Research-use notice: This review discusses published research and regulatory information. It is not medical advice or a recommendation for human use. First Due Biotech products are offered strictly for laboratory research use only and are not for human consumption.
Executive assessment
Ipamorelin, development code NNC 26-0161, is a synthetic amidated pentapeptide with sequence Aib–His–D-2-Nal–D-Phe–Lys–NH₂. It is a functional agonist of the ghrelin/growth-hormone-secretagogue receptor GHS-R1a. P001–P003
One small controlled human experiment established acute systemic pharmacokinetics and a transient GH pulse. It did not assess therapeutic outcomes or broad endocrine selectivity. P004
The only published controlled patient trial enrolled 117 bowel-resection participants and missed its primary postoperative-ileus endpoint, with no significant key or secondary efficacy difference. A later completed 320-participant Phase 2 trial has no posted results or located publication. P005–P006
Preclinical findings include rat growth, bone-size and mineral-content changes, feeding and adiposity, glucocorticoid-catabolism measures, gastrointestinal transit, pain behavior, and other model-specific outcomes. Many studies are sponsor-linked, related through recurring authors, or lack independent same-model replication. Positive rat gastrointestinal findings did not translate into efficacy in the published human trial.
No adequate public chronic toxicology, carcinogenicity, reproductive/developmental, immunogenicity, or long-term clinical safety package was located. No therapeutic regulatory approval was identified, and WADA explicitly prohibits Ipamorelin. P001, P017–P019
Evidence-strength summary
| Area | Strength | Principal limitation |
|---|---|---|
| Chemical identity | High | Salt and product-description ambiguity |
| GHS-R1a target assignment | Moderate-to-high | No modern broad human receptor/off-target panel |
| Acute human GH release | Moderate | One small, acute, men-only experiment |
| Human endocrine selectivity | Very low / absent | Foundational cortisol/ACTH evidence is swine |
| Acute human PK | Moderate | Single exposure, limited population and route |
| Postoperative-ileus efficacy | Moderate evidence of no demonstrated benefit | One negative trial; larger trial unpublished |
| Human muscle, fat, sleep, healing, cognition | Absent | No direct Ipamorelin-only trials |
| Rat growth and bone-size findings | Low-to-moderate preclinical | Surrogates and limited independence |
| GI motility | Low-to-moderate preclinical | Sponsor network; failed clinical translation |
| Formal toxicology and chronic safety | Absent / insufficient | Core public packages missing |
| Regulatory nonapproval and WADA status | High | Requires periodic status review |
Identity and nomenclature
The defined free-base peptide is Aib–His–D-2-Nal–D-Phe–Lys–NH₂, formula C38H49N9O5, molecular weight approximately 711.9 g/mol. Identifiers include CAS 170851-70-4, PubChem CID 9831659, ChEMBL CHEMBL58547, and UNII Y9M3S784Z6. P001
Development aliases include NNC 26-0161, NNC-26-0161, and NNC-260161. NN703/tabimorelin is a different molecule from the same medicinal-chemistry program and must not be treated as an Ipamorelin alias. P001, P003
FDA documented inconsistent free-base and acetate nomenclature and certificates. A Helsinn patent specifies a diacetate formulation, while foundational material was reportedly a trifluoroacetate. These labels do not establish equivalence in identity, purity, stability, PK, or toxicology. P001, P003
Development history
Novo Nordisk investigators developed shortened GHRP-derived peptides intended to retain GH release while reducing ACTH and cortisol responses seen with earlier secretagogues. Raun et al. introduced Ipamorelin in 1998. P002
Sapphire Therapeutics later developed a postoperative-ileus program, which Helsinn acquired in 2009. The first Phase 2 cohort became the negative Beck publication; the second Phase 2 cohort remains unpublished. A later review states that development was discontinued after disappointing efficacy, although no contemporaneous company discontinuation record was located. P005–P007
Patents establish chronology, formulations, and claimed uses. They do not establish clinical efficacy, approval, or an adequate safety package. P003
Target and selectivity
Ipamorelin is a ghrelin mimetic and functional GHS-R1a agonist. The proximal action involves GH release through hypothalamic and pituitary signaling, dependent on residual pituitary capacity. P001–P002
Raun et al. demonstrated GH secretion in primary rat pituitary cells and in rats and swine. In conscious swine, Ipamorelin increased GH without statistically significant ACTH or cortisol changes in the comparison with GHRP-2 and GHRP-6; FSH, LH, prolactin, and TSH were also unchanged in that experiment. P002
The result supports pharmacodynamic selectivity in swine. It does not establish:
- human cortisol, ACTH, or prolactin neutrality;
- exclusive GHS-R1a binding;
- broad molecular off-target selectivity;
- Ipamorelin-specific biased signaling;
- absence of appetite or metabolic effects.
No verified primary recombinant-human-GHS-R1a equilibrium-binding study, broad off-target panel, knockout/rescue experiment, or Ipamorelin-specific β-arrestin comparison was located.
Human pharmacokinetics and endocrine response
Gobburu et al. reported the only identified human PK/PD publication. Following one systemic exposure in healthy men, disposition was approximately linear and fit a two-compartment model. Reported terminal half-life was approximately two hours, clearance 0.078 L/h/kg, and steady-state distribution volume 0.22 L/kg. GH peaked within the first hour and declined toward negligible levels within several hours. P004
Public sources contain an unresolved discrepancy in the enrolled number. Between-person pharmacodynamic variability exceeded PK variability, and adverse events were not adequately reported.
No qualifying human study established oral bioavailability, other-route PK, repeat-exposure accumulation, metabolite identity, mass balance, sustained IGF-1 change, or human ACTH, cortisol, prolactin, insulin, gonadotropin, TSH, or appetite response.
