In pharmacology, the elimination half-life shows how long a molecule stays in circulation. After one half-life 50% remains; after two, 25%; after five, about 3%, which is why a substance is usually considered almost fully eliminated after five half-lives.
Natural peptides usually have very short half-lives. Endogenous GLP-1 lasts only a few minutes because the enzyme DPP-4 breaks it down and the kidney filters it. Analogue engineering aims to lengthen it: replacing amino acids at cleavage points, attaching fatty acids that bind to albumin or adding affinity complexes such as DAC.
The contrast is clear in the somatotropic axis: CJC-1295 without DAC (Mod GRF 1-29) lasts on the order of minutes, whereas the DAC version is measured in days. Same base sequence, completely different pharmacokinetics.
Half-life in the body should not be confused with stability in the vial: they are different concepts. A peptide with a short plasma half-life can be very stable when freeze-dried, and vice versa.
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Learn it in depth at the Peptide University
- Pharmacokinetics: ADME and parameters · Module 2
- Half-life engineering · Module 2
- Levels of structure and structure-activity relationship · Module 1
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).