X0306 4 2021-02-17 0 0001656536 Decibel Therapeutics, Inc. DBTX 0001534265 Casdin Partners Master Fund, L.P. 1350 AVENUE OF THE AMERICAS, SUITE 2600 NEW YORK NY 10019 0 0 1 0 Common Stock 2021-02-17 4 C 0 546421 A 546421 I See footnote Common Stock 2021-02-17 4 P 0 575000 18.00 A 1121421 I See footnote Series D Preferred Stock 2021-02-17 4 C 0 2896032 0.00 D Common Stock 546421 0 I See footnote On February 17, 2021, the Series D Preferred Stock automatically converted into Common Stock on a 5.3-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 securities are owned directly by Casdin Partners Master Fund, L.P. and may be deemed to be indirectly beneficially owned by (i) Casdin Capital, LLC, the investment adviser to Casdin Partners Master Fund, L.P., (ii) Casdin Partners GP, LLC, the general partner of Casdin Partners Master Fund L.P., and (iii) Eli Casdin, the managing member of Casdin Capital, LLC and Casdin Partners GP, LLC. /s/ Eli Casdin, Managing Member of the General Partner of Casdin Partners Master Fund, L.P. 2021-02-19