Exploiting Screening Technologies for the Discovery of Anti-Infective and Anti-Inflammatory Peptides

Abstract

Advancements in our understanding of the processes that surround the molecular basis of disease, and a desire to tackle ‘undruggable targets’ that cannot be targeted by small molecules, have driven the emergence of a new paradigm of peptide and protein therapeutics. Their exquisite potency, target specificity, and favourable safety profiles have led to renewed interest in peptides and proteins as drug leads. Developments in high-throughput screening methodologies, such as phage display and mRNA display, have enabled the rapid discovery of de novo peptide therapeutics targeting a wide array of disease-associated proteins. However, peptide therapeutics face challenges with membrane permeability, evidenced by the fact that over 90% of peptides in active clinical trials target extracellular proteins. Additionally, unmodified peptides are susceptible to endogenous protease degradation and exhibit relatively short in vivo half-lives due to hepatic and renal clearance.

The incorporation of unnatural functionalities to a peptide has become a prevalent approach for refining the pharmacodynamic and pharmacokinetic attributes of therapeutic agents. To this end, this thesis details the use of screening technologies to modulate the properties of anti infective and anti-inflammatory peptides through rational design, peptide conjugation, and mirror-image synthesis. Chapter 2 describes the structure-activity relationship analysis of a SARS-CoV-2 main protease inhibitor to enhance its cell permeability and antiviral activity against SARS-CoV-2 in a cellular model of infection. Chapter 3 focusses on the exploitation of phage display to identify novel “knob domains” that bind to human and mouse serum albumin to modulate the pharmacokinetic properties of peptide-knob conjugates. Finally, Chapter 4 details the synthesis of mirror-image proteins for use as bait in a ‘mirror image RaPID mRNA display’ platform to generate a series of D-macrocyclic ligands with enhanced stability profiles.