Seattle Genetics, Genentech Lymphoma Drug Passes Early Test with “Naked” Antibody

Xconomy Seattle — 

Seattle Genetics gets attention for its “empowered” antibody that targets tumor cells with a potent toxin, but today it presented some impressive data from a more typical “naked” antibody that doesn’t carry an extra lethal toxin.

The Bothell, WA-based biotech company (NASDAQ: SGEN) said today that half of the 30 patients with diffuse large B-cell lymphoma had their tumors completely or partially go away when they got the company’s experimental antibody, dacetuzumab. The trial was conducted in patients who had relapsed after prior therapies, and the experimental drug was given in combination with a common antibody, rituximab (Rituxan) and chemotherapy. The results were presented today at the American Society of Hematology’s annual meeting in New Orleans.

The results represent a comeback for the Seattle Genetics drug, which failed in a larger trial of 224 patients that was halted two months ago. Still, the drug has been a high priority for the company since January 2007, when it struck a partnership with Genentech, which is now owned by Roche. Both Genentech and Roche are deeply familiar with rituximab, which hits a target on tumor cells called CD20. The original drug, first approved in 1997, has become a commercial hit, generating $2.59 billion in U.S. sales last year. Yet as good as it is, patients eventually see their disease spread, and relapse. So Seattle Genetics moved to combine its antibody with rituximab. The Seattle Genetics drug designed to hit a different target, CD40, found on many types of malignant B cells and acts in a complementary way.

The data in the early-stage trial, which combines the Seattle Genetics drug with rituximab were “remarkable,” said David Miller, president of Seattle-based Biotech Stock Research, who covers Seattle Genetics. He attended the presentation in New Orleans, and summarized the data in a note to clients.

While the trial didn’t have any control group to offer a solid comparison, the researcher presenting the data said that patients at this stage of disease who get Eli Lilly’s chemotherapy agent gemcitabine (Gemzar) in combination treatments are expected to have tumor shrinkage rates of around 20 percent, far below the 50 percent seen in this study, Miller wrote in a note to clients.

Side effects have been known to derail companies that gave patients more than one antibody drug at a time, but Seattle Genetics said the majority of side effects were mild to moderate in this trial. Nausea, fatigue, and a depletion of platelet cells in the blood were the most common side effects.

Researchers found that eight out of 30 evaluable patients on the drug had their tumors completely disappear, and another seven of them had partial shrinkage. The tumor shrinkage lasted a median of 5.1 months, researchers said.

Based on the findings, Seattle Genetics and its partner, the Genentech unit of Roche, will decide what to do next based on findings in 2010 from a pair of additional early-stage trials in follicular lymphoma and multiple myeloma. The companies are also developing a gene signature test which is supposed to predict which patients are more likely to respond to treatment with dacetuzumab, and which ones won’t be helped.

Diffuse Large B-cell Lymphoma makes up about 30 percent of the cases of patients with non-Hodgkin’s lymphoma, making it the most common subtype of that malignancy. About 66,000 new cases of non-Hodgkin’s lymphoma are expected to be diagnosed this year in the U.S., and about 19,500 people are expected to die from the disease, according to the American Cancer Society. Diffuse large B-cell lymphoma is the form of cancer that Microsoft co-founder Paul Allen was diagnosed with last month.