Kosan Biosciences has reported interim results from two clinical trials of KOS-953,
the company's proprietary formulation of the Hsp90 inhibitor 17-AAG. Data from
a Phase I single-agent clinical trial and a Phase Ib combination trial of KOS-953
co-administered with bortezomib (Velcade) demonstrated early signs of anticancer
activity and tolerability in patients with relapsed-refractory multiple myeloma.
Interim results of the Phase Ib combination trial of KOS-953 co-administered with bortezomib (BZ) in patients with relapsed-refractory multiple myeloma included data from 18 previously treated patients, 78 percent of whom were BZ-refractory and 67 percent of whom had failed transplantation.
The ongoing trial is a dose-escalation study designed to define the recommended Phase II dose of KOS-953 and BZ, and to evaluate the pharmacokinetics and biological activity of the two drugs in combination. Toxicity was primarily mild-to-moderate fatigue and gastrointestinal symptoms. No additive toxicity has been observed and no cardiovascular toxicity was noted.