Satraplatin's regulatory review is rolling right along, literally.

GPC Biotech AG began a rolling submission of the chemotherapy's new drug application to the FDA, filing the chemistry, manufacturing and controls section. That procedure allows companies with fast-track status to submit sections of the NDA to the agency as they become available, which "is nice because it allows the review process to begin before the complete dossier has been submitted," explained Laurie Doyle, GPC Biotech's associate director of investor relations and corporate communications.

The company, which is based in Martinsried, Germany, is seeking satraplatin approval in combination with prednisone as a second-line chemotherapy treatment for patients with hormone-refractory prostate cancer. The platinum-based compound received fast-track designation in that indication two years ago.

The company recently reached its targeted enrollment of 912 patients in a Phase III registration trial of its lead candidate. Called the SPARC trial, the study is measuring the difference in progression-free survival between patients receiving satraplatin and prednisone compared to those receiving placebo and prednisone as its primary endpoint. They receive treatments every day for five days, a cycle that is repeated every 35 days.

SPARC (Satraplatin and Prednisone Against Refractory Cancer) began a little more than two years ago under a special protocol assessment from the FDA, and European regulatory authorities also have provided a scientific advice letter that confers similar study design benefits. It is being conducted on both sides of the Atlantic and fully funded by GPC Biotech, which also is getting input through a joint development committee with representatives from Spectrum Pharmaceuticals Inc., the company from which GPC Biotech licensed the compound.

"The plan," Doyle said, "is to use this as the basis for filing both in the U.S. and in Europe."

Attention will focus next on an interim efficacy analysis, scheduled to occur by the end of the next quarter. Doyle said GPC Biotech expects the independent data monitoring board to "recommend that we continue the trial to its fruition, as planned." Should that happen, the company expects to complete its NDA filing sometime in the second half of next year, after which the FDA would have 60 days to determine whether to act on the application. Doyle said GPC Biotech would hope for a priority review.

The company is positioning satraplatin for a market that last year generated more than $2.2 billion in worldwide sales. But unlike already-marketed platinum drugs, all of which require intravenous administration, satraplatin is an orally bioavailable compound and is given as capsules that patients can take at home. "It's the only oral platinum in advanced clinical development," Doyle said, adding that such a product opportunity is exciting because the reimbursement landscape for oral anticancer drugs is changing for the better. "And for patients, it gives them a sense of control and certainly more convenient."

Should GPC Biotech prove successful in its satraplatin endeavors, Irvine, Calif.-based Spectrum would receive up to $18 million in milestone payments. GPC Biotech paid $2 million up front for the compound's worldwide rights and already has given Spectrum $2 million in milestone money. GPC Biotech is footing the bill for all development expenses, and once satraplatin begins producing revenue, GPC Biotech would owe Spectrum a royalty rate on net sales in the low double-digit range.

The company plans to partner its non-U.S. rights, but would "like to be in the driver's seat" in the U.S. market, Doyle said. Those plans could include solo promotional efforts, a co-promotion deal or the use of another company's oncology sales team. Looking broadly, GPC Biotech envisions wide use of satraplatin, which Doyle said has less toxicity than other platinum-based drugs. Phase II trials have been completed in patients with hormone-refractory prostate cancer, ovarian cancer and small-cell lung cancer.

Also, promising early clinical results have resulted when satraplatin is combined with radiation therapy, with a Phase I/II study under way to evaluate that combination in patients with non-small-cell lung cancer. Such a treatment paradigm would underscore the convenience of satraplatin's oral dosing, compared to intravenous delivery, when coupled with radiation by reducing patients' need to shuttle between two administration sites. Several other studies evaluating satraplatin include a Phase II monotherapy trial among metastatic breast cancer patients, a Phase II combination trial with Taxol (paclitaxel) for inoperable lung cancer and a Phase I combination trial with Taxotere (docetaxel) that just began in patients with advanced solid tumors.

Beyond satraplatin, the company also is developing a monoclonal antibody with a novel mechanism of action against a variety of lymphoid tumors. That product, 1D09C3, is in Phase I development. Other development and discovery programs are focused on kinase inhibitors.

GPC Biotech has U.S. subsidiary operations in Waltham, Mass., and Princeton, N.J.