Exhibit 3.1

AMENDMENT TO THE AMENDED AND RESTATED BYLAWS OF SUNESIS PHARMACEUTICALS, INC.

The Amended and Restated Bylaws (the “Bylaws”) of Sunesis Pharmaceuticals, Inc., a Delaware corporation, are hereby amended as follows, effective immediately, by adding a new Article XI, which shall read in its entirety as follows:

ARTICLE XI – EXCLUSIVE FORUM

(i) Unless the corporation consents in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware (or, if and only if the Court of Chancery of the State of Delaware lacks subject matter jurisdiction, any state court located within the State of Delaware or, if and only if all such state courts lack subject matter jurisdiction, the federal district court for the District of Delaware) and any appellate court therefrom shall be the sole and exclusive forum for the following claims or causes of action under Delaware statutory or common law: (A) any derivative claim or cause of action brought on behalf of the corporation; (B) any claim or cause of action for breach of a fiduciary duty owed by any current or former director, officer or other employee of the corporation, to the corporation or the corporation’s stockholders; (C) any claim or cause of action against the corporation or any current or former director, officer or other employee of the corporation, arising out of or pursuant to any provision of the DGCL, these bylaws (as may be amended from time to time); (D) any claim or cause of action seeking to interpret, apply, enforce or determine the validity of these bylaws (as may be amended from time to time, including any right, obligation, or remedy thereunder); (E) any claim or cause of action as to which the DGCL confers jurisdiction on the Court of Chancery of the State of Delaware; and (F) any claim or cause of action against the corporation or any current or former director, officer or other employee of the corporation, governed by the internal-affairs doctrine or otherwise related to the corporation’s internal affairs, in all cases to the fullest extent permitted by law and subject to the court having personal jurisdiction over the indispensable parties named as defendants. This Article XI shall not apply to claims or causes of action brought to enforce a duty or liability created by the Securities Act of 1933, as amended (the “1933 Act”), or the Securities Exchange Act of 1934, as amended, or any other claim for which the federal courts have exclusive jurisdiction.

(ii) Unless the corporation consents in writing to the selection of an alternative forum, to the fullest extent permitted by law, the federal district courts of the United States of America shall be the exclusive forum for the resolution of any complaint asserting a cause of action arising under the 1933 Act.

(iii) Any person or entity holding, owning or otherwise acquiring any interest in any security of the corporation shall be deemed to have notice of and consented to the provisions of these bylaws.