Seattle Genetics’ Dark Horse Drug Candidate Approaches Home Stretch in Leukemia Study

Xconomy Seattle — 

[Correction: 10:05 am Pacific] The buzz around Seattle Genetics (NASDAQ: SGEN) has been about whether it will finally prove, after more than a decade, that an “empowered antibody” can be an effective treatment for cancer. But while fewer people are watching, the company is eagerly awaiting clinical results for a traditional antibody that also has the potential to help cancer patients live longer—and could generate real cash.

The lesser-known drug is called lintuzumab, or SGN-33. This is a so-called “naked” antibody, a Y-shaped protein that’s genetically engineered to zero in on a specific marker on cancer cells that’s seldom found on healthy cells. In this case, the drug is made to hit a marker on tumors of patients with acute myeloid leukemia. Sometime between late this month and August, the company expects to rip off the blind from a study of 210 patients, which will say whether the new drug can help some very sick, elderly patients live a few months longer with acceptable side effects.

Acute myeloid leukemia is a fast-growing, aggressive form of cancer that often strikes people over the age of 60, and makes them too frail to withstand the high-dose chemotherapy they are prescribed. Life expectancy, based on past studies, is usually about 4-6 months. Seattle Genetics decided to swing for the fence in this tough-to-treat group of people after preliminary studies 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, CEO Clay Siegall says. If the company can prove its drug helps people live longer with this nasty malignancy, then Seattle Genetics could be in a position to offer this new drug for sale in the not-so-distant future. The disease kills an estimated 8,950 people a year in the U.S., according to the American Cancer Society. [Correction 10:05 am Pacific: An earlier version said lintuzumab could be ready for sale next year, but the company says it hasn’t provided guidance yet on timing.]

Clay Siegall

Clay Siegall

“This is a big unmet need, which is partly why we were excited to embark on this trial,” says Siegall. “We’re hopeful this trial will be successful. If it is, it will be exciting for patients and for Seattle Genetics.”

Wall Street isn’t giving this drug much of a chance. One of the bullish analysts covering the company, Cory Kasimov of JP Morgan, said the consensus among investors is that the lintuzumab trial will fail because of the tough patient population and a “lack of convincing earlier-stage data.” Kasimov gives it a 30 percent shot of winning FDA approval and generating peak annual sales of $350 million by 2016.

This big trial began back in September 2007. The company explained some of the rationale a few months later when it presented early stage results at a meeting of the American Society of Hematology. Of 17 patients who got a variety of doses, five patients had complete tumor remission, while two more had a partial shrinkage of their tumors. The drug was well-tolerated, and patients didn’t develop antibodies to attack the drug itself as a foreign invader, which is known to happen.

Those findings were enough for Seattle Genetics to invest some significant money to get a definitive answer from this ongoing trial, which might be enough to persuade the FDA to clear this drug for sale. The study enrolled 210 patients, and randomly assigned them to get a low-dose chemotherapy drug in addition to the Seattle Genetics treatment, or the low-dose chemotherapy alone. The main goal is to show whether the new drug can help patients live longer—the gold standard measurement in cancer trials. The trial is statistically designed to show a 29 percent lower risk of death … Next Page »

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