Diagram of the Typical Process of Gene Therapy for Hematopoietic Disorders. Hematopoietic stem and progenitor cells (HSPCs) can be modified directly, as is the case for currently used therapies. The genetically modified HSPCs are then transplanted back into the patient. When HSPCs are modified directly, modification may not occur in every cell. Goodman MA et al, Ther Adv Hematol. 15(5):302-315, copyright © 2016 by SAGE Publications. Reprinted by Permission of SAGE.