Andrew Anzalone Confidentiality, Assignment and Nonsolicitation Agreement, dated October 16, 2020

In consideration and as a condition of the commencement of my employment or my continued employment by Prime Medicine, Inc. (including its subsidiaries and other affiliates and its and their successors and assigns, the “Company”), I enter into this Employee Confidentiality, Assignment and Nonsolicitation Agreement (the “Agreement”) and agree as follows:

1. Proprietary Information. I agree that all information, whether or not in writing, concerning the Company’s business, technology, business relationships or financial affairs that the Company has not released to the general public (collectively, “Proprietary Information”) and all tangible embodiments thereof are and will be the exclusive property of the Company. By way of illustration, Proprietary Information may include information or material that has not been made generally available to the public, such as: (a) corporate information, including plans, strategies, methods, policies, resolutions, negotiations or litigation; (b) marketing information, including strategies, methods, customer or business partner identities or other information about customers, business partners, prospect identities or other information about prospects, or market analyses or projections; (c) financial information, including cost and performance data, debt arrangements, equity structure, investors and holdings, purchasing and sales data and price lists; (d) operational and technological or scientific information, including plans, specifications, manuals, forms, templates, software, pre-clinical and clinical testing data and strategies, research and development strategies, designs, methods, procedures, formulae, data, reports, discoveries, inventions, improvements, concepts, ideas, and other Developments (as defined below), know-how and trade secrets; and (e) personnel information, including personnel lists, reporting or organizational structure, resumes, personnel data, performance evaluations and termination arrangements or documents. By way of further illustration, Proprietary Information does not include any information or material that I knew prior to the commencement of my service at the Company, whether as an employee or as a consultant, as evidenced by tangible and contemporaneous record (such excluded information, “Excluded Information”). Proprietary Information also includes information received in confidence by the Company from its customers, suppliers, business partners or other third parties except Excluded Information.

2. Recognition of Company’s Rights. I will not, at any time, without the Company’s prior written permission, either during or after my employment, disclose any Proprietary Information to anyone outside of the Company except in the good faith performance of my duties to the Company as directed by the Chief Executive Officer of the Company (the “CEO”) or another duly authorized officer of the Company, or use or permit to be used any Proprietary Information for any purpose other than the performance of my duties as an employee of the Company. I will reasonably cooperate with the Company and use reasonable efforts at Company’s expense to prevent the unauthorized disclosure of all Proprietary Information. I will deliver to the Company all copies and other tangible embodiments of Proprietary Information in my possession or control upon the earlier of a request by the Company or termination of my employment.

3. Rights of Others. I understand that the Company is now and may hereafter be subject to nondisclosure or confidentiality agreements with third persons that require the Company to protect or refrain from use or disclosure of proprietary information. I agree to be bound by the terms of such agreements in the event I have access to such proprietary information to the extent that they do not conflict with the provisions hereof with respect to what constitutes Proprietary Information and are otherwise reasonable in their terms. I understand that the Company strictly prohibits me from using or disclosing confidential or proprietary information that I know or believe to belong to any other person or entity (including any employer or former employer), in connection with my employment consistent with the provisions hereof with respect to what constitutes Proprietary Information. In addition, I agree not to bring any confidential information that I know or believe to belong to any other person or entity onto Company premises or into Company workspaces.

4. Commitment to Company; Avoidance of Conflict of Interest. Subject to the terms of my offer letter with the Company, while an employee of the Company, I will devote my full-time efforts to the Company’s business and I will not, directly or indirectly, engage in any other business activity, except as expressly authorized in writing and in advance by the CEO. I will advise the CEO at such time as any activity of either the Company or another business presents me with a conflict of interest or the appearance of a conflict of interest as an employee of the Company. I

will take whatever reasonable action is requested of me by the Company to resolve any conflict or appearance of conflict which it finds to exist.

