BioWorld International Correspondent

Shares in GPC Biotech AG surged Monday on news that the company's lead compound, the orally available platinum analogue satraplatin, attained the primary endpoint in a Phase III registration trial of the compound as a second-line therapy in hormone refractory prostate cancer.

The stock (Frankfurt:GPC) peaked at €16.70 (US$21.30) during trading on the Frankfurt Stock Exchange, and closed at €14.70, up 36.4 percent from Friday's close of €10.78.

Its European marketing partner, Boulder, Colo.-based Pharmion Corp., also climbed strongly on the news, with shares (NASDAQ:PHRM) jumping $3.60, or 20 percent to close at $21.61. Spectrum Pharmaceuticals Inc., of Irvine, Calif., which licensed the drug to GPC in 2002, also benefited, with its shares (NASDAQ:SPPI) soaring 45.6 percent Monday, or $1.59, to close at $5.08

The study, which involved 950 patients recruited through 200 treatment centers in 15 countries, evaluated satraplatin in combination with prednisone vs. prednisone plus placebo. Patients in the treatment arm had a 40 percent reduction in the overall risk of disease progression compared with those in the control arm. The result was highly statistically significant (p=0.00001).

The improvement in progression-free survival (PFS) increased over time. At the 50th percentile, GPC said, there was a 13 percent improvement in PFS in the treated group vs. the control arm (11 weeks vs. 9.7 weeks). At the 75th percentile, that gap widened to an 89 percent improvement in PFS (36 weeks vs. 19 weeks).

After six months, 30 percent of satraplatin-treated patients had not progressed, whereas the equivalent statistic for the placebo group was 17 percent. At 12 months, 16 percent of patients in the treatment group had not progressed, compared with 7 percent of patients in the control arm.

"I believe we have accomplished one of the most important corporate milestones in the history of GPC Biotech," GPC Biotech CEO Bernd Seizinger said on a conference call.

The company plans to complete a rolling new drug application submission, based on the PFS data, by year's end. Pharmion aims to submit a marketing authorization application to the London-based European Medicines Agency during the first half of next year.

Survival data are not yet available, as more than half of the participants are still alive, Seizinger said. The company originally anticipated that the data would be available by mid-2007 but has pushed back that date to the fall.

"Overall survival for an oncology trial is a gold standard for approval of a drug worldwide," said Tom McKearn, vice president for strategic clinical affairs at GPC. "It is an extremely valuable and important part of the overall trial."

Daniel Wendorff, analyst at WestLB AG in Dusseldorf, Germany, said the data were "a home run," and added that the study is "definitely a transforming event for a company like GPC Biotech."

"It looks like they can really hit survival benefit at the end of the study, and that's going to be very important in marketing this drug and establishing it as gold standard," said Markus Metzger, analyst at Vontobel AG, in Cologne, Germany. "Every company that wants to enter the market [would have to] do trials head to head with satraplatin. It's always difficult to show any additional benefit."

Wendorff has forecast revenues of $526 million for satraplatin as a second-line therapy in hormone-refractory prostate cancer. The company has almost a dozen pilot studies under way that are evaluating the potential of the compound in other cancer indications and in differing combinations. Seizinger said GPC Biotech will focus on combinations that involve other orally available compounds and on drugs that offer novel mechanisms of action, such as kinase inhibitors.

"If the line extension studies prove to show the potential of satraplatin, it definitely would become a blockbuster," Wendorff said.

The compound has potential as first-line therapy in prostate cancer, Metzger said, as New York based Bristol-Myers Squibb Co. previously demonstrated efficacy with the compound in that indication, although it never progressed the program.

Spectrum could receive milestone payments related to acceptance and approval of applications in the U.S. and Europe of about $20 million, with milestones hinged on sales after that. Spectrum also would receive royalties and has co-promotion rights in the U.S.

GPC out-licensed rights for Europe, the Middle-East and Australia and New Zealand to Pharmion in 2005, in a deal worth up to $270 million in regulatory and sales-related milestone payments, plus royalties ranging from 26 percent to 30 percent. It has retained rights to the compound North America and Asia. It is in the process of building a commercial infrastructure in the U.S., but is seeking partners for the latter territory, Seizinger said, calling the region "mission impossible for us."