What the DAC is
Both molecules descend from the 1-29 fragment of human growth-hormone-releasing hormone, the shortest piece of the 44-residue hormone that keeps full activity [6]. ConjuChem's chemists in Montreal first made that fragment harder to cut by swapping four residues (D-alanine at 2, glutamine at 8, alanine at 15, leucine at 27). In the laboratory, its albumin conjugates resisted dipeptidyl peptidase IV [3].
Then they added a thirtieth residue, a lysine carrying an N-epsilon-3-maleimidopropionamide group. The maleimide reacts with the one free thiol on serum albumin, cysteine 34, and from then on the peptide travels as an albumin conjugate. In rats, a Western blot found the peptide on the albumin band 15 minutes after injection, and CJC-1295 was still present in plasma beyond 72 hours [3].
"DAC" stands for Drug Affinity Complex, ConjuChem's trade name for that tail. Remove it and what remains is the 29-residue tetrasubstituted analogue. The literature never gave the tail-less peptide a name, because ConjuChem did not develop it as a product, and the forum name Mod GRF 1-29 filled the gap. The tail weighs 279.4 daltons, the difference between the two masses in Table 1.
Half-life: minutes versus a week
In healthy adults, CJC-1295 with DAC had an estimated half-life of 5.8 to 8.1 days. A single administration kept mean GH 2 to 10-fold above baseline for 6 days or more and IGF-1 1.5 to 3-fold above baseline for 9 to 11 days [1]. Ionescu and Frohman round it to an 8-day half-life in their own paper [2].
For the linker-free peptide there is no human number, because nobody has published a pharmacokinetic study of it. Two published results come closest. Corpas and colleagues found the parent GHRH(1-29) sequence had to be given repeatedly each day to sustain its effect in older men [4]. In the ConjuChem rat study, GH was compared over the first two hours, where CJC-1295 gave 4 times the GH area under the curve of hGRF(1-29), and the DAC form alone was followed beyond 72 hours [3]. The four substitutions slow enzymatic breakdown, but the honest description of the no-DAC half-life remains "minutes, not measured".
Pulse versus plateau
The objection to a week-long GHRH signal was physiological. GH is secreted in pulses, and a continuous stimulus might flatten the pattern that tissues seem to need. Ionescu and Frohman tested exactly that. Healthy men aged 20 to 40 had blood drawn every 20 minutes for 12 hours overnight, received one administration in one of two study arms, and repeated the night of sampling a week later.
The pulses came back with the same frequency and the same amplitude. What the administration had changed was the floor. Trough GH was 7.5 times higher (P < 0.0001), mean GH rose 46 % and IGF-1 rose 45 %, and the two arms gave the same result [2].
The no-DAC form works the other way by construction. Each administration is a single stimulus that the pituitary answers with one pulse and then clears. Ipamorelin behaves the same way. Infused over 15 minutes in healthy men, it gave one GH episode peaking at 0.67 hours, then a decline, at every level tested [5]. Put the two shapes side by side and the logic of the research blend appears. Two short-acting peptides, two receptors, one pulse each.
GH secretion was increased after CJC-1295 administration with preserved pulsatility. The frequency and magnitude of GH secretory pulses were unaltered.
Which is better?
"Better" has no answer in the literature, because no study has put the two forms side by side. What the papers do show is that they were built for different jobs. The DAC form was designed as a long-acting drug candidate, and it did raise GH and IGF-1 for days after one administration in healthy adults [1]. Its phase 2 trial in HIV-associated visceral obesity was terminated in September 2006 with no results posted, so no disease outcome was ever measured [7]. The no-DAC form has no trial at all. The question of safety is covered in the CJC-1295 side effects guide, and the older GHRH analogue in the sermorelin comparison.
Which one belongs in a blend
A "CJC-1295 ipamorelin" vial pairs a GHRH-receptor agonist with a ghrelin-receptor agonist so that both act on the same pulse. Ipamorelin is gone within hours. A GHRH analogue that persists for a week does not act on that pulse, it acts on all of them. That is why the blend sold in the research market uses the no-DAC form, and why a listing that combines the DAC form with ipamorelin describes two halves working on different time scales. The pairing itself is explained on the CJC-1295 ipamorelin main page.
Telling them apart on a certificate
The label cannot settle which form is in a vial. The mass can. The lysine and maleimidopropionyl group add 279.4 daltons, so a deconvoluted mass near 3,647 is the DAC form and one near 3,368 is the no-DAC form, whatever the label says. That arithmetic needs nothing beyond the sequence published in 2005 [3]. The OXpeptides blend this site links to is labelled Mod GRF 1-29 (no DAC) plus ipamorelin, and its product page names Janoshik as the testing laboratory, for HPLC purity and mass-spectrometry identity; the report on the current lot is pending. When it is published, the mass on that certificate is the number to check. The same shop sells CJC-1295 with DAC as a separate 5 mg vial; there the certificate should read close to 3,647.
