Presentation - World Federation of Hemophilia

Curing Bleeding Disorders: Gene Therapy- A Means to the End? 5th WFH Global Forum on Safety and Supply of Treatment Products for Bleeding Disorders 25 September 07 Glenn Pierce MD PhD San Francisco, California The First "Gene Transfer" Experiments: Early Years- Proof of Principle Established • Brinkhous: allotransplantation of spleen into FVIII deficient dogs (1967) – short term cures, not reproduced in humans (Hathaway, 1969) In parallel: • Thomas: orthotopic liver transplants in dogs successful (1969) – Hemophilia A cured in humans (Lewis, Starzl, 1985) – FIX deficiency also cured •Genes=DNA, 1953 •Watson and Crick • Brinkhous: liver transplants in porcine vWD successful (1976) – not effective in humans, species differences (1991) •Biotech industry born •1976 (Genentech) •1st recombinant DNA produced drugs: early 1980s (insulin) Gene Therapy: 1980s to Early 1990s • Genes for FVIII and FIX cloned early 1980s • Concept of gene therapy established: hemophilia recognized as “low hanging fruit” – Cause of hemophilia known, 1-2% would be useful, precise regulation not required, protein needs to circulate in blood • First immunodeficiency disease trial initiated 1989 • First NHF-NIH collaborative workshop organized 1992 – – – – Education, advocacy, cross-fertilization between HTCs-Gn Therapists Hemophilia gene therapy unit established at NIH $11 million funding for 5 years obtained from Congress 1994 8 grants distributed- most seeded clinical trials in late 1990s • Biotechnology companies have high level interest – Genetic Therapy Inc obtained rights to Factor IX (Brit. Biotech) and VIII (Genetics Institute/Wyeth) genes for Gene Rx – Viagene (Chiron) developed collaboration for Factor VIII gene (Bayer) – Somatix starts FVIII gene therapy program; patents to use specific cell types for ex vivo therapy; collaboration to use devices (Baxter) • Academic centers established early research programs – UNC, Chapel Hill; Salk; U Wash; Baylor Will the prediction come true? Pierce, Hemalog, Summer 1990 This goal was a catalyst Advocacy, Education and Fundraising Gene Therapy Workshops Established •Initiated 1996, 8 held to date with scientists from academia, industry, government •Review status, identify scientific priorities for further research and funding •Chair: Pierce •Co-chairs, Verma, High, VandenDriessche (2008) •Novel technologies sessions included Animal Models Essential in Hemophilia Research Dog models: • Naturally occurring: FVIII and FIX • Mimics human condition • Basis for all current products Mouse models: • FVIII and FIX knockout mice created Hem B Lifelong cures in animals beginning in late 1990s FVIII KO Liver and Muscle AAV2 Injection in Hem B Dogs: Multi-year Cures; Factor IX Expression More Efficient in Liver 1000 9% 12% 5% cFIX (ng/ml) 100 0.3% 10 Liver 1 Liver 2 Liver 3 Muscle 0 2 5 8 14 17 21 24 27 32 46 68 1 Weeks Nakai et al, Blood 1998; Grimm et al Blood 2003 NHF MASAC recommendations US Gene Therapy Clinical Trials: 41 Subjects Trial Started Hemophilia A (12) Therapy type Ex vivo plasmid i.p. injection Status Completed Phase I Completed Phase I Completed Phase I Completed Phase I Trial Terminated Transkaryotic Dec 1998 Therapies High/Kay/ Avigen Chiron Jun 1999 Jun 1999 B (7) A (13) B (8) In vivo AAV i.m. injection In vivo retroviral i.v. infusion In vivo AAV liver-targeted infusion In vivo adenoviral i.v. infusion High/Kay/ Avigen Jun 2001 Jun 2001 Genstar Therapeutics A (1) One Factor IX trial in China: 2 subjects, early 90s, ex vivo, likely insufficient numbers of cells delivered, little reported 1 Step Forward, 2 Steps Back? • NHF workshop topics have covered the entire field • Sept. 1999 - Patient death attributed to adenoviral therapy – Subsequent safety reviews, Congressional Inquiries • 2002– Two X-SCIDS subjects cured by gene therapy develop leukemia: FDA places all Retroviral Clinical Trials on Hold – Today, over 30 patients treated and cured • Multiple diseases cured in animals, variable toxicities infrequently observed • Hemophilia gene therapy trials: 2 unexpected adverse events, little efficacy detected in humans- in contrast to animals • 2007- Rheumatoid arthritis patient receiving AAV gene therapy dies, investigation in progress Or 2 Steps Forward, 1 Step Back? Delivery of New Genes AAV Target Cell