X0306 4 2014-07-23 0 0001597553 Sage Therapeutics, Inc. SAGE 0001219042 NELSEN ROBERT 8725 WEST HIGGINS ROAD, SUITE 290 CHICAGO IL 60631 1 0 1 0 Common Stock 2014-07-23 4 C 0 1587301 A 1587301 I See Footnotes Common Stock 2014-07-23 4 C 0 2380951 A 3968252 I See Footnotes Common Stock 2014-07-23 4 C 0 281137 A 4249389 I See Footnotes Series A Preferred Stock 2014-07-23 4 C 0 5000000 D Common Stock 1587301 0 I See Footnotes Series B Preferred Stock 2014-07-23 4 C 0 7500000 D Common Stock 2380951 0 I See Footnotes Series C Preferred Stock 2014-07-23 4 C 0 885583 D Common Stock 281137 0 I See Footnotes The Series A Preferred Stock automatically converted into Common Stock on a 3.15-for-1 basis at the closing of the Issuer's initial public offering for no consideration, and had no expiration date The Series B Preferred Stock automatically converted into Common Stock on a 3.15-for-1 basis at the closing of the Issuer's initial public offering for no consideration, and had no expiration date The Series C Preferred Stock automatically converted into Common Stock on a 3.15-for-1 basis at the closing of the Issuer's initial public offering for no consideration, and had no expiration date ARCH Venture Partners VII, L.P. (the "GPLP"), as the sole general partner of ARCH Venture Fund VII, L.P. ("ARCH"), may be deemed to beneficially own certain of the shares held by ARCH. The GPLP disclaims beneficial ownership of all shares held by ARCH in which the GPLP does not have an actual pecuniary interest. ARCH Venture Partners VII, LLC (the "GPLLC"), as the sole general partner of the GPLP, may be deemed to beneficially own certain of the shares held by ARCH. The GPLLC disclaims beneficial ownership of all shares held by ARCH in which it does not have an actual pecuniary interest. (Continued from Footnote 4) The managing directors of the GPLLC, the Reporting Person, Keith Crandell and Clinton Bybee (together, the "Managing Directors"), are deemed to have voting and dispositive power over the shares held by ARCH, and may be deemed to beneficially own certain of the shares held by ARCH. The Reporting Person disclaims beneficial ownership of all shares held by ARCH in which he does not have an actual pecuniary interest. /s/ Laurie Burlingame, as Attorney-in-Fact for Robert T. Nelsen 2014-07-23