Blueprint Medicines Corporation Gross-Up Payment Agreement Related to Sanofi Merger

Notwithstanding anything to the contrary in any Company Plan, if any compensatory payment or benefit (including payments and benefits received pursuant to this Agreement) you receive (or retain) in connection with the Merger, and the transactions contemplated by the Merger Agreement, from the Company or otherwise (each, a “Payment”), other than the Pro-rated 2025 Bonus (as defined in the Company Disclosure Letter to the Merger Agreement), would (i) constitute a “parachute payment” within the meaning of Section 280G of the Code, and (ii) be subject to the excise tax imposed by Section 4999 of the Code (the “Excise Tax”), then the Company shall pay, and you shall be entitled to receive from the Company, an additional payment or payments in an amount equal to such Excise Tax (the “Excise Tax Payment(s)”) plus the amount necessary to put you in the same after-tax position (taking into account (a) any income or employment taxes, (b) any interest or penalties imposed with respect to such taxes, and (c) any additional Excise Tax imposed by Section 4999 of the Code) as if you had not received the Excise Tax Payment(s) (the “Make Whole Payment(s)” and collectively with the Excise Tax Payment(s), the “Gross Up Payment(s)”). Notwithstanding anything to the contrary herein, the maximum aggregate value of the Gross-Up Payment(s) that may be paid to you and to any other individual who has entered into a substantially similar agreement with the Company that provides for tax reimbursement payments under Section 4999 of the Code in connection with the Merger, or to a taxing authority on your behalf or on behalf of any other such individuals, including any Gross-Up Payment(s) that may be payable in connection with an audit or contested audit, as described below, shall not exceed an aggregate amount of $25,000,000 (the “Maximum Payment Amount”) and, if the aggregate Gross-Up Payment(s) paid or payable to you and any other such individuals exceed the Maximum Payment Amount, then such Gross-Up Payment(s) shall be reduced proportionally such that the aggregate Gross-Up Payment(s) to you and any other individuals equals the Maximum Payment Amount, in such manner as may be determined by the Company at the time such Gross Up Payment(s) is to be made. The Company’s obligation to make any Gross-Up Payment(s) under this Agreement shall not be conditioned upon your continued employment or termination of employment or the reduction of any amount of payments or benefits otherwise due or payable to you in connection with the transactions contemplated by the Merger Agreement[; provided, that, contemporaneously with your execution of this Agreement, and in consideration thereof, you will enter into the Executive Restrictive Covenant Agreement, dated as of the date hereof].

All determinations required to be made under this Agreement, including whether and when a Gross-Up Payment is required, the amount of any such Gross-Up Payment, the allocation of the value of any mitigation actions and the assumptions to be utilized in arriving at such determination, shall be made by a public accounting firm or other consultant selected by, and acting at the direction of, Parent (the “Accounting Firm”). For purposes of this Agreement, “Accounting Firm” means Golden Parachute Tax Solutions LLC, provided, that, if Golden Parachute Tax Solutions LLC withdraws, or is terminated, from its provision of services to Parent with respect to this Agreement, then Accounting Firm shall mean an independent nationally recognized accounting firm or other consultant selected by Parent. For purposes of determining the amount of the Gross-Up Payment(s), you shall be deemed to have: (x) paid federal income taxes at the highest marginal rate of federal income and employment taxation applicable to you for the calendar year in which the Gross-Up Payment(s) (or a portion thereof) is to be made, and (y) paid applicable state and local income taxes at the highest rate of taxation applicable to you for the calendar year in which the Gross-Up Payment(s) (or a portion thereof) is to be made (based on the state in which you reside at the relevant time), net of the maximum reduction in federal income taxes which could be obtained from deduction of such state and local taxes. The Accounting Firm may make such other reasonable assumptions and approximations concerning applicable taxes and may rely on reasonable, good-faith interpretations concerning the application of Section 280G and 4999 of the Code to the Payments. The Company shall cause Parent to request that the Accounting Firm provide detailed supporting calculations to both Parent and you within fifteen (15) business days of a Payment or such earlier time as is reasonably requested by Parent. All fees and expenses of the Accounting Firm shall be borne solely by Parent or the Company. Parent shall have a reasonable opportunity to review and comment on any draft determination by the Accounting Firm, and Parent shall have the right, acting in good faith, to approve or reject the Accounting Firm’s determination. Following final approval by Parent, any such determination shall be binding upon Parent, the Company and you (unless such determination is later determined to be an Incorrect Determination (as defined below)).

You shall notify the Parent in writing of any claim by any taxing authority that, if successful, would require the payment by the Company of any Gross-Up Payment(s). Such notification shall be given as soon as practicable, but no later than ten (10) business days after you are informed in writing of such claim. You are required to provide the Parent with a copy of the notice of claim by the taxing authority and the date set forth in the claim that the taxing authority specifies as the due date for payment of such claim. You may not pay such claim prior to the expiration of the thirty (30) day period following the date on which you give such notice to Parent (or such shorter period ending on the date that any payment of taxes with respect to such claim is due).

