Crescent Biopharma CMO sells 623 shares at $17.90

CBIO’s Chief Medical Officer sold a small block of shares under a pre-set Rule 10b5-1 plan solely to cover taxes on vested restricted stock units.

Rhea-AI Filing Summary

CRESCENT BIOPHARMA, INC. (CBIO) reported that its Chief Medical Officer, Ellie Eunkyung Im, sold 623 Ordinary Shares on September 16, 2026 at a weighted average price of $17.90 per share, leaving her with 21,446 shares held directly.

According to the company’s disclosure, these shares were automatically sold to satisfy tax withholding obligations arising from the settlement of restricted stock units granted on December 15, 2025, and were effected pursuant to a Rule 10b5-1 trading instruction adopted on February 25, 2026. The price reflects multiple trades between $17.10 and $19.17 per share.

Insider Trade Summary 10b5-1

Net Seller: 623 shares

Net Sell 1 txn

Insider Im Ellie Eunkyung

Role Chief Medical Officer

Sold 623 shs ($11K)

Type	Security	Shares	Price	Value
Sale	Ordinary Shares F1, F2	623	$17.90	$11K

Holdings After Transaction: Ordinary Shares — 21,446 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. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the Reporting Person on February 25, 2026, solely with the intent to cover taxes in connection with the vesting of the restricted stock units.
2. F2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $17.10 to $19.17, 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: 623 shares Weighted average sale price: $17.90 per share Sale price range: $17.10–$19.17 per share +3 more

6 metrics

Shares sold 623 shares Ordinary Shares sold by CBIO Chief Medical Officer on September 16, 2026

Weighted average sale price $17.90 per share Average price for 623 CBIO shares sold on September 16, 2026

Sale price range $17.10–$19.17 per share Range of prices for multiple CBIO share sale transactions

Shares owned after transaction 21,446 shares Direct CBIO holdings of Chief Medical Officer after September 16, 2026 sale

RSU grant date December 15, 2025 Restricted stock units whose settlement triggered tax-related sale

Rule 10b5-1 plan adoption date February 25, 2026 Pre-set trading instruction covering the tax-withholding share sale

Key Terms

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

4 terms

Rule 10b5-1 regulatory

"The sales ... were effected pursuant to a Rule 10b5-1 instruction adopted"

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"

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 ... to satisfy tax withholding obligations"

weighted average price financial

"The price reported ... is a weighted average price"

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

FAQ

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

What insider transaction did CBIO disclose for its Chief Medical Officer?

CBIO disclosed that Chief Medical Officer Ellie Eunkyung Im sold 623 Ordinary Shares on September 16, 2026, at a weighted average price of $17.90 per share, leaving her with 21,446 shares held directly after the transaction.

Why did the CBIO Chief Medical Officer sell 623 shares?

The 623 CBIO shares were automatically sold to satisfy tax withholding obligations related to the settlement of restricted stock units granted on December 15, 2025. The filing states the sale was made solely to cover these taxes.

Was the CBIO insider sale made under a Rule 10b5-1 trading plan?

Yes. The filing states the CBIO Chief Medical Officer’s sales were effected pursuant to a Rule 10b5-1 instruction adopted on February 25, 2026, with the stated intent to cover taxes from vesting restricted stock units.

What price range did the CBIO shares sell for in this insider transaction?

The reported $17.90 figure is a weighted average price. The CBIO shares were sold in multiple transactions at prices ranging from $17.10 to $19.17 per share, inclusive, according to the disclosure footnote.

How many CBIO shares does the Chief Medical Officer own after this sale?

After selling 623 shares, the CBIO Chief Medical Officer directly owns 21,446 Ordinary Shares, as reported in the Form 4 following the September 16, 2026 transaction.

Does the Form 4 say how many shares were sold in total by the CBIO insider?

Yes. The Form 4 reports that the CBIO Chief Medical Officer sold a total of 623 Ordinary Shares in this transaction, all tied to satisfying tax withholding obligations on restricted stock unit settlement.

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

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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^*

Im Ellie Eunkyung

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Medical 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		623(1)	D	$17.9(2)	21,446	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. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the Reporting Person on February 25, 2026, solely with the intent to cover taxes in connection with the vesting of the restricted stock units.

2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $17.10 to $19.17, 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:

	/s/ Barbara Bispham Hale, as attorney-in-fact for Ellie Im	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)