Proteasome Inhibition With Bortezomib (PS-341): A Phase I Study With Pharmacodynamic End Points Using a Day 1 and Day 4 Schedule in a 14-Day Cycle

Bortezomib (PS-341) is a novel antineoplastic agent that is well tolerated at doses not exceeding 3.0 mg (equivalent to 1.75 mg/m2), repeated on D1 and D4 every other week. This dose correlates with 70% inhibition of 20S proteasome activity. DLTs include neuropathy, fatigue, and diarrhea.