Less than six months after submitting a new drug application, Onyx Pharmaceuticals Inc. and partner Bayer Pharmaceuticals Corp. gained marketing approval for Nexavar in patients with advanced renal-cell carcinoma.

"This marks our emergence as a new entrant in the U.S. oncology market," said Hollings Renton, president and CEO of Emeryville, Calif.-based Onyx, which began collaborating with Bayer more than 10 years ago. The FDA approval triggered a $10 million milestone payment to Onyx. The company said it expected to begin shipping Nexavar within 24 hours of approval.

"We believe this is just the first step in having the full potential of Nexavar as an anticancer agent," Renton said during a conference call, adding that the drug also is being tested in Phase III trials as a treatment for advanced hepatocellular carcinoma and metastatic melanoma, with a third Phase III expected to start next year in non-small-cell lung cancer.

Nexavar (sorafenib) is an oral multi-kinase inhibitor designed to target serine/threonine and receptor tyrosine kinases in both the tumor cell and tumor vasculature. Study results showed that it "doubled progression-free survival and, in interim analysis, showed a 28 percent reduction in the risk of death for Nexavar-treated patients," Renton said.

In fact, those early results were so promising, investigators began offering the drug to trial patients who previously had been receiving placebo. Onyx and Bayer also have been providing Nexavar through an expanded access program, through which the drug has been administered to an additional 2,000 advanced kidney cancer patients. (See BioWorld Today, April 19, 2005.)

Nexavar's approval stemmed from Phase III data showing that patients receiving the drug had a median value of progression-free survival of six months vs. three months for those given placebo. That trial is ongoing, and on the safety side, Grade 3 and 4 treatment-emergent adverse events were reported in 31 percent of the treated population, compared to 22 percent for the placebo group.

Shares of Onyx (NASDAQ:ONXX) closed at $29.15 Tuesday, up $1.11.

Though it's the first FDA-approved treatment for kidney cancer in more than 10 years, Nexavar's place in the market could be threatened by Sutent, a multitargeted oral compound waiting in the wings. Phase II data presented in May at the American Society of Clinical Oncology in Orlando, Fla., demonstrated that the drug, from New York-based Pfizer Inc., had a time to progression of 8.7 months, and showed partial response rates of 40 percent. (See BioWorld Today, May 17, 2005.)

Pfizer filed for marketing approval of Sutent in August, a month after the Nexavar NDA, for metastatic renal-cell carcinoma and malignant gastrointestinal stromal tumors. Sutent also was granted priority review, so an approval could come early next year.

Another potential competitor could end up being South San Francisco-based Genentech Inc.'s Avastin (bevacizumab), a VEGF inhibitor, in clinical development as a treatment for renal-cell cancer.

While Onyx anticipates competition in the kidney cancer market, "we believe that having compelling data, and a somewhat earlier than expected approval, gives us a distinct competitive advantage," said Ed Kenney, executive vice president and chief business officer.

The companies have priced Nexavar at $4,333 for a one-month supply. In the U.S., about 37,000 people are diagnosed with renal-cell carcinoma each year, with about 102,000 dying from the disease annually.

Onyx and West Haven, Conn.-based Bayer have a 50/50 profit-sharing arrangement in the U.S. For the rest of the world, Onyx's share is less than 50 percent. The only exception is Japan, where Bayer agreed to fund all product development, and Onyx is entitled to a royalty payment.

Onyx brought in $136.5 million through a public offering last month, in part to help fund commercialization activities associated with Nexavar. The company expects to end the year with a cash position of $290 million.