Plexxikon has announced encouraging Phase I clinical data for PLX4032, a highly selective novel treatment that targets a specific cancer-causing mutation that occurs in about 50% of melanomas.

During the trial tumour shrinkage was observed in nearly all of the evaluable patients in the extension study, reflecting a 70% response rate.

Plexxikon chief executive officer Peter Hirth said that based on these results the company would move quickly to advance to pivotal trials.

“The results are encouraging in terms of efficacy and safety. Our precision engineering of new drug candidates could confer a safety advantage compared to other less targeted agents,” Hirth said.

During treatment, which was well tolerated, partial responses of greater than 30% tumour regression by Response Evaluation Criteria in Solid Tumors criteria have been observed in 18 patients, with 15 patients showing responses of greater than 50%.

Plexxikon and Roche are co-developing PLX4032 under a 2006 license and collaboration agreement.

Larger clinical trials to support a registration programme for product approval are expected to start shortly.