Bayer, Onyx Drug Shrinks Tumors in Some Patients

About 35 percent of patients on an experimental drug being developed by Bayer AG and Onyx Pharmaceuticals experienced a reduction in their kidney cancer tumors of 25 percent within three months, researchers said on Saturday.

The results are significant because the drug, sorafenib, could provide a less-toxic treatment alternative than drugs currently used for kidney cancer, also known as renal cell cancer. In addition, the drug is a pill, as opposed to injections that are often used to treat kidney cancer. The experimental drug was tested in a mid-stage, or Phase II clinical trial of 106 kidney-cancer patients. Of those 106 patients, 37 saw their tumors shrink by 25 percent or more in the first 12 weeks of treatment and 45 had their disease “stabilize” — meaning tumors shrank less than 25 percent or grew no more than 25 percent. The clinical trial, which was presented at an annual meeting of the American Society of Clinical Oncology, did not compare the drug to any other therapy. Patients whose tumor progress “stabilized” after 12 weeks were then randomized and given either the drug or a placebo. Results from the progress of those patients — which could be important to uncovering the drug’s true effectiveness — could be available this summer or fall. Onyx, a small biotechnology company, and German drugmaker Bayer intend to enroll a total of 800 patients in a Phase III clinical trial. Sorafenib, known as BAY 43-9006 for Bayer’s development purposes, is a member of the new category of drugs generally known as anti-angiogenesis inhibitors, designed to starve tumors of the blood they need to thrive. The drug blocks a blood-vessel promoter, Raf kinase, an enzyme that acts as a control switch for the RAF gene, which helps control tumor growth. It has also been shown to block a protein called Vascular Endothelial Growth Factor, which plays a key role in the growth of blood vessels. Dr. Mark Ratain, a University of Chicago researcher who was the primary investigator for the trial, said he envisions the oral treatment being used as a chronic-care drug, with patients being monitored often to see if their disease has progressed to the point where they need more serious therapy. “It is not going to be a cure and it is not going to result in long-term disease survival,” he said. “But it is potentially an appropriate first-line therapy.” Drugs currently used for cases of serious kidney cancer include interferons, or injected versions of proteins that the body uses to fight viruses, or interleukin-2, a cellular hormone normally produced by white cells that is central to the functioning of the human immune system, including the rejection or destruction of tumor cells. Both drugs are considered heavy-duty and can be toxic. Of the patients who had the most robust response — 25 percent tumor reduction or greater — the median time before the disease progressed again was 48 weeks, a delay Ratain considers strong, if not outstanding.(Source: American Society of Clinical Oncology: Reuters Health News: Jed Seltzer: June 2004)