Exhibit 1.1

AMENDMENT NO. 1 TO THE SALES AGREEMENT

July 7, 2021

JEFFERIES LLC

520 Madison Avenue

New York, New York 10022

Ladies and Gentlemen:

This Amendment No. 1 to the Sales Agreement (this “Amendment”) is entered into as of the date first written above by Beam Therapeutics Inc., a Delaware corporation (the “Company”), and Jefferies LLC (the “Agent”), that are parties to that certain Sales Agreement, dated April 1, 2021 (the “Original Agreement”) relating to the offering of up to $300,000,000 of the Company’s Common Shares (as defined below).

On the date hereof, the Company has filed or will file a Prospectus Supplement relating to the offering of an additional $500,000,000 of the Company’s Common Shares.

This amendment, among other items, increases the aggregate offering price to $800,000,000. All capitalized terms not defined herein shall have the meanings ascribed to them in the Original Agreement (the “July Prospectus Supplement”).

The parties, intending to be legally bound, hereby amend the Original Agreement as follows:

1. The preamble to the Original Agreement is hereby deleted in its entirety and replaced with the following:

“Beam Therapeutics Inc., a Delaware corporation (the “Company”), proposes, subject to the terms and conditions stated herein, to issue and sell from time to time through Jefferies LLC, as sales agent and/or principal (the “Agent”), shares of the Company’s common stock, par value $0.01 per share (the “Common Shares”), having an aggregate offering price of up to $800,000,000 on the terms set forth in this sales agreement (this “Agreement”).”

2. For the avoidance of doubt, any reference to “Prospectus” in the Original Agreement shall be deemed to include the July 2021 Prospectus Supplement.

3. Section 4(p) of the Original Agreement is hereby amended as follows:

“Opinion and 10b-5 Statement of Counsel for the Company. (i) On or prior to the date of the first Issuance Notice and on or prior to each Triggering Event Date occurring on or before July 1, 2021, Ropes & Gray LLP shall have furnished to the Agent their written opinion and 10b-5 statement, as the case may be, in form and substance reasonably satisfactory to the Representatives, and (ii) on or prior to each Triggering Event Date occurring after July 1, 2021, Wilmer Cuttler Pickering Hale and Dorr LLP, counsel for the Company, shall have furnished to the Agent their written opinion and 10b-5 statement in form and substance reasonably satisfactory to the Representatives.”

4. The fourth paragraph of Section 8(d) of the Original Agreement is hereby deleted in its entirety and replaced with the following:

“Wilmer Cutler Pickering Hale and Dorr LLP

60 State Street

Boston, Massachusetts 02109

Facsimile: (617) 526-5000

Attention: Cynthia T. Mazareas”

5. The Company represents and warrants to, and agrees with the Agent that: (a) this Amendment has been duly authorized, executed and delivered by, and is a valid and binding agreement of, the Company, enforceable in accordance with its terms, except as rights to indemnification hereunder may be limited by applicable law and except as the enforcement hereof may be limited by bankruptcy, insolvency, reorganization, moratorium or other similar laws relating to or affecting the rights and remedies of creditors or by general equitable principles; and (b) that on the date hereof, the Company will file a Prospectus Supplement pursuant to Rule 424(b) under the Securities Act reflecting this Amendment and a Current Report on Form 8-K disclosing this Amendment.

6. Without limiting any other agreement, including Section 3(d), as applicable, the Company agrees to pay all costs, fees and expenses incurred in connection with entering into this Amendment and the performance of the Company’s obligations under the Original Agreement as amended by this Amendment and the transactions contemplated hereby and thereby, including without limitation, (i) all filing fees, attorneys’ fees and expenses incurred by the Company or any Agent in connection with qualifying or registering (or obtaining exemptions from the qualification or registration of) all or any part of the Shares authorized by this Amendment for offer and sale under the state securities or blue sky laws or the provincial securities laws of Canada, and, if requested by an Agent, preparing and printing a “Blue Sky Survey” or memorandum and a “Canadian wrapper” and any supplements thereto, advising the Agent of such qualifications, registrations, determinations and exemptions and (ii) the reasonable fees and disbursements of the Agent’s counsel, including the reasonable fees and expenses of counsel for the Agent in connection with, FINRA review, if any, and approval of the Agent’s participation in the offering and distribution of the Shares authorized by this Amendment. The fees and disbursements of Agent’s counsel pursuant to subsections (i) and (ii) above shall not exceed $75,000. For the avoidance of doubt, the $75,0000 of fees and disbursements of Agent’s counsel that may become payable by the Company hereunder shall be in addition to the fees and disbursements of Agent’s counsel in connection with entering into the Original Agreement that are payable by the Company under Section 3(d) of the Original Agreement and up to $25,000 of fees and disbursements of Agent’s Counsel that may become payable by the Company pursuant to Section 3(d) of the Original Agreement in connection with each Triggering Event Date on which the Company is required to provide a certificate pursuant to Section 4(o) of the Original Agreement.

7. The Original Agreement, as amended by this Amendment, agreement of the parties to this Agreement and supersedes all prior written or oral and all contemporaneous oral agreements, understandings and negotiations with respect to the subject matter hereof. This Amendment may not be amended or modified unless in writing by all of the parties hereto, and no condition herein (express or implied) may be waived unless waived in writing by each party whom the condition is meant to benefit. The Section headings herein are for the convenience of the parties only and shall not affect the construction or interpretation of this Amendment.

