Preclinical &Phase I/II Trials Of AAV-AAT Vectors

University Of Florida, Gainesville FL

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Abstract

[unreadable] DESCRIPTION (provided by applicant): [unreadable] We propose here a competitive supplement to our existing R01 (HL69877) on recombinant adeno-associated virus (rAAV) alpha-1 antitrypsin (AAT) gene therapy for alpha-1 antitrypsin deficiency (AATD). AATD represents an attractive target for gene therapy, since it is a fairly common single gene disease with a well-established correlation between clinical disease and circulating plasma levels (under 11 micromolar). Current intravenous (IV) protein replacement therapies are licensed by FDA as being safe and effective for replacement of plasma levels, and these provide a useful proof-of-concept for gene therapy, since they have been very safe and have not ever been associated with the development of anti-AAT antibodies. Nonetheless, there is a clinical need for gene therapy, since the protein replacement is in short supply and most be given by weekly IV infusion. Our group is currently performing a phase I safety and dose-finding study of a recombinant adeno-associated virus serotype 2 (rAAV2)-AAT vector given by intramuscular (M) administration to AATD patients, as funded on the original proposal (HL69877). Preliminary results indicate that there are no obvious vector-related toxicities. However, mouse data suggests that this same rAAVAAT gene cassette will produce much higher serum levels of AAT if it is packaged in an AAV serotype 1 (pseudotyped) capsid. The original funded proposal also covered formal GLP-preclinical toxicology testing of rAAV 1- AAT. These studies are essentially complete. The results indicate a lack of any vector-mediated adverse effects. Biodistribution of rAAV 1-AAT is very distinct from rAAV2-AAT, however, with much higher copy numbers of rAAV-AAT DNA in the blood and gonads of injected mice. Because of the blood and gonad positivity in the mice, a rabbit biodistribution study was done, which showed that vector DNA was transiently present in semen as well. These studies will help to identify the timing of semen studies and the duration of barrier contraceptive use that will be required in clinical studies. The current application is for a phase I trial of IM administration in AATD patients who meet entry criteria. It will cover the same dose range as the current rAAV2-AAT study (approximately 2xl0(12) to 7x10(13) vector genomes per patient). Like the currently active study, there will be 4 dosage cohorts, with 3 subjects in each cohort. The identical structure of the rAAVl-AAT and rAAV2-AAT clinical trials will allow for retrospective comparison of the dose-ranging data and allow one to determine whether the potency advantage predicted by the mouse studies will hold true in humans. It is hoped that the combined data from these two studies will provide important dose-ranging information for all human uses of rAAV vectors by the IM route. [unreadable] [unreadable]