Smoothing the crescent curve: sickle cell disease

Donor chimerism and immune reconstitution following haploidentical transplantation in sickle cell disease

Introduction

We previously reported the initial results of a phase II multicenter transplant trial using haploidentical parental donors for children and aolescents with high-risk sickle cell disease achieving excellent survival with exceptionally low rates of graft-versus-host disease and resolution of sickle cell disease symptoms. To investigate human leukocyte antigen (HLA) sensitization, graft characteristics, donor chimerism, and immune reconstitution in these recipients.

Methods

CD34 cells were enriched using the CliniMACS^® system with a target dose of 10 x 10⁶ CD34⁺ cells/kg with a peripheral blood mononuclear cell (PBMNC) addback dose of 2x10⁵ CD3/kg in the final product. Pre-transplant HLA antibodies were characterized. Donor chimerism was monitored 1-24 months post-transplant. Comprehensive assessment of immune reconstitution included lymphocyte subsets, plasma cytokines, complement levels, anti-viral T-cell responses, activation markers, and cytokine production. Infections were monitored.

Results

HLA antibodies were detected in 7 of 11 (64%) evaluable patients but rarely were against donor antigens. Myeloid engraftment was rapid (100%) at a median of 9 days. At 30 days, donor chimerism was 93-99% and natural killer cell levels were restored. By 60 days, CD19 B cells were normal. CD8 and CD4 T-cells levels were normal by 279 and 365 days, respectively. Activated CD4 and CD8 T-cells were elevated at 100-365 days post-transplant while naïve cells remained below baseline. Tregs were elevated at 100-270 days post-transplant, returning to baseline levels at one year. At one year, C3 and C4 levels were above baseline and CH50 levels were near baseline. At one year, cytokine levels were not significantly different from baseline.

Discussion

These results suggest that haploidentical transplantation with CD34-enriched cells and peripheral blood mononuclear cell addback results in rapid engraftment, sustained donor chimerism and broad-based immune reconstitution.

Significant improvement of child physical and emotional functioning after familial haploidentical stem cell transplant

Allogeneic stem cell transplantation (AlloSCT) represents the only curative therapy for sickle cell disease (SCD). However, limited availability of matched related donors and suboptimal outcomes following AlloSCT with unrelated donors has led to investigation of alternative donors. Among children with high-risk SCD, we evaluated health-related quality of life (HRQoL) impact in the two years following familial haploidentical SCT. HRQoL was collected from parent and child raters, using the Child Health Ratings Inventories Generic measure and haploidentical SCT-specific module. Repeated measures models were fit to assess HRQoL changes over time and by rater. Nineteen children (mean age 12.9 yrs [standard deviation, 5.3]; 63% male) and their parents were included. There were no differences in the 2-yr trajectories of child physical or emotional functioning (EF) by rater. Child physical functioning and EF scores were significantly lower at day +45 than baseline, but scores recovered by day +180. There was significant improvement in EF (p = 0.03) at 2 yrs vs baseline. A similar pattern of scores over time was seen for parent ratings of child's global HRQoL. Despite treatment intensity in the initial months following AlloSCT, patient scores recovered or exceeded baseline scores at two years. This trial is registered at clinicaltrials.gov (NCT01461837).

Stable to improved cardiac and pulmonary function in children with high-risk sickle cell disease following haploidentical stem cell transplantation

Children with sickle cell disease (SCD) are at high-risk of progressive, chronic pulmonary and cardiac dysfunction. In this prospective multicenter Phase II trial of myeloimmunoablative conditioning followed by haploidentical stem cell transplantation in children with high-risk SCD, 19 patients, 2.0-21.0 years of age, were enrolled with one or more of the following: history of (1) overt stroke; (2) silent stroke; (3) elevated transcranial Doppler velocity; (4) multiple vaso-occlusive crises; and/or (5) two or more acute chest syndromes and received haploidentical transplants from 18 parental donors. Cardiac and pulmonary centralized cores were established. Pulmonary function results were expressed as percent of the median of healthy reference cohorts, matched for age, sex, height and race. At 2 years, pulmonary functions including forced expiratory volume (FEV), FEV₁/ forced vital capacity (FVC), total lung capacity (TLC), diffusing capacity of lung for carbon monoxide (DLCO) were stable to improved compared to baseline values. Importantly, specific airway conductance was significantly improved at 2 years (p < 0.004). Left ventricular systolic function (fractional shortening) and tricuspid regurgitant velocity were stable at 2 years. These results demonstrate that haploidentical stem cell transplantation can stabilize or improve cardiopulmonary function in patients with SCD.

Treosulfan-Based Conditioning Regimen in Sibling and Alternative Donor Hematopoietic Stem Cell Transplantation for Children with Sickle Cell Disease

BACKGROUND AND OBJECTIVES

Lack of suitable donors and regimen related toxicity are major barriers for hematopoietic stem cell transplantation (HSCT) in patients with sickle cell disease (SCD). The aim of the study is the assessment of efficacy and toxicity of Treosulfan-based conditioning regimen for SCD also when alternative donors such as mismatched unrelated donor and haploidentical donor are employed.

METHODS

We report our single-center experience: 11 patients with SCD received HSCT with a Treosulfan/Thiotepa/Fludarabine/Anti-thymoglobulin conditioning regimen between 2010 and 2015. The donor was a matched sibling donor (n= 7), a haploidentical parent (n= 2), a matched unrelated donor (n= 1) or a mismatched unrelated donor (n=1). The haploidentical and mismatched unrelated donor grafts were manipulated by removing TCRαβ and CD19 positive cells.

RESULTS

All patients survived the procedure and achieved stable engraftment. Stable mixed chimerism was observed in 5/11 patients. Grade III-IV regimen related toxicity was limited to mucositis and no grade III-IV graft-versus-host disease (GvHD) occurred. No SCD manifestation was observed post transplant and cerebral vasculopathy improved in 3/5 evaluable patients. Organ function evaluation showed no pulmonary, cardiac or renal toxicity but gonadal failure occurred in 1/4 evaluable patients.

CONCLUSION

Our data suggest that Treosulfan is associated with low toxicity and may be employed also for unrelated and haploidentical donor HSCT.