8. The invalidity or unenforceability of any section, paragraph or provision of this Amendment shall not affect the validity or enforceability of any other section, paragraph or provision hereof. If any section, paragraph or provision of this Amendment is for any reason determined to be invalid or unenforceable, there shall be deemed to be made such minor changes (and only such minor changes) as are necessary to make it valid and enforceable. All references in the Original Agreement to the “Agreement” shall mean the Original Agreement as amended by this Amendment; provided, however, that all references to “date of this Agreement” in the Original Agreement shall continue to refer to the date of the Original Agreement, unless amended otherwise herein and except with respect to the first paragraph of Section 2, Section 2(b) “Compliance with Registration Requirements,” and Section 8(a) “Press Release and Disclosure,” where references to “date of this Agreement” in the Original Agreement shall mean refer to each of the date of the Original Agreement and the date of this Amendment.

9. This Amendment shall be governed by and construed in accordance with the internal laws of the State of New York applicable to agreements made and to be performed in such state. Any legal suit, action or proceeding arising out of or based upon this Amendment or the transactions contemplated hereby or by the Original Agreement may be instituted in the federal courts of the United States of America located in the Borough of Manhattan in the City of New York or the courts of the State of New York in each case located in the Borough of Manhattan in the City of New York (collectively, the “Specified Courts”), and each party irrevocably submits to the exclusive jurisdiction (except for proceedings instituted in regard to the enforcement of a judgment of any such court, as to which such jurisdiction is non-exclusive) of such courts in any such suit, action or proceeding. Service of any process, summons, notice or document by mail to such party’s address set forth in the Original Agreement shall be effective service of process for any suit, action or other proceeding brought in any such court. The parties irrevocably and unconditionally waive any objection to the laying of venue of any suit, action or other proceeding in the Specified Courts and irrevocably and unconditionally waive and agree not to plead or claim in any such court that any such suit, action or other proceeding brought in any such court has been brought in an inconvenient forum.

10. This Amendment may be executed in any number of counterparts, each of which shall be deemed to be an original, but all such counterparts shall together constitute one and the same instrument. Delivery of an executed amendment by one party to the other may be made by facsimile, electronic mail or other transmission method as permitted by applicable law, and the parties hereto agree that any counterpart so delivered shall be deemed to have been duly and validly delivered and be valid and effective for all purposes. A party’s electronic signature (complying with the New York Electronic Signatures and Records Act (N.Y. State Tech. §§ 301-309), as amended from time to time, or other applicable law) of this Amendment shall have the same validity and effect as a signature affixed by the party’s hand.

[Remainder of Page Intentionally Blank]

If the foregoing correctly sets forth the understanding between the Company and the Agent, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding amendment to the Original Agreement between the Company and the Agent.

[Signature Page to Amendment No. 1 to the Sales Agreement]

Exhibit 5.1

Beam Therapeutics Inc.

26 Landsdowne Street

Cambridge, MA 02139

Ladies and Gentlemen:

This opinion is being furnished to you in connection with (i) the Registration Statement on Form S-3ASR (File No. 333-254946) (the “Registration Statement”) filed by Beam Therapeutics Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), for the registration of, among other things, an indeterminate number of shares of Common Stock, $0.01 par value per share, of the Company, which may be issued from time to time on a delayed or continuous basis pursuant to Rule 415 under the Securities Act, as set forth in the Registration Statement and the prospectus contained therein (the “Base Prospectus”) and (ii) the prospectus supplement, dated July 7, 2021 (the “Prospectus Supplement” and, together with the Base Prospectus, the “Prospectus”) relating to the issuance and sale from time to time by the Company of shares of Common Stock with an aggregate offering price of up to $500,000,000 (the “Shares”).

The Shares are to be issued and sold by the Company pursuant to a Sales Agreement, dated August 1, 2021, as amended by Amendment No. 1 to Sales Agreement, dated as of July 7, 2021, (as amended, the “Sales Agreement”), between the Company and Jefferies LLC. We are acting as counsel for the Company in connection with the issue and sale by the Company of the Shares. We have examined copies of the Registration Statement and the Prospectus as filed with the Commission. We have also examined and relied upon the Sales Agreement, minutes of meetings of the stockholders and the Board of Directors of the Company, including committees thereof as provided to us by the Company, stock record books of the Company as provided to us by the Company, the Certificate of Incorporation and By-laws of the Company, each as restated and/or amended to date, and such other documents as we have deemed necessary for purposes of rendering the opinions hereinafter set forth.

In our examination of the foregoing documents, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as copies, the authenticity of the originals of such latter documents and the legal competence of all signatories to such documents. Further, we have assumed that the Company will not issue and sell pursuant to the Sales Agreement such number of Shares that would cause the Company not to satisfy the eligibility requirements for Form S-3ASR (including Instruction I.B.6. thereof).

We express no opinion herein as to the laws of any state or jurisdiction other than the General Corporation Law of the State of Delaware and the federal laws of the United States of America.

Based upon and subject to the foregoing, we are of the opinion that the Shares have been duly authorized for issuance and, when the Shares are issued and paid for in accordance with the terms and conditions of the Sales Agreement, the Shares will be validly issued, fully paid and nonassessable.

Please note that we are opining only as to the matters expressly set forth herein, and no opinion should be inferred as to any other matters. This opinion is based upon currently existing statutes, rules, regulations and judicial decisions, and we disclaim any obligation to advise you of any change in any of these sources of law or subsequent legal or factual developments which might affect any matters or opinions set forth herein.

We hereby consent to the filing of this opinion with the Commission in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act as an exhibit to the Current Report on Form 8-K to be filed by the Company on the date hereof in connection with the issuance and sale of the Shares and to the use of our name therein and in the related Prospectus Supplement under the caption “Legal Matters.” In giving such consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

Very truly yours,

WILMER CUTLER PICKERING

HALE AND DORR LLP