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Protein Deficiency Diseases

Developing gene therapy and immunomodulation strategies to treat hemophilia patients.

Gene Therapy for Hemophilia Treatment

Our lab focuses on the development of better treatment for hemophilia patients. One goal is to improve the current costly and inconvenient treatment of repeated infusion of protein products. To achieve this goal, we are developing safer and more efficient gene therapy approaches suitable for clinical applications.

Our previous study was the first to use non-viral naked DNA delivery to achieve phenotypic correction in hemophilia A and B mouse models by a hydrodynamics-based delivery method. We have since investigated clinically feasible US-mediated gene transfer strategies and have gained significant progress in mice, rats, and more recently very encouraging preliminary results in pig and dog experiments using reporter genes.  Recently we have also demonstrated that therapeutic levels of FVIII were achieved in hemophilia A mice by ultrasound and microbubble-facilitated gene transfer.  In order to facilitate the eventual translation of these technologies into human application, we have developed ultrasound systems and new generations of transducers to successfully apply ultrasound technology for treating large tissue volumes in large animal models. Recently, we have also synthesized and screened for the best custom-made, targeted microbubbles to further improve gene transfer efficiency. These projects will facilitate the translation of this novel technology into human application and could change fundamentally the way hemophilia patients are treated, with better patient outcomes. We would like to explore the possibility of clinical trial using this new technology. 

Furthermore, intraosseous (IO) infusion of lentiviral vectors (LVs) for in situ gene transfer into bone marrow may avoid specific challenges posed by ex vivo gene delivery, including, in particular, the requirement of pre-conditioning. We have successfully transduced a high percentage of primitive hematopoietic stem cells (HSCs) (up to 50%) in bone marrow following IO delivery of high-titer LVs. Furthermore, by IO delivery of G-F8-LV encoding a factor VIII (FVIII) transgene directed by a platelet-specific, glycoprotein-1bα promoter, we achieved long-term platelet-specific expression of FVIII, resulting in partial correction of hemophilia A. Similar clinical benefit with G-F8-LV was achieved in animals with pre-existing anti-FVIII inhibitors. These findings further support platelets as an ideal FVIII delivery vehicle, as FVIII, stored in α-granules, is protected from neutralizing antibodies and, during bleeding, activated platelets locally excrete FVIII to promote clot formation.  Overall, a single IO infusion of G-F8-LV was sufficient to correct hemophilia phenotype for long term. We are currently improving further the constructs and delivery protocols. We would like to push this new methodology for clinical trials in the near future.

Immunomodulation for Hemophilia Inhibitors

30% of the hemophilia A patients develop inhibitor antibodies against factor VIII following protein replacement therapy. Current tolerance induction protocol involves long time administration of high doses of factor VIII, which is both inconvenient and very costly. One third of the patients fail to induce tolerance using this protocol. Prophylactic tolerance induction protocols involving a short immunosuppressive regimen with minimum side effects and toxicity are highly promising strategies for patients at high risk. Our lab has developed several potent immunotherapies to prevent inhibitory antibody production in hemophilia A mice, including agents to block costimulatory pathways such as CTLA4-Ig combined with anti-CD40L, and anti-ICOS, agents to deplete T cells such as anti-CD3, or agents to induce Treg cell expansion such as IL2-IL2mAb complexes, which can be administered in combination with repeated injections of low doses of FVIII to induce long-term tolerance of FVIII. These new transient immunosuppression strategies for tolerance induction can not only reduce the costs, but also shorten the treatment time and increase the success rate. Clinical testing of some of these regimens is highly anticipated.

Contact

Center for Immunity and Immunotherapies

For questions or inquiries, ciitadmin@seattlechildrens.org
(206) 884-7315

Address

Seattle Children's Research Institute
CIIT
1900 9th Avenue
Seattle, WA 98101

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