ORLANDO, Fla. & BERKELEY, Calif.--(BUSINESS WIRE)--Plexxikon Inc. today announced preliminary data from a Phase 1 clinical study investigating PLX4032 (R7204). PLX4032 is a novel, oral and highly selective drug that targets the BRAFV600E cancer-causing mutation that occurs in most melanomas and about eight percent of all solid tumors. In patients whose cancer harbors this mutation and who were treated with therapeutic doses of PLX4032, tumor shrinkage and extended progression-free survival have been observed. Currently, two extension studies are being conducted in mutation-positive melanoma and colorectal cancer patients. Following the initial positive findings announced today, larger clinical trials to support a registration program for product approval are targeted to start later in 2009. Plexxikon and Roche are co-developing PLX4032 under their 2006 license and collaboration agreement.