Reslizumab is a humanized IgG4/κ monoclonal antibody that targets IL-5 molecules, with the K_d value of 81pM^[1]. Reslizumab binds to the α chain of the IL-5 receptor on the surface of eosinophils, thereby inhibiting the proliferation of eosinophils, Reslizumab can be metabolized through enzymatic protein hydrolysis into small peptides and amino acids^[2]. Reslizumab has been widely used in animal models of asthma to control asthma symptoms and improve lung function^[3].

In vitro, Reslizumab significantly inhibited the proliferation of TF-1 cells stimulated by IL-5 after 48 hours of treatment, with an IC₅₀ value of 0.091nM^[4].

In vivo, seven days after intraperitoneal injection of a single dose of 200mg/kg Reslizumab, the number of eosinophils in the blood and the level of serum IL-5 in the ovalbumin (OVA)-treated mice were significantly reduced, without affecting the production of IL-13^[5]. In OVA-sensitized guinea pig model, Reslizumab (1mg/kg) administered intraperitoneally 2 hours before the OVA challenge reduced eosinophilia, airway hyperreactivity, and bronchoconstriction^[6].

References:
[1] Padilla Galo A, Labor M, Tiotiu A, et al. Impact of reslizumab on outcomes of severe asthmatic patients: current perspectives[J]. Patient Related Outcome Measures, 2018: 267-273.
[2] Hom S, Pisano M. Reslizumab (Cinqair): an interleukin-5 antagonist for severe asthma of the eosinophilic phenotype[J]. Pharmacy and Therapeutics, 2017, 42(9): 564.
[3] Xu Y, Yang L, Zhao T, et al. Multifunctional Gold Nanoclusters for a Lung Tissue Distribution Study of a Novel Anti-asthma Inhaled Antibody[J]. Analytical Chemistry, 2025, 97(36): 19635-19653.
[4] Liddament M, Husten J, Estephan T, et al. Higher binding affinity and in vitro potency of reslizumab for interleukin-5 compared with mepolizumab[J]. Allergy, Asthma & Immunology Research, 2018, 11(2): 291-298.
[5] Kageyama K, Kikuchi E, Hoshino N. Effect of anti-interleukin-5 antibody on development of vasculitis in an ovalbumin-induced eosinophilic vasculitis mouse model[J]. Frontiers in Pharmacology, 2025, 16: 1546785.
[6] Egan R W, Athwal D, Bodmer M W, et al. Effect of Sch 55700, a humanized monoclonal antibody to human interleukin-5, on eosinophilic responses and bronchial hyperreactivity[J]. Arzneimittelforschung, 1999, 49(09): 779-790.