A reduced-toxicity regimen is associated with durable engraftment and clinical cure of nonmalignant genetic diseases among children undergoing blood and marrow transplantation with an HLA-matched related donor

Hematopoietic stem cell transplantation for B-thalassemia major with alemtuzumab

While matched related donor (MRD) allogeneic hematopoietic stem cell transplantation (HSCT) is a curative option for transfusion-dependent beta-thalassemia (TDT), the use of alternative sources has increased, resulting in the exploration of novel transplant-conditioning regimens to reduce the contribution of graft-versus-host disease (GVHD) and graft failure (GF) to transplant-related morbidity and mortality. Alemtuzumab is a CD52 monoclonal antibody that has been successfully incorporated into myeloablative conditioning regimens for other hematologic conditions, yet there have been limited studies regarding the use of alemtuzumab in HSCT for TDT. The purpose of this study was to evaluate engraftment, incidence of GVHD, and transplant related morbidity and mortality in patients with TDT who received alemtuzumab in addition to standard busulfan-based conditioning. The primary endpoint was severe GVHD-free, event-free survival (GEFS). Our cohort included 24 patients with a median age of 6.8 years (range 1.5-14.9). Eleven patients received a 10/10 MRD HSCT, eleven 10/10 unrelated donor (UD), and two mismatched UD. All patients achieved primary engraftment. For all patients, 5-year GEFS was 77.4% and 5-year overall survival (OS) was 91%. The 5-year cumulative incidence of GF (attributed to poor graft function) without loss of donor chimerism was 13.8% (95% CI: 4.5, 35.3). We report low rates of significant acute GVHD grade II-IV (12.5%) and chronic GVHD (4.4%). Younger age and MRD were associated with significantly improved GEFS, OS and EFS. Our results show that the use of alemtuzumab promotes stable engraftment, may reduce rates of severe GVHD, and results in acceptable GEFS, OS, and EFS.

Matched related hematopoietic cell transplant for sickle cell disease with alemtuzumab: the Texas Children's Hospital experience

Serotherapeutic agents facilitate engraftment and prevent graft-versus-host disease (GVHD) following hematopoietic stem cell transplant. Anti-thymocyte globulin is generally added to conditioning chemotherapy for matched related donor transplant (MRD-HCT) for sickle cell disease (SCD). Alemtuzumab, however, is appealing due to its broad lymphocyte killing that may achieve very low rejection and GVHD rates. To assess the impact of alemtuzumab in MRD-HCT for SCD, we retrospectively reviewed transplant-related outcomes and markers of immunity in 38 consecutive patients at Texas Children's Hospital having received myeloablative conditioning with alemtuzumab. Median follow-up was 4.8 years (range: 0.2-17). All patients engrafted. Donor chimerism was mixed in 47.1% of patients at ≥2-years. Donor chimerism <50% was uncommon (n = 2). One patient with low myeloid chimerism (19%) had sickle-related hemolysis at 10-years. Incidence of acute GVHD grade II-IV (5.3%) and extensive chronic GVHD (2.8%) was very low. Five-year event-free survival (EFS) and composite chronic GVHD-EFS were excellent at 94.7% (95% CI: 80.3, 98.6) and 89.2% (95% CI: 73.7, 95.8), respectively. Infections did not contribute to mortality although cytomegalovirus reactivation occurred commonly in the first 3 months after transplant. Our data suggest potential for alemtuzumab in myeloablative transplant for children with SCD although further evaluation in older patients and with unrelated donors is warranted.

Exploration of the relationship between intestinal flora changes and gut acute graft-versus-host disease after hematopoietic stem cell transplantation

BACKGROUND

Acute graft-versus-host disease (aGVHD) is a life-threatening factor for post-hematopoietic stem cell transplantation (HSCT) patients. To investigate the relationship between intestinal flora changes and gut aGVHD after HSCT, we performed this cross-sectional study.

METHODS

We selected children from our medical center from July 2016 to January 2017. Fifty-six samples from 42 patients and 6 samples from normal children met the study criteria and were analyzed. Fecal 16S RNA sequencing was completed before transplantation or on days 7, 28 or 100 post-transplantation. The intestinal infection and GVHD clinical data were retrospectively analyzed, and the survival risk factors were analyzed. Correlation analysis was performed with the feces bioinformatic data.

RESULTS

The GVHD group alpha diversity was the lowest, which was significantly different than that of the non-diarrhea group (P value=0.032). A richer posttransplantation relative abundance of Moraxellaceae was conducive to survival, while that of Enterococcaceae and Alphaproteobacteria was not. Similarly, a rich relative abundance of Proteobacteria, Gammaproteobacteria and Odoribacteraceae in the intestinal flora before HSCT contributed to patient death thereafter. Regarding diarrhea, the GVHD group exhibited a richer Pasteurellales and Pasteurellaceae relative abundances, which showed strong correlations with diarrhea severity. Peptostreptococcaceae, Bifidobacteriales and Bifidobacteriaceae were richer in relative abundance in the intestinal infection group and correlated with pretransplant characteristics.

