Short-Term Immunosuppression in Rats Induces Prolonged Immune Tolerance Towards a Human Monoclonal Antibody, Erenumab.

Administration of human therapeutic proteins such as monoclonal antibodies (mAb) to animals during preclinical drug development often leads to the development of anti-drug antibodies (ADA). ADA may reduce the systemic exposure of the mAb by enhancing its immune-complex mediated clearance. Thus, ADA may hinder the preclinical pharmacokinetic and toxicology assessments of mAbs. To mitigate this effect, we explored the ability of short-term administration of immunosuppressants to induce prolonged immune tolerance towards a human mAb, erenumab, in rats. In two studies, we investigated dosing regimens using the immunosuppressants methotrexate and tacrolimus/sirolimus combination, and compared them to non-immunosuppressed control groups. Each study comprised three phases: induction (weeks 1-4), washout (weeks 5-8), and rechallenge (weeks 9-12). Animals received mAb during the induction and rechallenge phase, while immunosuppression was limited to the induction and washout phase. Blood samples were collected at predefined time-points for erenumab and ADA quantification. The tacrolimus/sirolimus regimen, but not the tested methotrexate regimens, completely prevented ADA formation in all treated animals relative to the control groups. The tacrolimus/sirolimus treated animals not only remained ADA-negative with initial immunosuppression during the induction phase but remained ADA-negative even after erenumab rechallenge suggesting the induction of immune-tolerance beyond the immunosuppressive treatment period. Correspondingly, erenumab systemic exposures were maintained throughout the study period in all animals in the tacrolimus/sirolimus group and were similar to the erenumab exposures in ADA-negative animals of the control group. In contrast, ADA-positive animals in the control group exhibited a 60-80% reduction in erenumab exposures.