X0306 4 2016-05-16 0 0001597553 Sage Therapeutics, Inc. SAGE 0001488495 Third Rock Ventures II, L.P. C/O THIRD ROCK VENTURES, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001614061 Third Rock Ventures GP II, L.P. 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001614073 TRV GP II, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001180428 LEVIN MARK J 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001192595 TEPPER ROBERT I 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 Common Stock 2016-05-16 4 S 0 850000 31.25 D 3892916 D Common Stock 65226 D Common Stock 65226 D The shares are directly held by Third Rock Ventures II, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP II, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP II, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin, Kevin Starr and Dr. Robert Tepper. Each of the Reporting Persons disclaims beneficial ownership of the shares except to the extent of their pecuniary interest therein, if any. The shares are directly hold by Dr. Robert Tepper. The shares are directly held by Mark Levin. /s/ Third Rock Ventures II, L.P. by Third Rock Ventures GP II, L.P. its general partner by TRV GP II, LLC its general partner 2016-05-18 /s/ Third Rock Ventures GP II, L.P. by TRV GP II, LLC its general partner 2016-05-18 /s/ TRV GP II, LLC 2016-05-18 /s/ Kevin Gillis by power of attorney for Mark Levin 2016-05-18 /s/ Kevin Gillis by power of attorney for Dr. Robert Tepper 2016-05-18