CONCLUSIONS

The gut microbiota diversity was lowest when gut aGVHD occurred, which was consistent with the clinically higher mortality rate and greater treatment difficulty. Pasteurellaceae played an important role in gut aGVHD and diarrhea severity. Bifidobacteriaceae led to infectious diarrhea after HSCT. Specific bacteria were biomarkers for survival: Moraxellaceae, Enterococcaceae and Alphaproteobacteria from the intestinal flora after HSCT and Proteobacteria, Gammaproteobacteria and Odoribacteraceae before HSCT.

Timing of Alemtuzumab With Respect to Day of Bone Marrow Infusion and its Effects Upon Engraftment and Graft-Versus-Host Disease in Patients With Sickle Cell Disease: A Single-Institutional Study

The possible impact of "late" alemtuzumab (administered on days -10 to -8) versus "early" alemtuzumab (-19 to -17) with respect to engraftment and acute/chronic graft-versus-host disease (GvHD) in a group of 25 pediatric patients with sickle cell disease undergoing bone marrow transplantation following conditioning with alemtuzumab, fludarabine, and melphalan is reported. The first 9 patients received "late" alemtuzumab followed by bone marrow transplantation from HLA-matched sibling donors. The next 16 patients undergoing matched sibling transplants received "early" alemtuzumab. In the "late" group, 1 patient (11%) developed acute GvHD. Six patients (67%) achieved sustained engraftment. Three patients (33%) experienced graft rejection, leading to termination of enrollment of patients on this regimen. In the "early" alemtuzumab group, acute and chronic GvHD developed in 43% and 25% patients, respectively. None of the patients experienced graft rejection in this group of patients. Three patients developed stable mixed chimerism and 13 patients demonstrated 100% donor chimerism at 1 year post-transplant and beyond. These results suggest a benefit with respect to engraftment of administering "early" versus "late" alemtuzumab in this reduced-intensity conditioning regimen, however, with the possible cost of an increase in acute, and possibly chronic GvHD.

Pharmacokinetics of alemtuzumab in pediatric patients undergoing ex vivo T-cell-depleted haploidentical hematopoietic cell transplantation

PURPOSE

Alemtuzumab is a humanized monoclonal antibody against CD52 which is predominantly present on T and B lymphocytes. Alemtuzumab has been used as part of conditioning regimens for prophylaxis against rejection and GVHD. While the mechanism of action is well understood, the pharmacokinetics of this drug in children needed to be studied in more detail especially in the setting of ex vivo T-cell-depleted hematopoietic cell transplantation (HCT).

METHODS

Serum alemtuzumab levels were measured at various time points in 13 patients who underwent haploidentical HCT utilizing ex vivo donor T-cell depletion. Alemtuzumab was administered subcutaneously at a cumulative dose of 45 mg/m² from days - 13 to - 11. A one-compartmental model was used to fit the data using non-linear mixed effects modeling.

RESULTS

We determined the median half-life to be 11 days. Alemtuzumab clearance increased with increasing baseline lymphocyte count (p = 0.008). Additionally, clearance increased with weight and age (p ≤ 0.035). AUC of alemtuzumab did not have any significant relationship with type of leukemia, overall survival, engraftment, immune reconstitution, mixed chimerism or GVHD, although the number of subjects in this pilot study was limited.

CONCLUSION

Absolute lymphocyte count and body weight affect alemtuzumab clearance. We also demonstrate feasibility of body-surface area-based dosing of alemtuzumab in pediatric HCT patients. Further studies are needed to evaluate the role of monitoring alemtuzumab serum concentrations to balance the prevention of graft rejection and GVHD with the promotion of rapid donor immune reconstitution.

Unrelated donor hematopoietic stem cell transplantation for the treatment of non-malignant genetic diseases: An alemtuzumab based regimen is associated with cure of clinical disease; earlier clearance of alemtuzumab may be associated with graft rejection

Hematopoietic stem cell transplantation (HSCT) with matched unrelated donors (MUD), offers potentially curative therapy for patients with non-malignant genetic diseases. In this pilot study conducted from 2006 to 2014, we report the outcomes of 15 patients with non-malignant genetic diseases who received a myeloablative regimen with a reduced cyclophosphamide dose, adjunctive serotherapy and MUD HSCT [intravenous alemtuzumab (52 mg/m(2) ), busulfan (16 mg/kg), fludarabine (140mg/m(2) ), and cyclophosphamide (105 mg/kg)]. Graft-versus-host-disease (GVHD) prophylaxis consisted of tacrolimus/cyclosporine and methylprednisolone. Median (range) time to neutrophil engraftment (>500 cells/µL) and platelet engraftment (>20,000/mm(3) ) were 15 (12-28) and 25 (17-30) days, respectively. At a median follow-up of 2 (0.2-5.4) years, the overall survival (OS) was 93.3% (95% CI: 0.61-0.99) and disease-free survival (DFS) was 73.3% (95% CI: 0.44-0.89). Among this small sample, earlier alemtuzumab clearance was significantly associated with graft rejection (P = 0.047), earlier PHA response (P = 0.009) and a trend toward earlier recovery of recent thymic emigrants (RTE) (P = 0.06). This regimen was associated with durable donor engraftment and relatively low rates of regimen related toxicity (RRT); future alemtuzumab pharmacokinetic studies may improve outcomes, by allowing targeted alemtuzumab clearance to reduce graft rejection and promote more rapid immune reconstitution.