A PHASE III STUDY OF PSC-833 IN COMBINATION WITH VINCRISTINE, DOXORUBICIN AND DEXAMETHASONE (PSC-833/VAD) VERSUS VAD ALONE IN PATIENTS WITH RELAPSING OR REFRACTORY MULTIPLE MYELOMA

OBJECTIVES:

• Compare the overall survival and objective response rate of patients with relapsed or refractory multiple myeloma treated with vincristine, doxorubicin, and dexamethasone (VAD) with or without PSC 833.
• Compare event free survival and subjective response in patients treated with these regimens.
• Correlate treatment outcome with p-glycoprotein expression.
• Determine whether prognostic factors previously determined to be useful in untreated patients (i.e., plasma cell labeling index and multidrug resistance determined from bone marrow aspirates, serum beta 2-microglobulin and interleukin-6 receptor levels) correlate with objective and subjective response and event-free and overall survival in patients treated with these regimens.
• Compare the toxicity of VAD with or without PSC 833.

OUTLINE: This is a randomized, multicenter study. Patients are stratified by response to prior treatment, prior doxorubicin and/or vincristine, prior autologous peripheral blood stem cell transplantation, and center.

Patients are randomized to 1 of 2 treatment arms:

• Arm I: The first group receives vincristine, doxorubicin, and dexamethasone (VAD). Patients receive higher dose vincristine IV over 96 hours and higher dose doxorubicin IV over 96 hours on days 1-4 and oral dexamethasone daily on days 1-4 and 15-18.
• Arm II: The second group receives VAD plus oral PSC 833. Patients receive oral PSC 833 every 6 hours beginning on day 1 and continuing for 20 doses. Patients receive lower dose vincristine IV over 96 hours and lower dose doxorubicin IV over 96 hours on days 2-5 and oral dexamethasone daily on days 2-5 and 16-19.