Quick comparison
| Feature | Sermorelin | CJC-1295 (with DAC) |
|---|---|---|
| Backbone | GHRH(1-29)-NH2, unmodified sequence | GHRH(1-29) with D-Ala2, Gln8, Ala15, Leu27 substitutions plus a C-terminal DAC maleimide-lysine group |
| Plasma half-life | ~11 to 12 minutes (human, IV or SC) | 5.8 to 8.1 days (human, measured) |
| Albumin binding | None | Covalent thioether bond at albumin Cys34 |
| GH release pattern | Discrete pulse, near baseline by ~3 hours | Sustained elevation for 6+ days; pulsatility preserved |
| Typical research dosing | Once daily, or single-dose pulse testing | Weekly or twice weekly |
| Pediatric GHD trial data | Yes, n=110 pivotal trial (Geref ISG, 1996) | No pediatric or disease-population trials published |
| Regulatory history | FDA approved 1997 (Geref Pediatric), discontinued 2008 | Never submitted for or granted regulatory approval |
What each compound is
Sermorelin is GHRH(1-29)-NH2, a 29-amino-acid fragment of endogenous growth hormone-releasing hormone that retains full receptor-binding activity. Serono developed it as Geref Pediatric and won FDA approval in 1997 for idiopathic growth hormone deficiency in children and for diagnostic testing of pituitary GH reserve. Serono discontinued the product in 2008 for commercial reasons, not safety or efficacy concerns. The sermorelin research overview covers its mechanism and trial record in full.
CJC-1295 starts from the same 29-residue fragment but carries four substitutions, D-Ala2, Gln8, Ala15, and Leu27, that block the enzyme dipeptidylpeptidase IV (DPP-IV) from cleaving it. The version most vendors sell under the plain name "CJC-1295" also carries a C-terminal maleimide-lysine group called the Drug Affinity Complex, or DAC. After injection, that group reacts with a free thiol on Cys34 of circulating serum albumin and forms a permanent covalent bond.
A separate form without the DAC group, usually labeled modified GRF 1-29 or CJC-1295 without DAC, has its own half-life and dosing profile; the CJC-1295 DAC vs no-DAC comparison covers that distinction on its own. This article compares sermorelin against CJC-1295 with DAC, the form most sources mean when they cite "CJC-1295" without qualification. Background on the compound family is also covered in the CJC-1295 and ipamorelin research overview.
Half-life: 11 minutes versus 8 days
Wilton and colleagues published the primary human pharmacokinetic data for GHRH(1-29) in Acta Paediatrica in 1993, testing intravenous and intranasal dosing in 30 healthy men aged 19 to 43 (Wilton et al., 1993, n=30). An IV dose of 1 to 2 mcg/kg produced maximal GH peaks of about 90 mU/L, and GH stayed elevated for roughly 3 hours despite the peptide's fast clearance from plasma. This 3-hour window, not the minute-scale half-life itself, is what limits sermorelin to short, time-locked research protocols.
Soule and colleagues quantified how a single amino acid substitution changes that clearance rate. In 10 normal men given constant intravenous infusions, unmodified GHRH(1-29) had a disappearance half-time of 4.3 minutes and a metabolic clearance rate of 39.7 mL/kg per minute. Substituting D-alanine at position 2 to block DPP-IV cleavage extended the half-time to 6.7 minutes and cut clearance to 21 mL/kg per minute (Soule et al., JCEM 1994, n=10). That single substitution is one of the four changes carried into CJC-1295, and it is the mechanistic basis for the commonly cited 11 to 12 minute clinical half-life of sermorelin dosed by bolus injection rather than constant infusion.
Teichman and colleagues ran the first human pharmacokinetic trial of CJC-1295 with DAC, two randomized, placebo-controlled, ascending-dose studies in adults aged 21 to 61, lasting 28 and 49 days (Teichman et al., JCEM 91(3):799, 2006). The measured half-life was 5.8 to 8.1 days, roughly a thousand times longer than sermorelin's, and it comes entirely from the covalent albumin linkage rather than from DPP-IV resistance.
A single injection produced dose-dependent GH increases of 2- to 10-fold lasting 6 or more days, and IGF-1 increases of 1.5- to 3-fold lasting 9 to 11 days. With repeated dosing, IGF-1 stayed above baseline for up to 28 days. No serious adverse reactions were reported in either study.
GH and IGF-1 response patterns
Because sermorelin acts through a brief pulse, its research value lies in triggering one measurable GH release tied to a specific injection time. The Wilton data show this clearly: even the lowest effective IV dose, 0.25 mcg/kg, produced a statistically significant GH rise, and the response scaled up to the 90 mU/L peak at 1 to 2 mcg/kg before falling back toward baseline within about 3 hours.
