X0306 4 2023-02-27 0 0001850838 Omega Therapeutics, Inc. OMGA 0001400240 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 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001761283 Flagship Pioneering Special Opportunities Fund II, L.P. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001222012 AFEYAN NOUBAR 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 1 0 1 0 Common Stock 2023-02-27 4 P 0 1993986 5.78 A 7508693 I By Flagship Pioneering Special Opportunities Fund II, L.P. Common Stock 2023-02-27 4 P 0 1329324 5.78 A 1329324 I By Flagship Pioneering Fund VII, L.P. Common Stock 1088470 I By Flagship V VentureLabs Rx Fund, L.P. Common Stock 5896386 I By Flagship Ventures Fund V, L.P. Common Stock 8617413 I By Flagship Pioneering Fund VI, L.P. Common Stock 970588 I By Nutritional Health LTP Fund, L.P. Common Stock 1617646 I By FPN, L.P. Common Stock 2197059 I By Flagship VentureLabs V, LLC On February 27, 2023, Flagship Pioneering Special Opportunities Fund II, L.P. ("Flagship Opportunities Fund II") and Flagship Pioneering Fund VII, L.P. ("Flagship Fund VII") purchased 1,993,986 shares and 1,329,324 shares, respectively, of the Issuer's Common Stock in a registered direct offering at a price of $5.78 per share pursuant to a Securities Purchase Agreement dated February 22, 2023. Represents shares held directly by 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 Chief Executive Officer, sole shareholder and director 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. Represents shares held directly by Flagship Fund VII. Flagship Pioneering Fund VII General Partner LLC ("Flagship Fund VII GP") is the general partner of Flagship Fund VII. Flagship Pioneering is the manager of Flagship Fund VII GP. Each of the reporting persons 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 V VentureLabs Rx Fund, L.P. ("Flagship Fund V Rx"). Flagship Ventures Fund V General Partner LLC ("Flagship V GP") is the general partner of Flagship Fund V Rx. Dr. Afeyan is the sole manager of Flagship V GP. Each of the reporting persons 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 Ventures Fund V, L.P. ("Flagship Fund V"). Flagship V GP is the general partner of Flagship Fund V. Each of the reporting persons 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 Fund VI, L.P. ("Flagship Fund VI"). Flagship Pioneering Fund VI General Partner LLC ("Flagship Fund VI GP") is the general partner of Flagship Fund VI. Flagship Pioneering is the manager of Flagship Fund VI GP. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein, if any. Represents shares held directly by Nutritional Health LTP Fund, L.P. ("Nutritional LTP"). Nutritional Health LTP Fund General Partner LLC ("Nutritional LTP GP") is the general partner of Nutritional LTP. Flagship Pioneering is the manager of Nutritional LTP GP. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein, if any. Represents shares held directly by FPN, L.P. ("FPN Fund"). FPN General Partner LLC ("FPN GP") is the general partner of FPN Fund. Flagship Pioneering is the manager of FPN GP. Each of the reporting persons 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 VentureLabs V, LLC ("VentureLabs V"). VentureLabs V Manager LLC ("VentureLabs V Manager") is the manager of VentureLabs V. Flagship Pioneering, Inc. ("Flagship Pioneering") is the manager of VentureLabs V Manager. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein, if any. Flagship Pioneering, Inc., By: /s/ Noubar B. Afeyan, Ph.D., Chief Executive Officer 2023-02-27 Flagship Pioneering Special Opportunities Fund II General Partner LLC, By: Flagship Pioneering, Inc. its manager, By: /s/ Noubar B. Afeyan Ph.D., Chief Executive Officer 2023-02-27 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., Chief Executive Officer 2023-02-27 /s/ Noubar B. Afeyan, Ph.D. 2023-02-27