CJC-1295 and Ipamorelin: Why the Two Peptides Appear Together in the Literature

Introduction

CJC-1295 and ipamorelin are two unrelated synthetic peptides that act on two different receptors on the pituitary cells that secrete growth hormone. CJC-1295 is a 29-amino-acid analogue of growth hormone-releasing hormone (GHRH) that binds the GHRH receptor, and ipamorelin is a pentapeptide growth hormone-releasing peptide (GHRP) that binds the ghrelin receptor GHS-R1a; no published clinical trial has studied the two together.

The phrase "CJC-1295 ipamorelin" does not name a single compound or a published study. This article classifies the two peptides, explains why two receptor classes are discussed side by side, reports with attribution what the literature on GHRH plus GHRP co-administration found, and states what has and has not been trialed.

Key facts

• CJC-1295 is a tetrasubstituted analogue of human GRF(1-29) identified by Jetté and colleagues at ConjuChem (Montreal) in 2005 [1].
• The DAC form of CJC-1295 carries an N-epsilon-3-maleimidopropionamide lysine that bonds to cysteine-34 of serum albumin; Teichman and colleagues estimated its half-life at 5.8 to 8.1 days in healthy adults [2].
• Ipamorelin is the pentapeptide Aib-His-D-2-Nal-D-Phe-Lys-NH2, published by Raun and colleagues at Novo Nordisk in 1998 [3].
• Ipamorelin acts at GHS-R1a, cloned by Howard and colleagues in 1996 [4]; its natural ligand ghrelin was identified in 1999 [5].
• Bowers and colleagues reported in 1990 that GHRP-6 with GHRH(1-44) produced synergistic growth hormone release in 18 normal men [6].
• Cheng and colleagues reported in 1989 that GHRP-6 and GRF act on rat pituitary cells through different receptors [7].
• A PubMed title-and-abstract search for both names returns no clinical trial of the pair, and ClinicalTrials.gov lists no registered study of the two together [8, 9].
• Neither CJC-1295 nor ipamorelin is an FDA-approved drug; both are supplied only as research-use-only reference materials [10].

What are CJC-1295 and ipamorelin?

CJC-1295 is a modified fragment of a human hormone, and ipamorelin is a fully synthetic sequence with no natural counterpart. The two were developed by different companies, in different decades, for different receptors.

CJC-1295 originated in a bioconjugation program at ConjuChem. Jetté and colleagues reported in Endocrinology in 2005 that they had prepared maleimido derivatives of human GRF(1-29), the active N-terminal fragment of GHRH, and that the best of them, CJC-1295, was a tetrasubstituted GRF(1-29) with an added maleimidopropionamide-lysine at the C-terminus that bound serum albumin in rats and remained detectable in plasma beyond 72 hours [1]. The four substitutions (D-Ala2, Gln8, Ala15, Leu27) were introduced for resistance to dipeptidyl peptidase-IV cleavage [1].

Ipamorelin came from the GHRP lineage that began with Bowers and Momany in the early 1980s [11]. Raun and colleagues at Novo Nordisk described it in the European Journal of Endocrinology in 1998 as a pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, that released growth hormone from rat pituitary cells and in rats and swine with potency similar to GHRP-6, while not raising ACTH or cortisol significantly in swine [3]. Ipamorelin is a ligand of GHS-R1a [3, 4]; the compound is covered question by question in the ipamorelin FAQ.

CJC-1295 is not a GHRP, and ipamorelin is not a GHRH analogue. The two names are frequently written as one phrase, but they refer to two distinct molecules with a 24-residue difference in length and no shared receptor.

Why do CJC-1295 and ipamorelin appear together in search and in the literature?

The pairing exists because growth hormone secretion is regulated through two separate receptor systems, and the literature on those two systems has been intertwined since the first synthetic GHRPs were characterized. GHRH, a hypothalamic hormone, acts on the GHRH receptor, a class B G protein-coupled receptor on pituitary somatotrophs. The GHRPs act on GHS-R1a, a class A G protein-coupled receptor that Howard and colleagues cloned in 1996 [4] and that Kojima and colleagues showed in 1999 to be the receptor for the stomach peptide ghrelin [5].

Cheng and colleagues at Merck established in 1989 that the two systems are distinct: in rat pituitary cells, GHRP-6 release of growth hormone was not blocked by a GRF antagonist, and GRF raised intracellular cAMP whereas GHRP-6 did not [7]. Bowers and colleagues extended the observation to humans in 1990 [6], and Ghigo, Arvat and colleagues reviewed the field in 1997 [12].

Because CJC-1295 is a GHRH-receptor ligand and ipamorelin is a GHS-R1a ligand, they are the two compounds most often discussed as modern representatives of each arm. The class distinction is explained in growth hormone secretagogues vs GHRH analogues, and the structural comparison in CJC-1295 vs ipamorelin.

Findings from research models do not establish safety or efficacy in humans. Sparta Labs makes no claims about the use of any compound discussed in this article.

What is the difference between CJC-1295 with DAC and without DAC?

