Atara Biotherapeutics has received the U.S. Food and Drug Administration’s green light to start clinical trials for its next-generation CAR T therapy, which specializes in treating solid tumors.

CAR T stands for chimeric antigen receptor T cells; they are genetically engineered to target a specific protein. In the case of Atara’s ATA2271, that target is mesothelin — an antigen present on the surface of solid tumor cells.

“CAR T cell therapies … have not yet proven effective in solid tumor settings,” Atara said in a statement. “Mesothelin ... is commonly expressed at high levels on the cell surface in many aggressive solid tumors including mesothelioma, ovarian cancer, pancreatic cancer, and non-small cell lung cancer.”

Atara is technically headquartered in South San Francisco but has large facilities in Westlake Village and Thousand Oaks to develop T-cell immunotherapies for cancer, autoimmune and viral diseases.

The company announced preclinical data for the therapy at this year’s American Association for Cancer Research virtual meeting in June. Data pointed to improved in vivo efficacy, or how well the therapy works in animal test subjects, compared to its first-generation CAR T therapy to target mesothelin.