CJC-1295 With DAC vs Without DAC: What the Drug Affinity Complex Changes

LynxLab · 24 October 2026 · 8 min read

How the drug affinity complex on CJC-1295 works, the 5.8 to 8.1 day half-life Teichman reported in JCEM in 2006, and how Mod GRF 1-29 differs in the lab.

Photo: Tara Winstead, Pexels

Two different molecules are sold under the name CJC-1295. One carries a chemical hook that fastens it to albumin in the bloodstream and keeps it circulating for about a week. The other has no hook, is cleared in hours, and is often labelled Mod GRF 1-29. The shared name hides a real difference, and the US Food and Drug Administration spent part of a December 2024 advisory meeting untangling it.

One name, two molecules

Both versions start from the same 29-amino-acid chain: a modified copy of the first 29 residues of growth hormone-releasing hormone (GHRH). The FDA's briefing document for its Pharmacy Compounding Advisory Committee of 4 December 2024 lists the lighter version as "CJC-1295 (free base)", a 29-residue peptide with a molecular weight of 3367.95 g/mol. The heavier version is the same chain with a maleimidopropionamide-lysine unit added at the C terminus, molecular weight 3647.95 g/mol.

The agency counted at least five distinct substances and nine different names in circulation. "Mod GRF 1-29", "tetra-substituted GRF (1-29)" and "CJC-1295 without DAC" all describe the lighter molecule. "CJC-1295 DAC" and "DAC:GRF" describe the heavier one. Shops add to the confusion by writing the name as CJC 1295, cjc1295 or just CJC, so a listing for cjc 1295 ipamorelin can mean either molecule until the certificate is read.

Anyone comparing a cjc-1295 + ipamorelin vial from one supplier with another needs to know which of the two is inside, and the molecular mass on the certificate of analysis is the quickest way to tell.

What GRF 1-29 is and why four residues were swapped

Native GHRH is 44 amino acids long. Its first 29 residues carry the full biological activity, and the native peptide has a half-life of about seven minutes in blood, according to the background section of Teichman and colleagues' 2006 paper in the Journal of Clinical Endocrinology and Metabolism. That short life is why plain GHRH needs daily or more frequent injection in any clinical setting.

Sermorelin, an unmodified GRF 1-29, was approved in the United States as Geref for short stature in children with growth hormone deficiency. The FDA briefing notes it is the only GH secretagogue of this type ever approved there, and that no such product has been approved for adults.

ConjuChem's chemists in Montreal swapped four amino acids, at positions 2, 8, 15 and 27, to make the chain resist breakdown by dipeptidyl peptidase IV and other proteases (Jetté et al., Endocrinology 2005). The result is the tetra-substituted GRF 1-29. On its own, that is the no-DAC molecule.

Those four substitutions are what make the GHRH analogue in a cjc 1295 ipamorelin blend different from sermorelin before any DAC is considered.

What the drug affinity complex does in the blood

DAC stands for drug affinity complex, ConjuChem's name for a lysine linked to maleimidopropionic acid at the end of the peptide. Maleimide reacts with a free thiol group. Human serum albumin has exactly one, at cysteine 34, so after injection the peptide bonds covalently to the most abundant protein in plasma.

Lucie Jetté and colleagues at ConjuChem published the design in Endocrinology in 2005. They made three maleimido derivatives of hGRF 1-29, conjugated them to human serum albumin, and showed that all three resisted dipeptidyl peptidase IV in vitro and still released growth hormone from cultured rat pituitary cells. In rats, the best candidate, CJC-1295, produced a 4-fold larger GH area under the curve over two hours than unmodified hGRF 1-29 and was still detectable in plasma beyond 72 hours.

Albumin circulates for roughly three weeks, so a peptide fixed to it inherits a long residence time. The peptide is not released later. It stays bound and still reaches its receptor.

That single reaction is the whole point of the DAC form, and the reason the two molecules behave so differently in a living system even though listings for cjc-1295 and ipamorelin for research rarely spell it out.

The Teichman 2006 trial: 5.8 to 8.1 days

The human pharmacokinetics come from one pair of studies. Sam Teichman, Lawrence Frohman and colleagues ran two randomised, placebo-controlled, double-blind ascending-dose trials in healthy adults aged 21 to 61, lasting 28 and 49 days, at two sites. The results appeared in JCEM in March 2006.

After a single subcutaneous injection, mean plasma GH rose 2- to 10-fold for six days or more, and mean IGF-I rose 1.5- to 3-fold for 9 to 11 days. The estimated half-life of CJC-1295 was 5.8 to 8.1 days. After weekly or fortnightly doses, mean IGF-I stayed above baseline for up to 28 days, and the authors described evidence of a cumulative effect.