5. Developments. I will make full and prompt disclosure to the Company of all inventions, discoveries, designs, developments, methods, modifications, improvements, processes, algorithms, data, databases, computer programs, research, formulae, techniques, trade secrets, graphics or images, and audio or visual works and other works of authorship, and other intellectual property, including works-in-process (collectively “Developments”) whether or not patentable or copyrightable, that are created, made, conceived or reduced to practice by me (alone or jointly with others) or under my direction during the period of my employment. I acknowledge that all work performed by me is on a “work for hire” basis, and I hereby do assign and transfer and, to the extent any such assignment cannot be made at present, will assign and transfer, to the Company and its successors and assigns all my right, title and interest in and to all Developments that (a) relate to the business of the Company or any of the products or services being researched, developed, manufactured or sold by the Company or which may be used with such products or services; or (b) result from tasks assigned to me by the Company; or (c) result from the use of premises or personal property (whether tangible or intangible) owned, leased or contracted for by the Company (“Company-Related Developments”), and all related patents, patent applications, trademarks and trademark applications, copyrights and copyright applications, sui generis database rights and other intellectual property rights in all countries and territories worldwide and under any international conventions (“Intellectual Property Rights”).

To preclude any possible uncertainty, if there are any Developments that I have, alone or jointly with others, conceived, developed or reduced to practice prior to the commencement of my employment with the Company that I consider to be my property or the property of third parties and that I wish to have excluded from the scope of this Agreement (“Prior Inventions”), I have set forth on Exhibit A attached hereto a complete list of those Prior Inventions. If disclosure of any such Prior Invention would cause me to violate any prior confidentiality agreement, I understand that I am not to list such Prior Inventions in Exhibit A but am only to disclose a cursory name for each such invention, a listing of the party(ies) to whom it belongs and the fact that full disclosure as to such inventions has not been made for that reason. If there are any patents or patent applications in which I am named as an inventor, other than those that have been assigned to the Company (“Other Patent Rights”), I have also listed those Other Patent Rights on Exhibit A. If no such disclosure is attached, I represent that there are no Prior Inventions or Other Patent Rights. If, in the course of my employment with the Company, I incorporate a Prior Invention into a Company product, process or machine, research or development program, or other work done for the Company, I hereby grant to the Company a nonexclusive, royalty-free, fully paid-up, irrevocable, worldwide license (with the full right to sublicense through multiple tiers) to make, have made, modify, use, sell, offer for sale and import such Prior Invention. Notwithstanding the foregoing, I will not incorporate, or permit to be incorporated, Prior Inventions in any Company-Related Development without the Company’s prior written consent.

This Agreement does not obligate me to assign to the Company any Development that, in the sole judgment of the Company, reasonably exercised, is developed entirely on my own time and does not relate to the business efforts or research and development efforts in which, during the period of my employment, the Company actually is engaged or reasonably would be engaged, and does not result from the use of premises or equipment owned or leased by the Company. However, I will also promptly disclose to the Company any such Developments for the purpose of determining whether they qualify for such exclusion. I understand that to the extent this Agreement is required to be construed in accordance with the laws of any state which precludes a requirement in an employee agreement to assign certain classes of inventions made by an employee, this Section 5 will be interpreted not to apply to any invention that a court rules and/or the Company agrees falls within such classes. I also hereby waive all claims to any moral rights or other special rights that I may have or accrue in any Company-Related Developments.

6. Documents and Other Materials. I will keep and maintain adequate and current records of all Proprietary Information and Company-Related Developments developed by me during my employment, which records will be available to and remain the sole property of the Company at all times.

All files, letters, notes, memoranda, reports, records, data, sketches, drawings, notebooks, layouts, charts, quotations and proposals, specification sheets, blueprints, models, prototypes, or other written, photographic or other tangible material containing Proprietary Information, whether created by me or others, which come into my custody or

possession, are the exclusive property of the Company to be used by me only in the performance of my duties for the Company. Any property situated on the Company’s premises and owned by the Company, including without limitation computers, disks and other storage media, filing cabinets or other work areas, is subject to inspection by the Company at any time with or without notice. In the event of the termination of my employment for any reason, I will deliver to the Company all Company property and equipment in my possession, custody or control, including all files, letters, notes, memoranda, reports, records, data, sketches, drawings, notebooks, layouts, charts, quotations and proposals, specification sheets, blueprints, models, prototypes, or other written, photographic or other tangible material containing Proprietary Information, and other materials of any nature pertaining to the Proprietary Information of the Company and to my work, and will not take or keep in my possession any of the foregoing or any copies.

