Human Growth Hormone-Releasing Factor (hGRF)1-29-Albumin Bioconjugates Activate the GRF Receptor on the Anterior Pituitary in Rats: Identification of CJC-1295 as a Long-Lasting GRF Analog
Jetté L, Léger R, Thibaudeau K, Benquet C, Robitaille M, Pellerin I
Endocrinology (2005)
CJC-1295 was identified as the lead compound from a panel of three hGRF(1-29)-albumin bioconjugates — present in rat plasma beyond 72 hours and producing a fourfold increase in GH AUC versus unmodified hGRF(1-29). This is the molecule's origin story.
This is the foundational discovery paper for CJC-1295 — published by Conjuchem (the Montreal biotech that developed the molecule) describing the chemistry, in vitro pharmacology, and in vivo rat pharmacokinetics that identified CJC-1295 from a panel of three candidate hGRF(1-29)-albumin bioconjugates. The Conjuchem team synthesized three maleimido derivatives of human growth-hormone-releasing factor 1-29 and conjugated them in vivo via the free thiol on Cys34 of circulating serum albumin — a "Drug Affinity Complex" (DAC) strategy designed to extend peptide half-life by hijacking albumin's 19-day plasma residence. All three human-serum-albumin conjugates showed enhanced in vitro stability against dipeptidyl-peptidase IV (the enzyme that cleaves native GHRH within minutes) and remained bioactive in a cultured rat anterior pituitary GH-secretion assay. The lead compound, CJC-1295, was selected on the basis of in vivo performance in Sprague-Dawley rats: it produced a fourfold increase in GH area-under-the-curve over a two-hour period compared with unmodified hGRF(1-29), and immunoreactive CJC-1295 persisted in rat plasma beyond 72 hours, with Western blot evidence of conjugated material at 24 hours and beyond. This is the receptor-pharmacology paper that establishes CJC-1295 as a stable, active, long-lasting GRF receptor agonist and lays the groundwork for the Phase 1 studies (Teichman 2006, Ionescu & Frohman 2006) that followed.
This is a preclinical paper — rat pharmacokinetics and cultured pituitary cell assays, not human data. The four-fold GH-AUC increase and >72-hour plasma residence are specific to the rat model and the bioconjugate's stability profile; human pharmacokinetics, established later in Teichman 2006, gave a longer half-life (5.8-8.1 days) consistent with the albumin-anchoring strategy but not identical to the rat profile. The paper is funded and authored entirely by Conjuchem (the developer), so the framing emphasizes positive selection of CJC-1295 over its sibling compounds; comparative pharmacodynamics of the other two candidates against CJC-1295 are reported but the explicit selection criteria are not deeply interrogated. The Western blot immunoreactivity assay confirms the presence of conjugated peptide but does not directly establish receptor occupancy or sustained signaling.
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