Phase II Trial Evaluating the Safety and Efficacy of Rituximab as Primary Treatment for Extensive Chronic Graft Versus Host Disease

Although allogeneic hematopoietic stem cell transplantation (HSCT) remains an important curative therapy for many patients with hematological malignancies, treatment-related morbidity and mortality continue to be a major challenge. Chronic GVHD remains a major complication following allogeneic HSCT, with more than half of patients being affected. Although cGVHD has been associated with decreased relapse risk due to the well documented graft-versus-malignancy effect, it is also associated with significant adverse consequences in terms of morbidity, mortality, quality-of-life, and treatment costs associated with HSCT.

Rituximab has been investigated in a small number of patients with refractory cGVHD using the standard regimen of 375 mg/m2/week for 4 weeks. Ratanatharathorn et al. documented a sustained response in four of eight patients with steroid-refractory cGVHD with diffuse or localized sclerodermatous manifestations. Similarly, Canninga-vanDijk et al. and Okamoto et al. observed cases with clinical, laboratory and histological improvement after Rituximab treatment. Cutler et al. reported the results of their phase I-II study with Rituximab in 21 patients with steroid-refractory cGVHD. Treatment was well tolerated, and toxicity limited to infectious events, without any hematological toxicities and only a significant reduction in circulating immunoglobulins documented after therapy. Objective responses were documented in 70% of patients (including 10% complete response) primarily for those with skin and musculoskeletal involvement, allowing tapering, and in some cases withdrawing, of previous immunosuppressant therapy. A correlation between clinical response and decrease in the titre of antibodies against Y chromosome-encoded minor HLA antigens was shown. The results of these preliminary studies highlight the potential therapeutic activity of Rituximab on some cGVHD manifestations and a particularly high efficacy for skin involvement, including scleroderma. Recently, Zaja et al. confirmed the activity of Rituximab in refractory cGVHD in a larger series of 38 patients. Treatment was generally well tolerated and nearly 60% and 50% of patients had a clinical improvement of their skin and mouth manifestations, respectively. The median time-to-response was nearly 2 months and in some cases responses were durable. Responses were also detectable in some patients with eye, liver, lung, gut and joint involvement, allowing reduction and/or suspension of previous baseline immunosuppressive therapy in a significant number of patients