CH1-specific affinity resins possess the potential of separating heterodimer from homodimers in asymmetric bispecific antibody purification.

CaptureSelect CH1-XL and Praesto 70 CH1 are two affinity media that specifically bind to the CH1 domain of an antibody. In the current work, we first demonstrated that these two CH1-specific affinity media bound to different monoclonal antibodies (mAbs) with varied strengths under identical conditions. We previously had observed the same on a Protein L-conjugated resin and showed that such a property could facilitate homodimer removal in asymmetric bispecific antibody (bsAb) purification. Next, using Praesto 70 CH1, we showed that a small difference in binding between two mAbs could be significantly exaggerated by adding sodium chloride to the mobile phase, further demonstrating this resin can potentially play a role in bsAb purification. Finally, with a concrete bsAb case study, we showed that, like Protein L, Praesto 70 CH1 could separate the target heterodimer from the homodimer by-product. Homodimers are common product-related impurities associated with the recombinant production of asymmetric bsAbs, which can be difficult to remove. Their removal, even a partial one, at the capture stage is a big advantage as it can alleviate the purification burden on subsequent polishing steps and render the overall process more robust. Therefore, Praesto 70 CH1's unique property is highly desirable, and this affinity resin can be a better alternative than Protein A for product capture in asymmetric bsAb purification.