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Crescent Biopharma, Inc.
CBIO
Amendment
Ownership

16.52%

Total Shares

6,602,408

Issuer CIK

1253689

Event Date

Jul 15, 2026

Accepted

Jul 20, 2026, 05:30 PM

SEC EDGARView Original Filing
Reporting Persons (4)
Joint Filing

This is a joint filing. The reported shares may overlap between reporting persons and should not be summed.

NameType% of ClassAggregateSole VotingShared Voting
Peter Harwin
Individual
16.52%6,602,4089,0236,593,385
Fairmount Funds Management LLC
Investment Adviser
16.50%6,593,38506,593,385
Fairmount Healthcare Fund II L.P.
Partnership
16.50%6,593,38506,593,385
Tomas Kiselak
Individual
16.50%6,593,38506,593,385
Disclosure Items (6)

Security Title

Ordinary Shares, $0.001 par value

Issuer Name

Crescent Biopharma, Inc.

Issuer Address

300 Fifth Avenue, Waltham, MA, 02451

Item 3 of the Statement is hereby amended and supplemented as follows: In aggregate, the Reporting Persons have voting and dispositive power over 6,593,385 Ordinary Shares of the Company, which is comprised of (a) 3,601,316 Ordinary Shares, (b) Pre-Funded Warrants to purchase up to 102,069 Ordinary Shares, the exercise of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Ordinary Shares (and therefore excluding 2,191,968 Ordinary Shares issuable upon exercise of the Pre-Funded Warrants in excess of the beneficial ownership limitation), and (c) 2,890,000 Ordinary Shares issuable upon conversion of 2,890 Series A Preferred Shares, the conversion of which is subject to a beneficial ownership limitation of 19.99% of the outstanding Ordinary Shares. On July 16, 2026, Fund II purchased a total of (i) 853,450 Ordinary Shares and (ii) Pre-Funded Warrants to purchase up to 525,897 Ordinary Shares for an aggregate purchase price of $20,000,005.60 in an underwritten public offering (the "Offering"). The securities were purchased with working capital.

Item 4 of the Statement is hereby amended and supplemented as follows: Fund II purchased the Ordinary Shares and Pre-funded Warrants referenced in Item 3 for investment purposes. Lock-Up Agreement In connection with the Company's underwritten public offering of Ordinary Shares and Pre-Funded Warrants that closed on July 16, 2026, the Reporting Persons entered into a customary lock-up letter agreement (the "Lock-Up Agreement") with Jefferies LLC and TD Securities (USA) LLC acting as the Representatives (collectively, the "Representatives") of the underwiters party to to an underwriting agreement with the Company. Pursuant to the Lock-Up Agreement, the Reporting Persons agreed to refrain from selling shares of the Company's securities without the consent of the Representatives, and other customary lock-up conditions, for a period of 60 days following the date of the final prospectus supplement for the offering. The foregoing description of the Lock-Up Agreement does not purport to be complete and is qualified in its entirety by reference to the Form of Lock-Up Agreement, which is filed as Exhibit 99.2 to this Schedule 13D and incorporated herein by reference. Pre-Funded Warrants The Pre-Funded Warrants purchased by Fund II in the offering have an exercise price of $0.001, are immediately exercisable at any time after the date of issuance and will not expire. A holder of Pre-Funded Warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 9.99%, as applicable, of the number of Ordinary Shares outstanding immediately after giving effect to such exercise. A holder of Pre-Funded Warrants may increase or decrease this percentage to a percentage not in excess of 19.99% by providing notice to the Company. Any increase in the percentage will not be effective until the 61st day after such notice is delivered. The foregoing description of the Pre-Funded Warrants does not purport to be complete and is qualified in its entirety by reference to the form of Pre-Funded Warrant, which is filed as Exhibit 99.3 hereto.

Percentage of Class

The information in rows 11 and 13 of each of the cover pages (including the explanatory note in the "Comments") of this Amendment No. 2 is incorporated by reference herein. In aggregate, the Reporting Persons' securities include (a) 3,601,316 Ordinary Shares, (b) 9,023 shares of Common Stock issuable upon the exercise of options held by the Reporting Persons that are currently exercisable or will be exercisable within 60 days of the date of this filing, (c) 2,890,000 Ordinary Shares issuable upon conversion of 2,890 shares of Series A Preferred Shares, and (d) 102,069 Ordinary Shares issuable upon exercise of Pre-Funded Warrants. The securities exclude 2,191,968 Ordinary Shares issuable upon exercise of Pre-Funded Warrants directly held by Fund II due to application of the beneficial ownership limitation. The exercise of the Pre-Funded Warrants is subject to a beneficial ownership limitation of 9.99% of the outstanding Ordinary Shares and the conversion of the Series A Preferred Shares is subject to a beneficial ownership limitation of 19.99%. At such time as Fairmount and its affiliates beneficially own 9.0% or less of the Ordinary Shares, the beneficial ownership limitation with respect to the Series A Preferred Shares will automatically reduce to 9.99%.

Number of Shares

The information in rows 7 through 10 of each of the cover pages of this Amendment No. 2 is incorporated by reference herein.

Transactions

Item 5(c) of the Schedule 13D is hereby supplemented as follows: On July 16, 2026, Fund II purchased in the Offering a total of (i) 853,450 Ordinary Shares at a price of $14.50 per share and (ii) Pre-Funded Warrants to purchase 525,897 Ordinary Shares at a purchase price of $14.499 per Pre-Funded Warrant, which represents the per share purchase price of the Ordinary Shares less the $0.001 per share exercise price for each Pre-Funded Warrant, for an aggregate purchase price of $20,000,005.60. On June 2, 2026, Mr. Harwin's stock options to purchase 9,023 Ordinary Shares at an exercise price of $15.30 per share, received as compensation for his service as a director of the Company, vested in full and became exercisable.

Shareholders

Fairmount is the investment manager to Fund II and has voting and dispositive power over Ordinary Shares held on behalf of Fund II.

The information set forth in Item 4 of this Amendment No. 2 is incorporated herein by reference.

99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 of the Reporting Persons' Schedule 13D filed with the SEC on December 8, 2025) 99.2 Lock-Up Agreement (incorporated by reference to Exhibit A to the Underwriting Agreement filed as Exhibit 1.1 of the Company's Form 8-K filed with the SEC on July 15, 2026) 99.3 Form of Pre-Funded Warrant (incorporated herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed on July 15, 2026)