Crescent Biopharma CEO sells 9,447 shares

CBIO’s chief executive officer reported automatic share sales under a Rule 10b5-1 plan to cover tax withholding from vesting restricted stock units.

Rhea-AI Filing Summary

CRESCENT BIOPHARMA, INC. (CBIO) reported that Chief Executive Officer and director Joshua T. Brumm sold Ordinary Shares in two transactions, totaling 9,447 shares, on September 16 and September 18, 2026. According to the company’s disclosure, the shares were automatically sold to satisfy tax withholding obligations upon settlement of previously granted restricted stock units and were effected under a Rule 10b5-1 trading instruction adopted on February 28, 2026.

Insider Trade Summary 10b5-1

Net Seller: 9,447 shares

Net Sell 2 txns

Insider Brumm Joshua T

Role Chief Executive Officer

Sold 9,447 shs ($160K)

Type	Security	Shares	Price	Value
Sale	Ordinary Shares F1, F2	7,837	$16.71	$131K
Sale	Ordinary Shares F1, F2	1,610	$17.90	$29K

Holdings After Transaction: Ordinary Shares — 271,765 shares (Direct)

Footnotes (2)

1. F1. Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the settlement of restricted stock units granted to the Reporting Person on December 15, 2025 and March 17, 2025. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on February 28, 2026, solely with the intent to cover taxes in connection with the vesting of the restricted stock units.
2. F2. The prices reported in Column 4 are weighted average prices. These shares were sold in multiple transactions at prices ranging from $17.10 to $19.17 on September 16, 2026 and from $16.15 to $17.23 on September 18, 2026, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price at which the transactions were effected.

Key Figures

Shares sold September 16, 2026: 1,610 shares Weighted average price September 16, 2026: $17.90 per share Shares sold September 18, 2026: 7,837 shares +4 more

7 metrics

Shares sold September 16, 2026 1,610 shares Ordinary Shares sold by CEO Joshua T. Brumm

Weighted average price September 16, 2026 $17.90 per share Ordinary Shares sale; individual trades ranged $17.10–$19.17

Shares sold September 18, 2026 7,837 shares Ordinary Shares sold by CEO Joshua T. Brumm

Weighted average price September 18, 2026 $16.71 per share Ordinary Shares sale; individual trades ranged $16.15–$17.23

Total shares sold 9,447 shares Combined Ordinary Shares sold across both transactions

Rule 10b5-1 plan adoption date February 28, 2026 Plan under which the tax-withholding sales were effected

RSU grant dates referenced December 15, 2025 and March 17, 2025 Restricted stock units whose vesting triggered tax-withholding sales

Key Terms

Rule 10b5-1, restricted stock units, tax withholding obligations, weighted average prices

4 terms

Rule 10b5-1 regulatory

"The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction"

Rule 10b5-1 is a regulation that allows company insiders to buy or sell their shares at predetermined times, even if they have access to non-public information. It acts like setting a schedule in advance for transactions, helping prevent accusations of unfair trading. This rule provides a way for insiders to plan trades transparently, giving investors confidence that these transactions are not based on hidden information.

restricted stock units financial

"in connection with the settlement of restricted stock units granted to the Reporting Person"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

tax withholding obligations financial

"shares automatically sold by the Reporting Person to satisfy tax withholding obligations"

weighted average prices financial

"The prices reported in Column 4 are weighted average prices."

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transactions did CBIO’s CEO report in this Form 4?

CBIO’s CEO Joshua T. Brumm reported two sales of Ordinary Shares on September 16, 2026 and September 18, 2026, together totaling 9,447 shares, as disclosed in the Form 4.

Why were CBIO shares sold by the CEO in this Form 4?

The filing states the shares were automatically sold to satisfy tax withholding obligations in connection with the settlement of restricted stock units granted on December 15, 2025 and March 17, 2025.

Were the CBIO CEO’s share sales made under a Rule 10b5-1 plan?

Yes. The disclosure notes the sales were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on February 28, 2026, solely with the intent to cover taxes from vesting restricted stock units.

How many CBIO shares did the CEO sell on each date and at what reported prices?

On September 16, 2026, the CEO sold 1,610 shares at a reported weighted average price of about $17.90. On September 18, 2026, he sold 7,837 shares at a reported weighted average price of about $16.71.

What price ranges applied to the CBIO CEO’s share sales reported here?

The filing reports that sales on September 16, 2026 occurred at prices from $17.10 to $19.17, and sales on September 18, 2026 occurred at prices from $16.15 to $17.23, with column prices given as weighted averages.

Does the Form 4 state the CEO’s share ownership after these CBIO transactions?

No. The non-derivative transaction rows report the sales but do not state a total number of shares held following the transactions in the provided data.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

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Available on EDGAR 09/18/2026 - 04:03 PM Accepted by SEC EDGAR 09/18/2026 - 04:02 PM Learn about SEC filing dates

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

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

X

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^*

Brumm Joshua T

(Last) (First) (Middle)

C/O CRESCENT BIOPHARMA, INC.

300 FIFTH AVENUE

(Street)

WALTHAM MASSACHUSETTS 02451

(City) (State) (Zip)

UNITED STATES

(Country)

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

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

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Executive Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/16/2026

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

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

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

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	09/16/2026		S		1,610(1)	D	$17.9(2)	279,602	D
Ordinary Shares	09/18/2026		S		7,837(1)	D	$16.71(2)	271,765	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

Explanation of Responses:

1. Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the settlement of restricted stock units granted to the Reporting Person on December 15, 2025 and March 17, 2025. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on February 28, 2026, solely with the intent to cover taxes in connection with the vesting of the restricted stock units.

2. The prices reported in Column 4 are weighted average prices. These shares were sold in multiple transactions at prices ranging from $17.10 to $19.17 on September 16, 2026 and from $16.15 to $17.23 on September 18, 2026, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price at which the transactions were effected.

Remarks:

Exhibit 24 - Power of Attorney

	/s/ Barbara Bispham Hale, as attorney-in-fact for Joshua T. Brumm	09/18/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)