Understanding in-vivo refolding of antibody fragments (Fab): Biosimilar Ranibizumab a case study

Abstract

In-vitro protein refolding is a major bottleneck step in the large-scale manufacturing of antibody fragments expressed in a microbial host system. The formation of an inter-chain disulfide bond is a key rate-limiting step during in-vitro refolding of antibody fragment therapeutics. In this investigation, we report the use of two redox mutant strains of E. coli viz., SHuffle® T7 (DE3) and SHuffle® T7 Express (DE3) possessing an oxidizing cytoplasm for the soluble expression of a refolded biosimilar antibody fragment. The effect of various critical process parameters on antibody fragment refolding yield was studied using a Design of Experiment (DoE) approach. The optimized upstream processing led to the expression of 167 ± 2.53 mg/L and 95 ± 1.44 mg/L of soluble refolded biosimilar Ranibizumab using the SHuffle® T7 (DE3) and SHuffle® T7 Express (DE3) strains, respectively, at the bioreactor scale. Physicochemical characteristics of the in-vivo refolded antibody fragment were studied and compared with an innovator molecule using various orthogonal analytical methods. A biological activity study of in-vivo refolded Ranibizumab using HUVEC cell-based bioassay proved that cell proliferation inhibition is comparable to the innovator Ranibizumab. The proposed strategy offers a time and cost-effective manufacturing platform for antibody fragments.