Significant Accounting Policies	9 Months Ended
Sep. 30, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	2. SIGNIFICANT ACCOUNTING POLICIES The significant accounting policies described in the Company’s audited financial statements as of and for the year ended December 31, 2016, and the notes thereto, which are included in the Company’s 2016 Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 16, 2017, have had no material changes during the three and nine months ended September 30, 2017. Unaudited Interim Financial Data The accompanying interim consolidated balance sheet as of September 30, 2017, the related interim consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2017 and 2016 and cash flows for the nine months ended September 30, 2017 and 2016, and the related interim information contained within the notes to the consolidated financial statements have been prepared in accordance with the rules and regulations of the SEC for interim financial information. Accordingly, they do not include all of the information and the notes required by U.S. GAAP for complete financial statements. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2017 and 2016 are unaudited. In the opinion of management, the unaudited interim consolidated financial statements reflect all adjustments, consisting of normal and recurring adjustments, necessary for the fair presentation of the Company’s financial position and results of operations for the three and nine months ended September 30, 2017 and 2016. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or any other interim period or future year or period. Principles of Consolidation The Company’s consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. Recently Issued Accounting Pronouncements The recently issued accounting pronouncements described in the Company’s audited financial statements as of and for the year ended December 31, 2016, and the notes thereto, which are included in the Company’s 2016 Annual Report on Form 10-K filed with the SEC on March 16, 2017, have had no material changes during the three and nine months ended September 30, 2017, except as described below. In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective on January 1, 2018 and earlier application is permitted only for annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. For the year ended December 31, 2016 and the nine months ended September 30, 2017, revenue was generated exclusively from the Pfizer Collaboration Agreement. The Company is currently evaluating the potential impact that ASU 2014-09 may have on its financial position and results of operations as it relates to this single arrangement, and expects to elect the modified retrospective application as its transition method. In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes (“ASU 2015-17”), which requires entities to present deferred tax assets and liabilities, along with any related valuation allowance, as noncurrent on the balance sheet. The new standard is effective for annual and interim periods beginning after December 15, 2016. During the three months ended March 31, 2017, the Company elected to adopt ASU 2015-17 on a prospective basis. The adoption of this standard resulted in the reclassification of short-term deferred tax assets to long-term deferred tax assets. In October 2016, the FASB issued Accounting Standards Update No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). The new standard requires companies to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. Prior to the issuance of this standard, existing guidance prohibited the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party. ASU 2016-16 will be effective for the Company in the first quarter of 2018 with early adoption permitted. The Company is currently evaluating the potential impact that the adoption of ASU 2016-16 may have on its consolidated financial statements.

2. SIGNIFICANT ACCOUNTING POLICIES

The significant accounting policies described in the Company’s audited financial statements as of and for the year ended December 31, 2016, and the notes thereto, which are included in the Company’s 2016 Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 16, 2017, have had no material changes during the three and nine months ended September 30, 2017.

Unaudited Interim Financial Data

The accompanying interim consolidated balance sheet as of September 30, 2017, the related interim consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2017 and 2016 and cash flows for the nine months ended September 30, 2017 and 2016, and the related interim information contained within the notes to the consolidated financial statements have been prepared in accordance with the rules and regulations of the SEC for interim financial information. Accordingly, they do not include all of the information and the notes required by U.S. GAAP for complete financial statements. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2017 and 2016 are unaudited. In the opinion of management, the unaudited interim consolidated financial statements reflect all adjustments, consisting of normal and recurring adjustments, necessary for the fair presentation of the Company’s financial position and results of operations for the three and nine months ended September 30, 2017 and 2016. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or any other interim period or future year or period.

Principles of Consolidation

The Company’s consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

Recently Issued Accounting Pronouncements

The recently issued accounting pronouncements described in the Company’s audited financial statements as of and for the year ended December 31, 2016, and the notes thereto, which are included in the Company’s 2016 Annual Report on Form 10-K filed with the SEC on March 16, 2017, have had no material changes during the three and nine months ended September 30, 2017, except as described below.

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective on January 1, 2018 and earlier application is permitted only for annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. For the year ended December 31, 2016 and the nine months ended September 30, 2017, revenue was generated exclusively from the Pfizer Collaboration Agreement. The Company is currently evaluating the potential impact that ASU 2014-09 may have on its financial position and results of operations as it relates to this single arrangement, and expects to elect the modified retrospective application as its transition method.

In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes (“ASU 2015-17”), which requires entities to present deferred tax assets and liabilities, along with any related valuation allowance, as noncurrent on the balance sheet. The new standard is effective for annual and interim periods beginning after December 15, 2016. During the three months ended March 31, 2017, the Company elected to adopt ASU 2015-17 on a prospective basis. The adoption of this standard resulted in the reclassification of short-term deferred tax assets to long-term deferred tax assets.

In October 2016, the FASB issued Accounting Standards Update No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). The new standard requires companies to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. Prior to the issuance of this standard, existing guidance prohibited the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party. ASU 2016-16 will be effective for the Company in the first quarter of 2018 with early adoption permitted. The Company is currently evaluating the potential impact that the adoption of ASU 2016-16 may have on its consolidated financial statements.