Human clinical evidence
ST-IPAM-201 / NCT00672074
Beck et al. reported a randomized, double-blind, placebo-controlled Phase 2 trial in adults undergoing bowel resection. The study randomized 117 participants and included 114 in the safety population. P005
The trial missed its primary endpoint and found no significant key or secondary efficacy difference in postoperative-ileus recovery. Positive preclinical motility findings therefore did not translate into demonstrated clinical benefit in this population.
Adverse events were frequent in both arms. Serious-event proportions were similar. Two deaths occurred in the Ipamorelin arm following severe postoperative complications, but causality was not established. Small numerical imbalances included hypokalemia, insomnia, and discharge hyperglycemia. P001, P005
HT-IPAM-202 / NCT01280344
The subsequent Phase 2 trial enrolled approximately 320 participants and is listed as completed. No results are posted and no results publication was located. P006
Its primary outcome is unknown/not public. It must not be counted as positive, negative, or confirmatory evidence.
NCT07717866
This unfinished observational registry combines multiple interventions and outcomes. It cannot isolate an Ipamorelin effect and provides no attributable efficacy or safety result. P007
Preclinical evidence
Growth and bone
Rat studies reported increased longitudinal growth and size-related bone mineral content. Volumetric density, weight-adjusted mineral content, biomechanical strength, fracture outcomes, and human bone effects were not established. P008
Catabolic models
Related Novo/Aarhus rat studies reported improvements in nitrogen balance, weight, or muscle-force measures during glucocorticoid-associated catabolism. P009
These combination and disease-model findings do not establish human hypertrophy, strength, recovery, or body-composition effects.
Feeding and adiposity
Lall et al. reported increased food intake and relative adiposity in GH-deficient and GH-intact mice. P010
This is a relatively independent adverse-direction finding. It does not establish a human outcome, but it directly prevents an evidence-based claim that Ipamorelin has demonstrated fat-loss or appetite-neutral effects.
Gastrointestinal transit
Venkova et al. and Greenwood-Van Meerveld et al. reported improvements in lower-GI transit, gastric emptying, small-intestinal transit, or contractile responses after surgical manipulation in rats. Pharmacologic blockade supported cholinergic and enteric-neural involvement. P011–P012
The studies belonged to one sponsor-associated program and partly overlapped patent experiments. Their central clinical prediction failed in the Beck trial.
Nociception and other models
A small rat study reported GHS-R-dependent changes in visceral and somatic pain behavior. A ferret study reported less delayed cisplatin-associated weight loss but no antiemetic effect. Other isolated studies examined pancreatic insulin secretion, pituitary morphology, and diabetic models. P013–P014
These signals are model-specific, sparsely replicated, and do not establish human analgesia, appetite support, endocrine benefit, or tissue protection.
Cross-compound misattribution
Common claims are frequently borrowed from other molecules:
- lean-mass findings from MK-677/ibutamoren;
- sleep findings from MK-677;
- visceral-fat findings from Tesamorelin;
- multi-day GH/IGF-1 findings from CJC-1295 with DAC;
- combination claims involving CJC-1295 without direct controlled Ipamorelin-combination evidence.
These compounds differ in structure, receptor pharmacology, PK, and evidence base. Their results cannot be attributed to Ipamorelin. P020
Safety and product-quality uncertainty
No complete public program was located for acute and repeat-dose toxicology, genotoxicity, reproductive/developmental toxicity, carcinogenicity, dedicated safety pharmacology, or validated clinical immunogenicity. P001
Clinical exposure is limited to one small acute experiment and perioperative trials. This cannot characterize chronic endocrine, glucose, cardiovascular, oncologic, reproductive, immunogenic, or rare adverse effects.
FDA identified concerns involving inadequate safety information, immunogenicity, impurities, and product characterization. Salt-form inconsistency, aggregation, endotoxin, bioburden, related substances, and residual solvents create a product-quality question separate from the pharmacology of a correctly identified peptide. P001
Regulatory and anti-doping status
No FDA, EMA, Health Canada, or TGA therapeutic approval was located. FDA recommended against adding Ipamorelin free base or acetate to the Section 503A Bulks List following a 2024 advisory vote of 0 yes and 12 no. P001, P015–P016
Australia’s scheduling does not authorize a therapeutic product. Health Canada has warned that unauthorized injectable peptide products may present serious risks. P018–P019
WADA’s 2026 list explicitly names Ipamorelin under S2.2.4 and prohibits it at all times. P017
Major limitations
- Only two controlled human primary publications were identified.
- The only published patient trial missed its primary endpoint.
- The largest completed trial remains unpublished.
- Human endocrine selectivity is inferred from swine data.
- Human outcome claims are often borrowed from different secretagogues.
- Preclinical clusters are frequently sponsor-linked or author-connected.
- Same-model independent replication is sparse.
- Animal biomarker and growth findings do not establish human outcomes.
- Public toxicology, immunogenicity, and long-term safety packages are inadequate.
- Free-base, acetate, diacetate, and historical TFA labels may not be interchangeable.
Evidence-weighted conclusion
Ipamorelin is a defined synthetic GHS-R1a agonist with established acute human GH target engagement. That is the strongest direct conclusion.
Its broader reputation is not supported by Ipamorelin-specific human evidence. Muscle gain, fat loss, sleep, recovery, healing, cognition, bone benefit, performance, anti-aging effects, endocrine selectivity, and chronic safety remain unestablished.
The postoperative-ileus program is especially informative: functional rat findings justified clinical testing, but the published patient trial was negative on its primary endpoint, and the larger completed trial remains unavailable. The evidence therefore supports proximal pharmacology, not demonstrated human therapeutic benefit.