Azathioprine/hydroxyurea preconditioning prior to nonmyeloablative matched sibling donor hematopoietic stem cell transplantation in adults with sickle cell disease: A prospective observational cohort study.

Nonmyeloablative, matched sibling donor hematopoietic stem cell transplantation with alemtuzumab/total body irradiation (TBI) conditioning is a curative therapy with low toxicity for adults with sickle cell disease (SCD). However, relatively low donor chimerism levels and graft rejection remain important challenges. We hypothesized that adding azathioprine/hydroxyurea preconditioning will improve donor chimerism levels and reduce graft failure rate. In this prospective cohort study, we enrolled consecutive adult patients with SCD undergoing matched sibling donor transplantation at the Amsterdam UMC. Patients received azathioprine 150 mg/day and hydroxyurea 25 mg/kg/day for 3 months prior to alemtuzumab 1 mg/kg and 300 cGy TBI conditioning. Twenty patients with SCD (median age 26 years [range 19-49], 13 females) were transplanted. Median follow-up was 46.0 months (IQR 21.8-57.9). One-year overall survival and event-free survival (graft failure or death) were both 95% (95% confidence interval 86-100). Mean donor myeloid and T-cell chimerism 1-year post-transplant were 95.2% (SD ±10.6) and 67.3% (±15.3), respectively. One patient (5%) experienced graft failure without autologous regeneration, resulting in infections and death. All other patients had a corrected SCD phenotype and were able to discontinue sirolimus. Three patients were successfully treated with alemtuzumab (1 mg/kg) after the transplant because of declining donor chimerism and cytopenias to revert impending graft rejection. Toxicity was mostly related to sirolimus and alemtuzumab. One patient developed steroid-responsive grade II intestinal acute graft-versus-host disease. Collectively, preconditioning with azathioprine/hydroxyurea prior to nonmyeloablative matched sibling donor transplantation resulted in excellent event-free survival and robust donor T-cell chimerism, enabling the successful withdrawal of sirolimus. ClinicalTrials.gov: NCT05249452.

Effect of allogeneic hematopoietic stem cell transplantation on sickle cell disease-related organ complications: A systematic review and meta-analysis.

Sickle cell disease (SCD)-related organ complications are a major cause of morbidity and mortality in patients with SCD. We sought to assess whether hematopoietic stem cell transplantation (HSCT) stabilizes, attenuates, or exacerbates organ decline. We performed a systematic review and meta-analysis of trials investigating organ function before and after HSCT in patients with SCD. We searched MEDLINE/PubMed and EMBASE up to September 21, 2023. Continuous data were expressed as standardized mean difference (SMD) and pooled in a weighted inverse-variance random-effects model; binomial data were expressed as risk ratio (RR) using the Mantel-Haenszel random-effects meta-analyses. Of 823 screened studies, 34 were included in this review. Of these, 17 (774 patients, 23.6% adults, 86.3% HLA-identical sibling donor, 56.7% myeloablative conditioning regimen) were included in the meta-analyses. Pulmonary function remained stable. Mean tricuspid regurgitant jet velocity decreased but did not reach statistical significance. In children, estimated glomerular filtration rate decreased (SMD -0.80, p = .01), and the presence of proteinuria increased (RR 2.00, p = <.01), while splenic uptake and phagocytic function improved (RR 0.31, p = <.01; RR 0.23, p = <.01). Cerebral blood flow improved (SMD -1.39, p = <.01), and a low incidence of stroke after transplantation in high-risk patients was found. Retinopathy and avascular osteonecrosis were investigated in only one study, showing no significant changes. While HSCT can improve some SCD-related organ dysfunctions, transplantation-related toxicity may have an adverse effect on others. Future research should focus on identifying individuals with SCD who might benefit most from HSCT and which forms of organ damage are more likely to exacerbate post-transplantation.

ATG versus PTCy in matched unrelated donor haematopoietic stem cell transplantations with non-myeloablative conditioning.

Graft-versus-host disease (GvHD) is a serious complication of allogeneic haematopoietic stem cell transplantation (HSCT). Both anti-thymocyte globulin (ATG) and post-transplant cyclophosphamide (PTCy) are used as lymphocyte-depleting strategies, yet a systematic comparison of transplantation outcomes between these two methods in matched unrelated donors (MUD) transplantations with non-myeloablative conditioning (NMC) is lacking. Adult patients with haematological malignancies who had undergone MUD HSCT with NMC regimens between 2014 and 2021 at 2 centres in Amsterdam (ATG: n = 95, PTCy: n = 90), were included in this retrospective study. Patient characteristics were comparable between the groups. The cumulative incidence of acute GvHD grade II-IV was 48% in the ATG group compared to 21% in the PTCy group (p < 0.001). The 3-year moderate/severe chronic GvHD was similar in both groups (p = 0.69). While the relapse rate was comparable between the groups (ATG 31% vs. PTCy 34%, p = 0.94), non-relapse mortality tended to be higher in the ATG group (17% vs. 9%, p = 0.069). Overall survival was similar in both groups (p = 0.12). In conclusion, PTCy-based regimens resulted in a significantly lower rate of acute GvHD than ATG-containing regimens in MUD transplantations with NMC. Whether PTCy results in improved overall survival as compared to ATG needs to be elucidated in larger prospective studies.

Haploidentical Allogeneic Stem Cell Transplantation in Sickle Cell Disease: A Systematic Review and Meta-Analysis.

Allogeneic hematopoietic stem cell transplantation (SCT) is the sole established curative treatment option for patients with sickle cell disease (SCD). However, a lack of HLA-identical sibling donors is a limiting factor. Haploidentical related donors are a promising donor pool, potentially extending SCT as a curative treatment option to a larger group of patients with no other meaningful treatment options for their severe SCD. In the present study, we aimed to systematically review the results of haploidentical SCT in patients with SCD. A comprehensive search was performed in MEDLINE/PubMed and Embase up to May 2021. Data were extracted by 2 reviewers independently, and the Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of the studies. Fourteen studies met our inclusion criteria. To provide an overview of the results of haploidentical SCT, we grouped the studies into myeloablative conditioning versus nonmyeloablative conditioning as well as into in vitro versus in vivo (ie, with post-transplantation cyclophosphamide) T cell depletion with a subgroup meta-analysis of proportions. All the included studies were observational cohort studies. Only 3 of these studies reported data for both matched sibling donor (MSD) SCT and haploidentical SCT. Based on a comparative meta-analysis of the 3 studies that included both haploidentical and MSD transplantation, graft failure was significantly higher in the haploidentical group than in the MSD group (odds ratio, 5.3; 95% confidence interval [CI], 1.0 to 27.6). Overall survival was not significantly different between the groups. A subgroup meta-analysis of the results of haploidentical SCT showed relatively low overall pooled proportions of graft failure (7%; 95% CI, 2% to 20%), acute graft-versus-host disease (GVHD) (4%; 95% CI, 2% to 12%), and chronic GVHD (11%; 95% CI, 7% to 16%). Overall survival (OS) was high in all the included studies (91%; 95% CI, 85% to 94%). Adjustments to the conditioning regimens, robust pretransplantation and post-transplantation T cell depletion, and improved supportive care have resulted in reduced graft failure and improved OS following haploidentical SCT in patients with SCD. We conclude that the safety of haploidentical SCT in SCD patients has improved significantly, and that this should be considered as a curative option in patients with severe SCD.