CJC-1295 and Ipamorelin: Why Research Pairs a GHRH Analogue with a Ghrelin Receptor Agonist

CJC-1295 and ipamorelin are often discussed as if they were one compound. They came from different drug programmes, act on different receptors and have very differently shaped evidence bases. This article covers the physiology behind the pairing, what the DAC actually is, where ipamorelin's selectivity claim comes from, and how much weight the data will bear.

Two signals to the same pituitary cell

Growth hormone (GH) is released in pulses from somatotroph cells in the anterior pituitary. Hypothalamic GHRH stimulates release, somatostatin suppresses it, and the insulin-like growth factor 1 (IGF-1) that GH induces feeds back to damp the system.

A second stimulatory pathway was found by working backwards from synthetic peptides such as GHRP-6, which released GH by a mechanism separate from GHRH before their target was known (Müller et al., 2015). The receptor was cloned in 1996 (Howard et al., 1996) and its natural ligand identified in 1999: ghrelin, a 28-residue stomach peptide that needs an octanoyl group on serine 3 to be active (Kojima et al., 1999). The receptor, GHS-R1a, sits on somatotrophs and on hypothalamic GHRH neurons (Müller et al., 2015).

Because the receptors are distinct, they can be stimulated together, and in people the effect is greater than additive. In a study of 18 healthy men, submaximal amounts of GHRP-6 combined with GHRH released GH synergistically (Bowers et al., 1990), and the same was later shown for ghrelin with GHRH (Hataya et al., 2001). That interaction is the scientific basis for the pairing.

CJC-1295 and the drug affinity complex

Native GHRH is short-lived. In healthy volunteers, intact GHRH(1-44) had a plasma half-life of about seven minutes, cleaved between residues 2 and 3 into an essentially inactive fragment (Frohman et al., 1986) by dipeptidyl peptidase IV (DPP-IV), a cut that a D-amino acid at position 1 or 2 blocks (Frohman et al., 1989).

CJC-1295, developed by ConjuChem in Montreal, starts from GHRH(1-29), the fragment also known as sermorelin (see our sermorelin research overview), with four substitutions: D-alanine at position 2, glutamine at 8, alanine at 15 and leucine at 27 (US FDA, 2024). A C-terminal lysine bearing a maleimidopropionamide group was then added. This is the drug affinity complex, or DAC: in the circulation the maleimide bonds to cysteine 34 of serum albumin, so the peptide travels attached to the most abundant protein in plasma (Jetté et al., 2005).

In rats, CJC-1295 gave a fourfold larger two-hour GH response than unmodified GHRH(1-29) and persisted in plasma beyond 72 hours (Jetté et al., 2005). In two randomised, placebo-controlled trials in healthy adults, a single injection raised mean GH two- to tenfold for at least six days and IGF-1 1.5- to threefold for 9 to 11 days, with an estimated half-life of 5.8 to 8.1 days (Teichman et al., 2006). Overnight sampling in healthy men showed that GH pulses kept their frequency and size while trough levels rose 7.5-fold and IGF-1 rose 45% (Ionescu and Frohman, 2006). The DAC form raises the floor beneath the pulses rather than replacing them. In mice lacking the GHRH gene, daily CJC-1295 normalised growth over five weeks (Alba et al., 2006).

With DAC versus without DAC

Much of the confusion is a naming problem. Every published human study used the DAC form. The peptide sold as "CJC-1295 without DAC", or Modified GRF (1-29), is the same tetrasubstituted 29-residue sequence without the lysine and maleimide, so it cannot bind albumin. It first appears in the literature in 2010, when Norway's doping control laboratory found this 29-residue amidated peptide in an unidentified seized preparation (Henninge et al., 2010; US FDA, 2024). The US FDA treats the two as distinct active moieties and flags the inconsistent naming as a risk in itself (US FDA, 2024).

Molecular weights are from the FDA review (US FDA, 2024); the gap of about 280 means mass spectrometry separates the two forms easily. The unconjugated peptide's D-alanine should resist DPP-IV, but its half-life and effects in humans have never been reported in a controlled study (Dominikowski et al., 2026).

