Why Some Leukemia Cells Resist STI-571

The antileukemia drug known as Gleevec or STI-571 has been heralded as the vanguard of a new generation of cancer chemotherapy agents, designed specifically to counteract the biochemical changes that make cells cancerous. Yet STI-571 shares an unfortunate characteristic with older, conventional drugs. Patients with advanced disease often relapse; their tumor cells become resistant and eventually grow out of control. Results published online by Science on 21 June (www.sciencexpress.org) now explain why this happens in STI-571, and perhaps point the way to improved therapies.