U.S. drug reviewers will ask an advisory panel if they should wait for more data before deciding whether to approve GPC Biotech proposed prostate cancer pill, a summary released Friday said.
Food and Drug Administration staff raised five issues with GPC's application for the drug Orplatna, known generically as satraplatin. The reviewers asked whether one of the main goals in a GPC study was an acceptable basis for approval, and if pain measurements were reliable, among other things.
The FDA will ask a panel of outside experts that meets Tuesday for input on those issues and whether officials should defer a decision on the drug until final survival data is available, the summary said. Those findings are expected near the end of 2007.
Orplatna is the lead product candidate for Germany-based GPC Biotech. The company's shares fell 34 percent in German trading, and took a similar fall on the Nasdaq . Shares of Spectrum Pharmaceuticals, which licensed the drug to GPC, were down nearly 29 percent on Nasdaq, while shares of Pharmion slid nearly 8 percent, also on Nasdaq.
Spectrum has the option to co-promote Orplatna in the U.S. Pharmion owns rights to sell the drug in Europe and some other territories.
GPC Biotech spokeswoman Laurie Doyle said the company had no comment on the FDA staff summary.
"We do remain convinced of the strength of satraplatin data," she said.
But Sal. Oppenheim analyst Christian Peter said Orplatna "is now in the emergency unit," adding: "It's almost certainly delayed."
GPC is seeking FDA clearance to sell the drug for patients with prostate cancer that has stopped responding to prior chemotherapy and resists hormone treatments.
Orplatna is a platinum-based drug that can kill cancer cells. Platinum therapies are commonly used in chemotherapy regimens, but the ones currently on the market must be given intravenously. Orplatna is a pill.
The company studied 950 patients treated with satraplatin plus the steroid prednisone or a placebo and prednisone.
FDA reviewers said Orplatna patients lived a median of 11.1 weeks without their disease getting worse, compared with 9.7 weeks for placebo patients. But they questioned whether that measurement was acceptable to support approval.
Two radiologists also disagreed on readings from 39 percent of patients, FDA staff said. "This raises the question whether (disease progression) could be reliably assessed," the reviewers said.
The FDA reviewers also said only half of the patients had been treated previously with the drug docetaxel, which has been shown to extend survival in patients with hormone-resistant prostate cancer.
The FDA usually follows recommendations from its advisory panels. An agency ruling on the drug is expected in August.
GPC Biotech, in a separate summary, said its main study was "well designed and well executed." The drug offers "disease control and pain control" in a patients with no approved treatment options and a short life-expectancy, the company added.