Calistoga Pharma

Calistoga Pharmaceuticals was a clinical-stage biotechnology company based in Seattle, Washington, specializing in the development of selective inhibitors of the phosphoinositide 3-kinase (PI3K) pathway. The company's lead product candidate, CAL-101 (now Zydelig), was the first isoform-selective PI3K delta inhibitor to enter clinical trials, targeting B-cell malignancies such as chronic lymphocytic leukemia and non-Hodgkin lymphoma. Calistoga's research focused on the role of the PI3K delta isoform in leukocyte signaling and its contribution to cancer cell survival and inflammatory responses. In 2011, the company was acquired by Gilead Sciences for $375 million upfront, with an additional $225 million in potential milestone payments. This acquisition led to the eventual FDA approval of Zydelig, marking a significant milestone in targeted therapy for hematologic cancers.