On Feb. 22, 2011, Foster City, Calif-based Gilead Sciences and Calistoga Pharmaceuticals announced Gilead’s acquisition of Calistoga for $375 million, plus milestones worth an additional $225 million. Calistoga, based in Seattle was founded in 1986 to develop the first selective inhibitor of PI3K-delta, a critical signaling molecule for many types of hematologic cancers.

In clinical studies Calistoga’s lead candidate (CAL-101) achieved positive early activity in patients with chronic lymphocytic leukemia and follicular lymphoma. Following further development, including FDA Breakthrough Therapy designation, Gilead achieved both FDA and EU approval in 2014 for CAL-101 (as brand name Zydelig) to treat CLL, FL, and small lymphocytic lymphoma.