Ionescu and Frohman examined what continuous CJC-1295 stimulation does to that same pulsatile system. In healthy men aged 20 to 40, they drew blood every 20 minutes across a 12-hour overnight period, once at baseline and again one week after a single injection of 60 or 90 mcg/kg (Ionescu and Frohman, JCEM 2006). Trough GH rose 7.5-fold (p<0.0001), mean overnight GH secretion rose 46% (p<0.01), and IGF-1 rose 45% (p<0.001).
The frequency and amplitude of individual GH pulses were unchanged, meaning the pituitary kept releasing GH in its normal pulsatile rhythm on top of a much higher floor. Neither dose produced a meaningfully different result from the other.
The practical contrast: sermorelin gives researchers one identifiable pulse to measure, while CJC-1295 with DAC raises the entire baseline for days without erasing the underlying pulse structure.
Trial history: pediatric evidence versus adult PK-only data
Sermorelin's clinical record includes disease-population outcome data. The pivotal trial, run by the Geref International Study Group and published in 1996, enrolled 110 previously untreated prepubertal children with growth hormone deficiency, of whom 86 were evaluable for efficacy, and treated them with 30 mcg/kg subcutaneous sermorelin once daily at bedtime (Geref International Study Group, 1996, n=110). Mean height velocity rose from 4.1 cm/yr at baseline to 8.0 cm/yr at 6 months, with about 74% of the cohort meeting the threshold for a clinically meaningful response. That trial formed the core of the FDA approval package for Geref Pediatric.
CJC-1295's published human data stop at Phase I/II pharmacokinetics and safety in healthy adults. The Teichman and the Ionescu/Frohman studies establish dose, half-life, and hormone response, but neither tested a disease population, and no pediatric growth hormone deficiency trial for CJC-1295 has been published. No head-to-head trial comparing sermorelin and CJC-1295 directly exists in the literature; every comparison, including this one, is built by placing separate trials with different populations and endpoints side by side.
Regulatory status differs sharply
Sermorelin carries a real regulatory history. It reached the U.S. market as Geref Pediatric in 1997 on the strength of the Geref ISG trial and was withdrawn in 2008 for commercial rather than safety reasons. Compounded sermorelin has circulated as a research and off-label product since then, but the original NDA-grade dataset still exists and is publicly reviewable.
CJC-1295 has no equivalent. It has never been submitted to the FDA, the EMA, or any other regulator, and no manufacturer publishes a safety dataset comparable in scale to Geref's pediatric program. What exists is the Teichman Phase I/II safety and PK data in a few dozen healthy adults across two short studies. Researchers should weigh that difference in evidentiary depth, not just the pharmacokinetic numbers, when designing a study around either compound.
Matching the compound to the protocol
For a protocol built around a single, time-locked GH pulse, such as a diagnostic-style pituitary reserve assessment, sermorelin's 11 to 12 minute half-life and roughly 3-hour GH window let a researcher anchor blood draws to a known injection time. The dosing calculator handles the reconstitution math needed to hit a specific per-injection dose.
For a protocol studying sustained IGF-1 elevation with fewer injections, CJC-1295 with DAC's multi-day half-life is the better match, with the tradeoff that IGF-1 can stay elevated for up to 28 days after repeated dosing. Any crossover or washout design needs to account for that tail before assuming a clean pre-treatment baseline.
A third option sits between the two. CJC-1295 without DAC, the modified GRF 1-29 form, has a half-life of roughly 30 minutes and is the standard GHRH partner for ipamorelin in pulse-timed protocols, since both peptides clear within a couple of hours of injection. The CJC-1295 and ipamorelin compound page lists current stock for that combination.
Storage and handling in tropical research environments
Sermorelin and both CJC-1295 forms ship as lyophilized powder, and lyophilized peptides degrade faster in heat and humidity than the manufacturer's cold-chain testing typically assumes. In Bali and across Indonesia, where ambient temperatures regularly exceed 30 degrees Celsius and relative humidity often reaches 80 to 90%, a dedicated freezer at -20 degrees Celsius or colder from the point of receipt is the baseline, not an optional upgrade. The full lyophilized peptide storage guide covers the underlying stability data.
After reconstitution with bacteriostatic water, both compounds are typically reported stable for 4 to 6 weeks when refrigerated at 2 to 8 degrees Celsius, and the covalent albumin bond on CJC-1295's DAC group does not change that storage requirement for the reconstituted solution. The peptide reconstitution guide walks through the step-by-step protocol for either compound.