IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Pre-clinical safety and toxicity dose-finding of a novel bi-cistronic High-Capacity adenoviral vector encoding Flt3L and TK: identification of a maximally tolerated dose in the brain with restricted biodistribution of vector genomes.
Autor/es:
PUNTEL; MUHAMMAD; XIONG; KELSON; SALEM; KROEGER; LIU; FARROKHI; LACAYO; PECHNICK; PALMER; NG; LOWENSTEIN; CASTRO
Lugar:
Seattle, Washington, US
Reunión:
Congreso; American Society for Gene Therapy Annual Meeting; 2011
Resumen:
Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor, is highly invasive, and invariably recurs killing the patient. Using a combined immunotherapy/conditional cytotoxic approach, we have previously demonstrated that intratumoral delivery of first generation adenoviral vectors (Ad) encoding the conditional cytotoxic gene, herpes simplex virus type 1-thimidine kinase (TK) and Fms-like Tyrosine Kinase 3 ligand (Flt3L) generates a tumor antigen specific anti-GBM immune response resulting in s long-term survival and immunological memory in over eight orthotopic rat and mouse models of GBM. The large cloning capacity of HC-Ads has allowed us to develop a single novel, bi-cistronic HC-Ad vector engineered for inducible expression of Flt3L using the TetOn regulatory system and constitutive expression of HSV1-TK; this simplifies downstream process development, improves the immunological safety profile, and facilitates clinical implementation. We assessed the safety profile of this novel dual HC-Ad vector in naive Lewis rats at three doses of HC-Ad vector, at short-term (5 days), medium-term (1 month) and long-term (12 months) time points. To identify the maximally tolerated dose in the brain, we assessed safety and toxicity as determined by biodistribution of vector genomes using real-time quantitative PCR (qPCR), levels of Flt3L in the serum, Ad-specific neutralizing antibodies, TK-specific serum antibodies, serum biochemistry, and a comprehensive panel of behavioral tests. HC-Ad vector genomes were below detectable limits in all peripheral organs tested and restricted to the tumor bearing brain hemisphere. At the highest dose tested (1x1010 vp), neuropathological analysis of brain sections reveled considerable disruption of the neuronal architecture and transient short-term inflammation. Levels of Flt3L in serum were only detectable at 5 days, but not at 1 month and 12 months post treatment. Biochemical laboratory parameters indicated normal liver and renal function for all doses. Analysis of amphetamine-induced rotational behavior, total locomotor activity and rearing activity did not reveal any behavioral abnormalities compared to age matched control animals, even at the high dose that caused neuropathology. These data reveal that 1x109 vp is the MTD in the naïve Lewis rat brain, thus further demonstrating the high safety profile of the dual HC-Ad vector administration, and supports further downstream process development for eventual implementation in human clinical trials.