Conditions: Severe Combined Immunodeficiency
Keywords: SCID Transplant Alemtuzumab Plerixafor
Allocation: NON_RANDOMIZED | Intervention model: PARALLEL
Enrollment: 7
Healthy volunteers: no

Brief summary:
The goal of this study is to develop a novel approach to hematopoietic stem cell transplantation for children with Severe Combined Immunodeficiency Disease (SCID) that eliminates the use of toxic chemotherapy conditioning and maximizes the likelihood of T and B cell immune reconstitution. Rather than classic chemotherapeutic agents, the investigators will utilize a targeted stem cell mobilizer, plerixafor, in combination with alemtuzumab, a monoclonal antibody. Correlative scientific questions will include: 1) efficacy and characteristics of host stem cell mobilization; and 2) alemtuzumab pharmacokinetics in very young children.

Detailed description:
The goal of this study is to develop an approach to hematopoietic stem cell transplantation for children with Severe Combined Immunodeficiency Disease (SCID) that eliminates the use of toxic chemotherapy conditioning and maximizes the likelihood of T and B cell immune reconstitution. SCID is a rare primary immunodeficiency disease in which there are multiple genotypes and phenotypes, and depending on various factors including the presence of B cell and NK cells, and the presence of maternal cells in the patient's circulation, there are numerous ways to approach a transplant. The major issues that must be addressed in any approach to transplantation for SCID are graft rejection and T and B cell immune reconstitution. Depending on the specific SCID diagnosis, the phenotype, and the presence of maternal engraftment at diagnosis, we will evaluate two transplant approaches that will attempt to optimize the engraftment of donor HSC and the likelihood of T and B cell reconstitution while eliminating the use of toxic chemotherapy conditioning.

1. Primary Objective: To determine if the administration of plerixafor \& filgrastim (G-CSF) prior to stem cell infusion results in increased donor stem cell occupancy of available bone marrow niches and B-cell engraftment in patients with SCID.
2. Secondary Objectives:

i. To determine if NK cell depletion with Alemtuzumab will overcome NK-mediated graft resistance in haplocompatible transplants for NK+ SCID.

ii. To determine the optimal dosing of Alemtuzumab in very young children. iii. To determine the immunophenotypic characteristics of CD34+ cells mobilized and engrafted in patients receiving plerixafor \& filgrastim prior to HCT.

iv. To determine the thymic output, as measured by T-cell receptor excision circles, in patients receiving haplocompatible transplants \& boosts.

Arms:
arm 1: Patients with SCID with:

i. NK- phenotype; ii. NK+ phenotype with 10/10 HLA-matched relative or unrelated donor; or iii. NK+ phenotype with maternal engraftment by STR analysis and undergoing haplocompatible HSCT from maternal donor Intervention: Transplant Conditioning with Mobilization Only arm 2: Patients with SCID with NK+ phenotype with HLA-mismatched donor Intervention: Transplant Conditioning with Mobilization and Alemtuzumab

Interventions: intervention 1: Transplant Conditioning with Mobilization Only intervention 2: Transplant Conditioning with Mobilization and Alemtuzumab
Intervention descriptions: intervention 1: Day -4: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day -3: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day -2: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day -1: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day 0: Plerixafor 240 mcg/kg subcutaneous 9-12 hours prior to transplant; Day 0 Transplant intervention 2: Day -7: Alemtuzumab 0.3 mg test dose then 0.3 mg/kg IV; Day -6: Alemtuzumab 0.3 mg/kg IV; Day -5: Alemtuzumab 0.3 mg/kg IV; Day -4: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day -3: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day -2: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day -1: Filgrastim (G-CSF) 5 mcg/kg IV q12 hours; Day 0: Plerixafor 240 mcg/kg subcutaneous 9-12 hours prior to transplant; Day 0: Transplant

Protocol document: