13D Filings
Crescent Biopharma, Inc.
CBIO
Amendment
Ownership

18.53%

Total Shares

5,643,482

Issuer CIK

1253689

CUSIP

G2545C104

Event Date

Dec 3, 2025

Accepted

Dec 8, 2025, 04:30 PM

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
Fairmount Funds Management LLC
Investment Adviser
18.53%5,643,48205,643,482
Fairmount Healthcare Fund II L.P.
Partnership
18.53%5,643,48205,643,482
Peter Evan Harwin
Individual
18.53%5,643,48205,643,482
Tomas Kiselak
Individual
18.53%5,643,48205,643,482
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 5,643,482 Ordinary Shares of the Company, which is comprised of (a) 2,747,866 Ordinary Shares, (b) Pre-Funded Warrants to purchase up to 5,616 Ordinary Shares, the exercise of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Ordinary Shares (and excluding 1,762,524 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 December 4, 2025, Fund II purchased a total of (i) 1,360,000 Ordinary Shares and (ii) Pre-Funded Warrants to purchase up to 131,434 Ordinary Shares through a private placement with the Company for an aggregate purchase price of $19,999,998.51. The securities were purchased with working capital.

Item 4 of the Statement is hereby amended and supplemented as follows: Subscription Agreement On December 4, 2025, the Company entered into a securities purchase agreement (the "Subscription Agreement") for a private investment in public equity ("PIPE") with certain institutional and accredited investors, including Fund II. The PIPE closed on December 8, 2025. Pursuant to the terms of the Subscription Agreement, Fund II purchased a total of 1,360,000 Ordinary Shares at a purchase price of $13.41 per share and Pre-Funded Warrants to purchase 131,434 Ordinary Shares at a purchase price of $13.409 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. The foregoing description of the Subscription Agreement does not purport to be complete and is qualified in its entirety by reference to the form of the Subscription Agreement, which is filed as Exhibit 99.2 hereto. Pre-Funded Warrants The Pre-Funded Warrants purchased by Fund II in the PIPE will be exercisable at any time after the date of issuance. 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. Registration Rights Agreement In connection with the PIPE, the Company and investors participating in the PIPE, including Fund II, entered into a registration rights agreement (the "Registration Rights Agreement"), which provides that the Company will register the resale of the Ordinary Shares and Pre-Funded Warrants sold in the PIPE. The Company is required to prepare and file an initial registration statement with the Securities and Exchange Commission no later than 30 days following the closing of the PIPE and to use its reasonable best efforts to have the initial registration statement and any amendment declared effective within 60 days thereafter, subject to certain exceptions. The Registration Rights Agreement also provides that the Company is required to indemnify the investors participating in the PIPE, their officers, directors, agents, partners, members, managers, stockholders, affiliates, investment advisers and employees under the registration statement from certain liabilities and pay all fees and expenses (excluding any legal fees of the selling holder(s), and any underwriting discounts and selling commissions) incident to the Company's obligations under the Registration Rights Agreement. The foregoing summary of the Registration Rights Agreement does not purport to be complete and is qualified in its entirety by reference to the form of Registration Rights Agreement, which is filed as Exhibit 99.4 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. 1 is incorporated by reference herein.

Number of Shares

The information in rows 7 through 10 of each of the cover pages of this Amendment No. 1 is incorporated by reference herein. The Reporting Persons' securities include (a) 2,747,866 Ordinary Shares, 2,890,000 Ordinary Shares issuable upon conversion of 2,890 shares of Series A Preferred Shares, and 5,616 Ordinary Shares issuable upon exercise of Pre-Funded Warrants directly held by Fund II and exclude (b) 1,762,524 Ordinary Shares issuable upon exercise of Pre-Funded Warrants directly held by Fund II. The exercise of the Pre-Funded Warrants is subject to a beneficial ownership limitation of 9.99% of the outstanding Ordinary Shares and the exercise of the Series A Preferred Shares is subject to a beneficial ownership limitation of 19.99%. The securities exclude Ordinary Shares issuable upon exercise of Pre-Funded Warrants in excess of the beneficial ownership limitation. 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%.

Transactions

On December 4, 2025, Fund II purchased a total of (i) 1,360,000 Ordinary Shares at a price of $13.41 per share and (ii) Pre-Funded Warrants to purchase 131,434 Ordinary Shares at a purchase price of $13.409 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, in the PIPE for an aggregate purchase price of $19,999,998.51.

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. 1 is incorporated herein by reference.

99.1 Joint Filing Agreement 99.2 Form of Securities Purchase Agreement, dated December 4, 2025, by and between Crescent Biopharma, Inc. and each purchaser thereto (incorporated herein by reference to Exhibit 10.2 of the Company's Current Report on Form 8-K filed on December 4, 2025) 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 December 4, 2025) 99.4 Form of Registration Rights Agreement, dated December 4, 2025, by and between Crescent Biopharma, Inc. and the other parties thereto (incorporated herein by reference to Exhibit 10.3 of the Company's Current Report on Form 8-K filed on December 4, 2025).