Sept. 30 (Bloomberg) -- Bayer AG and Onyx Pharmaceuticals Inc.’s Nexavar cancer drug failed to slow the progression of breast cancer in the second of four studies that combine the medicine with different types of chemotherapy.

The pill in combination with chemotherapy drug paclitaxel showed a “positive trend” toward helping women live longer without their disease getting worse though the results weren’t statistically significant, the two drugmakers said in an e- mailed statement today. Bayer and Onyx didn’t say how long it took the women’s tumors to progress.

“These encouraging data warrant further investigation,” lead scientist William Gradishar, a professor of medicine at Northwestern University, said in the statement, adding that women with advanced breast cancer often lack treatment options.

Results of a different trial presented last week at the European Cancer Organization and European Society for Medical Oncology conference in Berlin showed that Nexavar delayed progression of breast cancer by 6.4 months when combined with Roche Holding AG’s chemotherapy pill Xeloda, compared with 4.1 months for chemotherapy alone. Bayer is now considering whether to begin the last stage of clinical trials needed before Nexavar, already approved for use in kidney and liver tumors, could be marketed for breast cancer as well.

Bayer will decide by early next year whether to move Nexavar into the final stage of clinical testing, Robert Rosen, head of global oncology at Bayer, said in an interview at last week’s conference. The German drugmaker doesn’t expect the medicine to reach the breast cancer market before late 2012.

Additional Trials

Bayer, based in Leverkusen, Germany, and Emeryville, California-based Onyx are conducting two more mid-stage trials of Nexavar in breast cancer, the companies said. Full results of the study reported today will be presented at a future medical conference.

Onyx shares fell $2.09, or 6.5 percent, to $29.97 at 4 p.m. New York time in Nasdaq Stock Market composite trading, the biggest single-day drop in eight weeks. Bayer declined 3.1 percent to close at 47.35 euros in Frankfurt trading.

Bayer forecasts that Nexavar may generate as much as 750 million euros ($1.1 billion) in annual sales for breast cancer if approved by regulators, Rosen said.

To contact the reporter on this story: Naomi Kresge in Zurich at nkresge@bloomberg.net

Last Updated: September 30, 2009 16:09 EDT