Atara Biotherapeutics Inc. plans to raise $100 million through a secondary stock offering, the company announced Tuesday.

The company, which is developing T-cell immunotherapy for cancer treatments, is headquartered in South San Francisco but its research and development operation is in Westlake Village.

All shares in the secondary offering will be sold by the company. J.P. Morgan and Cowen Group will act as joint book-running managers. The offering is based on a shelf registration filed in November 2015.

The company announced the offering after market close on Tuesday. Shares of Atara (ATRA) closed Tuesday unchanged at $18.10 on the Nasdaq.