31 research outputs found
Evolution of the Alpha-1 Antitrypsin Muscle Gene Therapy: Translation from Clinical Trial to Benchtop and Back Again
Get PDFAlpha-one antitrypsin (AAT) deficiency is a genetic disease affecting the lungs due to inadequate anti-protease activity in the pulmonary interstitium. On-going human trials use intra-muscular delivery of adeno-associated virus (rAAV1), allowing expressing myofibers to secrete normal (M)AAT protein. In the Phase IIa trial, patients in the highest dose cohort (6x1012vg/kg) were given 100 intra-muscular (IM) injections of undiluted vector, with serum AAT levels still substantially below target levels. Previous work has shown that delivering rAAV vector to the musculature via limb perfusion leads to widespread gene expression in myofibers. We hypothesize that widespread delivery would result in an overall increase in serum AAT levels with the same dose of AAV gene therapy vector and allow for increased volume and thereby dose of vector. In macaques, similar serum myc-tagged rhAAT was produced using regional venous infusion when compared to direct IM delivery at the same total vg dose with either rAAV1 or rAAV8, while not being limited to a small volume as with IM injection. These data prove the concept that a 30-fold expanded volume of rAAV-AAT could be delivered to myofibers using limb perfusion without loss of potency on a per vg basis, thereby enabling potential achievement of therapeutic AAT levels in patients. This will allow us to proceed to a phase IIb clinical trial in AAT patients employing venous limb perfusion
Serum Levels of Alpha-1 Antitrypsin following Vascular Limb or Intra-Muscular Delivery of AAV1 or AAV8 Gene Therapy Vectors in Rhesus Macaques
Get PDFAlpha-one antitrypsin (AAT) deficiency is a genetic disease that results in both lung disease and potentially liver failure in affected patients. In un-affected people AAT is produced in the liver and secreted to act as an anti-protease (primarily counteracting the effects of neutrophil elastase) in the lung. On-going human clinical trials have focused on intra-muscular delivery of adeno-associated virus (AAV1) to patients. The goal of delivery to the muscle is to have the myocytes serve as bio-factories to produce normal AAT protein and secrete it into the blood where it can exert its normal function in the lung. In the last Phase II trial patients in the highest dose cohort were given 100 intra-muscular (IM) injections with serum AAT levels still below therapeutic thresholds.
Previous work has shown that delivering AAV vector to the musculature of the limb via the vasculature, while blood flow is obstructed using a tourniquet, leads to wide-spread gene expression in myocytes. We hypothesize that local delivery via IM injection results in saturated AAT expression within the myocytes surrounding the injection sight and that a more widespread delivery would result in an overall increase in serum AAT levels with the same dose of AAV gene therapy vector due to production by a larger overall number of myocytes. We have been able to show that we can attain similar or slightly higher (573.0 ng/ml versus 562.5 ng/nl) serum AAT levels using a vascular delivery method in rhesus macaques when compared to IM delivery. These results have been obtained using AAV1. Animals receiving either AAV1 or AAV8 show a decrease in muscle immune cell infiltrates following intra-vascular delivery versus IM delivery, which may improve long-term expression. Serum AAT data from animals dosed using AAV8, a serotype shown to better target muscle following vascular delivery, are currently being processed
Bridging from Intramuscular to Limb Perfusion Delivery of rAAV: Optimization in a Non-human Primate Study
Get PDFPhase 1 and phase 2 gene therapy trials using intramuscular (IM) administration of a recombinant adeno-associated virus serotype 1 (rAAV1) for replacement of serum alpha-1 antitrypsin (AAT) deficiency have shown long-term (5-year) stable transgene expression at approximately 2% to 3% of therapeutic levels, arguing for the long-term viability of this approach to gene replacement of secreted serum protein deficiencies. However, achieving these levels required 100 IM injections to deliver 135 mL of vector, and further dose escalation is limited by the scalability of direct IM injection. To further advance the dose escalation, we sought to bridge the rAAV-AAT clinical development program to regional limb perfusion, comparing two methods previously established for gene therapy, peripheral venous limb perfusion (VLP) and an intra-arterial push and dwell (IAPD) using rAAV1 and rAAV8 in a non-human primate (rhesus macaque) study. The rhesus AAT transgene was used with a c-myc tag to enable quantification of transgene expression. 5 cohorts of animals were treated with rAAV1-IM, rAAV1-VLP, rAAV1-IAPD, rAAV8-VLP, and rAAV8-IAPD (n = 2-3), with a dose of 6 x 10(12) vg/kg. All methods were well tolerated clinically. Potency, as determined by serum levels of AAT, of rAAV1 by the VLP method was twice that observed with direct IM injection; 90 mug/mL with VLP versus 38 mug/mL with direct IM injection. There was an approximately 25-fold advantage in estimated vector genomes retained within the muscle tissue with VLP and a 5-fold improvement in the ratio of total vector genomes retained within muscle as compared with liver. The other methods were intermediate in the potency and retention of vector genomes. Examination of muscle enzyme (CK) levels indicated rAAV1-VLP to be equally safe as compared with IM injection, while the IAPD method showed significant CK elevation. Overall, rAAV1-VLP demonstrates higher potency per vector genome injected and a greater total vector retention within the muscle, as compared to IM injection, while enabling a much greater total dose to be delivered, with equivalent safety. These data provide the basis for continuation of the dose escalation of the rAAV1-AAT program in patients and bode well for rAAV-VLP as a platform for replacement of secreted proteins
