HLA-haploidentical stem cell transplantation for chronic granulomatous disease: an EBMT-IEWP retrospective study

• In the absence of an HLA-identical donor, haploidentical HSCT with either TCRαβ/CD19 depletion or PTCY is a feasible option in CGD.

• Graft failure remains challenging. Cumulative incidence of aGVHD grade II to IV but not III to IV was significantly higher after PTCY.

Chronic granulomatous disease (CGD) is an inborn error of immunity characterized by defective NADPH oxidase function, leading to impaired microbial killing, recurrent infections and granulomatous inflammation. Allogenic hematopoietic stem cell transplantation (HSCT) is a curative treatment for CGD, particularly effective when a fully HLA-matched donor is available. However, the place of HLA-haploidentical HSCT remains less established. This retrospective, multicenter study analyzed outcomes of 64 CGD patients (53 males, 46 with X-linked CGD) who underwent a first HSCT with HLA-haploidentical family donors either with in vitro TCRαβ/CD19 depletion or in vivo depletion using post-transplant cyclophosphamide (PTCY). The mean age at transplant was 5.8 years (0-33 years). Patients exhibited a high disease burden prior to HSCT, with 45% experiencing infections in the 6 months prior to HSCT and 67% exhibiting inflammation. Outcomes in the entire cohort showed a 3-year overall survival (OS), event-free survival (EFS) and GvHD grade III to IV-free, event-free survival (GEFS) of 75.9%, of 70.2%, and of 56.1% respectively and were not impacted by the type of depletion or age. The cumulative incidence (CI) of primary graft failure was 20.6%. The CI of grade II to IV acute GvHD was higher in the PTCY group (p=0.04) whereas the CI of GVH grade III to IV was not. These results indicate that HLA-haploidentical HSCT is a feasible transplant option for CGD patients lacking HLA-matched donors. Further refinement of transplant protocols is necessary to mitigate graft failure and acute GvHD, ultimately improving access and outcomes for this life-saving therapy.