Singapore, Dec 13, 2011: Plexxikon, a member of Daiichi Sankyo Group, has announced scientific findings from preclinical studies showing that treatment with a novel oral agent, PLX3397, selectively inhibited key cancer-driving Flt3 mutations that occur in 20-30 percent of acute myeloid leukemia (AML) patients. In a preclinical model of AML, PLX3397 showed significant tumor regression. This preclinical work also showed that PLX3397 retained activity against certain drug-resistant forms of mutated Flt3 that can occur with other treatments.

“Given PLX3397’s selectivity for relevant mutations, we are exploring this potential personalized medicine for AML patients with Flt3 mutations,” said K. Peter Hirth, chief executive officer of Plexxikon. “Plexxikon’s hallmark capability to design selective kinase inhibitors enables clinical researchers to test the hypotheses of such targeted therapies directly and rapidly.”

Phase 1 dose escalation testing in patients with solid tumors has been completed, and showed that PLX3397 reached therapeutic drug levels that were well tolerated at the doses tested. Two Phase 2 studies are now under way to further evaluate PLX3397, including one study in Hodgkin lymphoma and another study recently initiated in patients with Flt3-mutated AML. Plasma from Phase 1 patients contained sufficient levels of PLX3397 to block signaling in Flt3-mutant AML cells ex vivo. Additionally, PLX3397 has been tested in primary AML patient blood samples, which showed a clear dose response to drug at clinically achievable drug levels.