Glossary
Analog
An analog is a purposely modified version of a parent peptide. Four ways peptides get modified, and why analog findings never carry over to native molecules.
A peptide analog is a molecule intentionally changed relative to a reference peptide yet still similar enough to engage the same target. Most analogs fall into four modification categories: residue swaps, non-natural amino acids such as Aib included; end-capping through acetylation or amidation; shortening or lengthening of the chain; and attachment of a fatty acid, a PEG chain or a DAC linker.
Why the analog concept is central
Nearly every commercially or scientifically interesting peptide is an analog. Semaglutide, for example, is a GLP-1 analog: an Aib at position 8 prevents DPP-4 cleavage and a C18 di-acid lets it bind albumin, stretching a half-life of about two minutes to around a week. IGF-1 LR3 swaps a single residue and lengthens the chain so binding proteins capture less of it. Each time, a minor structural edit yields a major change in behaviour.
For exactly that reason, results cannot be carried across. An analog and its native sequence parent are cleared differently, select receptors differently and frequently have different off-target profiles, so data on one do not count as evidence for the other — and human trial results for a licensed analog tell us nothing about an unstudied research-grade relative. Compare fragments; see why the IGF modifications exist.
Related terms
recombinant · cyclic peptide