OTL-300 is a gene therapy drug product consisting of autologous hematopoietic stem/progenitor cluster of differentiation (CD) 34+ cells genetically modified with a lentiviral vector (GLOBE) encoding the human beta globin gene. The TIGET-BTHAL is a phase I/II study evaluating safety and efficacy of OTL-300 in subjects with transfusion dependent beta-thalassemia for 2 years post gene-therapy. Here, HBB is linked to beta thalassemia.