Phase I/II Clinical Trial Stem Cell Gene Therapy in RAG1-Deficient SCID

Overview

This trial is a prospective, non-randomized, open-label, multicentre single-arm phase I/II intervention trial in children up to 24 months of age with RAG1-deficient SCID and an indication for allogeneic hematopoietic stem cell transplantation but lacking an HLA-matched donor. The trial involves infusion of autologous CD34+ cells transduced with the pCCL.MND.coRAG1.wpre lentiviral vector (hereafter called RAG1 LV CD34+ cells) in up to 10 patients with RAG1-deficient SCID. Patients will be regularly monitored for 5 years after infusion. Follow up as part of routine clinical care for post-transplant patients will be annual after this, for at least 15 years after IMP infusion.

Severe combined immunodeficiency (SCID) is a genetically heterogeneous life-threatening disease characterized by severely impaired T cell development with or without impaired natural killer (NK) and B cell development or function depending on the genetic defect. Mutations in recombination activating genes 1 and 2 (RAG1 and RAG2) represent about 20% of all types of SCID. SCID is a paediatric emergency since it leads to severe, life-threatening and recurrent infections often in combination with protracted diarrhoea and failure to thrive. When left untreated, it is usually fatal within the first year of life. Currently, the only curative treatment option for RAG-deficient SCID is allogeneic hematopoietic stem cell transplantation (HSCT). Despite improvements in HSCT in recent years, this treatment is associated with serious potential complications like graft-versus-host disease which results in an unfavourable outcome, particularly in patients who lack a human leukocyte antigen (HLA)-matched donor. In recent years, gene therapy based on transplantation of autologous gene-corrected hematopoietic stem cells (HSC) has evolved as an effective and safe therapeutic option for X-linked and ADA-deficient forms of SCID. We have recently demonstrated that gene therapy using lentiviral (LV) self-inactivating (SIN) vectors expressing codon-optimized human RAG1 in a mouse model for RAG1-deficient SCID effectively restores T and B cell development and function. In this phase I/II intervention trial safety and efficacy of gene therapy using gene-corrected autologous CD34+-selected mobilized peripheral cells will be investigated in patients with RAG1-deficient SCID with an indication for allogeneic HSCT but lacking an HLA-identical sibling/ family donor.