An experimental drug to treat Hodgkin lymphoma and similar cancers showed a strong patient response in early clinical trials...

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An experimental drug to treat Hodgkin lymphoma and similar cancers showed a strong patient response in early clinical trials, Seattle Genetics said Tuesday.

The Bothell company said that of 38 patients being evaluated, five saw their tumors disappear and seven showed significant reductions. The disease remained stable in 15 patients, while it progressed in 11 patients.

In total, about 81 percent of the observed patients saw at least some reduction in their tumors, the company said.

Seattle Genetics has begun talking with the U.S. Food and Drug Administration about an accelerated process to approve the drug for patients with relapsed or refractory Hodgkin lymphoma, which currently have no treatment, said Chief Executive Clay Siegall. The FDA can speed the approval of therapies treating unmet medical needs.

The company hopes to have a plan for two pivotal clinical studies by the end of the year for the product, known as SGN-35. If all conditions are met, it could get a regulatory nod as early as 18 months from the beginning of the studies, Siegall said.

“We think it’s likely that this will be our first product to be approved,” Siegall said.

The therapy, still in early experimentation in humans, could overtake Seattle Genetics oncology compounds SGN-33 and SGN-40, which are in more advanced clinical trials.

SGN-40, a treatment for slow-growing non-Hodgkin lymphoma and other ailments, brought Seattle Genetics a lucrative partnership with biotech giant Genentech in early 2007. Currently the company has seven products in its research pipeline.

Seattle Genetics’ data for the drug, presented at the American Society of Clinical Oncology annual meeting in Chicago, is “fabulous,” said David Miller, an analyst with Seattle-based Biotech Stock Research. “I’d be surprised if this doesn’t move into a pivotal trial.”

SGN-35 has gotten a lot of attention from potential partners, said Siegall. The company, which had more than $167 million in cash and investments as of March 31, is mostly interested in deals where a partner would take over the launch of the product outside of the United States, he said.

Shares of Seattle Genetics, the largest independent biotech company in the Seattle area by market capitalization, traded down 4.89 percent Tuesday to $8.56.

Ángel González: 206-515-5644 or agonzalez@seattletimes.com