7. Enforcement of Intellectual Property Rights. I will cooperate fully with the Company, at Company’s expense, both during and after my employment with the Company, with respect to the procurement, maintenance and enforcement of Intellectual Property Rights in Company-Related Developments. I will sign, both during and after my employment, all papers, including without limitation copyright applications, patent applications, declarations, oaths, assignments of priority rights, and powers of attorney, which the Company may deem necessary or desirable in order to protect its rights and interests in any Company-Related Development or Intellectual Property Rights therein, subject to the provisions and statements in such documents being acceptable to me.

8. Nonsolicitation.

In order to protect the Company’s Proprietary Information and goodwill, during my employment and for a period of: (i) one (1) year following the date of the cessation of my employment with the Company (the “Last Date of Employment”), or (ii) two (2) years following the Last Date of Employment if a court of competent jurisdiction determines that I have breached my fiduciary duty to the Company or if I have unlawfully taken, physically or electronically, property belonging to the Company (in either case the “Restricted Period”):

(a)    I shall not, directly or indirectly, in any manner, other than for the benefit of the Company, solicit or transact any business with any of the customers of the Company or any of its vendors. For purposes of this Agreement, (i) customers shall include then current customers to which the Company provided products or services during the twelve months prior to the Last Date of Employment (the “One Year Lookback”) and customer prospects that the Company solicited during the One Year Lookback and that I had significant contact with or learned confidential information about in the course of my employment, and (ii) vendors shall include then current vendors and vendors that provided services to or in connection with the Company during the One Year Lookback.

(b)    I shall not, directly or indirectly, in any manner, solicit, entice or attempt to persuade any employee or consultant of the Company to leave the Company for any reason or otherwise participate in or facilitate the hire, directly or through another entity, of any person who is then employed or engaged by the Company.

9. Government Contracts. I acknowledge that the Company may have from time to time agreements with other persons or with the United States Government or its agencies that impose obligations or restrictions on the Company regarding inventions made during the course of work under such agreements or regarding the confidential nature of such work. I agree to comply with any such obligations or restrictions upon the direction of the Company. In addition to the rights assigned under Section 5, I also assign to the Company (or any of its nominees) all rights that I have or acquired in any Developments, full title to which is required to be in the United States under any contract between the Company and the United States or any of its agencies.

10. Prior Agreements. I hereby represent that, except as I have fully disclosed previously in writing to the Company, I am not bound by the terms of any agreement with any previous or current employer or other party to refrain from using or disclosing any trade secret or confidential or proprietary information in the course of my employment with the Company or to refrain from competing, directly or indirectly, with the business of such employer or any other party. I further represent that my performance of all the terms of this Agreement as an employee of the Company does not and will not breach any agreement to keep in confidence proprietary information, knowledge or data acquired by me in confidence or in trust prior to my employment with the Company.

I will not disclose to the Company or induce the Company to use any confidential or proprietary information or material belonging to any previous employer or others.

11. Remedies Upon Breach. I understand that the restrictions contained in this Agreement are necessary for the protection of the business and goodwill of the Company and I consider them to be reasonable for such purpose. Any breach of this Agreement is likely to cause the Company substantial and irrevocable damage and therefore, in the event of such breach, the Company, in addition to such other remedies which may be available, will be entitled to specific performance and other injunctive relief, without the posting of a bond. I further acknowledge that a court may render an award extending the Restricted Period as one of the remedies in the event of my violation of this Agreement. In the event that Company seeks injunctive relief, Company shall provide me at least five business days advance written notice of any hearing. Such notice shall include copies of any court filings and be by overnight delivery service at my personal address, and also by email.

12. Use of Voice, Image and Likeness. I give the Company permission to use any and all of my voice, image and likeness, with or without using my name, in connection with the products and/or services of the Company, for the purposes of advertising and promoting such products and/or services and/or the Company, and/or for other purposes deemed appropriate by the Company in its reasonable discretion, except to the extent prohibited by law.

13. No Employment Obligation. I understand that this Agreement does not create an obligation on the Company or any other person to continue my employment. I acknowledge that, unless otherwise agreed in a formal written employment agreement signed on behalf of the Company by CEO or another duly authorized officer of the Company, my employment with the Company is at will and therefore may be terminated by the Company or me at any time and for any reason, with or without cause.

