CJC-1295 and Ipamorelin Research Guide: DAC vs No-DAC and the Blend Explained

CJC-1295 and ipamorelin are two growth hormone secretagogues that act on different receptors on the same pituitary cell: CJC-1295 is a tetrasubstituted GHRH(1-29) analogue that binds the GHRH receptor, while ipamorelin is a selective pentapeptide agonist of the ghrelin receptor GHS-R1a. This guide explains the DAC and no-DAC forms of CJC-1295, the chemistry of ipamorelin, why the two are supplied as a blend, and how to record concentrations for laboratory solution preparation.

Updated 10 September 2026~13 min readReviewed by the GenoPept technical team

What are CJC-1295 and ipamorelin?

CJC-1295 is a synthetic analogue of the first 29 residues of human growth hormone-releasing hormone, engineered for resistance to enzymatic degradation. Ipamorelin is a five-residue synthetic ghrelin mimetic that occupies the growth hormone secretagogue receptor 1a. Neither is growth hormone; both act upstream, on the pituitary somatotroph, to increase release of the hormone the cell already stores.

They are catalogued together because they represent the two halves of the secretagogue field. Everything downstream — GH release, hepatic IGF-I induction, negative feedback — is shared. Everything upstream, from receptor class to second messenger to structural chemistry, is different.

For a laboratory, the practical consequence is that these two compounds behave differently in solution, have different stability profiles, and require separate molar calculations despite often arriving in the same box.

CJC-1295 chemistry: the GRF(1-29) backbone

Native human GHRH is 44 residues long, but the first 29 carry essentially all of the receptor-activating information. That fragment — marketed pharmaceutically as sermorelin — is the starting point for CJC-1295.

Unmodified GRF(1-29) is fragile in serum. Dipeptidyl peptidase-4 removes the N-terminal dipeptide within minutes, and the resulting GRF(3-29) has negligible receptor activity. Two further liabilities exist in the sequence: Asn⁸ is prone to deamidation and Met²⁷ to oxidation, both of which degrade a stored or reconstituted peptide.

The four substitutions

CJC-1295 addresses all three problems at once. Relative to native GHRH(1-29) it substitutes:

1. Ala² → D-Ala². The D-configuration is not recognised by DPP-4, so the N-terminus survives.
2. Asn⁸ → Gln⁸. Removes the asparagine that would otherwise deamidate via a succinimide intermediate.
3. Gly¹⁵ → Ala¹⁵. Stabilises the helical conformation the GHRH receptor recognises.
4. Met²⁷ → Leu²⁷. Eliminates the oxidation-sensitive thioether without changing side-chain bulk appreciably.

These four changes define the peptide sold as both CJC-1295 with DAC and CJC-1295 no DAC. The names differ only by what is attached at the C-terminal end.

DAC vs no-DAC: what the affinity complex does

The drug affinity complex is a maleimidopropionyl group carried on an added Lys³⁰. Maleimides react selectively and rapidly with free thiols, and serum albumin presents an accessible unpaired cysteine. The result is a covalent peptide-albumin conjugate that circulates with the carrier protein rather than being cleared as a small peptide.

That single modification is the whole difference between the two products. The receptor-binding face of the molecule is unchanged; only its residence time in a biological matrix changes.

Teichman and colleagues reported in the Journal of Clinical Endocrinology & Metabolism that single administration of CJC-1295 with DAC to healthy adults produced elevations of GH and IGF-I lasting days rather than minutes. In a companion 2006 paper, Ionescu and Frohman addressed the obvious concern — that continuous GHRH-receptor occupancy might flatten the pulse pattern — and reported that pulsatile GH secretion persisted.

Ipamorelin chemistry and selectivity

Ipamorelin is a pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂. Three of its five positions are non-standard: Aib (2-aminoisobutyric acid) at the N-terminus, D-2-naphthylalanine at position 3, and D-phenylalanine at position 4. The C-terminus is amidated. Every one of those features is a protease countermeasure.

Raun and colleagues published its characterisation in European Journal of Endocrinology in 1998 under the title that has followed it since: the first selective growth hormone secretagogue. In their rodent and swine work, ipamorelin released GH with potency comparable to GHRP-6 but did not produce the parallel rises in adrenocorticotropic hormone, cortisol and prolactin that the earlier hexapeptides caused.

Why the two are studied together

The short answer: they are not redundant. A GHRH-receptor agonist raises cAMP in the somatotroph; a GHS-R1a agonist raises intracellular calcium and simultaneously reduces hypothalamic somatostatin tone. Occupying both receptors produces a larger GH response in published pituitary and whole-animal work than occupying either alone.

There is a second, more subtle rationale. Because GHRH analogues cannot overcome a high somatostatin state, their effect is timing-dependent. GHS-R1a agonists are less constrained in that respect, so the combination widens the window in which a measurable response can be obtained — useful in experimental designs where sampling times are fixed.

Specifications and verified identity data

The three catalogue items differ substantially in mass. Any protocol expressed in nM or µM requires the molecular weight of the specific compound, not of the pairing.

Reconstitution and concentration reference

All three items are supplied lyophilised. The figures below are a concentration reference for preparing laboratory stock solutions; they are not an amount for administration to any person or animal.

1. Equilibrate the vial. Allow the sealed vial to reach room temperature before removing the flip cap, so moisture does not condense on the cake.
2. Add diluent down the wall. Bacteriostatic water is the usual choice for multi-draw stocks. Direct the stream at the glass, not at the cake.
3. Swirl, do not shake. Ipamorelin dissolves quickly; the 29-residue peptides can take a minute or two. Shear and foaming both promote aggregation.
4. Inspect against light. A correct solution is clear and colourless with no visible particulates or fibrils.
5. Aliquot and label. Record compound, batch, diluent, volume and resulting mg/mL on every tube.
6. Convert to molarity per compound. Divide mg/mL by the specific molecular weight — never use a single figure for a blend.

Working with a blended vial

A combined CJC-1295 ipamorelin vial contains two peptides of very different mass in one lyophilised cake. Reconstituting it produces a single solution with two independent molar concentrations, and every downstream calculation has to keep them separate.

Two practical consequences follow. First, the certificate of analysis for a blend reports purity and mass confirmation for each component; read both. Second, an HPLC trace of a blend shows two main peaks rather than one, so “purity” is reported per component, not as a single number for the vial.

What the published evidence does and does not show

CJC-1295 with DAC has published human pharmacokinetic and pharmacodynamic data from the two 2006 JCEM papers cited below. Those studies establish that the compound raises GH and IGF-I and that pulsatility is preserved. They do not establish clinical outcomes, and no late-phase programme for CJC-1295 has been completed.

Ipamorelin’s characterisation rests principally on the 1998 Raun paper and subsequent preclinical work. Its selectivity claim is a preclinical finding in defined species and models, not a general property that can be assumed to transfer.

The synergy argument between GHRH analogues and GHRPs is well supported at the level of GH release in pituitary and animal studies, tracing back to the Bowers hexapeptide work of the 1980s and the receptor identification of Howard and colleagues in 1996. Whether that acute synergy produces any durable change is a separate question the literature has largely not answered.