 Strimvelis is indicated for the treatment of people with severe combined immunodeficiency due to adenosine deaminase deficiency (ADA-SCID), for whom no suitable human leukocyte antigen (HLA)-matched related stem cell donor is available.The treatment is personalized for each person; hematopoietic stem cell (HSCs) are extracted from the person and purified so that only CD34-expressing cells remain.Those cells are cultured with cytokines and growth factors and then transduced with a gammaretrovirus containing the human adenosine deaminase gene and then reinfused into the person.