Carrier Protein
A protein that binds to and transports other molecules through the bloodstream. Some therapeutic peptides are engineered to bind carrier proteins such as albumin to extend their duration of action. Semaglutide's fatty acid modification enables albumin binding, extending its half-life to approximately one week.
Technical Context
Albumin is the most abundant plasma protein (approximately 35-50 g/L) with a half-life of approximately 19 days. Its abundance and long half-life make it an ideal carrier for peptide drugs designed with albumin-binding modifications. Beyond non-covalent albumin binding (semaglutide, liraglutide, somapacitan), some drug design strategies use direct covalent albumin conjugation or albumin-binding domains fused to therapeutic peptides. The albumin recycling pathway (via the neonatal Fc receptor, FcRn) contributes to the long circulation time of albumin-bound drugs. Romiplostim uses a different carrier strategy — it is fused to an Fc antibody fragment for extended half-life.