Development of a novel capture step for purification of antigen binding fragments (Fabs)

Antigen binding fragments (Fabs) are an emerging class of biotherapeutics, widely accepted as an alternative to the traditional monoclonal antibodies (mAbs). The small size of the Fabs offers better tissue penetrability and lack of Fc region, thereby resulting in reduced side effects. However, since Fab molecules lack Fc region, Protein A chromatography (the ubiquitous capture step in mAb platforms) cannot be employed. Conventional Fab purification platforms employ affinity-based Protein L chromatography for capture, which is effective but just like Protein A an expensive step to use in commercial production. In this paper, we propose use of salt precipitation followed by hydrophobic interaction chromatography (HIC) as a capture chromatography step for Fabs. The precipitation step enhanced the purity from 30 % to 65 % and the HIC chromatography step further raising it to 80 % (by RP-HPLC) with a combined process recovery of greater than 95 %. The proposed capture process offers a substantial advantage with respect to the cost of goods when compared to the traditional, affinity-based approaches.