Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The condensed consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for a fair presentation of the periods presented. The balance sheet as of December 31, 2018 was derived from the audited consolidated financial statements as of that date. These interim financial results are not necessarily indicative of results to be expected for the full year or any other period. These unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2018. Adopted Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASC 842”). ASC 842 is aimed at making leasing activities more transparent and comparable, 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. ASC 842 is effective for Sunesis’ interim and annual reporting periods during the year ending December 31, 2019, and all annual and interim reporting periods thereafter. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases, ASU 2018-11, Leases (Topic 842): Targeted Improvements and issued ASU 2019-01, Leases (Topic 842): Codification Improvements in March 2019. These pronouncements have the same effective date as the new leases standard and provide additional guidance, clarification and practical expedients to reduce the cost and complexity of applying the new standard. The Company adopted the new guidance on January 1, 2019 using the modified retrospective method at the effective date. The Company has elected the package of practical expedients permitted under ASC 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company made an accounting policy election to combine the lease and non-lease components and the short-term lease practical expedients allowed under ASC 842. As a result of the adoption of ASC 842, the Company recognized on January 1, 2019 (a) a lease liability of approximately $1,362,000, which represents the present value of the remaining lease payments of approximately $1,434,000, discounted using the Company’s incremental borrowing rate of 4.0%, and (b) a right-of-use (“ROU”) asset equal to the lease liability of approximately $1,362,000. Once recorded, the Company also evaluates the right-of-use asset for impairment as part of an asset group, following the principles of ASC 360, Property, Plant, and Equipment. The adoption of the new standard resulted in changes to the Company’s accounting policies for leases as detailed below. In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. The amendments in this ASU expand the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. This new guidance is effective for the Company in fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted. On January 1, 2019, the Company adopted this new guidance and the measurement of equity-classified nonemployee awards will be fixed at the grant date. Upon adoption, the Company applied the new guidance to equity-classified nonemployee awards for which a measurement date has not been established and compared the cumulative amounts that were recorded for its nonemployee share-based payments through the end of December 31, 2018 to the cumulative amounts that should be recognized at the adoption date to calculate the transition adjustment. On January 1, 2019, the Company recognized the transition adjustment as an adjustment to retained earnings, which had no material impact on the Company’s unaudited condensed consolidated financial statements or related footnote disclosures. Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments, which will require a reporting entity to use a new forward-looking impairment model for most financial assets that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, credit losses will be recognized as allowances rather than as reductions in amortized cost. The standard will be effective for annual periods beginning after December 15, 2019, with early adoption permitted beginning in 2019. Entities will apply the guidance as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company does not expect the adoption of this standard will have a material impact on its financial statements and accompanying footnotes. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. The amendments in this ASU modify the disclosure requirements on fair value measurements in Topic 820 based on the concepts in the Concepts Statement, Conceptual Framework for Financial Reporting—Chapter 8: Notes to Financial Statements, including the consideration of costs and benefits. This new guidance is effective for the Company in fiscal years beginning after December 15, 2019, including interim periods within that fiscal year. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2018-13 will have on its financial statements and accompanying footnotes. Leases The Company determines if an arrangement is or contains a lease at inception. In determining whether an arrangement is a lease, the Company considers whether (1) explicitly or implicitly identified assets have been deployed in the arrangement and (2) the Company obtains substantially all of the economic benefits from the use of that underlying asset and directs how and for what purpose the asset is used during the term of the contract. ROU assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term. When an implicit rate is not readily determinable, the Company uses its incremental borrowing rate based on the information available at commencement date for new leases or effective date for existing leases, in determining the present value of lease payments. Leases may contain initial periods of free rent and/or periodic escalations. When such items are included in a lease agreement, the Company records rent expense on a straight-line basis over the initial term of a lease. The difference between the rent payment and the straight-line rent expense is recorded as a deferred rent liability. The Company expenses any additional payments under its operating leases for taxes, insurance or other operating expenses as incurred. Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Sunesis Europe Limited, a United Kingdom corporation. All intercompany balances and transactions have been eliminated in consolidation. Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s condensed consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of equity and related instruments, debt instruments, revenue recognition, stock-based compensation, ROU assets, lease liabilities, and clinical trial accounting. Fair Value Measurements The Company measures cash equivalents at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1 - quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date. Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly. Level 3 - unobservable inputs. The carrying amounts of the Company’s financial instruments, including cash, prepayments, accounts payable, accrued liabilities, and notes payable approximated their fair value as of March 31, 2019 and December 31, 2018.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2019

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The condensed consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for a fair presentation of the periods presented. The balance sheet as of December 31, 2018 was derived from the audited consolidated financial statements as of that date. These interim financial results are not necessarily indicative of results to be expected for the full year or any other period. These unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2018.

Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASC 842”). ASC 842 is aimed at making leasing activities more transparent and comparable, 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. ASC 842 is effective for Sunesis’ interim and annual reporting periods during the year ending December 31, 2019, and all annual and interim reporting periods thereafter. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases, ASU 2018-11, Leases (Topic 842): Targeted Improvements and issued ASU 2019-01, Leases (Topic 842): Codification Improvements in March 2019. These pronouncements have the same effective date as the new leases standard and provide additional guidance, clarification and practical expedients to reduce the cost and complexity of applying the new standard. The Company adopted the new guidance on January 1, 2019 using the modified retrospective method at the effective date.

The Company has elected the package of practical expedients permitted under ASC 842. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in ASC Topic 842 at lease commencement. In addition, the Company made an accounting policy election to combine the lease and non-lease components and the short-term lease practical expedients allowed under ASC 842. As a result of the adoption of ASC 842, the Company recognized on January 1, 2019 (a) a lease liability of approximately $1,362,000, which represents the present value of the remaining lease payments of approximately $1,434,000, discounted using the Company’s incremental borrowing rate of 4.0%, and (b) a right-of-use (“ROU”) asset equal to the lease liability of approximately $1,362,000. Once recorded, the Company also evaluates the right-of-use asset for impairment as part of an asset group, following the principles of ASC 360, Property, Plant, and Equipment. The adoption of the new standard resulted in changes to the Company’s accounting policies for leases as detailed below.

In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. The amendments in this ASU expand the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. This new guidance is effective for the Company in fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted. On January 1, 2019, the Company adopted this new guidance and the measurement of equity-classified nonemployee awards will be fixed at the grant date. Upon adoption, the Company applied the new guidance to equity-classified nonemployee awards for which a measurement date has not been established and compared the cumulative amounts that were recorded for its nonemployee share-based payments through the end of December 31, 2018 to the cumulative amounts that should be recognized at the adoption date to calculate the transition adjustment. On January 1, 2019, the Company recognized the transition adjustment as an adjustment to retained earnings, which had no material impact on the Company’s unaudited condensed consolidated financial statements or related footnote disclosures.

Recent Accounting Pronouncements

In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments, which will require a reporting entity to use a new forward-looking impairment model for most financial assets that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, credit losses will be recognized as allowances rather than as reductions in amortized cost. The standard will be effective for annual periods beginning after December 15, 2019, with early adoption permitted beginning in 2019. Entities will apply the guidance as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company does not expect the adoption of this standard will have a material impact on its financial statements and accompanying footnotes.

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. The amendments in this ASU modify the disclosure requirements on fair value measurements in Topic 820 based on the concepts in the Concepts Statement, Conceptual Framework for Financial Reporting—Chapter 8: Notes to Financial Statements, including the consideration of costs and benefits. This new guidance is effective for the Company in fiscal years beginning after December 15, 2019, including interim periods within that fiscal year. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2018-13 will have on its financial statements and accompanying footnotes.

Leases

The Company determines if an arrangement is or contains a lease at inception. In determining whether an arrangement is a lease, the Company considers whether (1) explicitly or implicitly identified assets have been deployed in the arrangement and (2) the Company obtains substantially all of the economic benefits from the use of that underlying asset and directs how and for what purpose the asset is used during the term of the contract.

ROU assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term. When an implicit rate is not readily determinable, the Company uses its incremental borrowing rate based on the information available at commencement date for new leases or effective date for existing leases, in determining the present value of lease payments.

Leases may contain initial periods of free rent and/or periodic escalations. When such items are included in a lease agreement, the Company records rent expense on a straight-line basis over the initial term of a lease. The difference between the rent payment and the straight-line rent expense is recorded as a deferred rent liability. The Company expenses any additional payments under its operating leases for taxes, insurance or other operating expenses as incurred.

Principles of Consolidation

The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Sunesis Europe Limited, a United Kingdom corporation. All intercompany balances and transactions have been eliminated in consolidation.

Significant Estimates and Judgments

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s condensed consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of equity and related instruments, debt instruments, revenue recognition, stock-based compensation, ROU assets, lease liabilities, and clinical trial accounting.

Fair Value Measurements

The Company measures cash equivalents at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP:

Level 1 - quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date.

Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly.

Level 3 - unobservable inputs.

The carrying amounts of the Company’s financial instruments, including cash, prepayments, accounts payable, accrued liabilities, and notes payable approximated their fair value as of March 31, 2019 and December 31, 2018.