Conclusions

In this paper, we have successfully developed an ELP-peptide fusion for the affinity precipitation of the therapeutically relevant small non-mAb biologic, AdP. Phage biopanning was first used to identify lead peptides which were then synthesized and evaluated for their binding to the target using fluorescence polarization. A fusion of the top lead peptide with ELP was then produced in E. coli and evaluated for its efficacy to both capture and elute the bioproduct. While binding was favored at low pH conditions, higher pH values were more useful for elution. In addition, the use of fluid phase modifiers, in particular arginine, were shown to further improve the elution behavior. Evaluation of the ELP-peptide with a crude mixture demonstrated that both high recovery (83%) and purity (88%) could be achieved using this affinity precipitation process. While this proof of concept study was successful, further mutagenesis studies could be carried out to improve both the binding and elution behavior of the peptide. This work establishes that peptides identified from phage display can be successfully employed in an ELP fusion format for the purification of a small therapeutic biologic by affinity precipitation. The results and approaches presented in this work can now be extended to other biologics for which there currently do not exist efficient affinity capture processes.