Seattle Genetics “Empowered Antibody” Wipes Out Hodgkin’s Tumors in Early Study

6/1/09Follow @xconomy

Seattle Genetics offered some more evidence, albeit quite preliminary, that suggests it may have a powerful new drug for Hodgkin’s disease and related lymphomas.

The Bothell, WA-based biotech company (NASDAQ: SGEN) said today about half of patients who failed on multiple previous treatments had their tumors shrink after taking its experimental SGN-35 drug, and more than one-third (10 out of 27 patients) had their tumors completely disappear. Seattle Genetics is presenting the results today at the American Society of Clinical Oncology meeting in Orlando, FL. This finding is from a study of patients who got SGN-35 infusions once a week in a variety of low doses to assess safety. Most side effects were mild in severity, and included nausea, fatigue, white blood cell depletion, and numbness in the fingers and toes, scientists said.

The data are from the first of three phases of clinical trials, and the study had no control group, so it’s impossible to say for sure how much better patients did on this drug than they might have done on some other treatment. But the findings verify results from a previous study that looked at the drug when given once every three weeks to 44 patients. SGN-35 is attempting to carve out a niche in the emerging field of “empowered antibodies,” which are designed to seek out cancer cells, spare healthy ones, and (here’s the special part) unload an extra lethal dose of a toxin to kill the tumor cells. If it can clear the next hurdle in clinical trials and win FDA approval, it would be a new treatment option for Hodgkin’s, a rare disease that was diagnosed in about 8,500 people in the U.S. last year, according to the American Cancer Society.

The data from this study “provide further clinical support for our aggressive development plans,” said Seattle Genetics CEO Clay Siegall in a statement. The company is considering other clinical trials of a once-weekly dosing schedule now, he added.

What’s especially intriguing about these results are how sick the patients were, and how the drug generated anti-tumor response even when given at very low doses. Patients entering the study had a median age of 34 years, but had experienced a median of five rounds of prior chemotherapy, and almost two-thirds had already gotten bone marrow stem cell transplants. They received doses ranging from 0.4 milligrams per kilogram of body weight, to 1.4 milligrams per kilogram—meaning that researchers mainly wanted to see how high they could elevate the dose while still maintaining an acceptable safety profile.

Of the patients who got 0.8 milligram per kilogram doses once a week—the kind of higher dose that’s closer to what might be used in later clinical trials and in regular medical practice—about half had their tumors completely disappear. The current pivotal trial is looking to enroll 100 patients who will take SGN-35 once every three weeks, at an even higher dose—1.8 milligrams per kilogram of body weight.

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