Safe and efficient transduction of the liver after peripheral vein infusion of self-complementary AAV vector results in stable therapeutic expression of human FIX in nonhuman primates

Department of Surgery, St. Jude Children's Research Hospital, Memphis, Tennessee, United States
Blood (Impact Factor: 9.78). 03/2007; 109(4):1414-21. DOI: 10.1182/blood-2006-03-010181
Source: PubMed

ABSTRACT The safety and efficacy of peripheral venous administration of a self-complementary adeno-associated viral vector encoding the human FIX gene (scAAV-LP1-hFIXco) was evaluated in nonhuman primates for gene therapy of hemophilia B. Peripheral vein infusion of 1x10(12) vg/kg scAAV-LP1-hFIXco pseudotyped with serotype 8 capsid, in 3 macaques, resulted in stable therapeutic expression (more than 9 months) of human FIX (hFIX) at levels (1.1+/-0.5 microg/mL, or 22% of normal) that were comparable to those achieved after direct delivery of the same vector dose into the portal circulation (1.3+/-0.3 microg/mL, or 26% of normal). Importantly, the pattern of vector biodistribution after systemic and portal vein administration of scAAV-LP1-hFIXco was almost identical. Additionally, comparable levels of gene transfer were achieved in macaques with preexisting immunity to AAV8 following peripheral vein administration of 1x10(12) vg/kg AAV5-pseudotyped scAAV-LP1-hFIXco. This confirms that alternative serotypes can circumvent preexisting naturally acquired immunity to AAV. Thus, peripheral venous administration of AAV5 and AAV8 vectors is safe and as effective at transducing the liver in nonhuman primates as direct vector administration into the portal circulation. These results should make vector administration to patients, especially those with a severe bleeding diathesis, significantly easier and safer.

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    ABSTRACT: Vector capsid dose-dependent inflammation of transduced liver has limited the ability of AAV factor IX (FIX) gene therapy vectors to reliably convert severe to mild hemophilia B in human clinical trials. These trials also identified the need to understand AAV neutralizing antibodies and AAV empty capsids in regards to their impact on clinical success. To address these safety concerns, we have used a scalable manufacturing process to produce GMP grade AAV8 expressing the FIXR338L gain-of-function variant with minimal (<10%) empty capsid and have performed comprehensive dose/response, bio-distribution and safety evaluations in clinically-relevant hemophilia models. The scAAV8.FIXR338L vector produced greater than 6-fold increased FIX specific activity compared to wild type FIX and demonstrated linear dose-responses from doses that produced 2% to 500% FIX activity, associated with dose-dependent hemostasis in a tail transection bleeding challenge. More importantly, using a bleeding model that closely mimics the clinical morbidity of hemophilic arthropathy, mice that received the scAAV8.FIXR338L vector developed minimal histopathologic findings of synovitis following hemarthosis, when compared with mice that received identical doses of wild type FIX vector. Hemostatically normal mice (n=20) and hemophilic (n=88) mice developed no FIX antibodies after peripheral I.V. vector delivery. No CD8+ T cell liver infiltrates were observed, despite the marked tropism of scAAV8.FIXR338L for the liver in a comprehensive biodistribution evaluation (N = 60 animals). With respect to the role of empty capsids, we demonstrated that in vivo FIXR338L expression was not influenced by the presence of AAV empty particles, either in the presence or absence of varying titers of AAV8-neutralizing antibodies. Necropsy of FIX-/- mice at 8-10 months after vector delivery revealed no microvascular or macrovascular thrombosis in mice expressing FIXR338L (plasma FIX activity 100-500%). These preclinical studies demonstrate a safety:efficacy profile supporting an ongoing Phase 1/2 human clinical trial of the scAAV8.FIXR338L vector (designated BAX335).
    Human Gene Therapy 11/2014; 26(2). DOI:10.1089/hum.2014.106 · 3.62 Impact Factor
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