Targeted IV busulfan and fludarabine followed by post-allogeneic hematopoietic cell transplantation rituximab demonstrate encouraging activity in CD20+ lymphoid malignancies without increased risk of infectious complications

We examined pharmacokinetic-targeted IV busulfan (75–170 mg/m², with target AUC of 3500–6000 μmol min) and fludarabine (40 mg/m²) × 4 days with rituximab (t-IV Bu/Flu + rituximab) 375 mg/m² on days +1 and +8 followed by allogeneic hematopoietic cell transplantation in 19 patients (median age 56, range 35–68 years) with CD20+ lymphoid malignancies. Median time to neutrophil and platelet engraftment was 15 and 12 days. The cumulative incidence of grade II–IV acute graft-versus-host disease (GVHD) was 58% (95% confidence interval, CI 39–85%), and chronic GVHD was 50% (95% CI 28–88%). With a median follow up of 7 (range 1–31) months, overall response was observed in 15, and stable or progressive disease in 4. Overall survival at 1 year was 67%. Engraftment, chimerism, and infectious complications did not differ significantly from a contemporaneous non-rituximab containing comparator group. The addition of rituximab 375 mg/m² to t-IV Bu/Flu does not appear to adversely affect engraftment, donor chimerism, or increase the risk of infectious complications.