A molecular add-on that causes a peptide to bind to a blood protein, dramatically slowing how quickly it’s cleared from the body.The DAC modification on CJC-1295 covalently binds to albumin after injection via a maleimide-thiol reaction. Albumin’s long half-life (~19 days) effectively extends CJC-1295 with DAC’s plasma half-life from minutes to 6–8 days, producing sustained GH elevation. CJC-1295 without DAC (Modified GRF 1-29) has a half-life of ~30 minutes and produces a discrete GH pulse that more closely mimics physiological secretion. The two compounds have the same binding target (GHRH receptor) but very different pharmacokinetic profiles — the choice between them is a decision about what pattern of GH stimulation you’re trying to produce.