Bayer and partner Onyx Pharmaceuticals have elected to break the blinding on a Phase III trial of their candidate drug for renal cell carcinoma, sorafenib, after promising data suggested it would be unethical to keep patients on placebo.

The two companies, after discussion with the trial’s oversight committee, have elected to switch all patients receiving placebo to sorafenib (formerly known as BAY 43-9006) in light of data revealing a marked improvement in progression-free survival with the active drug. The results of the 800-patient study are scheduled for presentation at the American Society of Clinical Oncology annual meeting next month.

Last month, Bayer and Onyx reported interim data showing that sorafenib met the primary endpoint for efficacy in the Phase III trial and would now press on with filing for approval of the drug in the US [[22/03/05b]]. Last year, the companies elected not to press ahead with an accelerated filing based on Phase II data, preferring to wait for the Phase III results, causing jitters among investors who see sorafenib as one of the most important new compounds in Bayer’s pipeline [[05/08/04e]].

Sorafenib works as a Raf kinase inhibitor, blocking proliferation of a tumour and interfering with its blood supply and starving it of oxygen and nutrients. It has been granted orphan status for the renal cell carcinoma indication in both the US and EU and is also in development as a treatment for advanced melanoma alongside carboplatin.