 10-K.

Revenue Recognition

The Company’s revenue to date has been generated primarily from licensing fees received under its collaborative licensing agreements with AbbVie Ltd. (AbbVie) and Kyowa Hakko Kirin Co., Ltd. (KHK) and reimbursements for expenses from KHK. The terms of the agreements include non-refundable upfront fees, funding of research and development activities, payments based upon achievement of milestones, and royalties on net product sales.

Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which 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 Topic 606, the entity performs the following five steps: (i) identify the promised goods or services in the contract with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including the constraint on variable consideration; (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.

At contract inception, the Company assesses the goods or services promised within each contract, 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.

Licenses of intellectual property: If a 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, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, 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, up-front 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 milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price, which is then allocated to each performance obligation. Milestone payments that are not within the control of the Company, such as approvals from regulators, are not considered probable of being achieved until those approvals are received. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones 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 license, collaboration, and other revenues and earnings in the period of adjustment and in future periods through the end of the performance obligation period.

Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) 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.

Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the licensee and, if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the customer exercises these options, any additional payments are recorded when the customer obtains control of the goods, which is upon delivery.

For a complete discussion of accounting for collaborative licensing agreements, see Note 3, Collaboration Agreements.

The Recent Accounting Pronouncements

The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012 (the JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected not to avail itself of this exemption from new or revised accounting standards, and, therefore, will be subject to the same new or revised accounting standards as public companies that are not emerging growth companies.

In May 2014, the Financial Accounting Standards Board (FASB) issued Topic 606, which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition (Topic 605). The FASB has subsequently issued a number of amendments to Topic 606. The Company adopted this new standard on January 1, 2018 using the modified retrospective transition method. As of January 1, 2018, upon adoption of Topic 606, the Company recorded a cumulative adjustment of $2,634,000 to increase accumulated deficit and increase deferred revenue. This adjustment was the remainder of the transaction price related to the $15,000,000 received milestones that were recognized under the prior milestone recognition methodology when the milestones were achieved in 2010 and 2012. For a complete discussion of accounting for collaborative licensing agreements, see Note 3, Collaboration Agreements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02), which supersedes ASC 840, Leases. ASU 2016-02 requires the recognition of lease assets and lease liabilities by lessees for those leases previously classified as operating leases. The standard is effective for public companies for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted.

The Company has not yet completed its final evaluation of the impact of this guidance, but it believes the primary change to the financial statements will relate to the recognition of right-of-use assets and offsetting lease liabilities in the consolidated balance sheet for operating leases. The Company will adopt ASU 2016–02 as of January 1, 2019 and will apply certain practical expedients offered in the guidance, such as those that state that the Company need not reassess whether expired or existing contracts contain leases, reevaluate the classification of expired or existing leases, or reassess initial direct costs for existing leases.