The difference is a single chemical group at the C-terminus. CJC-1295 with DAC carries the N-epsilon-3-maleimidopropionamide derivative of lysine that Jetté and colleagues described, which forms a covalent bond with the free thiol of cysteine-34 on circulating serum albumin [1].

Teichman and colleagues reported in 2006 that in healthy adults this conjugation gave an estimated half-life of 5.8 to 8.1 days, with growth hormone concentrations raised for 6 days or more after a single subcutaneous administration in their two placebo-controlled trials [2]. Ionescu and Frohman reported in the same year that pulsatile growth hormone secretion persisted during continuous stimulation by CJC-1295 [13].

"CJC-1295 without DAC" is a catalog name, not a name used in the primary literature. It designates the same tetrasubstituted GRF(1-29) sequence (D-Ala2, Gln8, Ala15, Leu27) without the maleimidopropionamide-lysine, so it cannot bind albumin and is expected to behave as a short-lived GHRH analogue in the manner of the parent GRF(1-29) fragment [1]. The two forms are compared residue by residue in CJC-1295 with DAC vs without DAC.

What has published research reported on GHRH analogues administered with GHRPs?

Published research on co-administration concerns GHRH or GRF(1-29) given with GHRP-6, hexarelin or ghrelin; it does not concern CJC-1295 or ipamorelin. The studies are listed in the table and described below as attributed reporting of what each trial did and found.

Study	Year	Compounds	Model	What was reported
Cheng et al. [7]	1989	GHRP-6 + GRF	Rat primary pituitary cells	Synergistic GH release at maximal concentrations; GRF raised cAMP, GHRP-6 did not; different receptors
Bowers et al. [6]	1990	GHRP-6 + GHRH(1-44)	18 normal men, intravenous bolus	Submaximal GHRP-6 with GHRH released GH synergistically; prolactin and cortisol rose about 2-fold only at the highest GHRP-6 amount
Popovic et al. [14]	1995	GHRP-6 + GHRH	12 patients with hypothalamopituitary disconnection, 11 controls	Synergy present in controls; GHRP-6 response and synergy absent after disconnection
Micic et al. [15]	1995	GHRP-6 + GHRH	9 young and 9 older healthy adults	Combined response greater than either alone in both groups; not reduced in older group
Arvat et al. [16]	2001	Ghrelin + GHRH; ghrelin + hexarelin	7 healthy men	Ghrelin with GHRH synergistic; ghrelin with hexarelin not additive
Teichman et al. [2]	2006	CJC-1295 alone	Healthy adults, two placebo-controlled trials	Half-life 5.8 to 8.1 days; GH raised for 6 days or more after a single administration
Raun et al. [3]	1998	Ipamorelin alone	Rat pituitary cells, rats, swine	GH release comparable to GHRP-6; no significant ACTH or cortisol rise in swine

Bowers and colleagues gave GHRP-6 by intravenous bolus to 18 normal men, alone and with GHRH(1-44), and reported that submaximal GHRP-6 with GHRH stimulated growth hormone release synergistically; they concluded that GHRP and GHRH act independently [6]. Popovic and colleagues reported that in 12 patients with functional stalk section the GHRP-6 response was blocked and the synergy seen in controls was lost, which they read as evidence of a hypothalamic site of GHRP-6 action [14].

Arvat and colleagues reported in 2001 that in seven young men ghrelin with GHRH-29 had a synergistic effect on growth hormone secretion, whereas ghrelin with hexarelin did not add to ghrelin alone [16]. None of these trials used CJC-1295 or ipamorelin; their relevance is that they established the GHRH receptor and GHS-R1a as separate systems. A parallel discussion for tesamorelin appears in tesamorelin and ipamorelin explained.

Has the CJC-1295 and ipamorelin combination itself been studied in a clinical trial?

No. A PubMed search for "ipamorelin" and "CJC-1295" in the title or abstract returned only narrative reviews, and no primary clinical study of the pair [8]. A ClinicalTrials.gov search for the two names together returned no registered study [9]. The pair has not been the subject of a published randomized trial, a pharmacokinetic study, or a registered investigation.

Each compound has been studied separately. CJC-1295 was examined in the healthy-adult trials of Teichman and colleagues [2] and Ionescu and Frohman [13], and ConjuChem registered one phase 2 study that is listed as terminated [17]. Ipamorelin was examined in the volunteer study of Gobburu and colleagues, which reported a terminal half-life of about 2 hours [18], and in the Helsinn phase 2 trial published by Beck and colleagues, which did not reach statistical significance on its primary endpoint [19].

Sigalos and Pastuszak reviewed growth hormone secretagogues as a class in 2018 and noted that few long-term, rigorously controlled studies exist [20]. No review identified by the search reports controlled data on CJC-1295 and ipamorelin administered to the same participants.

How are the two supplied as research materials?

Sparta Labs supplies the compounds separately, as research-use-only reference materials, and this article describes the published literature and not a procedure for combining them. Research-grade CJC-1295 with DAC, CJC-1295 without DAC and ipamorelin are three distinct catalog items, each produced by solid-phase peptide synthesis, purified by reversed-phase HPLC, and documented on its own certificate of analysis reporting chromatographic purity and mass-spectrometric identity.

