Because the proteasome performs housekeeping functions within all mammalian cells, Millennium Pharmaceutical Inc.'s LDP-341 dipeptide proteasome inhibitor has been treated with skepticism as a potential cancer therapy, with critics postulating that the product will have toxic side effects. MLNM last week presented data in multiple myeloma patients using a dosing schedule that seems to minimize adverse events, but the ability of the product to effect a durable response without long term side effects remains to be seen.

At the American Society of Hematology meeting in Orlando, MLNM presented preliminary results from 54 evaluable patients in a Phase II trial of LDP-341 (formerly PS-341), showing that 52% of patients had a response and 85% had a response or stable disease after two cycles of treatment. Each cycle consisted of weekly therapy at a dose of 1.3 mg/m2 for two weeks followed by one week of rest.