CJC-1295 Dr.

Research literature

CJC-1295: mechanism, Phase 1 pharmacokinetics, and the receptor biology underlying a long-acting GHRH analog.

What the literature covers

The published CJC-1295 evidence base is narrow but specific. Two controlled human trials from 2006 — both randomized and placebo-controlled — established that a single injection raises growth hormone two- to ten-fold for six or more days and lifts IGF-1 for up to eleven days. A notable finding is that natural growth hormone pulses are preserved: the compound raises the floor of GH secretion without disrupting the episodic peaks that mark healthy pituitary function. Below that core human data sits a wider set of mechanistic research: rat and mouse models, molecular pharmacology of the albumin-conjugation chemistry, a 2025 mapping of the sleep-circuit neurons that gate overnight GH release, and a 2024–2025 review of the broader GHRH analog class. This page presents all of it, layered clearly by species and evidence strength.

Reading note

CJC-1295's human evidence base is small. Two Phase 1/2 randomized placebo-controlled trials, both published in 2006, account for most of the direct human pharmacokinetic and pharmacodynamic data. The mechanistic picture is richer — built from in vitro receptor pharmacology, rodent models, and the larger GHRH analog literature extending to 2024–2025. This page summarizes both layers and distinguishes them clearly.

Molecular structure and the DAC modification

Native growth hormone-releasing hormone (GHRH) is a 44-amino-acid hypothalamic peptide. Its plasma half-life is under 10 minutes because dipeptidyl peptidase-IV (DPP-IV) cleaves the Ala-Tyr bond at position 2, inactivating the peptide [7]. First-generation GHRH analogs achieved some DPP-IV resistance by substituting D-Ala at position 2 — extending half-life to tens of minutes.

CJC-1295 makes four substitutions in the first 29 residues of GHRH: D-Ala at position 2 (DPP-IV cleavage blocked), Ala at position 8 (asparagine rearrangement reduced), Glu at position 15 (bioactivity maintained), and Leu at position 27 (methionine oxidation prevented) [7]. The DAC variant adds a 30th residue: N-epsilon-3-maleimidopropionamide-lysine at the C-terminus. After subcutaneous injection, this maleimide group reacts with the free thiol of Cys34 of circulating serum albumin, forming a stable thioether bond and producing a conjugate of approximately 67 kDa [8]. The conjugate is too large for renal filtration and is shielded from proteolytic degradation by the albumin shell — effectively hitchhiking on albumin's 19–21-day endogenous half-life and extending CJC-1295's effective half-life to 5.8–8.1 days [2][8].

The practical result: a single subcutaneous injection maintains continuous GHRH-R engagement across multiple days. The Modified GRF 1-29 variant (same four substitutions, no maleimide) has a half-life of approximately 30 minutes and produces a shorter, more conventional GHRH-like pulse — a pharmacologically distinct compound despite sharing the four-substitution scaffold.

GHRH-R signal transduction

GHRH-R is a Gαs-coupled receptor. Binding of CJC-1295 — or native GHRH — triggers the following cascade [13]:

  1. Gαs activation of adenylyl cyclase → intracellular cAMP rises.
  2. cAMP activates protein kinase A (PKA).
  3. PKA phosphorylates CREB, driving Pit-1 transcription factor expression and GH gene transcription.
  4. PKA also opens voltage-gated calcium channels → direct GH secretory granule exocytosis.
  5. Released GH activates hepatic GH receptors → JAK2/STAT5 signaling → IGF-1 synthesis and secretion [12].
  6. IGF-1 drives skeletal muscle anabolism via PI3K/Akt/mTORC1 → p70S6K phosphorylation → enhanced ribosomal protein translation [12].

GH also acts directly on adipocytes, activating hormone-sensitive lipase — particularly in visceral depots — driving lipolysis. Related GHRH agonist analogs have been shown to reduce visceral fat in animal models via this GH-mediated pathway, and the FDA-approved tesamorelin (a structurally distinct GHRH analog) has produced statistically significant visceral fat reduction in human trials — providing proof-of-concept for GHRH analog body composition effects in humans, though no equivalent Phase 3 data exists for CJC-1295 [16].

Extrapituitary GHRH-R distribution — confirmed in cardiac myocytes, lymphocytes, gonads, skin, and kidney — raises the possibility of direct peripheral effects independent of GH/IGF-1, but human data on these pathways for CJC-1295 specifically is absent [13].

Phase 1 pharmacokinetics: what the Teichman et al. 2006 trial measured

Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, and Frohman LA published the definitive CJC-1295 Phase 1/2 data in the Journal of Clinical Endocrinology and Metabolism in 2006 (DOI 10.1210/jc.2005-1536) [1]. Key findings:

  • Single subcutaneous doses of 30, 60, 90, and 120 μg/kg were studied in healthy adults aged 21–61 years.
  • GH rose 2- to 10-fold above baseline across dose cohorts, with elevation sustained for six or more days after a single injection [1].
  • No serious adverse events were reported at 30 or 60 μg/kg. The 120 μg/kg cohort showed increased adverse events, establishing a safety margin for the lower doses.
  • IGF-1 rose 1.5- to 3-fold and remained above baseline for 9–11 days after a single injection [2].
  • With repeated dosing, cumulative IGF-1 remained above baseline for up to 28 days [2].
  • Estimated effective half-life: 5.8–8.1 days, consistent with the albumin-conjugation pharmacology [2].

