A new peptide ligation method that leaves no chemical scars at joining sites was used to synthesize tirzepatide from scratch, potentially enabling cheaper production of complex peptide drugs.
Total synthesis of tirzepatideFirst reported chemical synthesis of tirzepatide using native residue-forming ligation, published in the Journal of the American Chemical Society
What the researchers found
Researchers developed new chemical building blocks (cyclic dipeptide-derived hydroxylamines) that enable peptide ligation at fully native sites — meaning no unnatural amino acids are left behind at the joining point. They demonstrated the method by synthesizing two challenging targets: ubiquitin (for protein research) and tirzepatide (the GLP-1/GIP dual agonist drug).
The tirzepatide synthesis was particularly notable because the drug contains non-standard features — amino-isobutyric acid (Aib) residues and a fatty acid side chain — that make it extremely difficult to produce by traditional methods. The new approach successfully joined unprotected peptide segments at 'nonobvious' junctions like Leu-Ile and Lys-Ile.
Why it matters
Tirzepatide (Mounjaro/Zepbound) is one of the most important peptide drugs ever developed, but its complex structure makes manufacturing challenging and expensive. This new ligation chemistry could enable more efficient synthesis of tirzepatide and similarly complex peptide therapeutics. By allowing native amino acid formation at ligation sites, it removes a key limitation that has restricted chemical synthesis approaches for large therapeutic peptides.
The numbers in context
Tirzepatide total synthesis achieved · ubiquitin synthesis demonstrated · Leu-Ile and Lys-Ile junctions enabled · native residue formation at ligation sites · Aib-containing peptide synthesized · fatty acid side chain incorporated
How the study worked
Organic chemistry method development. Researchers designed cyclic dipeptide-derived hydroxylamine building blocks for KAHA (α-ketoacid-hydroxylamine) ligation. They optimized reaction conditions for native residue formation, then demonstrated the approach by synthesizing selectively protected ubiquitin monomers and performing the total chemical synthesis of tirzepatide.
Who was studied
Not applicable (chemical synthesis methodology)
What this study cannot tell us
Pure chemistry methodology — no biological testing of the synthesized tirzepatide. Scalability to manufacturing quantities was not demonstrated. The building blocks require multi-step preparation from dipeptides. Cost comparison with existing tirzepatide manufacturing (recombinant production) was not addressed. Limited to specific ligation junctions.
How to read the evidence
Preliminary — this is a chemistry methods paper published in JACS (a top-tier journal). The chemical synthesis is rigorously demonstrated, but there is no biological validation of the product and no scalability data. The significance is in enabling new synthetic routes, not in direct therapeutic evidence.
When this study was published
Published in 2025. This is cutting-edge synthetic chemistry reflecting the current intense interest in tirzepatide manufacturing. As patent landscapes evolve, efficient chemical synthesis routes could become commercially important for generic production.
The bigger picture
As peptide drugs become the most valuable class of therapeutics (tirzepatide alone generates billions in revenue), manufacturing efficiency is a major bottleneck. Most complex peptides are made by recombinant DNA technology in living cells, which is expensive and has limitations. Chemical synthesis offers an alternative that's more flexible and scalable, but has been held back by the 'scar problem' — unnatural residues at ligation sites. This JACS paper solves that problem for a commercially important drug, potentially opening the door to cheaper generic versions of complex peptide therapeutics.
Questions still open
- Could this ligation chemistry reduce the manufacturing cost of tirzepatide enough to lower drug prices?
- Is the synthesized tirzepatide biologically equivalent to the recombinantly produced version used clinically?
- Can this approach be scaled to kilogram quantities needed for pharmaceutical production?
Common questions
Why is synthesizing tirzepatide so difficult?
Could this make tirzepatide cheaper?
Read the original research
Cyclic Hydroxylamines for Native Residue-Forming Peptide Ligations: Synthesis of Ubiquitin and Tirzepatide.
Journal of the American Chemical Society, 147(38), 34238-34243
Citation
Han, Jiling; Hirao, Kohtaro; Mikami, Toshiki; Nötel, Nicolas Y; Seidl, Leonardo L; Bode, Jeffrey W. (2025). Cyclic Hydroxylamines for Native Residue-Forming Peptide Ligations: Synthesis of Ubiquitin and Tirzepatide.. Journal of the American Chemical Society, 147(38), 34238-34243. https://doi.org/10.1021/jacs.5c11881