therapeutic peptide

A therapeutic peptide is a drug made from a short chain of amino acids, the same building blocks that make up proteins, just far fewer of them. If a protein is a long sentence, a peptide is a short phrase: big enough to fold into a specific shape and grip a target precisely, yet small enough to sit between classic small molecules and full biologics.

Peptides typically range from a couple to a few dozen amino acids. That size lets them bind large, flat target surfaces, such as the contact patch between two proteins, that ordinary small molecules struggle to engage, while still being more affordable and easier to make than full antibodies.

Their weakness is fragility. Natural peptides are quickly chopped up by digestive and blood enzymes and cleared by the kidney, so they usually need injection and have short action. Chemists fight this with tricks such as unnatural amino acids, cyclization, and chemical staples to slow degradation; a peptide redesigned to be more druglike is called a peptidomimetic.