EX-5.1

Exhibit 5.1

LOGO

July 28, 2023

Inozyme Pharma, Inc.

321 Summer Street, Suite 400

Boston, Massachusetts 02210

Re: Inozyme Pharma, Inc.

Registration Statement on Form S-3 (File No. 333-258702)

Ladies and Gentlemen:

This opinion is furnished to you in connection with (i) the above-referenced registration statement (the “Registration Statement”) on Form S-3 (filed by Inozyme Pharma, 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, shares of Common Stock, $0.0001 par value per share, of the Company (the “Common Stock”), and (ii) the prospectus supplement, dated July 27, 2023 (the “Prospectus Supplement” and, together with the prospectus contained in the Registration Statement, the “Prospectus”), relating to the issuance and sale by the Company pursuant to the Registration Statement of up to 14,375,000 shares of Common Stock, including up to 1,875,000 shares of Common Stock issuable upon exercise of an option to purchase additional shares granted by the Company (collectively, the “Shares”).

The Shares are to be offered and sold by the Company pursuant to an underwriting agreement, dated July 27, 2023 (the “Underwriting Agreement”), entered into by and among the Company and BofA Securities, Inc., Cowen and Company, L.L.C., and Piper Sandler & Co., as representatives of the several underwriters named in the Underwriting Agreement, which is being filed as Exhibit 1.1 to the Company’s Current Report on Form 8-K, filed on the date hereof.

We are acting as counsel for the Company in connection with the issue and sale by the Company of the Shares. We have examined and relied upon a signed copy of the Registration Statement and a copy of the Prospectus, each as filed with the Commission. We have also examined and relied upon the Underwriting Agreement, minutes of meetings and actions of the stockholders and the Board of Directors of the Company as provided to us by the Company, the Certificate of Incorporation and Bylaws 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.

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 such Shares are issued and paid for in accordance with the terms and conditions of the Underwriting Agreement, such Shares will be validly issued, fully paid and nonassessable.