IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Dose escalation of therapeutic high-capacity, gutless adenoviral vectors in the naïve rat brain: pre-clinical safety and toxicity evaluation as a prelude to a Phase I clinical trial for glioma.
Autor/es:
MUHAMMAD; PUNTEL; 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) carries a dismal prognosis with a median survival of 18-21 months post-diagnosis. We have recently demonstrated the therapeutic efficacy and high safety profile of intratumoral delivery of a novel, combined gene therapy consisting of first generation, or high-capacity adenoviral vectors (HC-Ads) encoding either the conditionally cytotoxic gene herpes simplex type 1-thymidine kinase (TK) or the immunostimulatory gene fms-like tyrosine kinase 3 ligand (Flt3L) transgenes in  a syngeneic, orthotopic rat model of GBM. In anticipation of an upcoming dose finding, Phase I clinical trial for primary GBM, we herein performed a thorough assessment of the safety and toxicity of HC-Ads encoding TK and Flt3L upon administration into the naïve rat brain. Lewis rats were injected intracranially with escalating doses of HC-Ad-TK and HC-Ad-TetON-Flt3L (1x108, 1x109, or 1x1010 vp of each) followed by systemic administration of gancyclovir and doxycycline. Rats were evaluated at 5 days, 1 month, 6 months and 12 months for biodistribution of HC-Ad vector genomes, HC-Ad vector induced behavioral deficiencies, neurotoxicity, peripheral blood cell counts and serum biochemistry, circulating levels of Flt3L, anti-adenovirus neutralizing antibodies, and anti-TK antibodies. Even at the highest dose tested, real-time quantitative PCR did not detect evidence of biodistribution of HC-Ad genomes to peripheral organs and a comprehensive panel of behavioral testing did not reveal any vector mediated abnormalities. Peripheral blood cell counts and serum biochemistry were within normal ranges during all time points, at all doses tested. Flt3L expression was tightly regulated, with expression dynamics that coincided with the administration of the inducer doxycycline. However, a comprehensive neuropathological panel revealed evidence of neurotoxicity at the highest dose tested (1x1010 vp of each), i.e. loss of brain tissue, and high levels of inflammation. We did not detect any evidence of neurotoxicity or long-term inflammation at either lower dose tested. Taken together, these data indicate that 1x109 vp of each HC-Ad is the maximally tolerated dose (MTD) that can be safely administered into the brains of naïve Lewis rats. These well controlled, non-clinical safety and toxicity studies are required by the FDA in order to file of an IND and constitute a major milestone in the path towards implementation of the first ever Phase I clinical trial for GBM using gutless, HC-Ad vectors.