BioWorld International Correspondent

MUNICH, Germany - A compound from GPC Biotech AG could mark a significant step forward in the treatment of prostate cancer. Phase III trials of satraplatin, a platinum derivative, showed a significant increase in the time to disease progression in patients with hormone-refractory prostate cancer (HRPC), doubling their progression-free survival time.

The results of the trial were presented Tuesday at the annual meeting of the American Society of Clinical Oncology in Chicago. The study followed patients who were treated with satraplatin plus prednisone, a standard synthetic hormone often used to treat advanced prostate cancer, and prednisone alone. Among fifty patients, the study found that the average time to disease progression was 5.2 months in those treated with satraplatin vs. 2.5 months for those without. The median overall survival time was 15 months for satraplatin patients compared with 12 months for patients in the control arm.

"Moreover, after six months, 41 percent of those treated with satraplatin were progression-free, vs. 22 percent in the study's control arm," Bernd Seizinger, CEO of Martinsried-based GPC, told BioWorld International. "With the small size of the trial, it's rewarding to have a statistically significant result, but the most remarkable result is the doubling of the time" to progression.

Patients with HRPC have a fairly advanced form of the disease, which is one of the most common cancers in the United States and Europe. At present, early stage prostate cancer is typically treated by radiotherapy or surgery, both of which have risks, including incontinence and impotence. Further treatment is usually synthetic hormones.

"Most patients initially respond very well," Seizinger said, "but the vast majority eventually develop a hormone-resistant form of cancer." He added that prostate cancer is not often treated with chemotherapy. "The situation is a little like breast cancer 10 years ago."

At the later stages of the disease, there is only a 34 percent five-year survival rate.

Seizinger said that one important characteristic of satraplatin is that it is the first platinum analogue that can be given as a pill and not injected intravenously. "This complements the increasing trend to outpatient treatment. It makes the compound particularly attractive for an eventual combination of radiotherapy and satraplatin."

While the company will pursue registration with the FDA for the indication of HPRC, Seizinger said that in Phase II trials promising signs of effectiveness against other cancers also were observed. "We saw activity in Phase II with female tumors, such as ovarian carcinoma, and also with small-cell lung cancer," he noted. He added that it is very common in oncology that a drug can be prescribed for applications beyond the one it is originally registered for, and that some drugs earn up to 95 percent of their sales in additional applications.

"Calculating just one indication, HRPC, satraplatin earnings could peak around $150 million annually," Seizinger said. Applications for earlier-stage prostate cancer or for other indications would be researched by GPC or a potential partner.

"We expect to move into registration trials in the third quarter of 2003," he said. Other trials could be conducted in parallel.

The next milestone in GPC's development of satraplatin will be FDA approval for the protocol of the registration trials, which the company expects to receive in the third quarter. "We will be using a surrogate endpoint, time to progression, which could speed up the trial," Seizinger said.

Noting the other advances announced at the conference, Seizinger added, "There is great momentum in oncology right now."