Seattle Genetics “Empowered Antibody” Shines at Blood Disease Meeting

12/6/08Follow @xconomy

The longer Seattle Genetics keeps following cancer patients who took its lead drug candidate, the better the data looks. The Bothell, WA-based biotech company released some stellar (albeit preliminary and without a control group) clinical trial results today that show its “empowered antibody” is able to wipe out aggressive forms of Hodgkin’s disease with minimal side effects.

Seattle Genetics (NASDAQ: SGEN), released the findings today at the American Society of Hematology annual meeting in San Francisco. The company made waves six months ago with an earlier peek of data at the American Society of Clinical Oncology, but now Seattle Genetics has more detailed follow-up to show how patients are doing over time.

The results are truly striking. The 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 in the body, avoid healthy tissues, and (here’s the special part) dump an extra lethal dose of chemotherapy inside the tumor cells.

Even under these grim circumstances, researchers found that 17 of the 44 patients (38 percent) had their tumors completely disappear or mostly go away. When they looked at patients who got higher doses that are more likely to be tested in late stages, the data look 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 measureable tumor shrinkage. Those numbers have improved since June, when 23 percent of patients were graded as having complete tumor eradication, and 81 percent of the evaluable patients at the time had some tumor shrinkage.

As time has gone on, the drug’s effect appears to be long-lasting, too. Researchers didn’t report on whether the drug actually helped people live longer—the gold standard of cancer drug development—but they did see that it kept their tumors from spreading for a median time of more than six months. That measurement, called progression-free survival, is a common goal of cancer studies accepted as a “surrogate” the FDA usually accepts as proof that a cancer drug is working.

“We are excited with the exceptional antitumor activity of SGN-35 and have plans to move this agent into pivotal trials in the near future,” said Clay Siegall, CEO of Seattle Genetics, in an e-mail right before he got on a plane to San Francisco to talk with researchers about the results.

Anas Younes, the director of lymphoma/myeloma at MD Anderson Cancer Center in Houston, TX, and the study’s presenting investigator, said in a statement that the data is “encouraging, and provide evidence that SGN-35 may offer an important new therapeutic option for patients in this setting.”

This study, however, had no control arm, so it’s impossible to accurately compare it to how patients would have done on other treatment. Based on this data, Seattle Genetics plans to start a more rigorous final-stage clinical trial program in the first half of 2009 that could lead to FDA approval to market SGN-35 as its first commercial product.

Getting the clinical trial plan properly designed to make sure SGN-35 is a success has been a top priority of the company for months, as I described in this profile in September with chief medical officer Tom Reynolds. The company has geared up, hiring 65 new employees this year to help do this right, says spokeswoman Peggy Pinkston.

The SGN-35 results overshadowed another data release from Seattle Genetics at the same medical meeting. The company said another antibody it’s developing, SGN-40 or dacetuzumab, caused complete or partial tumor shrinkage in about 10 percent of 38 patients in a clinical trial. The patients were elderly (median age, 72) and very sick, having had a median of four prior rounds of chemotherapy to treat an aggressive form of lymphoma called diffuse large B-Cell lymphoma.

The SGN-40 drug is different from others on the market for lymphoma, like Genentech and Biogen Idec’s rituximab (Rituxan), because it’s designed to hit a different protein target called CD-40. Seattle Genetics is developing the product in a partnership with Genentech (NYSE: DNA). Separately, the companies said they found in animal tests that a combination of rituximab and the newer product was better at treating cancer than either drug on its own. Seattle Genetics and Genentech are running three separate clinical trials of combinations of SGN-40 to see which is most promising, Reynolds said in a statement.

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  • Cindy Reed

    would like to know if a trial is being done with SGN-35 for patients who have had allo transplants?