Paving its way for an eventual biologics license application, Cell Genesys Inc. received a special protocol assessment from the FDA for its upcoming Phase III trial of the GVAX prostate cancer vaccine.

The South San Francisco-based company plans to begin the trial, the first of two, at the end of the second quarter.

"We expect to enroll somewhere in the neighborhood of 500 to 600 patients in the study," said Jennifer Cook Williams, director of corporate communications and investor relations for Cell Genesys. "The endpoint will be survival and there will be a complementary trial, which we hope to start in late 2004 or early 2005."

A special protocol assessment (SPA) ensures that the design of a Phase III trial will meet the objectives needed to support a BLA. When the FDA issues an SPA, it essentially provides the company with a binding written agreement that the design and analysis of the study are adequate to support a license application submission. Positive data, of course, remain the crux of any application.

"It means they would accept a BLA for filing," Williams told BioWorld Today. "It doesn't mean they would approve the product."

Cell Genesys plans to conduct the two Phase III trials of GVAX in hormone-refractory prostate cancer patients with radiologic evidence of metastatic disease. The first trial - called VITAL-1 - will enroll chemotherapy-na ve, asymptomatic patients without cancer-related pain and will look at the survival benefit of patients treated with GVAX, compared with those treated with taxane chemotherapy. The second trial - called VITAL-2 - will enroll symptomatic patients and will look at palliation of bone pain, comparing GVAX plus taxane to taxane alone. Both trials will enroll patients with all levels of Gleason scores - a measure of the aggressiveness of prostate cancer. VITAL-1 and VITAL-2 will look at palliation of bone pain and survival as secondary endpoints, respectively.

"We expect them to take between 2.5 and 3.5 years," Williams said. Therefore, a BLA could be filed sometime in 2007.

In previous studies, GVAX vaccine showed a favorable survival benefit when compared with the survival of patients treated with taxane chemotherapy, the most widely used therapy of metastatic prostate cancer patients. In September 2002, final data of its first Phase II trial of GVAX in patients with hormone-refractory metastatic prostate cancer showed the median survival in two dose groups was 26.2 months. The trial enrolled 34 patients with radiologic evidence of metastases. They were treated for six months, with only the vaccine. The company now hopes to confirm those results in the larger, randomized, controlled Phase III trial.

Cell Genesys also expects to report Phase II data of GVAX involving 80 patients with advanced hormone-refractory prostate cancer with evidence of metastasis to bone and other sites in June at the 2004 American Society of Clinical Oncology meeting.

Aside from prostate cancer, GVAX vaccines are being studied in Phase I/II and Phase II trials for lung cancer, pancreatic cancer, leukemia and myeloma. The products are whole-cell vaccines designed to stimulate an immune response against the patient's tumor. They are comprised of genetically modified tumor cells that secrete granulocyte macrophage colony-stimulating factor, an immune stimulatory hormone known to play a role in triggering the body's immune response. The treatment appears to be well tolerated in the more than 600 patients treated with them to date.

In addition to GVAX, Cell Genesys is working on two other cancer product platforms: oncolytic virus therapies and anti-angiogenesis therapies. Its oncolytic virus therapies include CG7870, which is in a Phase I/II study evaluating it plus radiation therapy for early stage prostate cancer. The company also is studying all three platforms in various preclinical trials.

In March, Cell Genesys raised $53.1 million in a public offering to help offset costs of the Phase III GVAX vaccine trials in prostate and lung cancer, both of which it plans to begin this year. (See BioWorld Today, March 18, 2004.)

Cell Genesys holds all rights to the GVAX portfolio, after the ending of a deal in 2002 with Tokyo-based Japan Tobacco Inc. for the lung cancer indication. (See BioWorld Today, Oct. 21, 2002.)

As for manufacturing, Cell Genesys expects to use its bioreactor manufacturing facility in Hayward, Calif., for Phase III trials and a potential market launch.

The company's stock (NASDAQ:CEGE) dropped 20 cents on Monday, to close at $10.05.