LAUSR

CJC-1295 is a peptide-based drug that stimulates the production of growth hormone (GH) from the pituitary gland. It incorporates a functional maleimido group at the C-terminus that allows it to covalently bind plasma proteins such as serum albumin. These CJC-1295-protein conjugates have a much greater half-life compared to the unconjugated peptide and are capable of stimulating GH production for more than six days in humans after a single administration. Conjugated CJC-1295 is difficult to detect in blood by mass spectrometry due to its low abundance, high molecular weight, and conjugation to a range of different protein substrates. Previously we described a screening procedure for the detection of CJC-1295 in equine plasma using an immuno-PCR assay. Here we demonstrate the confirmation of CJC-1295 in equine plasma by LC-MS/MS after immuno-affinity capture and tryptic digestion. Using this method, CJC-1295 was identified down to concentrations as low as 180 pg/mL in 1 mL of equine plasma.