Shares of Atara Biotherapeutics Inc. rose nearly 19 percent Friday after the company announced approval from the U.S. Food and Drug Administration to conduct Phase 3 clinical studies on its experimental drug tabelecleucel.

Atara is headquartered in South San Francisco but its research and development operation is in Westlake Village. The company researches treatments in T-cell immunotherapy.

The FDA authorization gives Atara permission to conduct late-stage studies on tabelecleucel as a treatment for Epstein-Barr virus. The company plans to start the trials soon.

“We expect tabelecleucel to be the first off-the-shelf T-cell immunotherapy to begin Phase 3 clinical development in the U.S.,” Dr. Isaac Ciechanover, chief executive, said in a statement. “Receiving clearance to initiate these studies is a significant milestone for Atara.”

Shares of Atara (ATRA) closed Friday up $2.85, or 18.7 percent, to $18.10 on the Nasdaq.