Peptide libraries have emerged as a transformative technology in drug discovery and development. These diverse collections of peptides, now mainly synthetic but also biological, enable researchers to rapidly and efficiently screen large numbers of peptide sequences for
desired biological activities. This article examines how crude peptide libraries have advanced from early research to become vital tools for target identification, epitope mapping, protein interaction studies, drug optimisation, functional analyses and screening campaigns. Furthermore, it explores how specialised libraries, such as stable isotope–labelled and T-cell–activating peptide libraries, are broadening the scope of peptide-based strategies for therapeutic discovery and mechanistic understanding.

Crude Peptide Libraries in Determining Druggable Targets

Crude peptide libraries are compositionally diverse collections of peptides used primarily for exploratory and high-throughput research applications. Despite their crude (less purified) nature, these libraries have significant value in several critical facets of drug discovery, starting with target identification and validation. As one of the foundational steps in drug discovery, target ID is the process of identifying biological targets linked to disease. Peptide libraries enable researchers to probe complex biological systems by testing thousands of peptides against potential target proteins or receptors. By identifying peptides that bind specifically to a target, researchers can validate whether that target is druggable and suitable for further development. This rapid, empirical approach helps accelerate early discovery phases
by spotlighting new therapeutic candidates and mechanisms.

The combinatorial nature of peptide libraries enables high-throughput screening of vast sequences, significantly reducing the time and cost compared to traditional methods. Automated systems rapidly assay thousands of peptides for binding or functional activity, providing rich datasets for downstream development. This scalability makes crude peptide libraries essential tools in the discovery pipeline, from academic research centres to pharmaceutical companies.