13G Filing: RA Capital Management and Sunesis Pharmaceuticals Inc (SNSS)

CUSIP No. 867328700

13G

Exhibit 1

JOINT FILING AGREEMENT

This Joint Filing Agreement,
dated as of November 10, 2017, is by and among RA Capital Management, LLC and Peter Kolchinsky (the foregoing are collectively
referred to herein as the “Filers”).

Each of the Filers
may be required to file with the United States Securities and Exchange Commission a statement on Schedule 13G and/or 13D with respect
to Common Stock, par value $0.0001 per share of Sunesis Pharmaceuticals, Inc. beneficially owned by them from time to time.

Pursuant to and in
accordance with Rule 13(d)(1)(k) promulgated under the Securities Exchange Act of 1934, as amended, the Filers hereby agree to
file a single statement on Schedule 13G and/or 13D (and any amendments thereto) on behalf of each of such parties, and hereby further
agree to file this Joint Filing Agreement as an exhibit to such statement, as required by such rule.

This Joint Filing Agreement
may be terminated by any of the Filers upon one week’s prior written notice or such lesser period of notice as the Filers
may mutually agree.

Executed and delivered
as of the date first above written.

RA CAPITAL MANAGEMENT, LLC

By: /s/ Rajeev Shah

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Rajeev Shah

Authorized Signatory

PETER KOLCHINSKY

/s/ Peter Kolchinsky

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