Gilead Sciences will acquire Calistoga Pharmaceuticals for $375 million, plus an additional $225 million if certain milestones are achieved. The transaction is expected to close in 2Q11. Calistoga is a privately held biotechnology company focused on developing therapies to treat cancer and inflammatory diseases. Calistoga’s portfolio includes compounds that selectively target isoforms of phosphoinositide-3 kinase (PI3K), a central signaling pathway related to cellular proliferation, survival...