Comparative assessment of immune complex-mediated hypersensitivity reactions with biotherapeutics in the non-human primate: Critical parameters, safety and lessons for future studies.

With the emergence of novel biotherapeutic formats and immunostimulatory biotherapeutics in cancer immunotherapy, an understanding of immune-complex (IC) mediated hypersensitivity reactions in toxicology studies - and their differentiation from pharmacology - remains key to the preclinical evaluation of these drugs. In this review we provide an in-depth evaluation and comparison of case examples where IC-mediated hypersensitivity reactions were observed in cynomolgus monkeys. We provide details of the parameters evaluated in each study to substantiate and guide the interpretation of these findings. Five study cases (1 therapeutic protein, 4 monoclonal antibodies) are discussed for which effects ranged from minor to fatal. Common characteristics are the high incidence of clinical signs, detectable antidrug antibodies, and accelerated drug clearance up to virtual loss of exposure. In our experience, measurement of cytokine levels in vivo and detection of complement (split products) were supportive markers in situations where coagulopathy was suspected to play a role in the observed effects. Recommendations are outlined to prepare for root-cause analysis of suspected hypersensitivity reactions. Overall, a thorough analysis of the findings has helped to start clinical trials despite major findings. The hypersensitivity reactions with our human(ized) immunoglobulins have not proven to be predictive for humans.

Inflammation and immunogenicity limit the utility of the rabbit as a nonclinical species for ocular biologic therapeutics.

The nonclinical safety evaluation of therapeutic drug candidates is commonly conducted in two species (rodent and non-rodent) in keeping with international health authority guidance. Biologic drugs typically have restricted species cross-reactivity, necessitating the evaluation of safety in non-human primates and thus limiting the utility of lower order species. Safety studies of cross-reactive ocular biologic drug candidates have been conducted in rabbits as a second toxicology species, despite the fact that rabbits are not a rodent species. Such studies are often confounded by the development of anti-drug antibodies and severe ocular inflammation, the latter requiring studies to be terminated prematurely for animal welfare reasons. Notably, these confounding factors preclude the interpretation of safety. Nonclinical toxicology programs should be designed with consideration of ethical animal use and 3Rs principles (Replacement, Reduction and Refinement). The experience of several pharmaceutical sponsors, demonstrating that toxicology studies of ocular (intravitreal and topical ocular) biologic drug candidates in the rabbit are of limited interpretive value, calls into question the utility of such studies in this species and indicates that such studies should not be conducted.