14. Survival and Assignment by the Company. I understand that my obligations under this Agreement will continue in accordance with its express terms regardless of any changes in my title, position, duties, salary, compensation or benefits or other terms and conditions of employment. I further understand that my obligations under this Agreement will continue following the termination of my employment regardless of the manner of such termination and will be binding upon my heirs, executors and administrators. The Company will have the right to assign this Agreement to its affiliates, successors and assigns. I expressly consent to be bound by the provisions of this Agreement for the benefit of the Company or any parent, subsidiary or affiliate to whose employ I may be transferred without the necessity that this Agreement be resigned at the time of such transfer.

15. Post-Employment Notifications. During the Restricted Period, I will notify the Company of any change in my address and of each subsequent employment or business activity, including the name and address of my employer or other post-Company employment plans and the nature of my activities.

16. Disclosures During Restricted Period. I will provide a copy of this Agreement to any person or entity with whom I may enter into a business relationship, whether as an employee, consultant, partner, coventurer or otherwise, prior to entering into such business relationship during the Restricted Period.

17. Severability. In case any provisions (or portions thereof) contained in this Agreement shall, for any reason, be held invalid, illegal or unenforceable in any respect, such invalidity, illegality or unenforceability shall not affect the other provisions of this Agreement, and this Agreement shall be construed as if such invalid, illegal or unenforceable provision had never been contained herein. If, moreover, any one or more of the provisions contained in this Agreement shall for any reason be held to be excessively broad as to duration, geographical scope, activity or subject, it shall be construed by limiting and reducing it, so as to be enforceable to the extent compatible with the applicable law as it shall then appear.

18. Waiver. I acknowledge and agree that no waiver of any of my obligations under this Agreement shall be effective unless made in writing by the Company. The failure of the Company to require my performance of any term or obligation of this Agreement, or the waiver of any breach of this Agreement, shall not prevent the Company’s subsequent enforcement of such term or obligation or be deemed a waiver of any subsequent breach.

19. Choice of Law and Jurisdiction. This Agreement will be deemed to be made and entered into in the Commonwealth of Massachusetts, and will in all respects be interpreted, enforced and governed under the laws of the Commonwealth of Massachusetts. I hereby consent to personal jurisdiction of the state and federal courts situated within Massachusetts for purposes of enforcing this Agreement, and waive any objection that I might have to personal jurisdiction or venue in those courts.

20. Protected Disclosures. I understand that nothing contained in this Agreement limits my ability to communicate with any federal, state or local governmental agency or commission or if required pursuant to applicable law, court order or subpoena, including to provide documents or other information, without notice to the Company. I also understand that nothing in this Agreement limits my ability to share compensation information concerning myself or others, except that this does not permit me to disclose compensation information concerning others that I obtain because my job responsibilities require or allow access to such information. Nothing in this Agreement prohibits me from providing documents or truthful testimony to the minimum extent reasonably necessary in pursuing or defending against any claim pursuant to any litigation or arbitration between me and the Company or any of its affiliates.

21. Defend Trade Secrets Act of 2016. I understand that pursuant to the federal Defend Trade Secrets Act of 2016, I shall not be held criminally or civilly liable under any federal or state trade secret law for the disclosure of a trade secret that (a) is made (i) in confidence to a federal, state, or local government official, either directly or indirectly, or to an attorney; and (ii) solely for the purpose of reporting or investigating a suspected violation of law; or (b) is made in a complaint or other document filed in a lawsuit or other proceeding, if such filing is made under seal.

22. Entire Agreement; Amendment. This Agreement constitutes the entire agreement between the Company and me with respect to the subject matter hereof, and supersedes all prior agreements or understandings, both written and oral, between the Company and me with respect to the subject matter hereof, but does not in any way merge with or supersede any other confidentiality, assignment of inventions or other restrictive covenant agreement or obligation entered into by the Company and me, which agreements and obligations shall supplement, and shall not limit or be limited by, this Agreement. This Agreement may be amended only in a written agreement executed by the CEO or another duly authorized officer of the Company and me.

IN WITNESS WHEREOF, the undersigned has executed this agreement as a sealed instrument as of the date set forth below.

SUBJECT:    Prior Inventions

The following is a complete list of all inventions or improvements relevant to the subject matter of my employment by the Company that have been made or conceived or first reduced to practice by me alone or jointly with others prior to my engagement by the Company: