Sermorelin and CJC-1295 share the same core sequence — the first 29 amino acids of growth hormone releasing hormone (GHRH 1-29). What differs is stability engineering. This article compares the two GHRH analogues across mechanism, half-life, and research model applicability.
Shared foundation — GHRH(1-29)
Native GHRH is a 44 amino-acid peptide. Research established that the first 29 amino acids retain full biological activity at the GHRH receptor. Both sermorelin and CJC-1295 use this active fragment as their core structure.
Sermorelin — the original
Sermorelin is GHRH(1-29) without modification. It was the first GHRH analogue to reach clinical use, originally marketed for paediatric growth hormone deficiency diagnosis. Without sequence modification, sermorelin is rapidly degraded by dipeptidyl peptidase IV (DPP-IV), giving it a plasma half-life of approximately 10 minutes.
Practical implication: sermorelin produces a brief GH pulse, similar to native GHRH. Research models requiring acute pulse studies use sermorelin because its short half-life preserves pulsatility.
CJC-1295 (no DAC) — stability engineered
CJC-1295 without drug affinity complex modifies the GHRH(1-29) sequence at four positions:
- Position 2: Ala → D-Ala (DPP-IV resistance)
- Position 8: Gln → no change in some versions; modified in others
- Position 15: Ala → unchanged in some; Asp in modified versions
- Position 27: Met → Leu (oxidation resistance)
These substitutions extend half-life from 10 minutes to approximately 30 minutes. The pulse is amplified compared with sermorelin but still preserves overall pulsatility.
CJC-1295 with DAC — albumin-anchored
The DAC modification adds a maleimidopropionic acid linker that binds covalently to serum albumin. Once bound to albumin (which has a ~19 day half-life), CJC-1295 DAC has a plasma half-life of approximately 8 days.
This dramatically changes the research model. Instead of a discrete pulse, CJC-1295 DAC produces near-continuous GHRH stimulation. Endogenous GH pulsatility is attenuated. See our detailed DAC vs non-DAC comparison.
Side-by-side
| Compound | Modifications | Half-life | Pulse pattern preserved |
|---|---|---|---|
| Sermorelin | None | ~10 min | Yes (mimics native GHRH) |
| CJC-1295 (no DAC) | 4 substitutions | ~30 min | Yes (amplified pulse) |
| CJC-1295 (DAC) | Substitutions + albumin linker | ~8 days | No (continuous tone) |
Which to use in which research model
- Acute GH pulse research — sermorelin (matches native GHRH timing)
- Pulse amplification studies — CJC-1295 (no DAC)
- Sustained GHRH receptor activation — CJC-1295 (DAC)
- Pulsatility preservation studies — sermorelin or non-DAC CJC-1295
- Pituitary function tests — sermorelin (historical standard)
Combination with GHRPs
All three GHRH analogues are commonly studied alongside ghrelin receptor agonists (ipamorelin, GHRP-2, hexarelin) in research models. The combination logic: GHRH activates one pathway; GHRP activates a different one (GHS-R1a); together they produce synergistic GH release greater than either alone.
With sermorelin or non-DAC CJC-1295, pulse timing alignment matters — the GHRH analogue and GHRP must peak concurrently. With DAC CJC-1295, the constant background means GHRP timing alone determines pulse amplitude.
Stability and reconstitution
| Compound | Reconstitution | Refrigerated shelf-life |
|---|---|---|
| Sermorelin | Bacteriostatic water, 1-2 mg/mL | ~4 weeks |
| CJC-1295 (no DAC) | Bacteriostatic water, 1-2 mg/mL | ~4 weeks |
| CJC-1295 (DAC) | Bacteriostatic water, 1-2 mg/mL | ~4 weeks (avoid multi-freeze-thaw) |
Chempeptides supplies all three with batch-specific CoA — see the research catalogue.
Research use only.