Sermorelin is native GHRH(1-29); CJC-1295 without DAC is the same 29 residues with four positions deliberately replaced. The substitutions at positions 2, 8, 15 and 27 exist to close three specific degradation routes — dipeptidyl peptidase-4 cleavage, asparagine deamidation and methionine oxidation — and they cost only 10 g/mol, taking the molecule from 3357.93 to 3367.93. In a CJC-1295 vs sermorelin comparison, the question is whether your protocol wants the native sequence as the biological reference, or a hardened analog that will survive handling and assay conditions unchanged.
Both are supplied as lyophilized powder in 2, 5 and 10 mg vials with lot-matched HPLC certificates: CJC-1295 (No DAC / Mod GRF 1-29) and sermorelin, both listed under GHRH analogs. Both are research chemicals for in-vitro and preclinical laboratory work only, not for human or veterinary use.
CJC-1295 (no DAC) vs sermorelin at a glance
| Attribute | CJC-1295 (No DAC / Mod GRF 1-29) | Sermorelin |
|---|---|---|
| Relationship to native GHRH | Tetrasubstituted analog of GHRH(1-29) | Native GHRH(1-29) amide, unmodified |
| Length | 29 residues, C-terminally amidated | 29 residues, C-terminally amidated |
| Substitutions | Positions 2, 8, 15 and 27 replaced | None |
| Receptor | Pituitary GHRH receptor | Pituitary GHRH receptor |
| CAS number | 863288-34-0 | 86168-78-7 |
| Molecular formula | C152H252N44O42 | C149H246N44O42S |
| Molecular weight | 3367.93 g/mol | 3357.93 g/mol |
| Contains methionine | No — replaced, hence no sulfur in the formula | Yes — the single sulfur atom in the formula |
| Oxidation liability | Low | Methionine sulfoxide formation, +16 Da |
| Deamidation liability | Low — asparagine replaced | Asparagine deamidation, +1 Da |
| DPP-4 susceptibility | Reduced by the position 2 substitution | Native — cleaved rapidly |
| Role in a study | Robust working analog; structure–activity comparator | Biological reference standard for the native ligand |
| Research sizes stocked | 2 mg, 5 mg, 10 mg | 2 mg, 5 mg, 10 mg |
| Purity | ≥99% HPLC, MS identity, lot-matched COA | ≥99% HPLC, MS identity, lot-matched COA |
Same receptor, same fragment, one is hardened
Decades of endocrine work established that the first 29 residues of the 44-residue hormone carry essentially all of the receptor-binding information, which is why GHRH(1-29) rather than full-length GHRH became the standard laboratory tool. Sermorelin is that fragment reproduced faithfully — a native sequence with a C-terminal amide, and nothing else changed.
CJC-1295 without DAC, more accurately called Modified GRF 1-29, is an analog of the same fragment. Each of its four substitutions is a targeted fix rather than an attempt to alter receptor behaviour, and understanding what each one does explains most of what separates the two compounds in practice.
Position 2 — blocking DPP-4
Dipeptidyl peptidase-4 removes the first two residues of native GHRH within minutes, destroying the N-terminus the receptor requires. Substituting a D-amino acid at position 2 blocks that cleavage sterically. In any assay run in serum, plasma or a tissue preparation with endogenous peptidase activity, this is the substitution that matters most: sermorelin degrades measurably during an extended incubation and the analog does not.
Position 8 — removing a deamidation site
Asparagine residues deamidate spontaneously in aqueous solution, converting to aspartate with a mass increase of 1 Da and a charge change. Replacing the asparagine at position 8 removes that route. A 1 Da shift is easy to overlook on a mass spectrum but produces a chemically distinct species with a different isoelectric behaviour.
Position 15 — conformational stabilisation
The substitution at position 15 is reported as a stabilising change to the peptide's helical character rather than a fix for a specific degradation reaction.
Position 27 — removing the methionine
This is the substitution visible in the molecular formulas. Sermorelin's formula contains a single sulfur atom; the analog's does not, because the methionine has been replaced. Methionine is the residue most prone to oxidation in stored peptides, converting to the sulfoxide with a 16 Da mass increase, and it does so on exposure to air, light, trace metals and time. Removing it removes the single largest storage liability in the molecule.
What this means for experimental design
The four substitutions do not change the receptor, and both compounds are studied for the same thing: signalling at the pituitary GHRH receptor, cyclic-AMP accumulation, and the pulsatile pattern of growth hormone release in intact animal preparations. What changes is how much of the compound you actually have at the end of an experiment.
