Exercise of Option. Effective as of today, , the undersigned (the “Optionee”) hereby elects to exercise Optionee’s option to purchase shares of the Common Stock (the “Shares”) of Gritstone Oncology, Inc., a Delaware corporation (the “Company”), under and pursuant to the Gritstone Oncology, Inc. 2015 Equity Incentive Plan, as amended from time to time (the “Plan”), and the Stock Option Grant Notice and Stock Option Agreement, dated (the “Option Agreement”). Capitalized terms used herein without definition shall have the meanings given in the Option Agreement.

Pursuant to the Stock Option Grant Notice (the “Grant Notice”) to which this Stock Option Agreement (the “Agreement”) is attached, Gritstone Oncology, Inc., a Delaware corporation (the “Company”), has granted to Optionee (as set forth in the Grant Notice) an option to purchase the number of Shares (as defined in the Grant Notice) under the Gritstone Oncology, Inc. 2015 Equity Incentive Plan (the “Plan”) indicated in the Grant Notice at the exercise price per share set forth in the Grant Notice (the “Exercise Price”).

Pursuant to its 2015 Equity Incentive Plan, as amended from time to time (the “Plan”), Gritstone Oncology, Inc., a Delaware corporation (the “Company”), hereby grants to the individual listed below (the “Optionee”), an option to purchase the number of shares of the Company’s Common Stock set forth below (the “Option”), subject to the terms and conditions set forth herein, in the Plan, and in the certain Stock Option Agreement attached hereto as Exhibit A (the “Option Agreement”), each of which is incorporated herein by reference. Unless otherwise defined herein, the terms defined in the Plan shall have the same defined meanings in this Stock Option Grant Notice (the “Grant Notice”) and the Option Agreement.

In connection with the purchase of the above-listed shares of Common Stock (the “Securities”) of Gritstone Oncology, Inc., a Delaware corporation (the “Company”), the undersigned (the “Optionee”) represents to the Company the following: