Prophylactic rituximab after allogeneic transplantation decreases B-cell alloimmunity with low chronic GVHD incidence

Abstract

B cells are involved in the pathogenesis of chronic GVHD (cGVHD). We hypothesized that prophylactic anti-B-cell therapy delivered 2 months after transplantation would decrease allogeneic donor B-cell immunity and possibly the incidence of cGVHD. Therefore, in the present study, patients with high-risk chronic lymphocytic leukemia (n = 22) and mantle-cell lymphoma (n = 13) received a total lymphoid irradiation of 80 cGy for 10 days and antithymocyte globulin 1.5 mg/kg/d for 5 days. Rituximab (375 mg/m(2)) was infused weekly on days 56, 63, 70, and 77 after transplantation. The incidence of acute GVHD was 6%. The cumulative incidence of cGVHD was 20%. Nonrelapse mortality was 3%. Rituximab treatment after allogeneic transplantation significantly reduced B-cell allogeneic immunity, with complete prevention of alloreactive H-Y Ab development in male patients with female donors (P = .01). Overall survival and freedom from progression at 4 years for chronic lymphocytic leukemia patients were 73% and 47%, respectively; for mantle-cell lymphoma patients, they were 69% and 53%, respectively.

Trial registration: ClinicalTrials.gov NCT00186628.

Figure 1

Trial schema. RIC using 80 cGy TLI for 10 days and ATG 1.5 mg/kg on days 1-5, followed by peripheral blood progenitor cell infusion on day 0. Rituximab infusion (375 mg/m²) was infused on days 56, 63, 70, 77. Cyclosporine and mycophenolate mofetil were used as primary GVHD prophylaxis. Triangles indicate time points for peripheral blood immune analyses.

Figure 2

B-cell reconstitution and rituximab quantification. (A) Blood CD19⁺CD5⁻CD23⁻ B-cell quantification. Blood samples collected from HLA identical donors (○), and study subjects (●) before TLI-ATG conditioning and 56 days after alloHCT were FACS analyzed to quantify CD19⁺ B cells. Recipient MCL and CLL cancer cells were excluded from this donor B-cell quantification by excluding CD5⁺ or CD23⁺ cells. Blood CD19⁺CD5⁻CD23⁻ B-cell quantification performed 90 and 180 days after alloHCT showed limited donor B-cell recovery after rituximab. For comparison, donor B-cell recovery 56 days after TLI-ATG alloHCT was determined in 19 patients who never received rituximab (▴) to control for passive transmission of rituximab infused before HCT. (B) Rituximab infused 6 months or less before HCT is detected by ELISA at transplantation. Blood collected immediately before conditioning was measured by ELISA for rituximab concentration (μg/mL; y-axis). Each pre-HCT rituximab level was related to the number of months since their last rituximab infusion (x-axis). (C) CLL decreases following rituximab infusion 56 days after alloHCT. Immunophenotyping detected persistent CD19⁺CD5⁺CD23⁺ CLL cells 56 days after HCT in most CLL patients. Ten of 16 (63%) patients had > 10 CD19⁺CD5⁺CD23⁺ cells/μL of peripheral blood. After rituximab infusion, only 4 of 20 had CLL detected by flow cytometry on day 90. Twelve MCL patients had negligible CD19⁺CD5⁺CD23⁻ cells in the blood measured on both days 56 and 90.

Figure 3

Only 20% of patients receiving rituximab prophylaxis developed cGVHD. The cumulative incidence of cGVHD at 4 years was 20% (95% CI, 6%-34%).

Figure 4

Rituximab prophylaxis prevents H-Y allogeneic Ab development. Blood IgGs against 5 H-Y antigens were determined by ELISA in 25 F → M HCT patients who never received rituximab after TLI-ATG (left panel) and 10 study patients treated with rituximab on days 56, 63, 70, and 77. These heat maps show that no alloreactive H-Y Abs developed in study patients receiving rituximab 2 months after TLI-ATG alloHCT, whereas 1 or more H-Y Abs developed in 56% (14 of 25) of patients receiving TLI-ATG without posttransplantation rituximab. Considering all patients who survived 9 months, rituximab prophylaxis prevents H-Y Ab development (P = .01).

Figure 5

Overall survival after rituximab prophylaxis exceeds 70%. For the CLL patients, the 4-year overall survival was 73% (95% CI, 57%-94%) and freedom from progression was 47% (95% CI, 30%-75%). For the MCL patients, the 4-year overall survival was 69% (95% CI, 48%-99%) and freedom from progression was 53% (95% CI, 31%-89%).