Evolution of Peripheral Blood Stem Cell Transplantation

AMD3100 redosing fails to repeatedly mobilize hematopoietic stem cells in the nonhuman primate and humanized mouse

AMD3100 (plerixafor) is a vital component of many clinical and preclinical transplant protocols, facilitating harvest of hematopoietic stem and progenitor cells through mobilization into the peripheral blood circulation. Repeat mobilization with AMD3100 is also necessary for many patients with suboptimal first stem cell collection or those requiring repeat transplantation. In this study we investigated the mobilization efficacy of repeated AMD3100 dosages in the nonhuman primate and humanized mouse models. In nonhuman primates, we observed effective mobilization after the first AMD3100 administration but a significantly poorer response in CD34⁺ and hematopoietic stem cell-enriched CD90⁺ cells with subsequent doses of the drug. A similar loss of efficacy with repeated administration was noted in immunodeficient mice engrafted with human CD34⁺ cells, in whom the total human white cell population, and particularly human hematopoietic stem and progenitor cells, mobilized significantly less effectively following a second AMD3100 administration when compared with the first dose. Together, our results are expected to inform future mobilization protocols for the purposes of peripheral blood hematopoietic stem cell extraction or for applications in which hematopoietic stem cells must be made accessible for in vivo-delivered gene targeting agents.

The Use of Post-transplantation Cyclophosphamide in Peripheral Blood HLA-matched Stem Cell Transplantation as Graft-versus-host Disease Prophylaxis in Patients With Malignant or Non-malignant Hematologic Disorders: A Single-center Experience of 52 Patients

INTRODUCTION

Studies addressing the utilization of post-transplant cyclophosphamide (CY) as graft-versus-host disease (GVHD) prophylaxis in allogeneic hemopoietic stem cell transplantation from matched sibling donors are limited and with controversial results. Chronic GVHD incidence necessitating systemic treatment is around 35% in peripheral blood stem cell transplantation (PBSCT) from human leukocyte antigen-matched sibling donors.

PATIENTS AND METHODS

In this study, high-dose CY was added to PBSCT aiming to reduce the incidence of GVHD to reach a lower figure compared with standard GVHD prophylaxis. Fifty-two patients with either benign or malignant hematologic disorders who underwent stem cell transplantation at Nasser Institute Hospital in Egypt from November 2017 to October 2018 were enrolled in this study. Fifty patients had fully human leukocyte antigen-matched siblings, whereas the remaining 2 patients had 1 locus class I mismatched donors. Pre-transplant conditioning regimen was fludarabine and busulfan (FLU/BU) in malignant cases (73.1%) and FLU/CY in benign hematologic disorders (26.9%) and 1 patient with hypocellular myelodysplastic syndrome. For GVHD prophylaxis, CY was given at a dose of 50 mg/kg/day on days 3 and 4 post-transplantation, and cyclosporine (CSA) starting day 5 in 96.1% of patients. For the 1-locus mismatched patients, both CSA and mycophenolate mofetil were administered starting day 5.

RESULTS

The 1-year incidence of acute GVHD (aGVHD) was 15.3% and for chronic GVHD (cGVHD) was 13.4%. Historical data of GVHD prophylaxis at our center using CSA and methotrexate showed an incidence of 37% for aGVHD and 33.9% for cGVHD.

CONCLUSIONS

Post-transplant CY GVHD prophylaxis led to significantly less aGVHD (P = .03) and cGVHD (P = .04).

CRISPR/Cas9 for the treatment of haematological diseases: a journey from bacteria to the bedside

Genome editing therapies represent a significant advancement in next-generation, precision medicine for the management of haematological diseases, and CRISPR/Cas9 has to date been the most successful implementation platform. From discovery in bacteria and archaea over three decades ago, through intensive basic research and pre-clinical development phases involving the modification of therapeutically relevant cell types, CRISPR/Cas9 genome editing is now being investigated in ongoing clinic trials. Despite the widespread enthusiasm brought by this new technology, significant challenges remain before genome editing can be routinely recommended and implemented in the clinic. These include risks of genotoxicity resulting from off-target DNA cleavage or chromosomal rearrangement, and suboptimal efficacy of homology-directed repair editing strategies, which thus limit therapeutic options. Practical hurdles such as high costs and inaccessibility to patients outside specialised centres must also be addressed. Future improvements in this rapidly developing field should circumvent current limitations with novel editing platforms and with the simplification of clinical protocols using in vivo delivery of editing reagents.