Cell Therapeutics, Inc. (CTI) reported preliminary phase I data on CT-2106, its polyglutamate camptothecin, at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics in Boston.

CT-2106 links 20S-camptothecin, one of the most potent forms of this widely used class of anti-cancer agents, to CTI's polyglutamate polymer. Despite encouraging activity, the National Cancer Institute halted its development of 20S-camptothecin in the 1970's as it was found to cause severe and unpredictable bladder toxicity.

According to the presentation, 19 patients with advanced cancers received increasing doses of CT-2106 over a ten-minute infusion. Side effects were generally mild to moderate with the dose-limiting toxicity being neutropenia (one patient with grade 4) and thromobocytopenia (three patients with grade 3). No severe bladder toxicity was reported. Four of the patients experienced disease control lasting nine weeks or longer. Of these, two patients with lung cancer had disease stabilization for more than six months.

"The current data indicate that when linked to our polyglutamate polymer, this potent camptothecin becomes a viable, attractive drug candidate," reported Jack W Singer, MD, research chair at CTI. "With Xyotax completing its phase III trials in lung cancer, this is the second drug candidate that CTI has linked to our polymer backbone, allowing us the opportunity to modify the two best-selling classes of anti-cancer drugs, the taxanes and camptothecins, making them potentially safer and more effective."

The multicenter, open-label trial seeks to determine the maximum tolerated dose of CT-2106 in patients with advanced malignancies. It also seeks to determine the response to the drug and its safety, tolerability and pharmacology. CT-2106 was administered at doses of 12, 25, 50, 75 and 105 mg/m2 every three weeks with at least three patients treated at each dose level.

"These data provide the justification and direction for moving CT-2106 into phase II development and additional validation of the polyglutamate drug technology," said Singer.