None of the three is an FDA-approved drug, and none is the investigational drug substance used in the trials cited above [10]. They are laboratory reagents for research that does not involve human administration.

Summary

CJC-1295 is a tetrasubstituted GRF(1-29) analogue acting at the GHRH receptor, identified by Jetté and colleagues in 2005; its DAC form binds albumin for a multi-day half-life. Ipamorelin is a Novo Nordisk pentapeptide acting at the ghrelin receptor GHS-R1a, published by Raun in 1998. The two appear together because Cheng (1989), Bowers (1990), Popovic (1995) and Arvat (2001) reported synergistic growth hormone release from GHRH plus a GHRP-class ligand. Those studies used GHRP-6, hexarelin or ghrelin; no trial has examined the pair. Sparta Labs supplies the compounds separately as research-use-only materials.

References

1. Jetté L, Léger R, Thibaudeau K, Benquet C, Robitaille M, Pellerin I, 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. 2005;146(7):3052-3058. PMID: 15817669. DOI: 10.1210/en.2004-1286
2. Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA. 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. 2006;91(3):799-805. PMID: 16352683. DOI: 10.1210/jc.2005-1536
3. Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561. PMID: 9849822. DOI: 10.1530/eje.0.1390552
4. Howard AD, Feighner SD, Cully DF, Arena JP, Liberator PA, Rosenblum CI, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996;273(5277):974-977. PMID: 8688086. DOI: 10.1126/science.273.5277.974
5. Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402(6762):656-660. PMID: 10604470. DOI: 10.1038/45230
6. Bowers CY, Reynolds GA, Durham D, Barrera CM, Pezzoli SS, Thorner MO. Growth hormone (GH)-releasing peptide stimulates GH release in normal men and acts synergistically with GH-releasing hormone. J Clin Endocrinol Metab. 1990;70(4):975-982. PMID: 2108187. DOI: 10.1210/jcem-70-4-975
7. Cheng K, Chan WW, Barreto A Jr, Convey EM, Smith RG. The synergistic effects of His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 on growth hormone (GH)-releasing factor-stimulated GH release and intracellular adenosine 3',5'-monophosphate accumulation in rat primary pituitary cell culture. Endocrinology. 1989;124(6):2791-2798. PMID: 2541999. DOI: 10.1210/endo-124-6-2791
8. National Library of Medicine. PubMed search: ipamorelin[tiab] AND CJC-1295[tiab]. Searched 11 September 2026. View on PubMed
9. National Library of Medicine. ClinicalTrials.gov search: ipamorelin AND CJC-1295. Searched 11 September 2026; no studies returned. ClinicalTrials.gov record
10. U.S. Food and Drug Administration. Drugs@FDA: FDA-Approved Drugs (database). Source: accessdata.fda.gov
11. Bowers CY, Momany FA, Reynolds GA, Hong A. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology. 1984;114(5):1537-1545. PMID: 6714155. DOI: 10.1210/endo-114-5-1537
12. Ghigo E, Arvat E, Muccioli G, Camanni F. Growth hormone-releasing peptides. Eur J Endocrinol. 1997;136(5):445-460. PMID: 9186261. DOI: 10.1530/eje.0.1360445
13. 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. 2006;91(12):4792-4797. PMID: 17018654. DOI: 10.1210/jc.2006-1702
14. Popovic V, Damjanovic S, Micic D, Djurovic M, Dieguez C, Casanueva FF. Blocked growth hormone-releasing peptide (GHRP-6)-induced GH secretion and absence of the synergic action of GHRP-6 plus GH-releasing hormone in patients with hypothalamopituitary disconnection: evidence that GHRP-6 main action is exerted at the hypothalamic level. J Clin Endocrinol Metab. 1995;80(3):942-947. PMID: 7883854. DOI: 10.1210/jcem.80.3.7883854
15. Micic D, Popovic V, Kendereski A, Macut D, Casanueva FF, Dieguez C. Growth hormone secretion after the administration of GHRP-6 or GHRH combined with GHRP-6 does not decline in late adulthood. Clin Endocrinol (Oxf). 1995;42(2):191-194. PMID: 7734029. DOI: 10.1111/j.1365-2265.1995.tb01861.x
16. Arvat E, Maccario M, Di Vito L, Broglio F, Benso A, Gottero C, et al. Endocrine activities of ghrelin, a natural growth hormone secretagogue (GHS), in humans: comparison and interactions with hexarelin, a nonnatural peptidyl GHS, and GH-releasing hormone. J Clin Endocrinol Metab. 2001;86(3):1169-1174. PMID: 11238504. DOI: 10.1210/jcem.86.3.7314
17. ConjuChem. A Study to Evaluate CJC 1295 in HIV Patients With Visceral Obesity. ClinicalTrials.gov identifier NCT00267527. Phase 2, listed as terminated. ClinicalTrials.gov record
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19. 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. 2014;29(12):1527-1534. PMID: 25331030. DOI: 10.1007/s00384-014-2030-8
20. Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev. 2018;6(1):45-53. PMID: 28400207. DOI: 10.1016/j.sxmr.2017.02.004