Carfilzomib, a new drug similar to Velcade (bor­tez­o­mib), has been shown to be effective against multiple myeloma in re­lapsed and refractory patients.

Like Velcade, car­filz­o­mib (also called PR-171) is a proteasome inhibitor that blocks the activity of proteasomes, cellular complexes that break down proteins.  Without proteasome activity, it is believed that cells self-induce death (apoptosis), thereby inhibiting tumor growth.

A Phase I study shows that car­filz­o­mib ther­apy results in greater than 80% proteasome inhibition.  Two ongoing Phase II studies have dem­onstrated complete or partial positive responses in 18% to 54% of patients, depending …