NeoThyTM immune-humanized mice can produce anti-drug antibodies to support immunogenicity assessment for biological drug products

Introduction – Assessment of immunogenicity for new therapeutic protein products and biosimilars is an important aspect of drug development and the safety evaluation process. Conventional animal models typically do not reliably predict immunogenicity, as the human drug is seen as foreign in the animal model. To address this need, we conducted a proof-of-concept study with neonatal thymus (NeoThy™) immune-humanized mice using drug products known to have higher rates of immunogenicity in patients. NeoThy immune-humanized mice develop a fully engrafted human immune system that includes a human thymus for proper T cell development capable of recognizing human versus foreign proteins. Objective – This study used infliximab and interferon-beta (IFN-β) as monotherapies and in combination to determine if NeoThy immune-humanized mice could produce specific adaptive immune responses to the drugs. Methods – NeoThy immune humanized mice were generated at two different locations, creating six experimental groups. Mice received infliximab, IFN-β, a combination of infliximab and IFN-β, positive or negative control with treatment schedule appropriate to the therapeutic. Peripheral blood/serum was collected on day 0, 21, 42, and 63; tissues (bone marrow, spleen, lymph nodes) were harvested at necropsy (day 63). Immune reconstitution and treatment effects were assessed with flow cytometry, proliferation, total IgM/IgG isotyping, anti-drug antibodies (ADA) ELISAs for infliximab and IFN-β, and histopathology. Results – NeoThy immune-humanized mice showed broad and ample human immune reconstitution with donor-dependent differences noted. We observed immune activation and B cell class switching including IgG_1–4 in most donors. In several cases, humanized mouse serum immunoglobulin levels approached or exceeded those from normal human serum, which was evaluated as a control. Binding ADAs to IFN-β and neutralizing ADAs to infliximab, were detected in multiple mice in a donor- and treatment-dependent manner. Conclusions – NeoThy immune-humanized mice mount human-like, donor-dependent immune responses to biologics, including class switching, antigen-specific proliferation, and ADA formation. These preliminary findings suggest that NeoThy immune-humanized mice have the biological ability to help assess immunogenicity risk, and other immunosafety considerations for biological drug products.