After progression-free survival data for satraplatin failed to wow an FDA advisory committee in July, GPC Biotech AG, along with partners Pharmion Corp. and Spectrum Pharmaceuticals Inc., hoped the drug's overall survival data would be impressive enough to clear the way for approval in second-line hormone-refractory prostate cancer.

Instead, the platinum-based therapy trial fell short, yet again. Top-line results from the 950-patient Phase III SPARC (Satraplatin and Prednisone Against Refractory Cancer) trial missed its overall survival endpoint. Patients in the satraplatin arm had a median overall survival of 61.3 weeks compared to 61.4 weeks for patients in the control arm, with a hazard ratio of 0.97.

Shares of GPC (NASDAQ:GPCB), which fell 25 percent on this summer's advisory panel vote, were pummeled again, dropping $6.44, or 56 percent, to close Wednesday at $5.

Spectrum and Pharmion, both of which have been emphasizing other pipeline offerings since the satraplatin's advisory panel debacle, fared better. Spectrum's stock (NASDAQ:SPPI) closed at $3.79, down 35 cents, or 8.5 percent, and Pharmion's stock (NASDAQ:PHRM) closed at $48.12, up 83 cents.

Though the data were disappointing for GPC and its partners, they came as no surprise to analyst Christopher Raymond, of Chicago-based Robert W. Baird & Co., "especially after the advisory meeting" in July, which raised concerns regarding the trial's design and questioned the way the progression-free survival endpoint was measured.

FDA briefing documents, released before that Oncology Drugs Advisory Committee meeting, also highlighted uneven treatment with Taxotere in the patient population. Taxotere (docetaxel) was approved in combination with prednisone for treating prostate cancer in February 2006, about midway through the SPARC study, so that only half the patients enrolled in SPARC had received previous Taxotere treatment. (See BioWorld Today, July 23, 2007.)

All of those considerations amounted to a "general sense that [satraplatin] probably wouldn't meet its survival endpoint," Raymond told BioWorld Today. And while "it's always easy to do Monday morning quarterbacking," he added, it does beg the question of "why the trial design was not more tightly controlled."

For Martinsried, Germany-based GPC, which withdrew its new drug application shortly after the ODAC meeting, the next step is to perform subset analyses from the trial. Though the company declined to go into specifics at this time, some of those subsets could include patients pre-treated with Taxotere, as well as subsets determined by different prognostic factors.

After concluding those analyses, GPC intends to meet with the FDA. "It's unlikely, however, that we would be able to do a filing based on any subgroup analysis," GPC CEO Bernd Seizinger said during the company's conference call. Though he called the Phase III miss "a major setback" for the company, he assured investors that it "doesn't mean that satraplatin is of no value as an asset to us." He said the company has ongoing Phase I and Phase II studies of satraplatin in combination with approved therapies in non-small-cell lung cancer and other solid tumors.

SPARC's overall survival data almost certainly will compromise Pharmion's European marketing application for satraplatin, currently under review. Pharmion submitted the filing in June with the progression-free survival data, intending to add the overall survival results during the review process. While the upcoming subset analyses offer "a glimmer of a chance" for satraplatin's approval in Europe, "I don't have great hope," Raymond said. "My assumption is that another trial" would be required.

In the meantime, Boulder, Colo.-based Pharmion is focusing on other late-stage programs. The company is gearing up to submit supplemental drug applications in the U.S. and Europe for Vidaza, to include data reported in August showing that the drug extended overall survival by 74 percent in higher-risk patients with myelodysplastic syndromes. And earlier this month, Pharmion initiated a 480-patient pivotal study of amrubicin, a third-generation anthracycline, in small-cell lung cancer.

Like Pharmion, Spectrum also has a late-stage portfolio. The Waltham, Mass.-based company is advancing EOquin (apaziquone for intravesical instillation) into a pivotal Phase III trial in bladder cancer and is looking to start Phase III trials next year of ozarelix, a luteinizing hormone-releasing hormone antagonist, in benign prostatic hyperplasia.

Spectrum licensed rights to satraplatin to GPC in 2002. GPC later signed Pharmion as its European partner, and in June, partnered the product in Japan with Tokyo-based Yakult Honsha Co. Ltd. In the Yakult deal, GPC received a $10 million payment and is entitled to potential undisclosed milestones and at least a 21 percent royalty rate on sales of satraplatin in Japan. (See BioWorld Today, June 26, 2007.)