Ambit Biosciences has entered into a $390 million agreement with Japan's Astellas Pharma to develop and commercialize FLT3 kinase inhibitors to treat cancer and other conditions. The deal will include Ambit's AC220, a kinase inhibitor currently in Phase II trials to treat a form of blood cancer called acute relapsed/refractory myeloid leukemia (AML). Astellas has agreed to pay Ambit $40 million up front, and up to $350 million in milestone payments. The two companies will collaborate on the development of AC220, although Astellas will fund all commercialization costs. They will also work together on a research and development program for a series of novel FLT3 inhibitors. Mutations in the FLT3 kinase are found in 25 to 40 percent of patients with AML. These mutations are associated with poor prognosis and decreased response to treatment. Protein kinases are enzymes that help regulate cellular function. Some kinases are known to play a role in the development of certain cancers. Kinase inhibitors may be able to block the activity of these enzymes and "switch off" the mechanism that causes disease. CGI Pharmaceuticals, Onyx Pharmaceuticals, Calistoga Pharmaceuticals and ProQinase are a handful of companies engaged in the development of kinase inhibitors.