Thoughtleader: Stephen Sherwin, Cell Genesys - Pharmaceutical Executive

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Thoughtleader: Stephen Sherwin, Cell Genesys
Taking the Plunge

Pharmaceutical Executive


By way of example, there were two Phase III failures last year in advanced pancreatic cancer. If you take a step back, you realize those patients may have no more than three to four months median survival. Most people believe immunization takes about six to 12 months. How can you possibly expect to have therapeutic benefit under those circumstances?

GVAX uses a multi-antigen approach. It is a series of products made from cell lines that can be mass produced and are not patient specific. The cells are irradiated so they can't grow and reproduce, and they're modified to produce the immune activator GM-CSF. Of course, tumor cells don't, under ordinary circumstances, make things to stimulate the immune system; they make things to suppress the immune system. But we have altered the tumor cells so as to stimulate an immune response against tumor cells.

What kind of results are you seeing?

We are encouraged by what we've seen across our Phase II studies. We have seen objective evidence of antitumor activity with a group of related products: prostate cancer, pancreatic cancer, all kinds of leukemia. And when you see consistency of data across multiple related products, your confidence builds.

Our trials have shown a potential survival benefit with a favorable side effect profile compared with traditional chemotherapies. When we took the survival signal and the side effect profile and put them together, we were convinced that it was appropriate to advance to Phase III. Our first Phase III study, VITAL-1, compares GVAX to Taxotere with the primary end point being improvement in survival, and it should be completed later this year. That's a 600-patient study enrolling now at about 120 sites in the United States and Canada. The second study, VITAL-2, is a newer study. It will probably involve 80 to 90 sites in the United States and Canada. That study compares GVAX with Taxotere to Taxotere alone. It also has survival as the primary end point.

What's the promise of the virus platform you're working on?

We have a Phase I trial going on in patients with recurring bladder cancer. We actually have had two acquisitions that bear on this platform: one in 2001, when we bought a private company called Calydon that had been working on these kinds of products, and another two years later with Novartis, where they contributed products and technology to our effort.

The idea of viral-based treatments for cancer is based on the fact that you can genetically alter these viruses to be more selective in the growth of cancer cells. Under normal circumstances, a virus lyses a cell, multiplies, and the cell bursts. If you could direct that specifically to a cancer cell, then you would have a potential therapy for cancer.

Our particular products are derived from adenovirus. One of the limitations of these viral therapies—which is true of the adenovirus therapies—is that eventually the body will mount an immune response against the virus. But what's interesting about our product CG0070 is that it also carries the GM-CSF gene. So we believe it could potentially work through two mechanisms: direct viral killing of the cancer cell and stimulating an immune response by way of the introduction of GM-CSF.

Are you planning to commercialize GVAX on your own or find a partner?

We are in active discussion with prospective partners at this time. One of the things that we're looking for in a potential partner is a company that can help us prepare for a successful launch and commercialization. That includes understanding the market and beginning to educate physicians who will use this product. We believe urologists and oncologists will use the product, and it's new to both groups. And it also means addressing reimbursement challenges.

How do you overcome skepticism toward unproven technologies?

That's one of the challenges that we have at Cell Genesys today. Not every investor and not every potential partner will be willing to hear our story. There are people who want to follow the second and third, not first, company to market. But it does mean that you have to ask yourself more frequently than not what your conviction is for pushing forward. You have to have perseverance and patience.


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