Gilead Sciences made its third major acquisition in the past eight months, buying privately held Calistoga Pharmaceuticals of Seattle for $375 million cash and $225 million in potential milestones.

Foster City, Calif.-based Gilead, which ended 2010 with $5.3 billion in cash, has made a series of acquisitions to diversify its portfolio by getting into oncology and inflammation treatments ahead of patent expirations for its HIV drugs, according to BioWorld Week. In December 2010, it bought privately held Arresto Biosciences for $225 million in cash plus milestones for its lead candidate AB0024 in phase I testing in solid tumors and idiopathic pulmonary fibrosis. Six months earlier Gilead added an early-stage kinase program by acquiring Branford, Conn.-based CGI Pharmaceuticals in a potential $120 million deal, including milestones.

The key to the Calistoga deal is lead candidate CAL-101, which targets phosphoinositide-3 kinase (PI3K) delta isoform and is in phase II studies as a single agent in patients with refractory indolent non-Hodgkin’s lymphoma (iNHL) and in combination with rituximab in treatment-naïve elderly patients with chronic lymphocytic leukemia (CLL).

The deal follows encouraging fourth-quarter and full-year 2010 results for Gilead that met or exceeded expectations. They included full-year product sales of $7.39 billion, up 14% over 2009, full-year total revenues of $7.95 billion, up 13%, and full-year non-GAAP earnings per share of $3.69, up 21%. The company reported product sales for the fourth quarter increased 7% to $1.93 billion from a year ago.