Single doses studied: four ascending levels, with 30 and 60 micrograms per kg best tolerated
GH rise: 2- to 10-fold, lasting 6 days or more
IGF-I rise: 1.5- to 3-fold, lasting 9 to 11 days
Serious adverse reactions: none reported in either study

Every one of those numbers belongs to the DAC molecule. There is no equivalent published human pharmacokinetic study of Mod GRF 1-29, which is worth remembering when a cjc-1295 + ipamorelin uk listing borrows the Teichman figures for a product that may not contain the DAC.

A week-long signal did not flatten GH pulses

Growth hormone is normally released in eight to ten pulses a day. A GHRH analogue sitting in the blood for a week might be expected to swamp that rhythm. Madalina Ionescu and Lawrence Frohman tested the question in a paper published in JCEM in December 2006.

They sampled blood every 20 minutes overnight for 12 hours in healthy men aged 20 to 40, before and one week after a single CJC-1295 injection. GH secretion increased with pulsatility preserved. The frequency and size of the pulses were unchanged, while trough and mean GH rose, and IGF-I increased by just under 50%. The authors described the compound as binding permanently to albumin with a half-life of eight days.

The finding is specific to the DAC form. Mod GRF 1-29 is gone within hours, so the question of whether a continuous signal disturbs pulsatility does not arise for it in the same way. Researchers who buy cjc-1295 + ipamorelin for a study of GH rhythm are therefore looking at two different experimental designs depending on the form.

What the difference means at the bench

In a culture dish, the DAC adds little. Jetté's team showed the albumin conjugates were active on pituitary cells, but a plate has no circulation to extend. What a cell assay measures is the receptor pharmacology of the 29-residue core, which the two forms share.

In an animal, they are different experiments. Mod GRF 1-29 gives a short pulse of GHRH receptor activation. The DAC form gives a plateau that lasts days and accumulates with repeated dosing. A protocol written for one does not transfer to the other, and the Teichman and Ionescu data describe only the DAC molecule.

Naming errors are a documented safety problem, not a pedantic one. The FDA briefing cites Henninge and colleagues (2010), who identified a preparation seized by Norwegian police in 2009 as containing a CJC-1295 sequence, and warns that inconsistent names mean a person "may be dosed with a different BDS than the physician ordered". For a research buyer the lesson is the same: read the mass spectrometry result on the lab reports rather than the label.

LynxLab stocks cjc-1295 ipamorelin 5+5mg for research use as a single 5mg + 5mg blend vial at £42.99, with both peptides tested to 99% purity and the lab report on the product page.

Where the regulators stand in 2026

On 4 December 2024 the FDA's Pharmacy Compounding Advisory Committee voted on five CJC-1295 substances nominated for the 503A bulks list, the list of ingredients US pharmacies may compound from. According to the final summary minutes, CJC-1295 free base was rejected 13 to 0, CJC-1295 acetate 12 to 1, and all three DAC forms 13 to 0 each.

The FDA's page on bulk substances that may present significant safety risks, current as of 22 April 2026, now lists CJC-1295 among substances whose nominations were withdrawn. The agency's note says compounded CJC-1295 "may pose risk for immunogenicity" and that it had "identified serious adverse events associated with CJC-1295 including increased heart rate and systemic vasodilatory reaction". Neither form is an approved medicine in any country.

In the UK, CJC-1295 is not a licensed medicine and is sold for laboratory research only. The 2026 WADA list applies to both forms, since the class covers GHRH "and its analogues". For the longer story of both peptides, including the 2006 trial that ended ConjuChem's programme, see the research record of ipamorelin and CJC-1295.

Frequently asked questions

Is CJC-1295 without DAC the same as Mod GRF 1-29?

Yes. Both names describe the 29-amino-acid GHRH analogue with substitutions at positions 2, 8, 15 and 27 and no albumin-binding group. The FDA's December 2024 briefing document calls it "CJC-1295 (free base)" and gives a molecular weight of 3367.95 g/mol, against 3647.95 g/mol for the DAC version.

How long does CJC-1295 with DAC last in the body?

Teichman and colleagues estimated a half-life of 5.8 to 8.1 days after a single subcutaneous dose in healthy adults (JCEM, 2006). GH stayed raised for six days or more and IGF-I for 9 to 11 days. Ionescu and Frohman later quoted a half-life of eight days.

Why did ConjuChem add the DAC to GRF 1-29?

Native GHRH has a half-life of around seven minutes, which rules out weekly dosing. ConjuChem's maleimidopropionic acid group reacts with cysteine 34 on serum albumin after injection, so the peptide circulates for as long as the albumin does. Jetté's 2005 rat study found the conjugate detectable beyond 72 hours.

Is CJC-1295 a licensed medicine in the UK?

No. It has never been approved as a medicine in the UK, the US or the EU, and ConjuChem's clinical programme stopped in 2006. It is sold in the UK for laboratory research only, and it appears by name on the WADA 2026 Prohibited List.

Sources

Research use only

CJC-1295 + Ipamorelin from LynxLab

5+5mg vials from £42.99. ≥99% purity, lab report on the page. Same-day dispatch, UK stock.

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