Document

We have acted as Cayman Islands legal advisers to Crescent Biopharma, Inc. (the "Company"), and we have examined the Registration Statement on Form S-8 to be filed by the Company with the United States Securities and Exchange Commission (including all supplements and amendments thereto, the "Registration Statement"), relating to the registration under the U.S. Securities Act of 1933, as amended (the "Securities Act"), of up to:

1.2,345,962 ordinary shares with a par value of US$0.001 per share in the capital of the Company ("Ordinary Shares") issuable under the Crescent Biopharma, Inc. 2025 Stock Incentive Plan (as amended and restated, the "2025 Plan") (the "2025 Plan Shares");

2.195,497 Ordinary Shares issuable under the Crescent Biopharma, Inc. 2025 Employee Stock Purchase Plan (as amended and restated, the "ESPP") (the "ESPP Shares");

4.1,250,000 Shares issuable under the Crescent Biopharma, Inc. 2025 Employment Inducement Incentive Award Plan (the "Inducement Plan" and, together with the 2025 Plan, the ESPP and the 2024 Plan, the "Plans") (the "Inducement Plan Shares" and, together with the 2025 Plan Shares, the ESPP Shares and the 2024 Plan Shares, the "Shares").

We are Cayman Islands Attorneys at Law and express no opinion as to any laws other than the laws of the Cayman Islands in force and as interpreted at the date of this opinion. We have not, for the purposes of this opinion, made any investigation of the laws, rules or regulations of any other jurisdiction.

Based upon the foregoing examinations and assumptions and upon such searches as we have conducted and having regard to legal considerations which we consider relevant, and under the laws of the Cayman Islands, we give the following opinions in relation to the matters set out below.

1.The Company is an exempted company registered by way of continuation with limited liability, validly existing under the laws of the Cayman Islands and in good standing with the Registrar of Companies in the Cayman Islands (the "Registrar").

2.The Shares, as contemplated by the Registration Statement, have been duly authorised by all necessary corporate action of the Company and, upon the issue of the Shares (by the entry of the name of the registered owner thereof in the register of members of the Company confirming that such Shares have been issued credited as fully paid), delivery and payment therefore by the purchaser in accordance with the Memorandum and Articles of Association (as defined in Schedule 1) and the Plans and in the manner contemplated by the Registration Statement, the Shares will be validly created, legally issued, fully paid and non-assessable (meaning that no additional sums may be levied on the holder thereof by the Company).

Our opinion as to the good standing of the Company is based solely upon receipt of the Certificate of Good Standing (as defined in Schedule 1) issued by the Registrar. The Company shall be deemed to be in good standing under Section 200A of the Companies Act (as amended) of the Cayman Islands (the "Companies Act") on the date of issue of the Certificate of Good Standing if all fees and penalties under the Companies Act have been paid and the Registrar has no knowledge that the Company is in default under the Companies Act.

This opinion is limited to the matters referred to herein and shall not be construed as extending to any other matter or document not referred to herein. This opinion is given solely for your benefit and the benefit of your legal advisers acting in that capacity in relation to this transaction and may not be relied upon by any other person, other than persons entitled to rely upon it pursuant to the provisions of the Securities Act, without our prior written consent.

We consent to the use of this opinion as an exhibit to the Registration Statement and further consent to all references to us in the Registration Statement and any amendments thereto.

1.The Certificate of Registration By Way of Continuation of the Company dated 16 June 2025, the Memorandum and Articles of Association of the Company adopted by special resolution on 5 June 2025 and effective as of 16 June 2025) (the "Memorandum and Articles of Association") and each of the Register of Directors, Register of Officers and Register of Mortgages and Charges of the Company (together, the "Company Records").

4.Copies of the executed written resolutions of the board of directors of the Company dated 19 September 2024, 13 June 2025 and 30 October 2025 (the "Resolutions").

1.The originals of all documents examined in connection with this opinion are authentic. The signatures, initials and seals on the documents reviewed are genuine and are those of a person or persons given power to execute the documents under the Resolutions (as defined in Schedule 1). All documents purporting to be sealed have been so sealed. All copies are complete and conform to their originals.

2.The Memorandum and Articles of Association reviewed by us will be the memorandum and articles of association of the Company in effect upon the issuance of the Shares.

4.All necessary actions were taken under the applicable U.S. laws to authorise the 2024 Plan and permit the issuance of the 2024 Plan Shares, and any and all consents, approvals and authorisations required to authorise the 2024 Plan and permit the issuance of the 2024 Plan Shares were obtained.

5.The Company will receive consideration in money or money’s worth for each Share offered by the Company when issued at the agreed issue price as per the terms of the Registration Statement, such price in any event not being less than the stated par or nominal value of each Share.

6.There are no provisions of the laws of any jurisdiction outside the Cayman Islands which would be contravened by issuance and allotment of the Shares and, insofar as any obligation expressed to be incurred under any of the documents is to be performed in or is otherwise subject to the laws of any jurisdiction outside the Cayman Islands, its performance will not be illegal by virtue of the laws of that jurisdiction.

7.The Company Records are complete and accurate and all matters required by law and the Memorandum and Articles of Association to be recorded therein are completely and accurately so recorded.

9.The Resolutions are and shall remain in full force and effect and have not been and will not be rescinded or amended. As applicable, the Resolutions were either (a) duly adopted at duly convened meetings of the Board of Directors and such meetings were held and conducted in accordance with the Memorandum and Articles of Association or constitutional documents and governing law of the Company in force at the relevant time, or (b) duly executed by or on behalf of each director or committee member and the signatures and initials thereon are those of a person or persons in whose name the Resolutions have been expressed to be signed and were adopted in accordance with the Memorandum and Articles of Association or constitutional documents and governing law of the Company in force at the relevant time.

10.The Registration Statement and each Plan conforms in every material respect to the latest drafts of the same produced to us and, where provided in successive drafts, have been marked up to indicate all changes to such documents.

11.Each of the Registration Statement and each Plan (including each award agreement issued pursuant thereto) will be duly authorised, executed and delivered by or on behalf of all relevant

parties prior to the issue of the Shares and will be legal, valid, binding and enforceable against all relevant parties in accordance with their terms under all relevant laws (other than the laws of the Cayman Islands).

12.All preconditions to the issue of the Shares under the terms of each Plan will be satisfied or duly waived prior to the issue of the Shares and there will be no breach of the terms of each Plan.


Crescent Biopharma, Inc. c/o Walkers Corporate Limited 190 Elgin Avenue George Town Grand Cayman KY1-9008 Cayman Islands


Walkers 190 Elgin Avenue, George Town Grand Cayman KY1-9001, Cayman Islands T +1 345 949 0100 F +1 345 949 7886 www.walkersglobal.com


6 November 2025			Our Ref: SF/af/C9608-195644


WALKERS


WALKERS


WALKERS