X0508 4 2023-08-11 1 0001821323 Sigilon Therapeutics, Inc. SGTX 0001724575 Flagship Ventures Fund V General Partner LLC C/O FLAGSHIP PIONEERING INC. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001627639 Flagship Ventures Fund V, L.P. C/O FLAGSHIP PIONEERING INC. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001761283 Flagship Pioneering Special Opportunities Fund II, L.P. C/O FLAGSHIP PIONEERING INC. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001826217 Flagship Pioneering Special Opportunities Fund II General Partner LLC C/O FLAGSHIP PIONEERING INC. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001400240 Flagship Pioneering Inc. C/O FLAGSHIP PIONEERING INC. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001222012 AFEYAN NOUBAR C/O FLAGSHIP PIONEERING INC. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0 Common Stock 2023-08-11 4 U 0 683760 14.92 D 0 I By Flagship Ventures Fund V, L.P. Common Stock 2023-08-11 4 U 0 113960 14.92 D 0 I By Flagship Pioneering Special Opportunities Fund II, L.P. Pursuant to the terms of that certain Agreement and Plan of Merger by and among the Issuer, Eli Lilly and Company and Shenandoah Acquisition Corporation, dated as of June 28, 2023, these shares were tendered in exchange for (a) $14.92 per share and (b) one contingent value right per Share (each, a "CVR"), which represents the contractual right to receive up to three contingent payments for an aggregate of up to $111.64 per CVR, without interest and less any applicable tax withholding, upon the achievement of certain specified milestones. Effective May 22, 2023, the Issuer effected a 1-for-13 reverse stock split (the "Reverse Split") of its issued and outstanding shares of Common Stock. Cash was paid in lieu of any fractional shares resulting from the Reverse Split. The share amounts in this Form 4 have been adjusted for the Reverse Split. Represents shares held directly by Flagship Ventures Fund V, L.P. ("Flagship Fund V"). Flagship Ventures Fund V General Partner LLC ("Flagship V GP") is the general partner of Flagship Fund V. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship V GP. Each of the reporting persons except Flagship Fund V disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein, if any. Represents shares held directly by Flagship Pioneering Special Opportunities Fund II, L.P. ("Flagship Opportunities Fund II"). Flagship Pioneering Special Opportunities Fund II General Partner LLC ("Flagship Opportunities Fund II GP") is the general partner of Flagship Opportunities Fund II. Flagship Pioneering, Inc. ("Flagship Pioneering") is the manager of Flagship Opportunities Fund II GP. Noubar B. Afeyan, Ph.D. is the CEO and sole stockholder of Flagship Pioneering. Each of the reporting persons except Flagship Opportunities Fund II disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein, if any. Flagship Ventures Fund V General Partner LLC, By: /s/ Noubar B. Afeyan Ph.D., Title: Manager 2023-08-15 Flagship Ventures Fund V, L.P., By: Flagship Ventures Fund V General Partner LLC, its general partner, By: /s/ Noubar B. Afeyan Ph.D., Title: Manager 2023-08-15 Flagship Pioneering Special Opportunities Fund II, L.P., By: Flagship Pioneering Special Opportunities Fund II General Partner LLC, its general partner, By: Flagship Pioneering, Inc. its manager, By: /s/ Noubar B. Afeyan Ph.D., Title: CEO 2023-08-15 Flagship Pioneering Special Opportunities Fund II General Partner LLC, By: Flagship Pioneering, Inc. its manager, By: /s/ Noubar B. Afeyan Ph.D., Title: CEO 2023-08-15 Flagship Pioneering, Inc., By: /s/ Noubar B. Afeyan Ph.D., Title: CEO 2023-08-15 /s/ Noubar B. Afeyan Ph.D. 2023-08-15