What is a GHRH analogue? Sermorelin, CJC-1295 and Tesamorelin

What is a GHRH analogue?

A GHRH analogue is a synthetic peptide structurally derived from growth hormone releasing hormone (GHRH), the endogenous hypothalamic peptide that in research models binds to the GHRH receptor (GHRHR) on cells of the anterior pituitary. This receptor is a G protein-coupled receptor that raises intracellular cAMP levels through adenylate cyclase activation, a signalling pathway linked in cell culture and animal studies to growth hormone release from somatotroph cells.

Molecular mechanism

The native GHRH molecule consists of 44 amino acids, of which the first 29-residue segment (GHRH(1-29)) forms the minimal sequence that retains receptor activity in vitro. Synthetic analogues are designed based on this fragment, with amino acid substitutions that affect resistance to enzymatic degradation by dipeptidyl peptidase-4 (DPP-4). DPP-4 cleaves the peptide bond between positions 2 and 3, giving the native peptide a very short plasma half-life. Analogues with modified amino acids at these positions show a slower degradation rate in research settings.

Half-life differences: the CJC-1295 example

CJC-1295 illustrates how structural modifications alter pharmacokinetics in model systems. The variant without Drug Affinity Complex (DAC), sometimes referred to as CJC-1295 without DAC or Mod GRF (1-29), carries amino acid substitutions that increase DPP-4 resistance relative to native GHRH, yet its plasma half-life remains on the order of minutes. The DAC variant additionally carries a maleimide group that binds covalently in vitro to the cysteine residue of serum albumin. This albumin binding substantially slows renal clearance and proteolytic degradation, producing a markedly extended half-life in research compared with the non-DAC variant.

Examples of model compounds in research

Sermorelin corresponds to the GHRH(1-29) fragment and is used in receptor binding studies as a reference compound for GHRHR activation. CJC-1295 serves as a model compound for studying the effect of albumin binding on peptide stability. Tesamorelin is a GHRH(1-44) analogue carrying a trans-3-hexenoyl group at the N-terminus, which affects stability against aminopeptidases, and is used in analytical research to characterise structure-stability relationships among GHRH analogues.

• GHRHR: G protein-coupled receptor signalling through cAMP
• DPP-4 resistance: determines plasma stability of the peptide
• DAC technology: albumin binding extends half-life in model systems
• For laboratory and analytical research use only