Preclinical Safety Studies of Enadenotucirev, a Chimeric Group B Human-Specific Oncolytic Adenovirus

Abstract

Enadenotucirev is an oncolytic group B adenovirus identified by a process of bio-selection for the ability to selectively propagate in and rapidly kill carcinoma cells. It is resistant to inactivation by human blood components, potentially enabling intravenous dosing in patients with metastatic cancer. However, there are no known permissive animal models described for group B adenoviruses that could facilitate a conventional approach to preclinical safety studies. In this manuscript, we describe our tailored preclinical strategy designed to evaluate the key biological properties of enadenotucirev. As enadenotucirev does not replicate in animal cells, a panel of primary human cells was used to evaluate enadenotucirev replication selectivity in vitro, demonstrating that virus genome levels were >100-fold lower in normal cells relative to tumor cells. Acute intravenous tolerability in mice was used to assess virus particle-mediated toxicology and effects on innate immunity. These studies showed that particle toxicity could be ameliorated by dose fractionation, using an initial dose of virus to condition the host such that cytokine responses to subsequent doses were significantly attenuated. This, in turn, supported the initiation of a phase I intravenous clinical trial with a starting dose of 1 × 1010 virus particles given on days 1, 3, and 5.

Innate immunity to adenovirus: lessons from mice

“…The major limitation of analyzing immune responses to HAdv in mouse experimental systems is that mice are not permissive to HAdv [1,135]; thus little, if any, information on specific tissues, cell types, and cellular receptors pertinent to explaining the pathogenesis of natural HAdv infection in humans can be derived from analyzing low-dose HAdv infections in mice. Nevertheless, the vast majority of findings discussed and conceptualized in this review were obtained upon administering mice intravenously with extremely high doses of viruses, a clinical scenario only observed in immunocompromised hosts with disseminated and often lethal natural HAdv infections [136][137][138][139][140].…”

External Beam Radiation Therapy and Enadenotucirev: Inhibition of the DDR and Mechanisms of Radiation-Mediated Virus Increase

“…We evaluated the impact of radiation on EnAd production in a pilot in vivo experiment to establish if this was consistent with findings in vitro. As adenoviruses are unable to replicate in murine cells [37,56], we used an immunodeficient SCID mouse model to allow for human HCT116…”

“…In contrast to Ad5-based vectors, for which neutralising antibodies are widespread in the general population, the seroprevalence of antibodies against group B adenovirus is low [35,36]. EnAd shows impressive selectivity for replication in human carcinoma cells from different types of cancers, including in a co-culture of cancer and normal cells in vitro [37], and has shown a promising targeting and safety profile in an early clinical trial [38]. EnAd can serve as an efficient vector for cancer-selective expression of immune-modulating biologics [39][40][41][42] and can be delivered via the bloodstream into the tumour following systemic administration to humans [43][44][45].…”

Cryo-EM structure of adenovirus type 3 fibre with desmoglein 2 shows a novel mode of receptor engagement

“…Desmoglein 2, a newly identified adenovirus receptor has been reported to be used by species B human adenoviruses such as HAd3, HAd7, HAd11 and HAd14 for cell infection 1 . As exemplified by HAd3 and HAd11, these viruses are used for cancer virotherapy 2,3,4 . The structure of the extracellular region of DSG2 containing four cadherin domains EC1 to EC4, has recently been solved by crystallography 5 .…”

“…The data presented here reveal a new mode of interaction for DSG2 interacting adenoviruses and provides new clues for the rational design of DSG2 interacting adenoviruses, subviral particles, or fibre knobs. Such vectors are currently undergoing a rapid development in therapy with HAd3, HAd11 being used in clinical trials 2,3,4 . Beside the use of oncolytic adenoviruses, HAd3 fibre-containing molecules such as penton-dodecahedron (symmetric particle harboring 12 fibres) or junction-openers (JOs) have been reported to act as enhancer of approved treatments in cancer therapies 1,10–12…”