AAV-mediated factor IX gene transfer to skeletal muscle in patients with severe hemophilia B.
Hemophilia B is an X-linked coagulopathy caused by absence of functional coagulation factor IX (F.IX). Previously, we established an experimental basis for gene transfer as a method of treating the disease in mice and hemophilic dogs through intramuscular injection of a recombinant adeno-associated viral (rAAV) vector expressing F.IX. In this study we investigated the safety of this approach in patients with hemophilia B. In an open-label dose-escalation study, adult men with severe hemophilia B (F.IX < 1%) due to a missense mutation were injected at multiple intramuscular sites with an rAAV vector. At doses ranging from 2 x 10(11) vector genomes (vg)/kg to 1.8 x 10(12) vg/kg, there was no evidence of local or systemic toxicity up to 40 months after injection. Muscle biopsies of injection sites performed 2 to 10 months after vector administration confirmed gene transfer as evidenced by Southern blot and transgene expression as evidenced by immunohistochemical staining. Pre-existing high-titer antibodies to AAV did not prevent gene transfer or expression. Despite strong evidence for gene transfer and expression, circulating levels of F.IX were in all cases less than 2% and most were less than 1%. Although more extensive transduction of muscle fibers will be required to develop a therapy that reliably raises circulating levels to more than 1% in all subjects, these results of the first parenteral administration of rAAV demonstrate that administration of AAV vector by the intramuscular route is safe at the doses tested and effects gene transfer and expression in humans in a manner similar to that seen in animals.
Manno
Catherine S
CS
Department of Pediatrics, University of Pennsylvania and the Children's Hospital of Philadelphia, PA, 19104, USA. manno@email.chop.edu
Chew
Amy J
AJ
Hutchison
Sylvia
S
Larson
Peter J
PJ
Herzog
Roland W
RW
Arruda
Valder R
VR
Tai
Shing Jen
SJ
Ragni
Margaret V
MV
Thompson
Arthur
A
Ozelo
Margareth
M
Couto
Linda B
LB
Leonard
Debra G B
DG
Johnson
Frederick A
FA
McClelland
Alan
A
Scallan
Ciaran
C
Skarsgard
Erik
E
Flake
Alan W
AW
Kay
Mark A
MA
High
Katherine A
KA
Glader
Bertil
B
D000328:Adult; D000368:Aged; D019943:Amino Acid Substitution; D001706:Biopsy; D003131:Combined Modality Therapy; D000229:Dependovirus / Q000235:genetics*; D005164:Factor IX / Q000032:analysis / Q000235:genetics* / Q000627:therapeutic use; D005240:Feasibility Studies; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000008:administration & dosage / Q000627:therapeutic use*; D015658:HIV Infections / Q000150:complications; D002836:Hemophilia B / Q000150:complications / Q000235:genetics / Q000628:therapy*; D006525:Hepatitis, Viral, Human / Q000150:complications; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D020125:Mutation, Missense; D011993:Recombinant Fusion Proteins / Q000032:analysis; D012449:Safety
D011993:Recombinant Fusion Proteins; D005164:Factor IX