Bortezomib, Dexamethasone and Rituximab (BDR) Is a Highly Active Regimen in the Primary Therapy of Waldenstrom’s Macroglobulinemia: Planned Interim Results of WMCTG Clinical Trial 05-180.

In previous studies, we demonstrated that Rituximab and Bortezomib are active agents as monotherapy in patients with Waldenstrom’s macroglobulinemia (WM), producing response rates of 40–80%. Moreover, we and others have demonstrated synergistic activity for these agents together, and with steroids in preclinical studies. As such, we examined the activity of combined bortezomib, dexamethasone and rituximab in patients with the consensus panel diagnosis of WM. Intended therapy consisted of IV bortezomib at 1.3 mg/m² and IV dexamethasone 40 mg on days 1,4,8, and 11, and Rituximab at 375 mg/m² on day 11 which constituted one cycle of therapy. Patients received four consecutive cycles, followed by a three month pause, and then 4 more cycles, each given three months apart. Ten patients are eligible for evaluation at interim analysis. Following a median of 4 cycles of therapy, median serum IgM levels for all evaluable patients declined from 5,095 (range 700–8030 mg/dL) to 2,850 (range 280–3660 mg/dL) (p=0.001). The overall response rate was 100%, with 5 and 5 patients achieving a minor (≥25% decrease in IgM) and major (≥50% decrease in IgM) response, respectively. Responses were prompt, and occurred at a median of 1.1 months. Therapy was well tolerated with III/IV toxicities consisting of sepsis (n=1), pneumonia (n=1), and thrombocytopenia (n=1). Four patients developed herpes zoster while on treatment, resulting in the implementation of prophylaxis for all patients with valcyclovir. At a median of 4 cycles, no sensory or motor neuropathies have occurred. The interim results of this study demonstrate that BDR is a highly active, and well-tolerated regimen in the primary therapy of WM.