Abstract
BACKGROUND: Eosinophilic asthma is a common subtype of severe asthma with high morbidity and mortality. The cytokine IL-5 has been shown to be a key driver of the development and progression of disease. Although approved monoclonal antibodies (mAbs) targeting IL-5/IL-5R have shown good safety and efficacy, some patients have inadequate responses and frequent dosing results in medication nonadherence. RESULTS: We constructed a novel trivalent bispecific nanobody (Nb) consisting of 3 VHHs that bind to 2 different epitopes of IL-5 and 1 epitope of albumin derived from immunized phage display libraries. This trivalent IL-5-HSA Nb exhibited similar IL-5/IL-5R blocking activities to mepolizumab (Nucala), an approved targeting IL-5 mAb. Surprisingly, this trivalent Nb was 58 times more active than mepolizumab in inhibiting TF-1-cell proliferation. In primate studies, the trivalent IL-5-HSA Nb showed excellent pharmacokinetic properties, and peripheral blood eosinophil levels remained significantly suppressed for two months after a single dose. In addition, the trivalent IL-5-HSA Nb could be produced on a large scale in a P. pastoris X-33 yeast system with high purity and good thermal stability. CONCLUSIONS: These findings suggest that the trivalent bispecific IL-5-HSA Nb has the potential to be a next-generation therapeutic agent targeting IL-5 for the treatment of severe eosinophilic asthma.