Nature Genetics
24, 257 - 261 (2000)
doi:10.1038/73464
Evidence for gene transfer and expression of factor IX in haemophilia
B patients treated with an AAV vectorMark A. Kay1, 2, Catherine S. Manno4, 5, Margaret V. Ragni7, Peter J. Larson4, 5, Linda B. Couto8, Alan McClelland8, Bertil Glader1, Amy J. Chew4, Shing J Tai4, Roland W. Herzog4, Valder Arruda4, Fred Johnson8, Ciaran Scallan8, Erik Skarsgard3, Alan W. Flake4, 6
& Katherine A. High4, 51
Departments of Pediatrics, Stanford University School
of Medicine, Palo Alto, California, USA.
2
Department of Genetics, Stanford University School
of Medicine, Palo Alto, California, USA.
3
Department of Surgery, Stanford University School of
Medicine, Palo Alto, California, USA.
4
The Children's Hospital of Philadelphia,
Philadelphia, Pennsylvania, USA. 5
Departments of Pediatrics, University of Pennsylvania
School of Medicine, Philadelphia, Pennsylvania,
USA. 6
Department of Surgery, University of Pennsylvania School
of Medicine, Philadelphia, Pennsylvania, USA
. 7
Department of Medicine, University of Pittsburgh School
of Medicine, Pittsburgh, Pennsylvania, USA
. 8
Avigen, Inc., Alameda, California
, USA.
Correspondence should be addressed to Katherine A. High high@email.chop.eduPre-clinical studies in mice and haemophilic dogs have shown that introduction
of an adeno-associated viral (AAV) vector encoding blood coagulation factor
IX (F.IX) into skeletal muscle results in sustained expression of F.IX at
levels sufficient to correct the haemophilic phenotype1,
2.
On the basis of these data and additional pre-clinical studies demonstrating
an absence of vector-related toxicity, we initiated a clinical study of intramuscular
injection of an AAV vector expressing human F.IX in adults with severe haemophilia
B. The study has a dose-escalation design, and all patients have now been
enrolled in the initial dose cohort (2 1011 vg/kg). Assessment
in the first three patients of safety and gene transfer and expression show
no evidence of germline transmission of vector sequences or formation of inhibitory
antibodies against F.IX. We found that the vector sequences are present in
muscle by PCR and Southern-blot analyses of muscle biopsies and we demonstrated
expression of F.IX by immunohistochemistry. We observed modest changes in
clinical endpoints including circulating levels of F.IX and frequency of F.IX
protein infusion. The evidence of gene expression at low doses of vector suggests
that dose calculations based on animal data may have overestimated the amount
of vector required to achieve therapeutic levels in humans, and that the approach
offers the possibility of converting severe haemophilia B to a milder form
of the disease.
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