[Form 4] CRESCENT BIOPHARMA, INC. Insider Trading Activity

Rhea-AI Filing Summary

Crescent Biopharma, Inc. reported new equity awards to officer Ryan Lynch, who serves as Treasurer, Senior Vice President of Finance and Chief Accounting Officer. On December 15, 2025, Lynch acquired 8,378 Ordinary Shares and an additional 4,000 Ordinary Shares through awards of Restricted Stock Units (RSUs), bringing his directly held Ordinary Shares to 12,378.

Each RSU represents a contingent right to receive one Ordinary Share, vesting in approximately equal three‑month installments through the four‑year anniversary of December 15, 2025, contingent on continued service. Lynch also received a stock option for 33,512 Ordinary Shares at an exercise price of $13.21 per share, exercisable until December 15, 2035. This option vests as to 1/48th of the grant on each monthly anniversary of December 15, 2025, also conditioned on continuous employment or service.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Lynch Ryan

(Last) (First) (Middle)

C/O CRESCENT BIOPHARMA, INC.

300 FIFTH AVENUE

(Street)

WALTHAM MA 02451

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
CRESCENT BIOPHARMA, INC. [ CBIO ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	See Remarks

3. Date of Earliest Transaction (Month/Day/Year)
12/15/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Ordinary Shares	12/15/2025		A		8,378	A	(1)	8,378	D
Ordinary Shares	12/15/2025		A		4,000	A	(1)	12,378	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (Right to Buy)	$13.21	12/15/2025		A		33,512		(2)	12/15/2035	Ordinary Shares	33,512	$0	33,512	D

Explanation of Responses:

1. Represents an award of Restricted Stock Units ("RSUs"). Each RSU represents a contingent right to receive one share of the Issuer's Ordinary Shares. The RSUs shall vest in approximately equal three-month installments through the four-year anniversary of December 15, 2025, subject to the Reporting Person remaining continuously employed by or providing services to the Issuer or its subsidiaries from December 15, 2025 through each such vesting date.

2. This Option represents a right to purchase shares of the Issuer's Ordinary Shares and vests with respect to 1/48th of the Option on each monthly anniversary of December 15, 2025, subject to the Reporting Person remaining continuously employed by or providing services to the Issuer or its subsidiaries from December 15, 2025 through each such vesting date.

Remarks:

Treasurer, Senior Vice President of Finance and Chief Accounting Officer.

	/s/ Barbara Bispham, as attorney-in-fact for Ryan Lynch	12/17/2025
	** Signature of Reporting Person	Date
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