Cici Yang, University of Guelph

Cici Yang[1], Igor R. Santos[1], Brad Thompson[2], Sarah K. Wootton[1]. [1] Department of Pathobiology, University of Guelph, Guelph, ON, Canada. [2] Wyvern Pharmaceuticals, Calgary, AB, Canada.

Fighting & Responding

The activation of toll-like receptor 9 (TLR9), an innate DNA sensor, unleashes pro-inflammatory cytokines and contributes to the maturation of antigen presenting cells. For many cancer treatments where monotherapy exerted limited effects, incorporating TLR9 stimulation reinvigorated the anti-tumour activity of the primary treatment. Given the adjuvant effect of TLR9 activation, it follows that TLR9 deficiency has been implicated in diminished responsiveness to cancer therapies. Here, we developed and evaluated the safety of an adeno-associated virus (AAV) vector encoding TLR9 to restore expression in individuals with TLR9 deficiency and augment the anti-tumour effect of concurrent cancer therapies. We first assessed biodistribution in mice 21 days following intraperitoneal administration of 1E11 vector genomes (vg) of AAV6.2FF-TLR9. RNA in-situ hybridization revealed TLR9 expression in the liver, spleen, pancreas, ovaries, heart, and inguinal lymph nodes, indicating systemic transduction and transcription following intraperitoneal delivery. To assess safety, mice and hamsters received a low (1.5E13 vg/kg) or high (4.5E13 vg/kg) dose of AAV6.2FF-TLR9 intraperitoneally and were evaluated at 1, 7, 28, and 56 days post-administration. Across both species and dosages, no adverse vector-related changes were observed upon histopathological examination. Only a few transient and inconsequential changes were observed in leukocyte counts, plasma biomarkers of hepatic dysfunction, and pro-inflammatory cytokine levels, indicative of the low immunogenicity of the vector. The broad tissue expression and favourable safety profile of intraperitoneally delivered AAV6.2FF-TLR9 support the progression of this vector toward clinical development as a novel adjunct to potentiate cancer therapies, especially in patients with TLR9 deficiency.