Gene therapy supports long-term reconstitution of patient hematopoietic stem cells in deficiency of adenosine deaminase 2.

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic autoinflammatory disorder characterized by systemic inflammation, vasculopathy, immunodeficiency, and bone marrow failure. Current therapies-including anti-TNF agents and allogeneic hematopoietic stem cell transplantation (HSCT)-have limitations, especially for patients with hematologic involvement or no matched donor. We developed a lentiviral vector (LV.ADA2) to restore ADA2 expression in patient hematopoietic stem and progenitor cells (HSPCs) and evaluated its safety and efficacy in preclinical models. LV.ADA2 transduction of mobilized peripheral blood HSPCs from healthy donors resulted in stable ADA2 expression and secretion without impairing clonogenicity, multilineage differentiation, or long-term engraftment in immunodeficient mice. In HSPCs from 12 DADA2 patients, LV.ADA2 restored ADA2 protein and enzymatic activity preserving colony-forming ability and multilineage differentiation in vitro. In vivo, gene-corrected patient-derived HSPCs sustained long-term engraftment and multilineage reconstitution comparable to healthy controls. Integration site analysis confirmed a polyclonal pattern of hematopoietic reconstitution across all experimental settings, with no evidence of clonal dominance. Together, these findings demonstrate that ADA2 gene therapy with a LV is safe, maintains HSPC functionality, and enables durable hematopoietic reconstitution in a mouse model, providing a strong foundation for clinical translation and as a curative alternative to allogeneic HSCT in DADA2.