If, after the receipt by you of any Gross-Up Payment(s) or payment by the Company of an amount on your behalf pursuant to this Agreement, you become entitled to receive any refund with respect to the Excise Tax or the Gross-Up Payment(s), as determined by you and/or your personal accountants, in good faith, following good faith consultation with Parent or the Company, you shall promptly pay to the Company the amount of such refund following receipt thereof (together with any interest paid or credited thereon after taxes applicable thereto). If, after payment by the Company of an amount on your behalf, a determination is made that you shall not be entitled to any refund with respect to such claim and Parent or the Company does not notify you in writing of its intent to contest such denial of refund prior to the expiration of thirty (30) days after such determination, then the amount of such payment shall offset, to the extent thereof, the amount of the Gross-Up Payment(s) required to be paid and shall count towards the Maximum Payment Amount.

It is intended that the Gross-Up Payment(s) satisfy an exemption from, or comply with, Section 409A of the Code and the Treasury Regulations promulgated thereunder. To the maximum extent possible, this Agreement shall be construed accordingly.

Any Gross-Up Payment(s), as determined pursuant to this Agreement, shall be paid by the Company to you (subject to all required applicable withholdings) no later than the date that the corresponding withholding of the Excise Tax is required to be remitted to the Internal Revenue Service or any other applicable taxing authority or, in the case of amounts relating to a claim described in Section 3 that does not result in the remittance of any federal, state, local and foreign income, excise, social security and other taxes, the calendar year in which the claim is finally settled or otherwise resolved. Notwithstanding any other provision of this Agreement, the Company may, in its sole discretion, withhold and pay over to the Internal Revenue Service or any other applicable taxing authority, for the benefit of you, all or any portion of any Gross-Up Payment(s), and you hereby consent to such withholding and such amounts withheld shall count towards the Maximum Payment Amount.

This Agreement is intended to bind and inure to the benefit of and be enforceable by you, the Company, and the Surviving Corporation and upon any other person or entity who is a successor by merger, acquisition, consolidation or otherwise to the business formerly carried on by the Company, and their respective successors, assigns, heirs, executors and administrators, without regard to whether or not such person or entity actively assumes any rights or duties hereunder; provided, however, that (i) you may not assign any duties hereunder and may not assign any rights hereunder (other than by will or the laws of descent and distribution) without the written consent of the Company, which consent shall not be withheld unreasonably and (ii) the Company may not assign any duties or rights hereunder (other than to an Affiliate, in which case the Company, as applicable, shall remain liable hereunder) without your written consent, which consent shall not be unreasonably withheld, conditioned or delayed. If you shall die while any amounts would be payable to you hereunder had you continued to live, all such amounts, unless otherwise provided herein, shall be paid in accordance with the terms of this Agreement to such person or persons appointed in writing to you to receive such amounts or, if no person is so appointed, to your estate. This Agreement sets forth the entire agreement between you and the Company with respect to Sections 280G and 4999 of the Code and any Gross-Up Payment(s) to be provided to you or on your behalf relating to such Sections 280G and 4999, and supersedes all prior and contemporaneous communications, agreements, and understandings, written or oral, with respect thereto, including but not limited to Section 5(b) of your written employment agreement with the Company. This Agreement may not be modified or amended, and no breach shall be deemed to be waived, unless agreed to in writing by you and the Company. This Agreement may be executed in two or more counterparts, each of which shall be an original and all of which together shall constitute one and the same instrument. The parties agree that this Agreement may be executed and delivered by electronic signatures and that the signatures appearing on this Agreement are the same as handwritten signatures for the purposes of validity, enforceability and admissibility. This is a Massachusetts contract and shall be governed and construed in accordance with the laws of the Commonwealth of Massachusetts, without regard to any conflict of laws principles that would result in the application of the laws of any other jurisdiction.

Any controversy or claim arising out of or relating to this Agreement or the breach thereof shall, to the fullest extent permitted by law, be settled by arbitration in any forum and form agreed upon by the parties or, in the absence of such an agreement, under the auspices of the American Arbitration Association (“AAA”) in Boston, Massachusetts in accordance with the Employment Dispute Resolution Rules of the AAA, including, but not limited to, the rules and procedures applicable to the selection of arbitrators. In the event that any person or entity other than you or the Company, as applicable, may be a party with regard to any such controversy or claim, such controversy or claim shall be submitted to arbitration subject to such other person or entity’s agreement. Judgment upon the award rendered by the arbitrator may be entered in any court having jurisdiction thereof. This Section 8 shall be specifically enforceable. The parties expressly waive the right to a jury trial for all claims subject to this arbitration provision. Notwithstanding the foregoing, this Section 8 shall not preclude either party from pursuing a court action for the sole purpose of obtaining a temporary restraining order or a preliminary injunction in circumstances in which such relief is appropriate; provided that any other relief shall be pursued through an arbitration proceeding pursuant to this Section 8.

All notices, requests, claims, demands and other communications hereunder must be in writing and must be given (and will be deemed to have been duly given): (a) when delivered, if delivered in Person, (b) when sent, if sent by email, (c) three (3) Business Days after sending, if sent by registered or certified mail (postage prepaid, return receipt requested) and (d) one (1) Business Day after sending, if sent by overnight courier, in each case, to the respective parties at the following addresses (or at such other address for a party as has been specified by like notice):

if to Parent or the Company:

if to you: