Discovery of Antivirals Using Phage Display

Abstract

The latest coronavirus disease outbreak, COVID-19, has brought attention to viral infections which have posed serious health threats to humankind throughout history. The rapid global spread of COVID-19 is attributed to the increased human mobility of today's world, yet the threat of viral infections to global public health is expected to increase continuously in part due to increasing human-animal interface. Development of antiviral agents is crucial to combat both existing and novel viral infections. Recently, there is a growing interest in peptide/protein-based drug molecules. Antibodies are becoming especially predominant in the drug market. Indeed, in a remarkably short period, four antibody therapeutics were authorized for emergency use in COVID-19 treatment in the US, Russia, and India as of November 2020. Phage display has been one of the most widely used screening methods for peptide/antibody drug discovery. Several phage display-derived biologics are already in the market, and the expiration of intellectual property rights of phage-display antibody discovery platforms suggests an increment in antibody drugs in the near future. This review summarizes the most common phage display libraries used in antiviral discovery, highlights the approaches employed to enhance the antiviral potency of selected peptides/antibody fragments, and finally provides a discussion about the present status of the developed antivirals in clinic.

Keywords: antigen-binding fragment; antiviral; bacteriophage; intrabody; nanobody; peptide; phage display; single-chain variable fragment; transbody.

Figure 1

Schematic representation of antibodies and antibody fragments. IgG1, immunoglobulin G1; HCAb, heavy chain-only antibody; Fc, crystallizable fragment; Fab, antigen-binding fragment; ScFv, single-chain variable fragment; CH1–CH2–CH3, constant domains of heavy chain; CL, constant domain of light chain; VH, variable domain of heavy chain; VL, variable domain of light chain; VHH, variable heavy chain of HCAb.