Cell Therapeutics' battered shares climbed nearly 37 percent yesterday after Chief Executive James Bianco announced additional data showing...

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Cell Therapeutics’ battered shares climbed nearly 37 percent yesterday after Chief Executive James Bianco announced additional data showing the Seattle company’s leading drug candidate was more effective in women with lung cancer than men.

Earlier this summer, the company announced it would seek regulatory approval of Xyotax, a reformulation of the widely used chemotherapy drug paclitaxel, based on results from its Phase 3 trials that showed women survived an average 9.5 months, compared with 7.8 months for those treated with existing products.

To that data, Cell Therapeutics yesterday added results from a Phase 2 clinical trial showing that women had a 36 percent probability of living one year, compared with 16 percent for men. The Phase 3 trials showed a similar benefit. Xyotax is also easier to administer and carries fewer side effects than other products, the company has reported.

Cell Therapeutics intends to use the data to seek approval of the drug for use in women from the Food and Drug Administration in the first half of next year. It would be the first “gender-specific filing that we’re aware of,” Bianco said at an investors conference in New York.

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Seattle biotech watcher David Miller was skeptical of Xyotax’s chances for approval on those grounds.

“I don’t think that the FDA is prepared to approve a lung-cancer drug that is gender-specific” without additional data to explain why, said Miller, president of Biotech Stock Research.

He pointed to the March issue of the journal of the American College of Chest Physicians, in which researchers studied a lung-cancer database.

“It seems clear that women with lung cancer have higher overall survival rates than their male counterparts … likely due to a variety of factors,” the researchers wrote.

Cell Therapeutics is evaluating whether higher estrogen levels affect how Xyotax is metabolized. It plans to have a study “up and under way shortly,” Bianco said.

The company’s stock ended the day at $2.90, up 78 cents. The stock has traded between $10.85 and $1.97 in the past year.

Sonus Pharmaceuticals, a Bothell biotech working on a new, less-toxic reformulation of paclitaxel, has said it expects to begin enrollment in its Phase 3 trials by the end of the month.

Sonus’ drug, Tocosol, would be a direct competitor with Xyotax, Miller said.

Benjamin J. Romano: 206-464-2149 or bromano@seattletimes.com