Ipamorelin and the selectivity question

Ipamorelin came from a Novo Nordisk chemistry programme. It is a pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, derived from the GHRP-1 series, and in rat pituitary cells it released GH with potency similar to GHRP-6, acting through a GHRP-like receptor rather than the GHRH receptor (Raun et al., 1998).

Its selectivity claim comes mainly from swine experiments in that 1998 report. GHRP-6 and GHRP-2 raised ACTH and cortisol; ipamorelin did not, even at more than 200 times the amount needed for half-maximal GH release, and none of the compounds changed FSH, LH, prolactin or TSH (Raun et al., 1998). Older peptides do affect other hormones in people: in healthy men, the highest GHRP-6 amount tested roughly doubled prolactin and cortisol (Bowers et al., 1990).

Two caveats apply. The selectivity is largely an animal finding: the human pharmacology study in healthy men, which found a single GH peak at about 40 minutes and a half-life of about two hours, measured ipamorelin and GH concentrations with no comparator secretagogue (Gobburu et al., 1999), and we found no published head-to-head human comparison with the older peptides. And selectivity concerns pituitary hormones, not everything the receptor does. GHS-R1a is also present in hypothalamic feeding circuits (Müller et al., 2015), and in mice ipamorelin increased body fat, including in GH-deficient animals, pointing to actions independent of GH (Lall et al., 2001).

The wider animal and clinical record

Most remaining ipamorelin data are from rodents. In adult female rats it increased longitudinal bone growth (Johansen et al., 1999) and bone mineral content, the latter explained by larger rather than denser bones (Svensson et al., 2000). In a rat model of postoperative ileus it shortened the time to first bowel movement (Venkova et al., 2009). That gut finding is the only one tested in patients: a phase 2 trial in 114 adults after bowel resection found no significant difference from placebo in time to first tolerated meal (p = 0.15) (Beck et al., 2014). A follow-on phase 2 study of 320 patients, completed in 2014, has no posted results and no peer-reviewed report that we could find (NCT01280344).

Why research pairs them

The pairing rests on three verified pieces: the two receptor pathways are synergistic in people (Bowers et al., 1990; Hataya et al., 2001), ipamorelin was the first ghrelin receptor agonist reported to match GHRH's selectivity for GH, in swine (Raun et al., 1998), and CJC-1295 offers a stabilised GHRH receptor agonist in short-acting or albumin-bound form.

The fourth piece, a study of the combination, does not exist. We found no peer-reviewed study of CJC-1295 in either form together with ipamorelin, and a 2026 review described the case for the pairing as largely anecdotal (Dominikowski et al., 2026). Synergy was shown with other molecules in single-session tests; that it holds for these two over longer periods is a reasonable hypothesis, not a result. Nor has any study compared the continuous signal of the DAC form with the brief one expected from the unconjugated peptide as a partner for ipamorelin.

An honest evidence assessment

Safety data are equally limited. The CJC-1295 trials reported injection-site reactions, headache, diarrhoea and transient flushing with low blood pressure, mostly at higher exposures, and the overnight study noted a rise in heart rate (Teichman et al., 2006; US FDA, 2024). The only patient trial, a ConjuChem phase 2 study in HIV-associated visceral obesity, was terminated in 2006 after a participant died of a myocardial infarction that the attending physician attributed most likely to undiagnosed coronary disease; its results were never published (NCT00267527; US FDA, 2024). In 2024 the FDA reviewed every form of CJC-1295 for its pharmacy compounding list and concluded that its criteria weighed against inclusion (US FDA, 2024).

In short: the physiology is sound and well replicated, the compound-level data are early and drawn from healthy volunteers or rodents, and the combination is untested.

Where these compounds sit at Peptx

Peptx supplies both compounds, and a CJC-1295 and ipamorelin blend, for laboratory research. UK stock and pricing are on the ipamorelin UK page and the CJC-1295 UK page, with independent lab tests in the COA library. Neither compound is an authorised medicine in the UK, EU or US, and both are sold strictly for research use, not for human consumption.

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