GRTS Gritstone bio Inc

United States

Securities and Exchange Commission

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant To Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

GRITSTONE BIO, INC.

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

SUPPLEMENT DATED MAY 10, 2024

TO PROXY STATEMENT DATED APRIL 29, 2024

FOR THE

ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD JUNE 17, 2024

The following supplemental information is being filed for the purpose of correcting a typographical error regarding the number of shares required for a quorum of stockholders, as described in the proxy materials of Gritstone bio, Inc. (the “Company”). There are no other modifications or supplements to the Company’s proxy statement on Schedule 14A filed with the Securities and Exchange Commission on April 29, 2024.

If you have already voted, you do not need to vote again unless you would like to change or revoke your prior vote on any proposal. If you would like to change or revoke your prior vote on any proposal, please refer to the proxy statement for instructions on how to do so.

What is the quorum requirement?

A quorum of stockholders is necessary to hold a valid meeting. A quorum will be present if the holders of a majority in voting power of the shares of common stock issued and outstanding and entitled to vote are present in attendance online or represented by proxy at the Annual Meeting. On the Record Date, there were 107,130,799 shares outstanding and entitled to vote. Accordingly, 53,565,401 shares must be represented by stockholders present at the Annual Meeting online or by proxy in order for there to be a quorum.

Your shares will be counted toward the quorum only if you submit a valid proxy or vote at the Annual Meeting. Abstentions, “Withhold” votes and broker non-votes will be counted toward the quorum requirement. If there is no quorum, either the chair of the Annual Meeting or a majority in voting power of the stockholders entitled to vote at the Annual Meeting, in attendance online or represented by proxy, may adjourn the Annual Meeting to another time or place.