Nucleus Adenovirus Retrovirus/Lentivirus Naked DNA Therapeutic Protein Viral Vector Interactions with Cells are Poorly Understood - ss rAAV + ss rAAV cytoplasm annealed ds rAAV mRNA mRNA mRNA ss rAAV pool circular monomer circular dimer nucleus now investigating episomal linear concatemer ? circular concatemer ? integrated monomer integrated concatemer mRNA Amazing Protein Kay et al, Nat Genet 2000; 24:257 Manno et al, Blood 2003; 101:2963 Arruda et al, Mol Therapy 2006; 14:452 Muscle delivery: Long term local expression (3.7 years) but insufficient circulating FIX Manno et al, Nat Med, 2006 12:342-7 Mingozzi et al, Nat Med, 2007 13: 419-22 Liver Delivery: Therapeutic circulating FIX levels but not sustained Activation of AAV-specific Memory CD8+ T cells Requires Cross Presentation of AAV Capsid • ~ 60% of human population have prior exposure to natural AAV infection, hence AAV neutralizing antibodies detected in blood • As expected, AAV-specific memory CD8+ T cells are also detected in healthy humans • The activation of AAV-specific memory CD8+ T cells by AAVFIX vector requires cross presentation of AAV capsid peptides by MHC class I • Intracellular trafficking of AAV from cytoplasm to nucleus involves proteasome, cross over to MHC I presentation pathway • Solutions to this problem? Manno, Pierce, Arruda et al, Nat Med, 2006 12:342-7 Vendenburghe et al, Nat Med 2006 12:967-71 Mingozzi et al, Nat Med, 2007 13: 419-22 Progress in AAV-mediated Gene Transfer for Hemophilia B Hemophilia Model 1999 2006 Robust levels of expression using either skeletal muscle or liver as target tissues Mice Extensive experience in mice Dogs F.IX expression levels of 1-2%, using either skeletal muscle or liver as target tissue Humans First experience with parenteral delivery of AAV, 3 subjects injected intramuscularly Robust levels of expression •5-10% by portal vein infusion. •4-25% by intravascular delivery to skeletal muscle 15 human subjects enrolled in AAV hemophilia B trials. •8 in muscle study •7 in liver study All potential problems identified? Couto, Pierce, Curr Opin Mol Ther 2003; 5:517 Workshops 2001/02: Unmet needs • Safer vectors – Control immune responses – Regulate gene expression, protein secretion • Effect of secondary diseases – Hepatitis, inhibitors • Recommendations for conduct of trials • Alternatives to gene therapy – Longer-lived molecules: enabling for gene therapy? – Transgenic animal produced clotting factors? • Progress with FIX/FVIII in dogs, humans • Science has changed, but Priorities, Issues have changed little through 2006 Workshops Why Pursue Gene Therapy? Global Reality • Emerging discussions at Workshops • 400,000 worldwide; 100,000 receive some Rx – 75% not diagnosed – Many die in childhood • Hemophilia not a priority with governments – Lack of infrastructure, training, education • Cost of treatment prohibitive – Therapy will not become affordable to most – Prevention of bleeding even more difficult Relationship of Economic Capacity to Number of Adults with Hemophilia* 4 3.5 Adults yrs 31< yrs 91> Ratio (P/Pc) 3 2.5 2 1.5 1 0.5 0 <$2000 $2000-10000 >$10000 Evatt and Robillard, 2000; 6:131-4 Haemophilia Per Capita Gross National Product *Data from 17 Randomly Selected Countries Can Gene Transfer Cure Hemophilia in the Developing World? • Barriers – – – – Cost: precedents established with recombinant factor Specialized expertise and equipment Highly experimental technology Safety not established: Risk/Benefit • Ethical issues • • Solutions – – – – Vaccine model (Kelley, Verma, Pierce Haemophilia 2002, 8:261-267) Academic-Industry, Government-Nonprofit collaborations >$500 million USD invested 2006 Workshop: J Thromb Haemost. 2007;55:901-6. Gene therapy, Status bioengineered clotting factors and novel technologies for hemophilia treatment. Pierce GF, Lillicrap D, Pipe SW, Vandendriessche T Next steps: New research hypotheses, new DNA delivery vectors required, evading host immunity, designer molecules Next workshop: February 2008 – – Hemophilia: The March Towards a Cure How does one prevent the pathology of hemophilia (eg, arthropathy, death)? Prevent bleeding… Pathology Paradigm Shift CURE Symptomatic treatment: on-demand therapy Regular, preventative treatment Reduced infusion frequency Curative therapy 1950s Proteins Genes 20xx If not gene therapy, then what?