--- title: "Macimorelin" canonical_url: https://bestpeptidecalculator.app/library/macimorelin description: "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." updated: 2026-11-07 publisher: Peptide Library notice: "Research and educational use only. Not medical advice." --- # 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. 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. Categories: Fat Loss, Muscle/Recovery. ## Classification - Type: FDA-approved oral ghrelin receptor agonist - Mechanism class: Growth Hormone Secretagogue - Development stage: Approved product - Regulatory class: FDA-approved medicine ## Mechanism 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. ## Properties - Molecular formula: C26H30N6O3 - Molecular weight: 474.6 g/mol - CAS number: 381231-18-1 - Studied routes: Oral ## Evidence - Evidence level: FDA Approved - Highest documented: Regulatory review (FDA label) - Human trials: 2 - Controlled human trials: 2 - Preclinical sources: 0 - Latest source: 2023 Each step shows whether the sources Peptide Library has reviewed include that kind of research. Counts are reviewed sources, not every study ever published. Reviews and programme summaries that describe human use are shown as "reported", not as trials, and registered trials without published results are listed but not counted. A higher step means research has progressed further; it does not mean a compound works better or is safer. Compounds whose evidence has not been reviewed yet show "Not reviewed" instead of a guess. ### Studies 1. MACRILEN (macimorelin) for oral solution — FDA prescribing information (Aeterna Zentaris), DailyMed. Regulatory label (FDA), human. Population: Adults being tested for growth hormone deficiency. Maximally stimulated growth hormone below 2.8 ng/mL confirms adult growth hormone deficiency [Source](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=aeb30f1a-4815-47ae-a2cb-b6b4e26372e1) 2. Garcia JM et al. Macimorelin as a Diagnostic Test for Adult GH Deficiency. J Clin Endocrinol Metab. 2018. 2018. Controlled human trial. Population: Adults with high (n=38), intermediate (n=37) and low (n=39) likelihood of growth hormone deficiency, and matched healthy controls (n=25). At a 2.8 ng/mL cutoff: sensitivity 87%, specificity 96%; reproducibility 97% on retesting (n=33) [Source](https://pubmed.ncbi.nlm.nih.gov/29860473/) 3. Herodes M et al. Pilot clinical trial of macimorelin to assess safety and efficacy in patients with cancer cachexia. J Cachexia Sarcopenia Muscle. 2023. 2023. Controlled human trial. Population: Patients with cancer cachexia (10 on macimorelin, 5 on placebo). No related adverse events; body weight and quality of life improved numerically but not significantly against placebo [Source](https://pubmed.ncbi.nlm.nih.gov/36860137/) ## Safety Human safety basis: FDA prescribing information ## Regulatory 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 - Availability: Prescription-Only ## 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. ### 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, 2023](https://pubmed.ncbi.nlm.nih.gov/36860137/) - [Safety, tolerability, pharmacokinetics, and pharmacodynamics of macimorelin in healthy adults: Results of a single-dose, randomized controlled study — Growth Horm IGF Res, 2020](https://pubmed.ncbi.nlm.nih.gov/32325373/) - [Macimorelin as a Diagnostic Test for Adult GH Deficiency — J Clin Endocrinol Metab, 2018](https://pubmed.ncbi.nlm.nih.gov/29860473/) - [The macimorelin-stimulated growth hormone test for adult growth hormone deficiency diagnosis — Expert Rev Mol Diagn, 2014](https://pubmed.ncbi.nlm.nih.gov/24834478/) - [Real-world diagnostic performance of the macimorelin stimulation test in the diagnosis of adult growth hormone deficiency — Pituitary, 2026](https://pubmed.ncbi.nlm.nih.gov/41793495/) Note: Dose figures are left out of this Markdown version. See the cited sources.