Seattle Genetics Unveils Pivotal Trial Plan for “Empowered Antibody”

Xconomy Seattle — 

Seattle Genetics has settled on the design of a clinical trial that could pave the way for its first marketed cancer drug. The Bothell, WA-based biotech company (NASDAQ: SGEN) said today it has reached an agreement with the FDA on the parameters of a pivotal clinical trial of its SGN-35 drug candidate as a treatment for Hodgkin’s disease.

The study will allow about 100 patients in the U.S., Canada and Europe with relapsed forms of Hodgkin’s to get the Seattle Genetics drug. The main goal will be to show tumor shrinkage—a quick assessment of whether a treatment works—while secondary goals will look at more time-consuming measurements like whether the drug slows the spread of cancer, how long the tumor shrinkage lasts, and whether it can help patients live longer. The company plans to start the trial before the end of March, and submit an application to the FDA for permission to market it in 2011.

Seattle Genetics has made this trial one of its top priorities after SGN-35 produced striking results in a trial last year. The previous trial monitored 44 patients with Hodgkin’s disease and other cancers of the blood that carry a signature protein target called CD-30. The patients were very sick, having relapsed after a median of three prior rounds of chemotherapies, leaving them with no FDA-approved treatment options. They enrolled in the study to get SGN-35, an engineered antibody designed to seek out cancer cells, avoid healthy tissues, and (here’s the special part) dump an extra lethal dose of a potent toxin inside cancer cells.

Even when patients were that sick, and essentially out of other options, researchers found that 17 of the 44 patients (38 percent) had their tumors completely disappear or mostly go away, according to research presented at the American Society of Hematology meeting last month in San Francisco. When researchers looked at patients who got higher doses, the data looked even better. Of the 28 patients who got those doses, about one-third had their tumors completely disappear, while 93 percent had at least some measurable tumor shrinkage. If these kinds of results can be confirmed in a more rigorous study, it could be an option for an estimated 10,000 patients in the U.S. with Hodgkin’s and related lymphomas, Seattle Genetics has said.

The Seattle Genetics trial isn’t required to randomly assign patients to a group taking its drug, or to a control group—a usual hallmark of pivotal clinical trial designs. That may make the results more difficult to interpret in the end, although it will keep the trial’s costs down, and encourage speedy enrollment because patients won’t have to worry about the chance of getting stuck in a control group.

The FDA agreed that this kind of trial could provide enough proof for approval because “relapsed and refractory Hodgkin lymphoma represents a life-threatening disease with unmet medical need,” says Seattle Genetics spokeswoman Peggy Pinkston, in an email. “There are limited therapeutic options and no clear standard of care in this setting. So, it was also agreed that an acceptable overall response rate and duration of response in a single-arm trial could meet the standards for accelerated approval.”

Seattle Genetics also plans to conduct a mid-stage trial of the drug in 50 patients with another malignancy, called anaplastic large cell lymphoma. In trials so far, five out of six patients with this disease had their tumors completely wiped out after taking the Seattle Genetics drug. These kind of results are rarely seen in cancer drugs.

“The data thus far from both of our phase I trials of SGN-35 have exceeded our expectations, including multiple complete and partial responses at well-tolerated doses, suggesting that this agent may address a substantial unmet medical need in patients with relapsed or refractory Hodgkin lymphoma,” said Seattle Genetics CEO Clay Siegall in a statement.