Preclinical Safety of APG777, A Novel Extended Half-Life Anti-Interleukin-13 Monoclonal Antibody, in Cynomolgus Monkeys

Interleukin-13 (IL-13) is a cytokine implicated in the pathophysiology of type 2 inflammatory diseases and is a clinically validated target in atopic dermatitis. APG777 is a humanized IgG1 monoclonal antibody with an optimized pharmacokinetic profile. APG777 has high affinity to IL-13 and includes a triple amino acid modification (the "YTE" modification) in its Fc region that is designed to extend its half-life. The current study examined the safety and potential toxicity of APG777 when given by once-weekly subcutaneous injection for 27 weeks to cynomolgus monkeys, and the potential reversibility of any findings following a 2-month recovery period. Toxicokinetic characteristics of APG777 were also determined. APG777 exhibited dose-proportional systemic exposure, with a half-life of approximately 28 days. No APG777-related adverse effects were noted in clinical observations, body weight, ophthalmology, electrocardiogram readings, neurologic parameters, hematology, coagulation, clinical chemistry, urinalysis, organ weights, or histopathology. Anti-drug antibodies were not detected in any APG777-exposed animals. Drug accumulation was evident over the study duration; however, there were no APG777-related adverse findings in any of the parameters analyzed. The no-observed-adverse-effect level (NOAEL) was 150 mg/kg/week. These findings provide preclinical evidence supporting continued clinical development of APG777 for IL-13-mediated diseases. The extended half-life of APG777 suggests potential benefits in reducing dosing frequency compared with existing IL-13-targeting therapies, which could improve treatment adherence and patient outcomes. The safety and efficacy of APG777 are currently being investigated in a Phase 2 clinical trial (NCT06395948) in patients with moderate-to-severe atopic dermatitis.