13G Filing: Biotechnology Value Fund LP and Syndax Pharmaceuticals Inc (SNDX)

Item 1(a).

Name of Issuer:

Syndax Pharmaceuticals, Inc., a Delaware corporation (the
“Issuer”).

Item 1(b).

Address of Issuer’s Principal Executive Offices:

35 Gatehouse Drive, Building D, Floor 3

Waltham, Massachusetts 02451

Item 2(a).

Name of Person Filing

Item 2(b).

Address of Principal Business Office or, if None, Residence

Item 2(c).

Citizenship

Biotechnology Value Fund, L.P. (“BVF”)

1 Sansome Street, 30^th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Fund II, L.P. (“BVF2”)

1 Sansome Street, 30^th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Trading Fund OS
LP (“Trading Fund OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

BVF Partners OS Ltd. (“Partners
OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

BVF Partners L.P. (“Partners”)

1 Sansome Street, 30th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF Inc.

1 Sansome Street, 30^th Floor

San Francisco, California 94104

Citizenship: Delaware

Mark N. Lampert (“Mr. Lampert”)

1 Sansome Street, 30^th Floor

San Francisco, California 94104

Citizenship: United States

Each of the foregoing is referred to
as a “Reporting Person” and collectively as the “Reporting Persons.”