X0306 4 2020-09-21 1 0001818794 Dyne Therapeutics, Inc. DYN 0001792126 Logos Global Management LP 1 LETTERMAN DRIVE, SUITE D3-700 SAN FRANCISCO CA 94129 0 0 1 0 Common Stock 2020-09-21 4 C 0 804392 A 804392 I See footnotes Common Stock 2020-09-21 4 P 0 700000 19.00 A 1504392 I See footnotes Series B Preferred Stock 2020-09-21 4 C 0 2668089 0.00 D Common Stock 804392 0 I See footnotes On September 21, 2020, the Series B Preferred Stock automatically converted into Common Stock on a 3.3169-for-one basis without payment of further consideration upon closing of the initial public offering of the Issuer's common stock. The shares had no expiration date. The reporting persons are Logos Opportunities Fund II LP (the "Fund"), Logos Global Management LP ("LGM"), Logos Global Management GP LLC ("LGM GP"), Logos Opportunities GP LLC ("Fund GP"), Logos GP LLC ("Logos GP"), Dr. Arsani William and Dr. Graham Walmsley. LGM is the investment adviser of private funds, including the Fund. LGM GP is the general partner of LGM. Fund GP is the general partner of the Fund. Logos GP is the manager of Fund GP. Dr. William and Dr. Walmsley are controlling persons of LGM and Logos GP and managers of the Fund. LGM is filing this report for itself and the other reporting persons. The reporting persons are filing this Form 3 jointly, but not as a group, and each expressly disclaims membership in a group within the meaning of Rule 13d-5(b) under the Securities Exchange Act of 1934. The Fund holds the securities reported herein directly for the benefit of its investors. The securities may be deemed to be indirectly beneficially owned by LGM as investment adviser to the Fund, by LGM GP as general partner of LGM, by Fund GP as general partner of the Fund, by Logos GP as manager of Fund GP and by Dr. William and Dr. Walmsley as controlling persons of LGM and Logos GP. The reporting persons disclaim beneficial ownership of such securities except to the extent of their pecuniary interest therein. /s/ Arsani William, Managing Partner 2020-09-23