# Rituximab added to conditioning regimen significantly improves erythroid engraftment in major incompatible ABO-group hematopoietic stem cell transplantation

## TL;DR

Adding rituximab to the treatment plan helps patients recover red blood cell function faster after a major ABO-incompatible stem cell transplant.

## Contribution

This study shows that rituximab improves red blood cell engraftment in ABO-incompatible stem cell transplants.

## Key findings

- Rituximab reduced time to transfusion independence by about two months compared to the control group.
- Multivariable analysis confirmed rituximab's positive effect on faster red blood cell engraftment.
- Higher pre-transplant anti-donor isohemagglutinin titers were linked to delayed transfusion independence.

## Abstract

ABO-group major incompatibility hematopoietic stem cell transplantation (HSCT) increases the risk of delayed red cell engraftment and other immunological complications. In this study, we evaluated the efficacy of pre-transplant infusion of rituximab in patients with ABO-incompatibility in improving red blood cell engraftment after HSCT, measured by time to reach transfusion independence. We performed a retrospective, single-center study including 131 consecutive patients transplanted with major or bidirectional ABO-incompatible grafts between 1st January 2013 and 31st December 2019. Fifty-one patients received an infusion of rituximab during the conditioning regimen, while 80 patients did not receive any additional preventive treatment. Time to transfusion independence was significantly reduced for patients treated with rituximab (1 month, 95% CI, 0.5–2) compared with the control group (3.2 months, 95% CI 1.5–3.2, p = 0.02). By multivariable analysis, rituximab use was associated with a faster red blood cell (RBC) engraftment (RR 1.88, 95% CI 1.17–3.03, p = 0.009), while a pre-transplant anti-donor isohemagglutinins titer >1:128 was associated with delayed transfusion independence (RR 0.61, 95% CI 0.37-0.99, p = 0.05). Although limited by the retrospective nature of the study, the results of this analysis suggest that rituximab added to conditioning regimens is feasible, safe, and able to improve post-transplant red blood cell engraftment.