Gene Therapy

The Adair lab is focused primarily on developing clinical applications of hematopoietic stem cell (HSC) gene therapy to treat a wide range of genetic defects and malignancies. HSCs are attractive targets for gene therapy given their ability to remain viable following ex-vivo manipulation. Despite this favorable amenability, HSC gene therapy is heavily limited in clinical applications due to concerns over safety as well as obstacles within gene therapy protocols (i.e. difficulties achieving successful genetic modification or transfer of genetic material, long-term engraftment of modified cells, side-effects of insertional mutagenesis, etc.). Much of the ongoing research within the Adair lab is centered on refining the HSC gene therapy process to alleviate these concerns and bring gene therapy treatments to the forefront of accepted medical practice. Specific disease applications of gene therapy include Fanconi anemia (FA), Hemoglobinopathies and Human Immunodeficiency Virus (HIV) infection.


Researcher working in the Adair lab

Fanconi Anemia

Fanconi anemia (FA) is a monogenic inherited disease affecting DNA repair which has many clinical manifestations. Of these, early bone marrow failure causes the greatest morbidity and mortality in FA patients. This disease is most commonly treated by allogeneic bone marrow transplantation; however donors can be difficult to find and the systemic defect in DNA repair requires reduced intensity conditioning prior to transplant, which increases complications such as graft vs. host disease. Autologous transplantation of gene corrected hematopoietic stem cells would negate these problems, thus making the gene therapy approach highly desirable.Despite being an early candidate disease for hematopoietic stem cell gene therapy, no successful therapeutic benefit has been achieved to date. This is primarily due to low numbers of hematopoietic stem cells in FA patients. Moreover, these cells are exquisitely fragile and respond poorly to manipulations required for successful gene transfer.

The Adair lab previously developed modified gene transfer protocols to preserve the few numbers of fragile stem cells available from FA patients by incorporating agents to prevent oxidative DNA damage and accomplish successful gene transfer with minimal manipulation in as short as 24 hours.Dr. Adair is currently leading a clinical trial investigating the potential for gene-corrected autologous hematopoietic stem cells to prevent bone marrow failure in FA patients who have defects in the FANCA gene, the most common FA genetic defect in the U.S. [NCT01331018]. This trial utilizes a self-inactivating lentivirus vector to transfer a functional copy of the FANCA gene into FA patient hematopoietic stem cells. The Adair lab oversees collection, manufacturing and infusion of these gene modified cells under cGMP guidelines. In addition, the Adair lab measures levels of gene modified cells and examines the clonal repertoire of engrafted gene modified cells in FA patients treated in this study.In collaboration with the laboratories of Hans-Peter Kiem and Pamela Becker, Dr. Adair measures clinical response in these patients 

Dr. Adair also works closely with the International Fanconi Anemia Gene Therapy Working Group to develop new approaches to gene therapy in this uniquely challenging disease setting. Current Adair lab research in gene therapy for FA uses mouse models of the disease to evaluate in vivo gene delivery, as well as modified protocols for ex vivo gene transfer which increase numbers of gene modified cells available for transplantation. 

researcher working in the Adair lab

Hemoglobinopathies

Approximately 1.1 million births worldwide are at risk for hemoglobinopathies every year, effecting as many as 25 in every 1,000 births in geographic regions where malaria falciparum is prevalent, owing to a natural resistance to malaria infection conferred by hemoglobin (Hb) genetic variance. In developed regions, patients live with chronic disease unless treated with an allogeneic hematopoietic stem cell transplant (HSCT) from an unaffected donor. If a donor is not identified, patients are at risk of iron overload from chronic transfusions. In underdeveloped regions, survival is significantly lower. For example, in Africa, childhood mortality is 40% in patients with hemoglobinopathies, compared to 16% in all children. Even when HSCT is available, complications such as infection and graft-versus-host disease arise, especially when the donor is unrelated or mismatched for human leukocyte antigens (HLA). Moreover, this treatment is not available on large scale and has been shown to be impacted by ethnicity in terms of complications experienced by patients that undergo HSCT and on the likelihood of identifying a HLA matched donor.

Retrovirus-mediated gene addition into hematopoietic stem and progenitor cells (HSPC) has demonstrated curative outcomes for hemoglobinopathies. However, only centers with Good Manufacturing Practices (GMP)-compliant facilities and the infrastructure to support them are capable of administering gene-modified cell products. Our lab developed a simplified manufacturing platform to automate this process in a small, mobile footprint that could be used in the patient’s room [Adair et al., Nature Communications, 2016]. Despite this major advance, limited quantities of therapeutic vector can be produced at GMP quality owing to the requirement for a living cell to assemble the viral particles and then subsequently purify these particles from cells and other cellular debris. This difficulty creates a major bottleneck to widespread use of this gene therapy treatment.

Gene editing has been proposed as a safer alternative to retrovirus-mediated gene transfer, made possible by the development of engineered nucleases such as clustered, regularly interspaced, short palindromic repeat (CRISPR)-Cas nucleases. While these designer nucleases are easier to synthesize than retroviruses, they can only target a break in the DNA. To engineer a precise genetic change at the break site, a DNA repair process known as homology directed repair (HDR) must be employed. For HDR to occur, a more complex payload must be delivered including the designer nuclease and a DNA template encoding the precise change. The Adair laboratory studies engineered nanomaterials that can passively administer all of the machinery required for precise genetic modification with specific efficacy in HSPC. While these nanoparticles therapeutically target hemoglobinopathies currently, they have broad potential across many diseases.

Researcher working in a cell processing facility

HIV

Human Immunodeficiency Virus (HIV) is a worldwide epidemic that has only been cured in a single case (the Berlin Patient) with a complex and unique treatment regimen that is not currently possible in all HIV+ patients. This patient received an allogeneic bone marrow transplant from a donor with a mutation in the CCR5 co-receptor for HIV infection. This rendered the transplanted bone marrow naturally resistant to HIV infection.  Gene therapy could be used to produce the same clinical benefit in a greater number of HIV+ patients by allowing genetic modification of a patient’s own cells. However, CCR5 is not the only coreceptor that HIV particles can utilize to infect blood cells. The Adair lab, in collaboration with the laboratory of Dr. Hans-Peter Kiem, developed a self-inactivating lentivirus vector for transfer of two therapeutic genes: (1) a short hairpin RNA which directs cellular degradation of CCR5 transcripts, and (2) a c peptide (mC46), which is expressed in the cell membrane and prevent fusion of HIV vector particles with the cell membrane regardless of which co-receptor is used for infection. This vector also encodes the P140K mutant MGMT transgene, which provides gene modified cells a selective advantage in vivo when a combination of alkylating agent chemotherapy and the wild-type MGMT inhibitor, O6-benzylguanine, are administered.

This vector is currently being applied in a phase I clinical trial of gene therapy for patients with AIDS lymphoma [NCT02343666]. The Adair laboratory oversees manufacturing and infusion of these gene modified cells under cGMP guidelines. In addition, the Adair lab measures levels of gene modified cells and examines the clonal repertoire of engrafted gene modified cells in patients treated in this study. Current research in the Adair lab seeks to refine closed system, automated manufacturing of gene modified blood cells to make gene and cell therapies more readily available in resource-challenged countries where the largest HIV+ populations reside.