West Coast Editor

Shares of GPC Biotech Inc., partner Pharmion Corp., and licensee Spectrum Pharmaceuticals Inc. continued to sink Tuesday as an FDA advisory panel debated the merits of satraplatin for second-line, hormone-refractory prostate cancer, in a closely watched case that had investors nervous because of briefing papers posted last week on the agency's website.

It was a nail biter. Not so much because backers of the companies feared satraplatin (branded Orplatna) wouldn't get approved, but because the unconventionally designed, progression-free survival (PFS) endpoint might mean a delay until regulators can see final survival data, near the end of this year.

And that's what happened. The Oncology Drugs Advisory Committee voted 12-0 to recommend that the agency wait for the overall survival results. All ears turned to GPC's conference call on the panel result, slated for 1 a.m. EDT today.

"The company had said that the FDA bought into this PFS analysis, and clearly the FDA had not," Ren Benjamin, analyst with Rodman & Renshaw, told BioWorld Today.

ODAC had five main concerns about the Phase III SPARC (Satraplatin and Prednisone Against Refractory Cancer) trial, which compared the oral platinum drug plus prednisone to placebo plus prednisone in 950 patients with HRPC.

Among the sticking points was the progression-free survival endpoint used by GPC, which combined radiologic review of tumors - the usual way to measure PFS - with factors such as an increase in pain. SPARC data reviewers differed on how well patients did on satraplatin, "which raises the question [of] whether progression could be reliably assessed in this trial." (See BioWorld Today, July 23, 2007.)

Benjamin said GPC "designed what I thought was a very rigorous endpoint" in PFS with several parts. "It was almost like they built a very tightly wound picket fence around each patient, and any way they moved - if one of the clinically meaningful indicators suggested they were progressing - then boom, they were marked as a progressor."

While GPC might have some trouble explaining the ODAC snafu to investors, Benjamin said the firm did the right thing for shareholders by using the co-primary endpoint.

"It's not necessarily that they lost out on the game," he said. "The FDA said, 'Overall survival is what you need,' and the company said, 'If we hit PFS, would you entertain accelerated approval?' and the FDA said yes."

But the multipart PFS endpoint wasn't up to FDA snuff, though apparently GPC believed it might be.

"They tried, and they failed," Benjamin said. "Now they'll have to wait for overall survival data, which they would have had to do anyway. Now we have to wait a year, just like we would have had to anyway."

Benjamin acknowledged that Thousand Oaks, Calif.-based Amgen Inc.'s Vectibix (panitumumab) was approved on PFS data, albeit PFS data of the more traditional kind.

"That goes to show you the relationship you have with the FDA is extremely important," he said. (See BioWorld Today, Sept. 29, 2006.)

Martinsried, Germany-based GPC's stock (NASDAQ:GPCB) closed Tuesday at $20.36, down 59 cents. Shares of Spectrum (NASDAQ:SPPI), of Waltham, Mass., ended the day at $4.80, down 50 cents. Boulder, Colo.-based Pharmion (NASDAQ:PHRM) finished at $24.62, down $1.08.