A Phase I Study of Arsenic Trioxide (Trisenox), Ascorbic Acid, and Bortezomib (Velcade) Combination Therapy in Patients with Relapsed/Refractory Mulitple Myeloma

Bortezomib is a well recognized standard therapy, however it is not curative for multiple myeloma. New agents and approaches are needed to overcome resistance in multiple myeloma. Arsenic trioxde (ATO) induces apoptosis of plasma cells through a number of mechanisms, including down regulation of gene overexpression, activating cell cycle arrest by inducing p21 cyclin-dependent kinase inhibitor protein, and by triggering apoptosis through caspase-3 in a dose dependent manner. This phase I study assessed the feasibility and tolerability of concomitant administration of arsenic trioxide (ATO), ascorbic acid (AA), and bortezomib (VelcadeÔ) (AAV) in patients with relapsed/refractory multiple myeloma.

A standard dose of ATO (0.25 mg/kg IV infused over 1–2 hours) and AA (1g IV infused over 15 minutes after infusion of ATO) were given once weekly × 2 with an escalating dose of bortezomib (cohort 1: 1 mg/m² or cohort 2: 1.3 mg/m² IV bolus on days 1, 8) of a 21 day cycle). ATO was given at least 1 hour prior to bortezomib and patients were allowed up to a maximum of 6–8 cycles.

A total of ten patients (median age, 62 years old) were enrolled with a median follow up of survivors of 25 months. Patients had an average of 4 prior failed therapies. Seven (70%) patients were refractory to bortezomib when previously administered. Despite our patient population being heavily pre-treated, objective responses were observed, with one partial response (Cohort 2), two minimal response (Cohort 1 and 2), and one stable disease (Cohort 2). To date, three of the 10 patients are continuing maintenance therapy 13–43 months from initiating this study.

Of the patients that completed the treatment, objective responses were observed despite suboptimal dosing and previous bortezomib treatment failure. Tolerability was observed in most patients as discontinuation was not due to treatment toxicities, but due to aggressiveness of disease. Further studies are warranted with a larger patient population to effectively determine the effectiveness of AAV in relapsed/refractory multiple myeloma.

Rizzieri:Cephalon: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Long:Millennium: Speakers Bureau. Gasparetto:Millennium: Speakers Bureau.