Plexxikon Inc. today announced encouraging clinical data from a Phase 1 extension study of PLX4032 (RG7204) in metastatic melanoma patients, which expand the results announced from the initial phase of the study. PLX4032 is a novel, oral and highly selective drug that targets the BRAFV600E cancer-causing mutation that occurs in about 50 percent of melanomas and about eight percent of all solid tumors. Tumor shrinkage has been observed in nearly all of the currently evaluable patients in the extension study, reflecting a 70 percent response rate. These data will be presented at the ECCO 15/ESMO 34 Joint Multidisciplinary Congress in Berlin, Germany. Larger clinical trials to support a registration program for product approval are targeted to start shortly. Plexxikon and Roche are co-developing PLX4032 under their 2006 license and collaboration agreement.
Patients who tested positive for the BRAFV600E mutation have been enrolled in the open-label, single-arm extension cohort. All patients have been treated with PLX4032 at 960 mg twice daily (BID), with anti-tumor effects measured by RECIST (Response Evaluation Criteria in Solid Tumors) every eight weeks. Patients will be treated until disease progression. Eligible patients for this trial must have progressed after at least one prior treatment. While enrollment for the melanoma extension cohort is complete, Plexxikon is enrolling a second cohort of patients with colorectal cancer and expects enrollment to be complete by year end.
Melanoma Extension Study Confirms Safety & Tumor Regression Seen in Phase 1 Dose Escalation Study
In an extension study of melanoma patients with the BRAFV600E mutation, 31 patients have been enrolled, most of whom have the worst stage of metastatic disease (Stage M1c), and who were treated with PLX4032 at 960 mg BID. Among the 27 evaluable patients to date, results confirm the preliminary safety and efficacy seen in the previous Phase 1 dose escalation study: