Transcode Therapeutics, Inc.

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APPENDIX A​

AMENDMENT NO. 2 TO

2021 STOCK OPTION AND INCENTIVE PLAN

WHEREAS, TransCode Therapeutics, Inc. (the “Company”) maintains the TransCode Therapeutics, Inc. 2021 Stock Option and Incentive Plan (the “Plan”) which was previously adopted by the Board of Directors of the Company (the “Board”);

WHEREAS, the Board believes that the number of shares of Stock (as defined in the Plan) remaining available for issuance under the Plan has become insufficient for the Company’s anticipated future needs under the Plan;

WHEREAS, the Board has determined that it is advisable and in the best interest of the Company and its stockholders to amend the Plan to increase the aggregate number of shares of Stock reserved for issuance under the Plan by 166,724 shares; and

WHEREAS, Section 16 of the Plan provides that the Board may amend the Plan at any time, subject to certain conditions set forth therein.

NOW, THEREFORE, the Plan is amended as follows:

Amendment of the Plan.

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Section 3(a) of the Plan is hereby amended and restated in its entirety to read as follows:

“Stock Issuable. As of the date of the Company’s 2025 Annual Meeting of Stockholders, the maximum number of shares of Stock reserved and available for issuance under the Plan shall be 171,751 shares (the “Initial Limit”), subject to adjustment as provided in this Section 3, plus on January 1, 2026 and each January 1 thereafter, the number of shares of Stock reserved and available for issuance under the Plan shall be cumulatively increased by the lesser of 5 percent (5%) of the number of shares of Stock issued and outstanding on the immediately preceding December 31 or such number of shares of Stock as determined by the Administrator (the “Annual Increase”). Subject to such overall limitation, the maximum aggregate number of shares of Stock that may be issued in the form of Incentive Stock Options shall not exceed the Initial Limit cumulatively increased on January 1, 2026 and on each January 1 thereafter by the lesser of the Annual Increase for such year or 10,715 shares of Stock, subject in all cases to adjustment as provided in this Section 3. For purposes of this limitation, the shares of Stock underlying any awards that are forfeited, canceled, held back upon exercise of an Option or settlement of an Award to cover the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of Stock or otherwise terminated under this Plan or the Company’s 2020 Stock Option and Incentive Plan (other than by exercise) shall be added back to the shares of Stock available for issuance under the Plan and, to the extent permitted under Section 422 of the Code and the regulations promulgated thereunder, the shares of Stock that may be issued as Incentive Stock Options. In the event the Company repurchases shares of Stock on the open market, such shares shall not be added to the shares of Stock available for issuance under the Plan. The shares available for issuance under the Plan may be authorized but unissued shares of Stock or shares of Stock reacquired by the Company.”

Miscellaneous.

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a. Effect. Except as amended hereby, the Plan shall remain in full force and effect.

b. Defined Terms. All capitalized terms used but not specifically defined herein shall have the same meanings given such terms in the Plan unless the context clearly indicates or dictates a contrary meaning.

c. Governing Law. This Amendment shall be governed by and construed in accordance with the General Corporation Law of the State of Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the State of Delaware, without regard to its principles of conflicts of laws that would result in the application of any law other than the law of the State of Delaware.

Date of approval by the Board of Directors: June 12, 2025

Date of approval by the Stockholders:

