Rituximab and subcutaneous 2-chloro-2'-deoxyadenosine combination treatment for patients with Waldenstrom macroglobulinemia: clinical and biologic results of a phase II multicenter study

Purpose: To assess the efficacy of 2-chloro-2′-deoxyadenosine (2-CdA) given subcutaneously (SC) in combination with rituximab in the treatment of newly diagnosed/pretreated patients with Waldenström macroglobulinemia (WM) and to correlate the response to treatment with biologic findings (immunophenotypic and pharmacogenomic analysis). Patients and Methods: From December 2003 to February 2007, 29 patients were enrolled. Intended therapy consisted of a combination of rituximab (375 mg/m2) on day 1 followed by 2-CdA 0.1 mg/kg (SC injection) for 5 consecutive days, administered monthly for four cycles. Anemia (n = 16), neurologic symptoms (n = 6), symptomatic cryoglobulinemia (n = 4), and thrombocytopenia (n = 3) represented the reasons for starting treatment. The expression of ζ chain-associated protein kinase 70 (Zap-70) and of seven genes involved in 2-CdA metabolism as markers of response to the combination treatment was evaluated. Results: With a median follow-up of 43 months, the overall response rate observed was 89.6%, with seven complete responses (CR), 16 partial responses, and three minor response, without any difference between newly or pretreated patients (P = .522). The therapy was well tolerated, except for transitory cardiac toxicity (n = 2) and intolerance to rituximab (n = 2). No major infections were observed despite the lack of antimicrobial prophylaxis. No patients developed transformation to high-grade non-Hodgkin's lymphoma nor myelodysplasia. Low expression levels of human concentrative nucleoside transporter 1 (hCNT1) were correlated with the failure to achieve a CR (P = .024), whereas no association with Zap-70 expression was found. Conclusion: The combination of rituximab and SC 2-CdA is safe and effective in patients with WM requiring treatment. The pharmacogenomic analysis associated with the study suggests hCNT1 might be beneficial in predicting clinical response to such a combination treatment.