04 Understanding HSC Gene Therapy
How is HSC Gene Therapy Made?
To understand the process by which lentiviral vectors used in hematopoietic stem cell (HSC) gene therapy are manufactured.
The HSC gene therapy manufacturing process is controlled through a series of steps.1-7
- The person receives a combination of medications designed to mobilize or release their HSPCs to move out of the bone marrow and into the blood. The HSPCs are collected through a process called apheresis or via bone marrow aspiration, a procedure involving use of a needle to withdraw a sample of the fluid portion of the bone marrow. The HSPCs are then transported to a manufacturing site.1-3
- The HSPCs are enriched for a particular type of cell called CD34+ cells. CD34+ cells are stimulated with growth factors to enhance uptake of the lentiviral vector. This is done by keeping them overnight in an incubator at body temperature.1-3
- The lentiviral vector is combined with the CD34+ cells, which are again placed in an incubator overnight to allow transfer of the therapeutic genetic material into the DNA of the target cells (transduction). This type of vector is designed to permanently integrate the therapeutic gene directly into the DNA of the HSPCs.1-3
- Transduced HSPCs (genetically modified stem and progenitor cells) are harvested, washed and cryopreserved (frozen at very low temperatures).1-3
- The genetically modified HSPCs undergo a series of quality control steps on the final gene therapy product before leaving the manufacturing site.1-3
- The person goes through a conditioning process to prepare their body to receive back their own genetically modified HSPCs. The cells are thawed and returned to the person via a one-time intravenous (IV) infusion.1-3
Additional Interesting Fact
Chemistry, manufacturing, and controls (called CMC for short) information must be included in new pharmaceutical product applications to the U.S. Food and Drug Administration. CMC specifies the manufacturing processes, product characteristics, and product testing that must be reviewed by FDA, to help provide consistency between batches.4
The steps in the HSC gene therapy manufacturing process include:
- HSPC mobilization and apheresis or bone marrow aspiration
- Enrichment of the HSPCs with CD34+ cells
- Combining the lentiviral vector with the CD34+ cells; the vector carries and delivers the new genetic material to the stem cells (transduction)
- Harvesting, washing, and cryopreservation of the transduced stem cells
- Quality control of the final gene therapy product
- Individualized conditioning to prepare the person’s body to receive back their own genetically modified HSPCs
- Thawing of the genetically modified HSPCs
- Reinfusion of the genetically modified HSPCs
Continue learning about HSC gene therapy in the next section
What is Conditioning?
To understand the purpose and intent of conditioning in lentiviral hematopoietic stem and progenitor cell gene therapy, and how the process works.
- Staal FJT, Aiuti A, Cavazzana M. Autologous stem-cell-based gene therapy for inherited disorders: state of the art and perspectives. Front Pediatr. 2019;7:443. [PubMed]
- Milone MC, O’Doherty U. Clinical use of lentiviral vectors. Leukemia 2018;32:1529. [PubMed]
- Bone marrow biopsy and aspiration. Mayo Clinic; 2021. https://www.mayoclinic.org/tests-procedures/bone-marrow-biopsy/about/pac-20393117. Accessed December 23, 2021.
- Chemistry, manufacturing, and controls (CMC) information for human gene therapy investigational new drug applications (INDs): guidance for industry. U.S. Department of Health and Human Services, Food and Drug Administration, Center for Biologics Evaluation and Research; 2020. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/chemistry-manufacturing-and-control-cmc-information-human-gene-therapy-investigational-new-drug. Accessed December 23, 2021.
- Drysdale CM, Tisdale JF, Uchida N. Immunoresponse to gene-modified hematopoietic stem cells. Mol Ther Methods Clin Dev. 2020;16:42-49. [PubMed]
- Piguet F, Alves S, Cartier N. Clinical gene therapy for neurodegenerative diseases: past, present, and future. Hum Gene Ther. 2017;28(11):988-1003. [PubMed]
- Capotondo A, Milazzo R, Politi LS, et al. Brain conditioning is instrumental for successful microglia reconstitution following hematopoietic stem cell transplantation. Proc Natl Acad Sci U S A. 2012;109(37):15018-15023. [PubMed]