Threshold is conducting early studies of TH-302 as a treatment for glioblastoma, the most aggressive type of brain cancer. The company said that so far, there are no side effects that limit dosing of the drug. Based on data from six patients, Threshold said those treated with a combination of TH-302 and the cancer drug Avastin had 128 days between the start of treatment and disease worsening.
The South San Francisco, Calif., company is studying the drug in patients whose disease has progressed despite previous treatment with Avastin and who are preparing for brain surgery. The company said that when the patients were treated with Avastin alone, they had an average of 89.5 days before disease progression. That treatment occurred before the start of the clinical trial.
Shares of Threshold fell 89 cents, or 12.3 percent, to close at $6.35. The stock is down 27 percent since Sept. 14, when Threshold reported data from a study of TH-302 as a treatment for pancreatic cancer.
In February Threshold said pancreatic cancer patients who were treated with TH-302 and the drug Gemzar had better progression-free survival — the time from the start of treatment until a patient’s cancer begins advancing again or the patient dies — than patients who took only Gemzar. The patients who were treated with TH-302 lived about two months longer before disease progression. The company is testing TH-302 as a treatment for a variety of cancers.
Despite the recent decline in Threshold shares, the stock has made large gains in 2012. The shares closed at $1.29 on Feb. 2. The next day, the company announced a development and marketing partnership with German drugmaker Merck KGaA and shares began to rise.