Fairmount Funds Management LLC → Korsana Biosciences, Inc. CYCN

The Reporting Persons own 19.99% of the Company in the aggregate, based upon the Company's aggregate outstanding shares as of September 8, 2026. The Reporting Persons' securities include (a) 2,691 shares of Common Stock issuable upon the exercise of options held directly by Mr. Kiselak that are currently exercisable or will be exercisable within 60 days of the date of this filing, (b) 6,911,174 shares of Common Stock directly held by Fund II and (c) 2,192,555 shares of Common Stock directly held by Co-Invest, and exclude (i) 2,074,000 shares of Common Stock issuable upon conversion of 2,074 shares of Series B Preferred Stock directly held by Fund II and (ii) 66,436 shares of Common Stock 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 19.99% of the outstanding shares of Common Stock and the conversion of the Series B Preferred Stock is subject to a beneficial ownership limitation of 19.99% of the outstanding shares of Common Stock. The securities exclude shares of Common Stock issuable upon exercise of Pre-Funded Warrants and conversion of Series B Preferred Stock in excess of such beneficial ownership limitations. At such time as Fairmount and its affiliates beneficially own 9.0% or less of the outstanding shares of Common Stock, the beneficial ownership limitation with respect to the Series B Preferred Stock will automatically reduce to 9.99%. Mr. Kiselak serves as a member of the board of directors of the Company, and, in such capacity, may have influence over the corporate activities of the Company, including activities which may relate to items described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. Except as described in this Schedule 13D, the Reporting Persons do not have any present plans or proposals that relate to or would result in any of the actions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D, although, the Reporting Persons, at any time and from time to time, may review, reconsider and change their position and/or change their purpose and/or develop such plans and may seek to influence management or the board of directors of the Company with respect to the business and affairs of the Company and may from time to time consider pursuing or proposing such matters with advisors, the Company or other persons. Initial Financing In November 2024, Pre-Merger Korsana (as defined below) issued and sold 4,000,000 shares of its Series Seed Preferred Stock to Fund II at a purchase price of $1.25 per share. In September 2025, Pre-Merger Korsana issued and sold an additional 6,000,000 shares of its Series Seed Preferred Stock to Fund II at a purchase price of $1.25 per share and 12,500,000 shares of its Series A Preferred Stock to Fund II at a purchase price of $2.00 per share. Agreement and Plan of Merger On April 1, 2026, the Company, a Massachusetts corporation, entered into the Agreement and Plan of Merger and Reorganization, dated as of April 1, 2026, which was subsequently amended on April 17, 2026 (as amended, the "Merger Agreement"), with Korsana Biosciences, Inc., a Delaware corporation ("Pre-Merger Korsana"), Cariboos Merger Sub Corp., a Delaware corporation and a wholly owned subsidiary of the Company ("First Merger Sub"), and Cariboos Merger Sub II, LLC, a Delaware limited liability company and wholly owned subsidiary of the Company ("Second Merger Sub"). Pursuant to the Merger Agreement, on September 8, 2026, First Merger Sub merged with and into Pre-Merger Korsana, pursuant to which Pre-Merger Korsana was the surviving corporation and became a wholly owned subsidiary of the Company (the "First Merger"). Immediately following the First Merger, Pre-Merger Korsana merged with and into Second Merger Sub, pursuant to which Second Merger Sub was the surviving entity (together with the First Merger, the "Merger"). After completion of the Merger, Second Merger Sub changed its name to Korsana Biosciences Operating Company, LLC and the Company changed its name to Korsana Biosciences, Inc. Following a reverse stock split effected by the Company, and as a result of and upon the effective time of the First Merger (the "First Effective Time"), (i) each then-outstanding share of Pre-Merger Korsana capital stock (including shares of Pre-Merger Korsana common stock issued in the Korsana Pre-Closing Financing (as defined below) and excluding shares to be canceled pursuant to the Merger Agreement and excluding dissenting shares) was converted solely into the right to receive a number of shares of Common Stock equal to the Exchange Ratio (the "Parent Common Stock Payment Shares"); (ii) to the extent the shares of Common Stock otherwise issuable to a holder would have exceeded that holder's Beneficial Ownership Limitation, the Company issued shares of Common Stock up to that limitation and, in lieu of the excess, pre-funded warrants to purchase a number of shares o