Seattle Genetics’ Dark Horse Drug Candidate Fails in Key Study

Xconomy Seattle — 

Seattle Genetics has struck out in its bid to treat one of the more aggressive forms of leukemia. The Bothell, WA-based biotech company (NASDAQ: SGEN) is announcing today that one of its experimental antibody drugs failed to help people with acute myeloid leukemia live longer in a clinical trial.

The study of 210 patients, which started back in September 2007 and cost the company millions of dollars, was designed to see whether a genetically engineered antibody called lintuzumab (SGN-33), plus a low-dose form of chemotherapy, could help people live longer than the low-dose chemotherapy alone. Seattle Genetics isn’t releasing specific details from the study, but says it saw “no statistically significant difference” in survival time between the two patient groups. Patients in both groups lived longer than studies from the past have suggested. The company is now halting further development of its drug candidate.

“We designed the right study for this disease, and this drug, and it was executed extremely well from an operational perspective. It provided us with exactly what we had been seeking, which was a clear answer. We’re disappointed with the answer, but every aspect of the trial was done the way we set out to do it,” says Seattle Genetics CEO Clay Siegall.

This is certainly a setback for Seattle Genetics, but it’s not a disaster. Most of the company’s $1.29 billion stock valuation is based on bullish expectations for a different drug candidate called brentuximab vedotin, or SGN-35. One of the bullish analysts covering the company, Cory Kasimov of JP Morgan, has been saying for months that investors are counting on brentuximab, but were expecting the lintuzumab trial to fail because of the tough patient population and a “lack of convincing earlier-stage data.” Kasimov gave the dark horse drug candidate about a 30 percent shot of winning FDA approval.

Clay Siegall

Clay Siegall

Still, it’s a disappointing moment for researchers and patients with acute myeloid leukemia. This is a fast-moving, aggressive form of cancer that often strikes people over the age of 60, and makes them too frail to withstand high-dose chemotherapy. Past studies have suggested these patients can expect to live about 4-6 months. Seattle Genetics decided to run this rigorous study after preliminary trials showed that a “mid-teens” percentage of patients saw some degree of partial or complete tumor shrinkage, and there were anecdotal reports of people living longer, Siegall told me back in this feature story in June. Because the Seattle Genetics antibody was so well tolerated, researchers hoped it could offer a new option for many frail elderly patients who can’t withstand the toxicity of high-dose chemotherapy. The disease kills an estimated 8,950 people a year in the U.S., according to the American Cancer Society.

By subtracting lintuzumab, Seattle Genetics expects to achieve “modest” savings, and switch over some of its people and money to other programs still showing promise in clinical trials. The highest profile program in the pipeline is brentuximab vedotin, which attaches toxins to an antibody to create an “empowered antibody” designed to have greater tumor-killing kick. That’s a different concept than the one being tested with lintuzumab, a so-called “naked antibody” without any toxins that could make it more potent. And Seattle Genetics has plenty of cash—$325 million reported at the end of June—remaining to bet on its empowered antibody programs, Siegall says. The company’s technology has seen increasing acceptance this year from partners,  including a recent deal with Roche’s Genentech unit.

If the company can repeat the results it obtained an an early study of brentuximab, investors will soon forget the lintuzumab experience. Results from a pivotal trial of more than 100 Hodgkin’s patients on brentuximab vedotin, and findings from a mid-stage study of 55 patients with another malignancy called anaplastic large cell lymphoma, are expected within the next six weeks. That drug is the centerpiece of a partnership with Cambridge, MA-based Millennium: The Takeda Oncology Company.

Seattle Genetics plans to discuss the lintuzumab results, and what it means in the context of its other programs, on a conference call with investors at 8:30 am Eastern/5:30 am Pacific. For those who want to listen in, you can find the webcast by going to the company’s website.

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3 responses to “Seattle Genetics’ Dark Horse Drug Candidate Fails in Key Study”

  1. What clinical trials are you working on for waldenstroms macroglobulinemia?

  2. Amerigo M. Cimino says:

    Genetically engineered drugs will only work on genetically engineered patients!
    Trial and error experiments, are just that, and the results are for the individual bein tested. There are many drugs that will “kill” cancer, but also kill the patient. Trying to sell hope, is very expensive. A suffeing patient will try anything, and the treatment of an individual patient, does not justify the use on every case! There is no “cure” for Cancer, only a possible aid for the patient to help rid it’s body of the particular alment! We all have cancer in our bodies, over active cancer cells are the problem! PATIENTS WHO HAVE CANCER REMOVED BY SURGERY, HAVE HAD THEIR CANCER RETURN.
    Good luck with you search!