July 18, 2018

Andrew Allen, M.D., Ph.D.
President and Chief Executive Officer
Gritstone Oncology, Inc.
5858 Horton Street, Suite 210
Emeryville, CA 94608

       Re: Gritstone Oncology, Inc.
           Amendment No. 1 to Draft Registration Statement on Form S-1
           Submitted July 9, 2018
           CIK No. 0001656634

Dear Dr. Allen:

      We have reviewed your amended draft registration statement and have the
comments. In some of our comments, we may ask you to provide us with
information so we
may better understand your disclosure.

       Please respond to this letter by providing the requested information and
either submitting
an amended draft registration statement or publicly filing your registration
statement on
EDGAR. If you do not believe our comments apply to your facts and circumstances
or do not
believe an amendment is appropriate, please tell us why in your response.

        After reviewing the information you provide in response to these
comments and your
amended draft registration statement or filed registration statement, we may
have additional
comments. Unless we note otherwise, our references to prior comments are to
comments in our
June 3, 2018 letter.

Amendment No. 1 to Draft Registration Statement on Form S-1

License Agreement with Arbutus Biopharma Corporation, page 121

1.     We note your revised disclosure in response to prior comment 5. Please
expand to
       indicate when the last-to-expire patent is currently scheduled to
 Andrew Allen, M.D., Ph.D.
Gritstone Oncology, Inc.
July 18, 2018
Page 2

       You may contact Rolf Sundwall at 202-551-3105 or Jim B. Rosenberg at
202-551-3679 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Ada D. Sarmento at 202-551-3798 or Mary Beth Breslin at 202-551-3625
with any other

FirstName LastNameAndrew Allen, M.D., Ph.D.
                                                         Division of
Corporation Finance
Comapany NameGritstone Oncology, Inc.
                                                         Office of Healthcare &
July 18, 2018 Page 2
cc:       Brian J. Cuneo, Esq.
FirstName LastName