Evidence for gene transfer and expression of factor IX in haemophilia B patients treated with an AAV vector

Abstract

Pre-clinical studies in mice and haemophilic dogs have shown that introduction of an adeno-associated viral (AAV) vector encoding blood coagulation factor IX (FIX) into skeletal muscle results in sustained expression of F.IX at levels sufficient to correct the haemophilic phenotype. 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 x 10(11) 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 FIX 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.

Neutralizing antibodies against adeno-associated virus examined prospectively in pediatric patients with hemophilia

“…5,6 Clinical trials with rAAV2 vectors have been performed in hemophilia B (factor IX deficiency) patients via intramuscular injection or by targeting the liver. 3,7 No specific side effects were observed from these trials. The most encouraging report thus far involves targeted liver transduction by rAAV2 vectors.…”

Recombinant AAV vector encoding human VEGF165 enhances wound healing

“…26,27 Since recombinant AAV (rAAV) vectors are devoid of any viral genes -which are expressed in trans for the packaging process -they elicit virtually no inflammatory or immune response in the sites of injection. 28,29 Consequently, transgene expression from these vectors has been shown to last for several months in vivo in a variety of tissues. 30 Besides being able to transduce human keratinocytes in vitro, 31,32 in the skin in vivo rAAV was observed to transduce hair follicles, sweat gland ducts 33 and the skeletal muscle layer which in rodents is associated with the dermis (panniculus carnosus).…”

Long-term correction of hyperphenylalaninemia by AAV-mediated gene transfer leads to behavioral recovery in phenylketonuria mice

“…4,5 On the other hand, adeno-associated virus (AAV) vectors comprise another class of gene delivery vehicles, which have been shown to stably transduce nondividing cells such as hepatocytes, muscle fibers and neurons. [6][7][8] In this study, we evaluated a recombinant AAV vector carrying the PAH gene in a mouse model of PKU (PAH enu2 strain). [9][10][11] A missense mutation (F263S) in the PAH gene was introduced into BTBR mouse strain by chemical mutagenesis, resulting in a loss of enzyme activity.…”