Synata Soars on Positive Breast Cancer Drug Trial Results

Synta Pharmaceuticals Corp. gained the most in more than four years after a small trial of its drug in breast cancer met goals warranting expansion of the study.

Synta increased 41 percent to $7.15 at 4 p.m. New York time for its biggest advance since March 2009. The shares of the Lexington, Massachusetts-based company are down 21 percent this year.

The experimental drug ganetespib helped enough patients with breast cancer to see a reduction in their tumors to move on to the second stage of the trial, Synta said today in a statement. The drug was being tested for 12 weeks in patients with newly diagnosed HER2-positive or triple-negative breast cancer.

“The results easily surpassed the expansion criteria of at least one objective tumor response in the first 15 patients enrolled,” George Zavoico, an analyst with MLV & Co., wrote today in a research note. “In our view, the results underscore ganetespib’s potential of treating multiple types of cancer.”

There will be about 234,580 new cases of breast cancer in the U.S. this year, and about 40,030 patients will die from the disease, according to estimates from the National Cancer Institute. Triple-negative breast cancer, which accounts for about 15 percent of cases, is particularly difficult to treat; it’s a generally fast-spreading cancer that won’t respond to hormone therapy or drugs targeting the protein HER2, according to the American Cancer Society.

Study Results

Of the first 10 patients with triple-negative breast cancer in the trial, two had an objective tumor response while three reached stable disease after 12 weeks of treatment, Synta said. Of five HER2-positive patients, two had objective tumor response and two reached stable disease.

The most common side effect was mild to moderate diarrhea that was generally manageable with standard medication, Synta said.

“These encouraging findings confirm prior signals of clinical activity seen with ganetespib in breast cancer,” Iman El-Hariry, Synta’s vice president of clinical research, said in the statement. “The favorable safety profile, clear single-agent clinical activity, and strong rationale for combination therapy suggest ganetespib may have broad potential utility in breast cancer.”

The drug also is being tested in lung and other cancers.

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