For short in-vitro work in defined buffer, the two are close to interchangeable and sermorelin's native sequence is arguably preferable, since it is the molecule the receptor evolved to bind. For anything longer, anything in serum, or anything where the same stock is used across weeks, the analog is the more reliable material simply because there are fewer ways for it to become something else.
The subtle failure mode with sermorelin is that its degradation products are not inert — a methionine sulfoxide or a deamidated species is still a peptide, still elutes near the parent, and may retain partial activity. A gradual potency drift across a long study is therefore easy to attribute to biology rather than to chemistry. Groups running sermorelin over extended periods should re-verify stock rather than assume stability.
Which to choose for which research question
Choose sermorelin as the biological reference
If the study needs the native ligand — establishing baseline receptor pharmacology, generating a reference concentration–response curve, or serving as the comparator against which analogs are judged — sermorelin is the correct material. It is also the appropriate choice when replicating older endocrine literature, much of which used the native fragment. Sermorelin additionally has a regulatory history that most research peptides lack: a sermorelin product was formerly marketed as a prescription medicine in the United States and has since been discontinued. That history attaches to the regulated pharmaceutical article, not to research-grade powder.
Choose the modified analog as the working compound
For serum-containing assays, multi-week animal protocols, long-lived stock solutions or any design where degradation would confound the readout, Modified GRF 1-29 is the more robust tool. It is also the standard comparator in structure–activity work asking how far a GHRH fragment can be modified before receptor behaviour changes.
Run both when stability is the variable
The pair forms a well-defined two-point series: identical receptor target, identical length, four defined substitutions. Comparing them under identical conditions is a direct test of how much an apparent potency difference reflects intrinsic pharmacology and how much reflects survival in the assay. Extending the series further, tesamorelin adds an N-terminal trans-3-hexenoyl group to the same fragment — see tesamorelin vs sermorelin — and CJC-1295 with DAC adds covalent albumin conjugation on top of the same substituted backbone.
Combination designs add a secretagogue
GHRH analogs and ghrelin-receptor secretagogues act at different receptors, which is why they are so often paired. We stock ipamorelin separately and co-formulated sermorelin with ipamorelin and CJC-1295 with ipamorelin vials; our overview of the secretagogue landscape maps how the family fits together.
Handling, reconstitution and storage differences
Both follow the standard protocol: sealed lyophilized vials held frozen, brought to room temperature before the stopper is pierced so moisture does not condense on cold powder, reconstituted by running diluent down the vial wall, dissolved without shaking, and aliquoted so stock is not repeatedly frozen and thawed.
Sermorelin needs more care within that protocol, and the reason is the methionine. Oxidation is accelerated by dissolved oxygen, by light and by trace metal ions, so sermorelin solutions are best prepared fresh, protected from light, and not left standing in partly filled tubes where headspace oxygen is abundant. Deamidation is base-catalysed, so holding sermorelin in alkaline buffer for extended periods is also worth avoiding. The modified analog is comparatively indifferent to all of this.
Concentration is a laboratory calculation, not a recommendation for use: a 5 mg vial reconstituted with 2 mL of diluent gives 2.5 mg/mL, or 2,500 mcg/mL, so 0.1 mL contains 250 mcg. Because the two masses differ by only 10 g/mol — about 0.3 percent — mass and molar concentrations are effectively interchangeable between them, which makes molar-matched comparison unusually easy. See our reconstitution guide and storage guide.
Purity, identity and COA checks
Request the lot-matched certificate for each vial and confirm HPLC purity with a visible chromatogram, a mass-spectrometric result matching the expected weight — 3367.93 g/mol for the analog and 3357.93 g/mol for sermorelin — and a lot number matching the vial. For sermorelin specifically, look for a satellite peak 16 Da above the parent mass, which indicates methionine sulfoxide, and for a 1 Da shift indicating deamidation; both are common in aged material and neither is visible from a purity percentage alone. For the analog, the relevant confirmation is that the formula contains no sulfur, which distinguishes it unambiguously from the native fragment. Our COA guide explains what a complete document should contain.
Regulatory framing
Both compounds are supplied as research chemicals for laboratory use only. Modified GRF 1-29 has no approved status anywhere. Sermorelin has a prescription history in the United States attached to a discontinued pharmaceutical product; that status belongs to the regulated article and not to research-grade powder. Nothing on this page is a protocol for human or veterinary use. For broader context see our growth and performance research overview.