Challenges and solutions for upstream processing of complex biologics

Unlike conventional monoclonal antibodies, complex biologics—such as bispecific antibodies (bsAbs) and fusion proteins—often face challenges including lower expression levels, higher mispairing rates, and greater sensitivity to culture conditions, which can collectively limit both titer and product quality. Leveraging process development case studies, this review systematically explores upstream bioprocessing strategies aimed at mitigating these challenges, with a focus on titer enhancement, lactate metabolism regulation, acidic charge variants control, reduction of aggregates and fragments, and glycosylation optimization. Finally, a perspective towards future upstream development strategies is discussed.