The experimental product, SGN-35, combines a cancer-seeking antibody with a tumor-killing chemical. The medicine cleared cancer to undetectable levels in 53 percent of those with anaplastic large cell lymphoma, and cut tumor size by at least half in an additional 33 percent, said Andrei Shustov, leader of the company-funded study. Seattle Genetics, of Bothell, Washington, plans to apply in the 2011 first half for U.S. approval of the drug, which would be its first on the market.
SGN-35 may be cleared late next year for this type of lymphoma and the more common Hodgkin’s form, and by 2015 may bring in $420 million in annual revenue, said Jason Kantor, an analyst with RBC Capital Markets in San Francisco. The drug uses an antibody to find and bind with a protein found on the surface of lymphoma cells, and blasts them with auristatin, a chemical that kills cancer by blocking cell division.
“I call these drugs guided missiles,” Shustov, a blood cancer specialist at the University of Washington in Seattle, said in a telephone interview on Dec. 1. “You have the warhead that is delivered by a smart carrier which is the antibody. It gets the drug to the target at very high concentrations.”
Seattle Genetics fell 2 cents to $15.21 at 4 p.m. in Nasdaq Stock Market composite trading. The shares have gained 50 percent this year.
SGN-35’s antibody and drug are held together by a linker, which releases the chemical only when it reaches and docks with the cancer cells. As a result, auristatin shouldn’t enter the bloodstream or reach healthy tissues, and should avoid the side effects of standard chemotherapy, Shustov said.
Anaplastic large cell lymphoma is a rare type of T-cell lymphoma diagnosed in 600 to 700 U.S. patients a year, Shustov said. Lymphomas are cancers that damage the lymphatic system, part of the body’s disease-fighting defenses.
T-cell lymphomas, which attack immune cells known as T- cells, are aggressive and hard to treat, with a cure rate of less than 20 percent, Shustov said. Twelve to 24 months after being diagnosed, half of patients are dead, he said.
“This is a very bad cancer,” Shustov said. Part of the reason prognosis is poor in T-cell lymphoma is that previous treatments haven’t targeted the right cells, he said.
In the trial Shustov led, 58 patients with anaplastic lymphoma were treated and studied for a median of six months. The patients ranged in age from 14 to 76 years, with a median age of 52, and had received one to six previous treatments with other therapies, he said.
Altogether, 86 percent of the patients in the study had their cancer cut in half or cleared to undetectable levels, 5 percent got worse, 3 percent had stable disease that didn’t improve and 5 percent weren’t available to be evaluated, Shustov said. Those numbers are comparable to what happens with newly diagnosed patients who are given multiple drugs at once.
“We’ve never before seen this rate of complete remissions in relapsed or refractory T-cell lymphomas treated with a single agent,” Shustov said. “We finally have a drug that will provide benefit for a majority of patients who had little hope of clearing the disease.”
Another company-funded study presented yesterday at the hematology meeting found that SGN-35 cleared cancer to undetectable levels in one third of patients with hard-to-treat Hodgkin’s lymphoma, and shrank tumors by half in an additional 40 percent.
The company currently has no products approved for commercial sale, and had an accumulated deficit of $427.4 million as of Sept. 30. SGN-35, or brentuximab vedotin, is the company’s lead product candidate.
Seattle Genetics has exclusive North American marketing rights to SGN-35. Takeda, based in Osaka, Japan, can sell the drug elsewhere. The companies share development costs equally, except in Japan where Takeda is solely responsible.
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