CJC-1295 vs Ipamorelin: Mechanism, Half-Life and Published Research

How is growth hormone release regulated?

Pituitary GH secretion is controlled by more than one signal. Growth-hormone-releasing hormone (GHRH) from the hypothalamus acts on its own receptor. A second receptor, the growth hormone secretagogue receptor (GHS-R), was cloned in 1996 from pituitary and hypothalamus and shown to be the target of synthetic GH secretagogues ^[1]. Its natural ligand, ghrelin, was identified in 1999 as a 28-amino-acid acylated peptide from the stomach, establishing that GH release can be regulated through a pathway distinct from GHRH ^[2].

CJC-1295 and Ipamorelin sit on opposite sides of this picture: CJC-1295 is a GHRH-receptor agonist, while Ipamorelin is a GHS-R (ghrelin-receptor) agonist. That difference explains most of the comparison below.

What is CJC-1295?

CJC-1295 is a synthetic analog of GHRH(1-29), the active fragment of GHRH. In the original description, researchers attached a reactive maleimide group to a tetrasubstituted hGRF(1-29) so that the peptide bonds covalently to serum albumin after administration. The albumin-bound conjugates were more stable against the enzyme dipeptidyl peptidase-IV in vitro, and in rats CJC-1295 remained present in plasma beyond 72 hours, with an immunoreactive species detected on the albumin band ^[3].

Research-peptide listings label this albumin-binding form "CJC-1295 with DAC". The extended half-life findings below were measured for this albumin-binding form. Products sold as "CJC-1295 without DAC" lack that group, so the long-acting data should not be assumed to apply to them.

What is Ipamorelin?

Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) developed at Novo Nordisk and described in 1998 as "the first selective growth hormone secretagogue" ^[6]. In rat pituitary cells it released GH with potency and efficacy similar to the older secretagogue GHRP-6, and antagonist profiling showed it acts through a GHRP-like receptor — the ghrelin receptor pathway ^[6].

Its distinguishing finding is selectivity. In swine, none of the secretagogues tested changed FSH, LH, prolactin or TSH; GHRP-6 and GHRP-2 raised ACTH and cortisol, but Ipamorelin did not raise ACTH or cortisol beyond the levels seen with GHRH stimulation, even at doses more than 200-fold above its ED50 for GH release ^[6].

CJC-1295 vs Ipamorelin at a glance

How do the half-lives of CJC-1295 and Ipamorelin compare?

They differ by roughly two orders of magnitude. In two randomized, placebo-controlled, double-blind trials in healthy adults aged 21–61, the estimated half-life of CJC-1295 was 5.8–8.1 days ^[4]. In a pharmacokinetic study in healthy male volunteers, Ipamorelin showed dose-proportional kinetics with a short terminal half-life of 2 hours ^[7].

GHRH itself is limited by a short duration of action, which was the stated motivation for developing a long-acting analog ^[4]. CJC-1295's long half-life comes from albumin binding ^[3], not from the GHRH(1-29) sequence alone.

What has research found about CJC-1295?

• In healthy adults, a single administration produced dose-dependent increases in mean plasma GH of 2- to 10-fold lasting 6 days or more, and in mean IGF-I of 1.5- to 3-fold for 9–11 days. With repeated administration, mean IGF-I stayed above baseline for up to 28 days, and no serious adverse reactions were reported ^[4].
• A follow-up study sampled GH every 20 minutes overnight in healthy men. One week after CJC-1295, GH pulse frequency and magnitude were unchanged, but trough (basal) GH rose 7.5-fold, mean GH by 46% and IGF-I by 45% ^[5]. The authors concluded that continuous GHRH stimulation increased GH secretion while preserving its pulsatile pattern.
• In rats, CJC-1295 produced a 4-fold larger GH area under the curve over 2 hours than unmodified hGRF(1-29) ^[3].

The pulsatility result matters for how CJC-1295 is interpreted in research. GH is normally released in pulses, and pulsatile secretion is considered important for many of the hormone's physiological effects ^[5]. A long-acting GHRH analog could, in principle, have flattened that pattern into a constant signal. Instead, the study found the pulse pattern intact while the baseline between pulses rose. Interestingly, the IGF-I increase did not correlate with any individual GH secretion parameter; the authors pointed to the large rise in trough GH as the likely driver of the IGF-I effect ^[5].

What has research found about Ipamorelin?

• Pharmacology: GH release in rat pituitary cells, anesthetized rats and conscious swine, with potency comparable to GHRP-6 and selectivity for GH over ACTH and cortisol ^[6].
• Human PK/PD: each exposure produced a single episode of GH release with a peak at about 0.67 hours, followed by exponential decline; variability between individuals was larger for the GH response than for the drug's kinetics ^[7].
• Clinical research: a multicenter Phase 2, randomized, placebo-controlled trial tested Ipamorelin for post-operative ileus after bowel resection (114 patients analyzed). It was well tolerated, but there were no significant differences from placebo in the key or secondary efficacy endpoints ^[8].

That last result is a useful reminder: activity at a receptor in pharmacology studies does not guarantee an effect on a clinical endpoint. Neither compound is an approved drug.

Why are CJC-1295 and Ipamorelin studied together?

Because they act through different receptors — the GHRH receptor and the ghrelin receptor, which represent distinct mechanisms for regulating GH release ^[2] — the two are frequently paired in GH-axis research designs. The published human data summarized above come from studies of each compound on its own; we are not aware of a peer-reviewed clinical study of the combination, so claims about how the pair performs together should be treated with caution.

ResearchChem carries the pairing as the CJC-1295 + Ipamorelin stack (5mg + 5mg), Ipamorelin on its own (10mg), and Tesamorelin, another GHRH analog that is often compared with this stack. Each is listed at 99.6% HPLC purity and stored at -20°C as a lyophilized powder; the certificate of analysis for any lot is available on request — see how to read a peptide COA.

All ResearchChem products are laboratory reagents for in-vitro research use only. They are not for human or veterinary use, and nothing in this article is medical advice or guidance on use.

Frequently asked questions

What is the difference between CJC-1295 and Ipamorelin?

CJC-1295 is a GHRH analog that acts on the GHRH receptor and, in its albumin-binding form, has a half-life of about 6–8 days. Ipamorelin is a pentapeptide ghrelin-receptor agonist with a half-life of about 2 hours.

What is the half-life of CJC-1295?

In healthy-adult trials of the albumin-binding (DAC) form, the estimated half-life was 5.8–8.1 days. That figure should not be assumed for CJC-1295 without DAC, which lacks the albumin-binding group.

What is the half-life of Ipamorelin?

A pharmacokinetic study in healthy volunteers reported a terminal half-life of about 2 hours.

Why is Ipamorelin called selective?

In the 1998 pharmacology study, Ipamorelin released GH without raising ACTH or cortisol above GHRH levels, unlike GHRP-6 and GHRP-2, and none of the secretagogues tested changed FSH, LH, prolactin or TSH.

Does CJC-1295 stop natural GH pulses?

Not in the published study. Overnight sampling in healthy men one week after CJC-1295 showed unchanged GH pulse frequency and magnitude, with a 7.5-fold rise in trough GH between pulses.

Are CJC-1295 or Ipamorelin approved drugs?

No. Both have been studied in clinical research, but neither is an approved medicine. ResearchChem sells them strictly as research-use-only laboratory reagents.

Cited studies

1. Howard AD, Feighner SD, Cully DF, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 273(5277):974–977 (1996). PubMed 8688086 DOI
2. Kojima M, Hosoda H, Date Y, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 402(6762):656–660 (1999). PubMed 10604470 DOI
3. Jetté L, Léger R, Thibaudeau K, et al. 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. Endocrinology. 146(7):3052–3058 (2005). PubMed 15817669 DOI
4. Teichman SL, Neale A, Lawrence B, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. J Clin Endocrinol Metab. 91(3):799–805 (2006). PubMed 16352683 DOI
5. Ionescu M, Frohman LA. Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. J Clin Endocrinol Metab. 91(12):4792–4797 (2006). PubMed 17018654 DOI
6. Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 139(5):552–561 (1998). PubMed 9849822 DOI
7. Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. 16(9):1412–1416 (1999). PubMed 10496658 DOI
8. Beck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis. 29(12):1527–1534 (2014). PubMed 25331030 DOI

Related compounds

• CJC-1295 + Ipamorelin — GH Peptide Stack
• Ipamorelin — GH Secretagogue
• Tesamorelin — GHRH Analog

Keep reading

• How to Read a Peptide Certificate of Analysis (COA)
• HPLC Peptide Purity Explained: What a 99.6% Result Means