X0508 4 2023-11-13 0001453687 Cartesian Therapeutics, Inc. RNAC 0002000002 Kalayoglu Murat C/O CARTESIAN THERAPEUTICS, INC. 65 GROVE STREET WATERTOWN MA 02472 1 0 1 0 0 Common Stock 2023-11-13 4 A 0 257739 0 A 257739 D Common Stock 2023-11-13 4 J 0 3303699 0 A 3303699 I by trust Series A Non-Voting Convertible Preferred Stock 2023-11-13 4 A 0 14755.609 A Common Stock 14755609 14755.609 D Series A Non-Voting Convertible Preferred Stock 2023-11-13 4 J 0 189136.767 A Common Stock 189136767 189136.767 I by trust Series A Non-Voting Convertible Preferred Stock 2023-11-13 4 P 0 619.627 249999.98 A Common Stock 619627 619.627 I by trust On November 13, 2023, Selecta Biosciences, Inc. (the "Company") acquired Cartesian Therapeutics, Inc. ("Cartesian") in accordance with the terms of an Agreement and Plan of Merger, dated November 13, 2023. These securities represent merger consideration payable as a result of the closing of the merger. Shares are held in a trust (the "Trust") for the benefit of the reporting person's spouse and children. The reporting person's spouse is a trustee of the trust. Following the approval by the Stockholders of the conversion of the Series A Non-Voting Convertible Preferred Stock of the Company ("Series A Preferred Stock") into shares of common stock of the Company ("Common Stock"), each share of Series A Preferred Stock will be convertible into 1,000 shares of Common Stock, subject to certain limitations, including that a holder of Series A Preferred Stock is prohibited from converting shares of Series Preferred Stock into shares of Common Stock if, as a result of such conversion, such holder, together with its affiliates, would beneficially own more than 19.9% of the total number of shares of Common Stock issued and outstanding immediately after giving effect to such conversion. On November 13, 2023, the Trust entered into a Securities Purchase Agreement with the Company and other investors, pursuant to which the Trust agreed to acquire 619.627 shares of Series A Preferred Stock. /s/ Murat Kalayoglu 2023-11-15