In this study, we investigate the in vitro and in vivo activities of GTL002, a novel Human Papilloma Virus (HPV)-specific immunotherapy aimed to treat infection by 6 high-risk HPVs responsible for 85% of cervical cancer worldwide.
GTL002 is made of 2 recombinant proteins based on Genticel’s vector called Vaxiclase (a modified Adenylate Cyclase protein from B. pertussis) comprising modified E7 proteins from HPV16, 18 and 45 (C216) and from HPV31, 33, 52 (C331). Each C216 & C331 protein was produced in E.coli using an improved phase I/II process. GTL002’s ability to target the integrin CD11b on antigen-presenting cell was assessed by competitive binding using a CD11b/CD18-expressing cell line. The immunogenicity was evaluated in inbred (C57BL/6), outbred (Swiss) mice and in Beagle dogs. Animals are injected intradermally with GTL002, adjuvanted either with co-formulated poly-ICLC, a TLR3 agonist, or with topical application of imiquimod 5% cream, a TLR7 agonist, at the injection site. E7-specific T cell responses were measured by an ex vivo IFNg ELISpot using overlapping peptides covering each of the 6 E7 proteins for restimulation of splenocytes. The cytotoxic T lymphocytes (CTL) were measured by an in vivo killing assay and the therapeutic efficacy was evaluated in a TC-1 tumor model in C57BL/6 mice. The T cell and antibody responses were followed in Beagle dogs weekly for 11 weeks.
C216 and C331 proteins are successfully produced after IPTG induction at 10L scale, and purified by chromatography. The production process is transferable and scalable at industrial scale. GTL002 is found to bind to CD11b with a Ki of 22 nM. GTL002 induces HPV16-, 18-, 33-, and 52 E7-specific T cell responses in C57BL/6 mice as well as HPV16 and HPV18 E7-specific CD8+ CTL in mice that are able to eradicate HPV16 E7-expressing TC-1 tumors. E7-specific T cell responses against HPV16-, 18-, 45-, 31-, and 52 are induced in Swiss mice. In Beagle dogs, administration of GTL002 on day 0, 21 and 42 is well tolerated whatever the adjuvant used. Local reactions are transient. Repeated administrations of GTL002 induce HPV16/18/45/31/33/52-E7-specific T-cell immune responses without increasing reactogenicity. There was a good immune response with both the co-formulated poly-ICLC and topical imiquimod.
The readily scalable and transferable process for commercial development, the broad immunogenicity against the 6 high-risk HPVs, the in vivo HPV16-E7 target cell efficacy and the good tolerance Beagle dogs, all together warrant GTL002 immunotherapy to move to human clinical development.