New Method for Discovering Targeted Drugs: Screening of Peptide Libraries Based on Phage Display Technology-Special Topic on Phage Display Technology-Tekbiotech-Yeast and Phage Display CRO, Expert in Nano-body and Antibody Drug Development

New Method for Discovering Targeted Drugs: Screening of Peptide Libraries Based on Phage Display Technology

What are Peptide Drugs?

Since Dr. Frederick Banting and his team extracted insulin in 1922 and applied it to the treatment of type I diabetes, peptide drugs have entered the public consciousness^[1]. Peptides, functioning as therapeutic agents such as hormones, neurotransmitters, growth factors, antimicrobials, and vaccines, play key roles in human physiology. Therapeutic peptides are generally considered to be sequences of fewer than 50 amino acid residues, with molecular weights falling between those of small molecules and proteins.

Compared to antibodies (intact proteins) and small molecules, therapeutic peptides offer several advantages. For instance, peptides often represent the smallest functional components of proteins, thus exhibiting higher selectivity and specificity. Second, the degradation products of peptides in the body are amino acids, resulting in lower toxicity. Third, relative to intact antibody proteins, peptides have lower immunogenicity. Fourth, as many peptides mimic endogenous signaling molecules, they possess high activity and can function at low concentrations. Most importantly, once a peptide sequence is identified, it can be rapidly and massively chemically synthesized using well-established solid-phase peptide synthesis technology, at a lower cost.So, how are therapeutic peptides discovered? This introduces a screening technology known as phage display technology.

How to Screen for Peptides Using Phage Display Technology?

Basic Principle: First, genes encoding the peptides are obtained via chemical synthesis, and the sequences are inserted into either the pIII or pVIII gene of the M13 phage (Figure 1). The coat protein pVIII enables multivalent display, but only short peptides can be displayed when fused to the pVIII gene. The phagemid is transfected into E. coli, cultured to the logarithmic phase, and then a helper phage is added (which contains all the genes required for assembling a complete phage, but its own packaging signal is disrupted). When the phage assembles inside the bacterium, the peptide is displayed on its surface. Theoretically, each bacterium produces one type of phage, and by purifying individual phage plaques, a phage library displaying different peptides is obtained for further screening.

Figure 1: Schematic diagram of M13 phage ^[2]

Screening Workflow: First, as described above, the library is constructed and amplified (Figure 2A). Second (Figure 2B), the disease target (e.g., a receptor on the cancer cell surface) is immobilized on a solid or liquid phase. Third (Figure 2C), the immobilized target is co-incubated with the phage library under specific conditions, and after multiple washes, unbound phages are removed (Figure 2D). Fourth (Figure 2E), bound phages are isolated through competitive elution. Fifth (Figure 2F, G), the target-bound phages are used to re-infect bacteria for amplification, serving as the starting library for the next round of screening.

Typically, three to five rounds of biopanning are required to isolate specific and high-affinity peptide binders. After biopanning, DNA sequencing and phage enzyme-linked immunosorbent assays are used to identify specific phages with high affinity. The key point of phage library screening lies in the one-to-one relationship between the displayed peptide on the phage surface and the DNA within the phage. Once a peptide that binds the target is identified, its genetic information is known, enabling large-scale production.

Figure 2: Screening workflow of phage display technology ^[2]

TekBiotech, based on phage display and yeast display technologies, has established a comprehensive targeted antibody drug discovery platform. We provide high-quality monoclonal antibody development services for scientists worldwide, covering various formats including scFv, VHH, and Fab. Furthermore, we can develop antibodies with diverse functional and structural characteristics, including but not limited to neutralizing antibodies, conformation-specific antibodies, and cross-reactive antibodies. Additionally, TekBiotech offers supporting downstream services such as antibody expression validation, antibody humanization design and validation, antibody affinity maturation, and CAR-T candidate sequence design, meeting the diverse needs of clients for antibody drug development.

References

[1] Xiao W, Jiang W, Chen Z, Huang Y, Mao J, Zheng W, Hu Y, Shi J. Advance in peptide-based drug development: delivery platforms, therapeutics and vaccines. Signal Transduct Target Ther. 2025 Mar 5;10(1):74.

[2] Saw PE, Song EW. Phage display screening of therapeutic peptide for cancer targeting and therapy. Protein Cell. 2019;10(11):787-807.

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