Chemistry and structure

How a 39-residue peptide was engineered to last a week

Tirzepatide is not a natural hormone; it is a designed peptide. The US label states plainly that it is based on the GIP sequence, with two non-coded amino acids built in at positions 2 and 13, a capped C-terminus, and a 20-carbon fatty diacid hung off lysine 20.

This unit opens the molecule up: the published architecture, the acylation that stretches its half-life to about five days, and how its receptor binding is deliberately lopsided.