A peptide is a naturally occurring or synthetic compound composed of two or more amino acids linked together by peptide bonds. Amino acids are the building blocks of proteins, and peptides are basically smaller, simpler versions of proteins.

Peptides can be produced both naturally within living organisms and synthetically in laboratory settings. The body generates various peptides organically, such as ribosomal and non-ribosomal peptides. In research and manufacturing, modern synthesis techniques—primarily solid-phase peptide synthesis (SPPS), though sometimes liquid-phase methods—enable the creation of countless peptide sequences with high precision and efficiency.

The concept of injecting peptides has been around for more than 100 years starting with insulin in 1921.