Sermorelin vs CJC-1295: A Research Comparison of GHRH Analogs
Sermorelin and CJC-1295 are both synthetic analogs of growth hormone-releasing hormone (GHRH), and both bind the same hypothalamic-pituitary GHRH receptor (GHRHR) to drive somatotroph signaling. The difference between them is entirely a matter of pharmacokinetic engineering — they share the receptor pharmacology but engage it over different time scales. For researchers selecting a GHRH analog for animal-study work, the choice depends on the temporal resolution and duration of receptor stimulation the experimental design requires.
This article compares the two compounds in research context. Both are supplied for in vitro and animal-study use only.
Quick reference
| Field | Sermorelin | CJC-1295 (no DAC) | CJC-1295 with DAC |
|---|---|---|---|
| CAS | 86168-78-7 | 863288-34-0 | 863288-34-0 (mod. form) |
| Sequence length | 29 aa | 30 aa (Mod-GRF 1-29) | 30 aa + DAC linker |
| Modifications | None (native GHRH 1-29) | D-Ala², Gln⁸, Ala¹⁵, Leu²⁷ substitutions | Same + maleimidopropionic acid for albumin conjugation |
| Molecular weight | ~3358 Da | ~3367 Da | ~3647 Da |
| Plasma half-life | ~10–12 min | ~30 min | ~6–8 days |
| GHRHR binding | Native affinity | Comparable to sermorelin | Comparable to sermorelin |
| Primary research use | Short-pulse GH-axis probing | Modest-duration receptor stimulation | Sustained receptor occupancy |
What sermorelin is
Sermorelin is the unmodified synthetic GHRH(1-29) fragment, the minimal sequence retaining full receptor-binding activity from the parent 44-residue GHRH peptide. It is the prototype against which the analog series is benchmarked. For a deeper background on GHRH biology and the analog class, see the sermorelin and GHRH analog research overview.
The unmodified peptide is rapidly degraded by DPP-4 cleavage at the N-terminal Tyr-Ala bond, limiting circulating half-life to roughly 10 minutes in animal models. For research designs that require a transient GH pulse — for example, somatotroph reserve testing or short-window pulsatility studies — that short half-life is a feature, not a bug.
What CJC-1295 without DAC is
CJC-1295 without DAC (also termed Mod-GRF 1-29) is the GHRH(1-29) backbone with four amino acid substitutions designed to block enzymatic degradation while preserving receptor binding:
- D-Ala² — blocks DPP-4 cleavage
- Gln⁸ — reduces asparagine deamidation
- Ala¹⁵ — increases stability and bioactivity
- Leu²⁷ — blocks methionine oxidation
The substitutions extend plasma half-life from ~10 minutes to ~30 minutes — a modest extension that keeps the analog within a pulse-physiology compatible window while reducing the proteolytic-degradation burden.
What CJC-1295 with DAC is
The DAC (“Drug Affinity Complex”) modification adds a maleimidopropionic acid moiety to the C-terminus of the Mod-GRF 1-29 backbone. The maleimide reacts with the free thiol on cysteine-34 of plasma albumin in vivo (or upon mixing with serum in vitro), forming a covalent peptide-albumin conjugate. The albumin-bound form has a circulating half-life of approximately 6–8 days in animal models.
The mechanistic consequence: continuous, low-level GHRH-receptor stimulation rather than a series of discrete pulses. This is a fundamentally different exposure profile from either sermorelin or non-DAC Mod-GRF 1-29.
Implications for receptor biology
GH secretion is intrinsically pulsatile, regulated by reciprocal GHRH (stimulatory) and somatostatin (inhibitory) tone from the hypothalamus. The somatotroph response to a GHRH-receptor agonist is shaped by:
- Pulse vs. continuous exposure — pulsed stimulation tends to elicit more robust transient GH release than continuous stimulation, because somatotrophs can re-prime between pulses.
- Somatostatin counter-tone — continuous GHRH-receptor stimulation may be partially countered by increased somatostatin release, blunting the integrated GH response.
- IGF-1 negative feedback — sustained GH elevation drives hepatic IGF-1, which feeds back to suppress somatotroph responsiveness.
For research purposes, this means the three compounds produce qualitatively different biological readouts:
- Sermorelin — discrete, short-pulse stimulation; useful for testing somatotroph reserve and acute response.
- CJC-1295 without DAC — intermediate pulse extension; useful for animal-model designs probing the pulse-duration parameter.
- CJC-1295 with DAC — continuous receptor occupancy; useful for chronic-exposure designs and integrated IGF-1-axis effects.
These are different research questions, not different efficacies.
Animal-study findings in research context
Published preclinical work using sermorelin includes investigations of somatotroph reserve in aging animal models, characterization of the GH-IGF-1 axis dynamic response, and use as a positive-control GHRH-receptor agonist in pharmacology screens. CJC-1295 (both forms) has appeared in animal-model work probing sustained-stimulation effects on the GH axis.
None of this published literature constitutes evidence of safety or efficacy in humans, and none of the compounds are recommended for human use.
CoA verification
All three compounds should have CoAs documenting:
– HPLC purity ≥99.0% with chromatogram
– Mass spec confirmation within ±0.5 Da of theoretical
– Net peptide content with counterion identified
– Lot number matching vial
For CJC-1295 with DAC, the maleimide functionality should be confirmed — the reactive intermediate is the structural feature that enables albumin conjugation, and its integrity is essential to the compound’s defining pharmacokinetic property.
Storage
All three are supplied lyophilized.
- Pre-reconstitution: 2–8°C, dry, dark. -20°C for archival storage.
- Post-reconstitution: 2–8°C in multi-dose diluent, use within ~28 days. CJC-1295 with DAC has somewhat reduced reconstituted stability owing to maleimide hydrolysis over time — refer to lot-specific CoA guidance.
Choosing between the three
- Pulse-physiology research, somatotroph reserve, short windows: sermorelin.
- Extended pulse research, intermediate duration: CJC-1295 without DAC.
- Chronic continuous-stimulation research, integrated IGF-1 effects: CJC-1295 with DAC.
Research Use Only. Not for use in or on humans or animals. Not a food, drug, cosmetic, or supplement.