Macimorelin
Macimorelin is an FDA-approved oral ghrelin receptor agonist in the Growth Hormone Secretagogue class. Macimorelin is a small peptidomimetic agonist at the growth hormone secretagogue receptor 1a in the pituitary and hypothalamus, the same receptor targeted by ghrelin.
For research use only.
Key Facts
- CAS
- 381231-18-1
- Molecular Weight (MW)
- 474.6 g/mol
- Half-life
- —
- FDA status
- Approved
- Administration Route
- oral
- Frequency
- —
- Last updated
- Aug 30, 2026
- Reviewed
- Aug 30, 2026
Research summary
Orally active ghrelin receptor agonist approved as a diagnostic agent for adult growth hormone deficiency. It is the first oral alternative to the insulin tolerance test for this indication.
Peptide Library's Macimorelin profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
Protocol
- Dosage Range
- —
- Frequency
- —
- Cycle
- —
- Administration Route
- oral
- Reconstitution Guide
- —
Sequence & molecular data
| Molecular formula | C26H30N6O3 |
|---|---|
| Molecular weight | 474.6 g/mol |
| CAS number | 381231-18-1 |
| PubChem CID | 9804938 |
| FDA UNII | 8680B21W73 |
| ChEMBL | CHEMBL278623 |
| DrugBank | DB13074 |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
Macimorelin is a small peptidomimetic agonist at the growth hormone secretagogue receptor 1a in the pituitary and hypothalamus, the same receptor targeted by ghrelin. Receptor activation stimulates growth hormone release, and the peak GH concentration after a weight-based oral dose distinguishes patients with adult growth hormone deficiency from those with intact somatotroph reserve.
Studies
- Pilot clinical trial of macimorelin to assess safety and efficacy in patients with cancer cachexia
- Safety, tolerability, pharmacokinetics, and pharmacodynamics of macimorelin in healthy adults: Results of a single-dose, randomized controlled study
- Macimorelin as a Diagnostic Test for Adult GH Deficiency
- The macimorelin-stimulated growth hormone test for adult growth hormone deficiency diagnosis
- Real-world diagnostic performance of the macimorelin stimulation test in the diagnosis of adult growth hormone deficiency
Regulatory & research status
Macimorelin is an FDA-approved product for specific labelled indications. Approval does not extend to the research contexts described on this page, and approved products are prescription medicines.
| FDA status | Approved |
|---|---|
| Research status | Approved product (see FDA status) |
| Availability | Prescription-Only |
| WADA (sport) | Unknown / Not Listed |
| Library classification | FDA-Approved |
Benefits
—
Potential Side Effects
No side effects listed yet for this entry.
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
Macimorelin: frequently asked questions
What is Macimorelin?
Orally active ghrelin receptor agonist approved as a diagnostic agent for adult growth hormone deficiency. It is the first oral alternative to the insulin tolerance test for this indication.
How does Macimorelin work?
Macimorelin is a small peptidomimetic agonist at the growth hormone secretagogue receptor 1a in the pituitary and hypothalamus, the same receptor targeted by ghrelin. Receptor activation stimulates growth hormone release, and the peak GH concentration after a weight-based oral dose distinguishes patients with adult growth hormone deficiency from those with intact somatotroph reserve.
Is Macimorelin FDA approved?
Yes. Macimorelin is approved by the FDA, and approved products are prescription medicines. Approval is always for specific indications studied in clinical trials, so an approved status does not mean the compound is approved for every use it is discussed for. Research-chemical material sold under the same name is not the approved product.
What peptides are similar to Macimorelin?
Compounds most often compared with Macimorelin include MK-677, Anamorelin, Tabimorelin and Relamorelin. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.
References
- Pilot clinical trial of macimorelin to assess safety and efficacy in patients with cancer cachexia — J Cachexia Sarcopenia Muscle, 2023External reference
- Safety, tolerability, pharmacokinetics, and pharmacodynamics of macimorelin in healthy adults: Results of a single-dose, randomized controlled study — Growth Horm IGF Res, 2020External reference
- Macimorelin as a Diagnostic Test for Adult GH Deficiency — J Clin Endocrinol Metab, 2018External reference
- The macimorelin-stimulated growth hormone test for adult growth hormone deficiency diagnosis — Expert Rev Mol Diagn, 2014External reference
- Real-world diagnostic performance of the macimorelin stimulation test in the diagnosis of adult growth hormone deficiency — Pituitary, 2026External reference
Related research, comparisons & guides
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Aug 30, 2026 · Version 1
This Macimorelin profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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