TRANSCODE THERAPEUTICS, INC.6 LIBERTY SQUARE, #2382BOSTON, MASSACHUSETTS 02109VOTE BY INTERNETBefore The Meeting - Go to www.proxyvote.com or scan the QR Barcode aboveUse the Internet to transmit your voting instructions and for electronic delivery ofinformation up until 11:59 p.m. Eastern Time the day before the cut-off date or meetingdate. Have your proxy card in hand when you access the web site and follow theinstructions to obtain your records and to create an electronic voting instruction form.During The Meeting - Go to www.virtualshareholdermeeting.com/RNAZ2025You may attend the meeting via the Internet and vote during the meeting. Have theinformation that is printed in the box marked by the arrow available and follow theinstructions.VOTE BY PHONE -1-800-690-6903 Use any touch-tone telephone to transmit your voting instructions up until 11:59 p.m.Eastern Time the day before the cut-off date or meeting date. Have your proxy card inhand when you call and then follow the instructions.VOTE BY MAILMark, sign and date your proxy card and return it in the postage-paid envelope wehave provided or return it to Vote Processing, c/o Broadridge, 51 Mercedes Way,Edgewood, NY 11717.TO VOTE, MARK BLOCKS BELOW IN BLUE OR BLACK INK AS FOLLOWS:V76815-P35863KEEP THIS PORTION FOR YOUR RECORDSTHIS PROXY CARD IS VALID ONLY WHEN SIGNED AND DATED.DETACH AND RETURN THIS PORTION ONLYTRANSCODE THERAPEUTICS, INC.The Board of Directors recommends you vote FOR thefollowing proposal:1. Election of DirectorsNominees are:For Withhold1a. Philippe P. Calais, PhD1b. Thomas A. Fitzgerald1c. Erik Manting, PhD1d. Magda Marquet, PhD4. Approval of a proposal to adjourn the Annual Meetingof Stockholders to a later date or dates, if necessary orappropriate, to permit further solicitation and vote ofproxies in the event that there are insufficient votes for,or otherwise in connection with, the approval of theamendment to the Company’s 2021 Stock Option andIncentive Plan proposal.For Against AbstainThe Board of Directors recommends you vote FOR thefollowing proposals:For Against AbstainNOTE: Such other business as may properly come before themeeting or any adjournment thereof.2. Approval of an amendment to the TransCodeTherapeutics, Inc. 2021 Stock Option and Incentive Planto increase the number of shares available for issuancethereunder by 166,724 shares.3. Ratification of the appointment of WithumSmith+Brown PCas the Company's independent registeredpublic accounting firm for the fiscal year endingDecember 31, 2025.Please sign exactly as your name(s) appear(s) hereon. When signing as attorney, executor,administrator, or other fiduciary, please give full title as such. Joint owners should eachsign personally. All holders must sign. If a corporation or partnership, please sign in fullcorporate or partnership name by authorized officer.Signature [PLEASE SIGN WITHIN BOX] Date Signature (Joint Owners) Date

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting:The Notice and Proxy Statement, Annual Report, Form 10-K, Amended Annual Report and Form 10-K/A are available at www.proxyvote.com.V76816-P35863P35863TRANSCODE THERAPEUTICS, INC.THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORSANNUAL MEETING OF STOCKHOLDERSAUGUST 29, 2025The undersigned, revoking all prior proxies, hereby appoints Thomas A. Fitzgerald, with full power of substitution, as proxy to represent and vote all common stock of TransCode Therapeutics, Inc. (the "Company") which the undersigned will be entitled to vote if personally present at the Annual Meeting of Stockholders (or any adjournment thereof) of the Company to be held on August 29, 2025, at 9:30 a.m., Eastern Time, upon the matters set forth in the Proxy Statement, a copy of which has been received by the undersigned. Each share of common stock is entitled to one vote.THIS PROXY, WHEN PROPERLY EXECUTED, WILL BE VOTED AS DIRECTED BY THE STOCKHOLDER(S). IF NO DIRECTIONS ARE INDICATED, THE PROXIES NAMED ABOVE WILL HAVE AUTHORITY TO VOTE 'FOR' THE DIRECTOR NOMINEES LISTED IN PROPOSAL 1 AND 'FOR' PROPOSALS 2 - 4. THE PROXIES ARE AUTHORIZED TO VOTE UPON SUCH OTHER BUSINESS AS MAY PROPERLY COME BEFORE THE MEETING.PLEASE MARK, SIGN, DATE AND RETURN THIS PROXY CARD PROMPTLY USING THE ENCLOSED REPLY ENVELOPECONTINUED AND TO BE SIGNED ON REVERSE SIDE