Updated with new stock price. SOUTH SAN FRANCISCO, Calif. ( TheStreet) -- Treatment with Threshold Pharmaceuticals' ( THLD) TH-302 helped patients with advanced pancreatic cancer extended by two months the time before their disease worsened, according to results of a phase II study released Monday. Shares of Threshold were up 65% to $5.82 in Tuesday trading. Threshold is developing TH-302 in a partnership signed recently with the German pharmaceutical company Merck KGaA. A phase III study of TH-302 in advanced soft-tissue sarcoma is underway. In the phase II study announced Monday, 214 patients with first-line advanced pancreatic cancer were randomized to treatment with either a low or high dose of TH-302 plus the gemcitabine or gemcitabine alone. Patients in the two TH-302 arms of the study went 5.6 months before their disease worsened compared to 3.6 months for patients treated with gemcitabine alone -- or a two-month difference in progression-free survival favoring TH-302, Threshold reported. Stated differently, treatment with TH-302 plus gemcitabine reduced the risk of pancreatic cancer worsening by 39% compared to gemcitabine alone. This result -- the primary endpoint of the phase II study -- was statistically significant. Patients treated with the high dose of TH-302 reported greater efficacy than those in in the low-dose arm, Threshold said, without providing details. Significant tumor shrinkage was reported by 22% of patients treated with TH-302 plus gemcitabine compared to 12% for patients treated with gemcitabine alone. Gemcitabine has long been used by itself to treat pancreatic cancer but efforts to add other drugs in combination have largely failed to demonstrate any significant benefit for patients.
The one notable exception is the combination of Eli Lilly's ( LLY) Tarceva plus gemcitabine. Last year, a triple combination of chemotherapy agents -- gemcitabine, oxaliplatin and irinotecan known as FOLFIRINOX -- demonstrated overall survival in pancreatic cancer of 11.1 months compared to 6.8 months for gemcitabine alone and a progression-free survival benefit of 6.4 months vs. 3.3 months. However, the FOLFIRINOX survival benefit came at the cost of significant and serious side effects for patients. Threshold said the TH-302-gemcitabine combination was well tolerated with chief side effects being skin and mucosal toxicities. Further details were withheld for presentation at a future medical meeting.