A critical companion finding came from Ionescu M and Frohman LA, also 2006, Journal of Clinical Endocrinology and Metabolism (DOI 10.1210/jc.2006-1702) [3]: pulsatile GH secretion was preserved. Basal GH rose 7.5-fold (P < 0.0001) and mean GH increased 46% (P < 0.01), but pulse frequency and amplitude characteristics were unchanged. IGF-1 rose 45% (P < 0.001). The mechanistic interpretation: CJC-1295 raises the set-point from which somatotrophs respond to endogenous GHRH signals rather than overriding the pulsatile architecture [17]. This distinguishes CJC-1295 pharmacologically from exogenous recombinant GH, which suppresses endogenous pulsatility via negative feedback.

A 2009 proteomics study (Sackmann-Sala L, Ding J, Frohman LA, Kopchick JJ) examined serum protein changes in 11 healthy young men who received 60–90 μg/kg CJC-1295 [6]. Five differentially expressed serum protein spots were identified via 2D gel electrophoresis and mass spectrometry. Immunoglobulin fragment intensity correlated linearly with IGF-1 levels (r² = 0.668, P = 0.002), offering a candidate biomarker panel for GH/IGF-1 axis activation [6].

Sleep-phase GH release and the 2025 circuit data

The largest GH pulse of the 24-hour cycle occurs during NREM slow-wave sleep. A 2025 study in Cell by Ding X, Hwang FJ, Silverman D et al. (DOI 10.1016/j.cell.2025.05.039) mapped the hypothalamic circuit mediating this relationship in mice using fiber photometry and optogenetics [14]. During NREM sleep, GHRH neuron activity moderately increases while somatostatin (SST) neuron activity decreases, shifting the hypothalamic balance toward net GH release. During REM sleep, both GHRH and SST activity surge simultaneously.

For CJC-1295 specifically, this circuit provides mechanistic context for the pharmacodynamic pattern Ionescu and Frohman observed [3]: continuous GHRH-R engagement by the long-acting analog primes somatotrophs across multiple sleep cycles, amplifying their responsiveness to endogenous GHRH surges during NREM — which explains why trough GH rises substantially while the pulse pattern itself is preserved. The somatotrophs are not overridden; they are preconditioned.

GH was also shown in the Ding et al. study to enhance locus coeruleus excitability as a negative feedback signal promoting wakefulness — a nuance relevant to understanding why supraphysiological GH elevation from any source can disrupt sleep architecture over time [14].

Extrapituitary GHRH analog biology

The 2024 Schally AV, Cai R, Zhang X et al. review in Reviews in Endocrine and Metabolic Disorders (DOI 10.1007/s11154-024-09929-2) summarized the GHRH agonist analog therapeutic landscape as of that year [16]. GHRH agonist analogs MR-409 and MR-502 — developed by the Schally laboratory, not the same as CJC-1295 — have shown in preclinical studies:

  • Cardioprotection in rat and swine infarction models: attenuated cardiac hypertrophy and improved myocardial function.
  • Islet survival in rodent diabetes models: increased islet size and improved glucose-responsive insulin secretion.
  • Wound healing: >50% increase in human dermal fibroblast proliferation in vitro and accelerated wound closure in mouse excision models via ERK and AKT signaling pathways [10].
  • Anti-tumor activity in human cancer xenograft models spanning lung, gastric, pancreatic, prostate, breast, colorectal, and ovarian cancer — mediated by direct extrapituitary GHRH-R signaling independent of pituitary GH [16].

All of these findings are preclinical. None are established for CJC-1295 directly in human studies. The GHRH-R distribution data (cardiac myocytes, lymphocytes, gonads, skin, kidney confirmed in the 2025 Halmos et al. receptor review) [13] establishes that the receptor target exists in peripheral tissues for CJC-1295 to engage, but whether CJC-1295 specifically produces these effects at pharmacologically relevant concentrations in humans has not been studied.

Regulatory and anti-doping record

Hennige J, Pepaj M, Hullstein I, and Hemmersbach P (2011, Drug Testing and Analysis, DOI 10.1002/dta.233) confirmed CJC-1295's 29-amino acid sequence by LC-HRMS/MS in an illicitly manufactured pharmaceutical preparation submitted to Norwegian anti-doping authorities [15]. The paper established that the compound was being synthesized and distributed outside clinical trial settings by 2011. WADA added it to the S2 Peptide Hormones prohibited list. Detection in accredited anti-doping labs via LC-HRMS/MS is confirmed [15].

The FDA evaluated CJC-1295 for Section 503A Category 2 classification in 2024 — the regulatory process that determines whether a compound may be compounded by pharmacies under the conditions of Section 503A of the Federal Food, Drug, and Cosmetic Act. The regulatory landscape for compounded peptides continues to evolve; the compound's status in pharmacy practice is not settled.