FOGHORN THERAPEUTICS INC. INCENTIVE STOCK OPTION AGREEMENT

Exhibit 10.13

FOGHORN THERAPEUTICS INC.

2020 EQUITY INCENTIVE PLAN

INCENTIVE STOCK OPTION AGREEMENT

This agreement (this “Agreement”) evidences a stock option granted by Foghorn Therapeutics Inc. (the “Company”) to the individual named above (the “Participant”), pursuant to and subject to the terms of the Foghorn Therapeutics Inc. 2020 Equity Incentive Plan (as from time to time amended and in effect, the “Plan”). Except as otherwise defined herein, all capitalized terms used herein have the same meaning as in the Plan.

1. Grant of the Stock Option. The Company grants to the Participant on the date set forth above (the “Date of Grant”) an option (the “Stock Option”) to purchase, pursuant to and subject to the terms set forth in this Agreement and in the Plan, up to the number of shares of Stock set forth above (the “Shares”) with an exercise price per Share as set forth above, in each case, subject to adjustment pursuant to Section 7 of the Plan in respect of transactions occurring after the date hereof.

The Stock Option evidenced by this Agreement is intended to be treated as an ISO to the maximum extent provided under the Code. To the extent the Stock Option does not qualify as an ISO, the Stock Option will be treated as an NSO. The Participant acknowledges and agrees that the Administrator may take any action permitted under the Plan without regard to the effect any such action or actions may have on the status of the Stock Option as a ISO and that such action or actions may cause the Stock Option to fail to be treated as an ISO. To the extent that the aggregate Fair Market Value (determined at the time of grant) of the Shares subject to the Stock Option and all other ISOs the Participant holds that are exercisable for the first time during any calendar year (under all plans of the Company and its subsidiaries) exceeds $100,000, the stock options held by the Participant or portions thereof that exceed such limit (according to the order in which they were granted in accordance with Section 422) will be treated as NSOs.

2. Vesting. The term “vest” as used herein with respect to the Stock Option or any portion thereof means to become exercisable, and the term “vested” with respect to the Stock Option or any portion thereof means that the Stock Option (or portion thereof) is then exercisable. Unless earlier terminated, forfeited, relinquished or expired, the Stock Option will vest [•].

3. Exercise of the Stock Option. No portion of the Stock Option may be exercised until such portion vests. Each election to exercise any vested portion of the Stock Option will be subject to the terms and conditions of the Plan and must be in written or electronic form acceptable to the Administrator, signed (including by electronic signature) by the Participant or, if at the relevant time the Stock Option has passed to the estate or beneficiary of the Participant or to a permitted transferee, such estate or beneficiary or permitted transferee. Each such written or

electronic exercise election must be received by the Company at its principal office or by such other party as the Administrator may prescribe and must be accompanied by payment in full of the exercise price by cash or check, through a broker-assisted exercise program acceptable to the Administrator, or as otherwise provided in the Plan. The latest date on which the Stock Option or any portion thereof may be exercised is the tenth (10th) anniversary of the Date of Grant (or the fifth (5th) anniversary, in the case of a ten percent (10%) stockholder within the meaning of Section 422(b)(6) of the Code) and, if not exercised by such date, the Stock Option or any remaining portion thereof will thereupon immediately terminate.

4. Cessation of Employment. If the Participant’s Employment ceases, except as expressly provided for in an employment agreement between the Participant and the Company that is in effect at the time of such termination, the Stock Option, to the extent not then vested, will be forfeited immediately for no consideration, and any vested portion of the Stock Option that is then outstanding will remain exercisable for the period described in Section 6(a)(4) of the Plan. The Participant acknowledges and agrees that in the event any portion of the Stock Option is exercised after the date that is three (3) months after the date of the cessation of the Participant’s employment with the Company and its subsidiaries (subject to certain limited exceptions), or any portion of the exercise price is satisfied through a broker-assisted exercise program, the Participant will lose the tax treatment afforded to ISOs under the Code with respect to any portion of the Stock Option so exercised.

5. Restrictions on Transfer; Disqualifying Dispositions. The Stock Option may not be transferred except as expressly permitted under Section 6(a)(3) of the Plan. If the Participant transfers or otherwise disposes of any Shares acquired upon exercise of the Stock Option within two (2) years from the Date of Grant or within one (1) year after such Shares were acquired pursuant to the exercise of the Stock Option, within fifteen (15) days following such transfer, the Participant will notify the Company in writing of such transfer or disposition.

6. Forfeiture; Recovery of Compensation. By accepting, or being deemed to have accepted, the Stock Option, the Participant expressly acknowledges and agrees that his or her rights, and those of any permitted transferee, with respect to the Stock Option, including the right to any Shares acquired under the Stock Option or proceeds from the disposition thereof, are subject to Section 6(a)(5) of the Plan (including any successor provision). The Participant further agrees to be bound by the terms of any clawback or recoupment policy of the Company that applies to incentive compensation that includes Awards such as the Stock Option. Nothing in the preceding sentence will be construed as limiting the general application of Section 8 of this Agreement.

7. Withholding. The Participant expressly acknowledges and agrees that the Participant’s rights hereunder, including the right to be issued Shares upon exercise of the Stock Option, are subject to the Participant promptly paying to the Company in cash or by check (or by such other means as may be acceptable to the Administrator) all taxes required to be withheld, if any. No Shares will be issued pursuant to the exercise of the Stock Option unless and until the person exercising the Stock Option has remitted to the Company an amount in cash sufficient to satisfy any federal, state or local tax withholding requirements, or has made other arrangements satisfactory to the Company with respect to such taxes. The Participant authorizes the Company and its subsidiaries to withhold the amount of such taxes from any amounts otherwise owed to the Participant, but nothing in this sentence will be construed as relieving the Participant of any liability for satisfying his or her obligation under the preceding provisions of this Section 7.

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8. Provisions of the Plan. This Agreement is subject in its entirety to the provisions of the Plan, which are incorporated herein by reference. A copy of the Plan as in effect on the Date of Grant has been made available to the Participant. By accepting, or being deemed to have accepted, the Stock Option, the Participant agrees to be bound by the terms of the Plan and this Agreement. In the event of any conflict between the terms of this Agreement and the Plan, the terms of the Plan will control.

9. Acknowledgements. This Agreement represents the entire agreement and understanding between the parties hereto with respect to the subject matter hereof, and supersedes all prior and contemporaneous communications, agreements and understandings, written or oral, relating thereto. This Agreement may be executed in counterparts (and may be delivered by email or other electronic means), each of which will be deemed an original and all of which together will constitute one and the same instrument.

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IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the date first written above.

[Signature Page to Stock Option Agreement]