Scientists Chemically Built a 165-Amino-Acid Protein From Scratch to Enable Mirror-Image Drug Discovery

What the researchers found

The researchers successfully synthesized the complete 165-amino-acid human interferon alpha-2b protein using native chemical ligation (NCL), which joins peptide fragments through chemical bonds at cysteine residues. The synthetic IFNα2b retained its biological properties.

This synthesis is an enabling step for mirror-image phage display — a technique where a D-amino acid version of the target protein is used to screen for L-peptide binders, which are then converted to D-peptide versions that resist protease degradation. The ultimate goal is to discover proteolysis-resistant D-peptide antagonists that block IFNα signaling.

Why it matters

Most peptide drugs are rapidly destroyed by enzymes in the body, limiting their use. D-peptides — made from mirror-image amino acids — are invisible to these enzymes and are therefore much more stable. Mirror-image phage display is a powerful technique for discovering D-peptide drugs, but it requires a chemically synthesized mirror-image version of the target protein. This synthesis of a 165-amino-acid protein demonstrates the feasibility of applying this approach to large targets like interferon.

How the study worked

The full 165-amino-acid IFNα2b protein was synthesized through native chemical ligation, a technique that chemically joins synthetic peptide fragments at cysteine residues to form native peptide bonds. The synthetic protein was then folded and tested for biological activity. The work represents the chemical manufacturing foundation needed for subsequent mirror-image phage display screening.

What this study cannot tell us

The abstract confirms biological activity but does not detail specific functional assays or quantitative comparisons with recombinant IFNα2b. The D-enantiomer of IFNα2b has not yet been synthesized or used for mirror-image phage display — this paper represents the L-form synthesis as proof of feasibility. The yield and scalability of the synthesis are not discussed. No D-peptide inhibitors have been identified yet.

How to read the evidence

This is a chemical synthesis and proof-of-concept study demonstrating feasibility. It is foundational enabling technology rather than a therapeutic study, and does not include clinical or in vivo data.

When this study was published

Published in 2015, this study represents an important milestone in peptide ligation chemistry. The mirror-image phage display approach it enables continues to advance as a drug discovery platform.

The bigger picture

This work sits at the frontier of peptide chemistry and drug discovery. Total chemical synthesis of proteins this large pushes the boundaries of what native chemical ligation can achieve. The mirror-image phage display approach has already yielded promising D-peptide drug candidates against smaller targets, and extending it to a 165-amino-acid cytokine like interferon alpha-2b could open new therapeutic avenues for autoimmune diseases and chronic viral infections.

Questions still open

• Can the D-enantiomer of IFNα2b be synthesized using the same approach and maintain structural integrity?
• How does the biological potency of chemically synthesized IFNα2b compare quantitatively to recombinant versions?
• What other large therapeutic proteins could benefit from this total synthesis and mirror-image drug discovery approach?

Common questions

Read the original research

Total chemical synthesis of human interferon alpha-2b via native chemical ligation.

Journal of peptide science : an official publication of the European Peptide Society, 21(7), 554-60

Citation

Li, Jing; Lehmann, Clara; Chen, Xishan; Romerio, Fabio; Lu, Wuyuan. (2015). Total chemical synthesis of human interferon alpha-2b via native chemical ligation.. Journal of peptide science : an official publication of the European Peptide Society, 21(7), 554-60. https://doi.org/10.1002/psc.2760