Hemophilia A is a congenital bleeding disorder caused by genetic mutations affecting a plasma protein, termed factor VIII (fVIII), whose function is to facilitate blood clotting. State of the art treatment for hemophilia A consists of frequent intravenous infusions of fVIII containing products. The current limitations to treating hemophilia are 1) the cost of fVIII products, 3) the development of immune responses against fVIII that block treatment efficacy, 3) morbidity due to joint disease resulting from repeated bleeding into individual joints and 4) the limitation of treatment to 30% of the world population. Due to the limited amount of fVIII needed to provide clinical benefit to the patient, hemophilia A is an attractive disease target for gene therapy, and three phase 1 clinical trials have been conducted. The outcome of these trials has been disappointing due to the extremely low, non-therapeutic levels of fVIII produced in each of the gene therapy strategies. We recently showed that a modified porcine fVIII transgene, designated BDDpfVIII, facilitates very high-level protein expression, and we demonstrated proof-of-concept that this transgene functions extremely efficiently in a mouse model of hemophilia A following transplantation of genetically-modified hematopoietic stem cells (HSCs). Specifically, we have shown that the expression of BDDpfVIII is superior to other bioengineered human fVIII expression constructs and that genetic modification and transplantation of HSCs results in curative fVIII levels. Additionally, curative fVIII activity levels are achieved after transplantation of BDDpfVIII-transduced HSCs following low-toxicity pre-transplantation conditioning with targeted immunosuppression, even in the context of pre-existing anti-human fVIII inhibitors. Therefore, we have overcome the major hurdle of low-level expression using a transgene that encodes a protein that has been used successfully in patients with hemophilia A. In the current application, we propose to more fully characterize the use of the high-expression construct and further our understanding of the critical parameters involved with this novel gene therapy strategy and study the biology of non-physiological BDDpfVIII expression in hematopoietic (blood) cells. To advance our studies toward clinical significance, we propose to 1) test clinically relevant HSC transplant conditioning regimens that more closely resemble those used routinely in human bone marrow transplant protocols and 2) test recombinant lentiviral vectors that have been demonstrated to display a reduction of insertional mutagenesis compared to oncoretroviruses. Finally, the optimized lentiviral vector(s) encoding BDDpfVIII will be tested for the ability to genetically modify human HSCs.

Public Health Relevance

Hemophilia A is a bleeding disorder caused by insufficiency of a blood clotting factor, designated factor VIII, for which gene therapy offers a potential cure. However, pre-clinical studies and clinical trials showed that a major limitation to a successful gene therapy treatment is the extremely poor expression of fVIII from the human fVIII transgene, which we recently overcame by introducing a porcine fVIII transgene. We demonstrated that use of the porcine transgene results in up to 100-fold greater fVIII production than the human version, and more recently, we demonstrated that a similar differential is observed following gene transfer into blood stem cells using recombinant retroviruses. Our current studies focus on better understanding the critical pharmacologic parameters involved in generating curative fVIII levels with this procedure using a mouse model of hemophilia A with the goal of understanding how this application can best be translated to clinical successes.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL092179-05
Application #
8434878
Study Section
Gene and Drug Delivery Systems Study Section (GDD)
Program Officer
Link, Rebecca P
Project Start
2009-04-01
Project End
2014-02-28
Budget Start
2013-03-01
Budget End
2014-02-28
Support Year
5
Fiscal Year
2013
Total Cost
$368,900
Indirect Cost
$130,900
Name
Emory University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
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Brown, Harrison C; Wright, J Fraser; Zhou, Shangzhen et al. (2014) Bioengineered coagulation factor VIII enables long-term correction of murine hemophilia A following liver-directed adeno-associated viral vector delivery. Mol Ther Methods Clin Dev 1:14036
Doering, Christopher B; Spencer, H Trent (2014) Replacing bad (F)actors: hemophilia. Hematology Am Soc Hematol Educ Program 2014:461-7
Johnston, J M; Denning, G; Doering, C B et al. (2013) Generation of an optimized lentiviral vector encoding a high-expression factor VIII transgene for gene therapy of hemophilia A. Gene Ther 20:607-15
Zakas, Philip M; Gangadharan, Bagirath; Almeida-Porada, Graca et al. (2012) Development and characterization of recombinant ovine coagulation factor VIII. PLoS One 7:e49481
Doshi, Bhavya S; Gangadharan, Bagirath; Doering, Christopher B et al. (2012) Potentiation of thrombin generation in hemophilia A plasma by coagulation factor VIII and characterization of antibody-specific inhibition. PLoS One 7:e48172
Summers, Ryan J; Meeks, Shannon L; Healey, John F et al. (2011) Factor VIII A3 domain substitution N1922S results in hemophilia A due to domain-specific misfolding and hyposecretion of functional protein. Blood 117:3190-8
Brown, Harrison C; Gangadharan, Bagirath; Doering, Christopher B (2011) Enhanced biosynthesis of coagulation factor VIII through diminished engagement of the unfolded protein response. J Biol Chem 286:24451-7
Zakas, Philip M; Spencer, H Trent; Doering, Christopher B (2011) Engineered Hematopoietic Stem Cells as Therapeutics for Hemophilia A. J Genet Syndr Gene Ther 1:
Doering, Christopher B; Archer, David; Spencer, H Trent (2010) Delivery of nucleic acid therapeutics by genetically engineered hematopoietic stem cells. Adv Drug Deliv Rev 62:1204-12

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