BioWorld International Correspondent
LONDON - Xenova Group plc said the U.S. National Cancer Institute started exploratory trials of tariquidar, seven months after two Phase III trials of the drug were halted for safety reasons.
At the same time, the company said its partner, QLT Inc., of Vancouver, British Columbia, completed a review of the Phase III trials in non-small-cell lung cancer. The review confirmed toxicity associated with chemotherapy was greater in patients receiving tariquidar than in those receiving placebo.
Daniel Abrams, group finance director at Xenova, told BioWorld International: "The market assumed tariquidar was dead. We don't want to overstate it, but there clearly is life there still."
The National Cancer Institute in Bethesda, Md., started a Phase I/II trial in non-small-cell lung cancer and cervical cancer, and a Phase II trial in adrenocortical cancer. The latter tumor is known to exhibit the multidrug resistance that tariquidar is designed to overcome.
Abrams said the collaboration between QLT and Slough-based Xenova is extant, and they are in discussions about the possibility of conducting further Phase II studies.
The reason for the higher toxicity in the tariquidar arms of the two studies has not been explained. While tariquidar's ability to prevent chemotherapeutic agents being pumped from cancer cells might be expected to result in an increase in toxicity, there was no sign of any associated benefits.
Although toxicity was higher, there were no new side effects.
"The reality is we need to do more studies, but the instinct of the NCI is that tariquidar was doing the job it was designed to do," Abrams said.
At the time the trials were stopped, 304 of an intended 1,000 patients had been enrolled. Xenova's shares lost half their value when the independent safety committee called a halt in May.