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Peptide

Macimorelin (Macrilen)

Macimorelin is an oral ghrelin receptor agonist peptidomimetic. FDA-approved in 2017 as first oral diagnostic for adult GH deficiency. Single dose 0.5 mg/kg. Phase 3: 82-87% sensitivity, 92-96% specificity at 2.7-5.1 ng/mL GH cutoff. Comparable accuracy to insulin tolerance test without hypoglycemia risk.

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Best evidence
Grade A
Conditions studied
1
Outcomes
5
Graded outcomes
3020

Evidence by condition

  • Strong
  • Moderate
  • Limited
  • Very limited

1 condition, plus general outcomes

Growth Hormone Deficiency

Growth Hormone Deficiency: outcomes studied for Macimorelin (Macrilen)
GradeOutcomeEffectSizeStudiesPeopleStudies list
GH Deficiency Diagnosis

Phase 3: 82-87% sensitivity, 92-96% specificity for AGHD diagnosis. Optimal GH cutoff 2.7-5.1 ng/mL. Accuracy comparable to insulin tolerance test (ITT). First FDA-approved oral GH stimulation test.

Improves (the measure goes up)Large effect13 studies

Studies that measured gh deficiency diagnosis

and 3 more in the citations list

Diagnostic Safety

No hypoglycemia risk unlike ITT. Well-tolerated single oral dose. Contraindicated only with strong CYP3A4 inhibitors. Can be used in patients where ITT is contraindicated (elderly, cardiovascular disease, seizure history).

Improves (the measure goes up)Large effect13 studies

Studies that measured diagnostic safety

and 3 more in the citations list

GH Stimulation Response

Robust GH release in healthy subjects. Peak response at 30-90 minutes. Reproducible test with low inter- and intra-individual variability. Blunted response (<5.1 ng/mL) indicates GH deficiency.

Improves (the measure goes up)Large effect12 studies

Studies that measured gh stimulation response

and 2 more in the citations list

General

General: outcomes studied for Macimorelin (Macrilen)
GradeOutcomeEffectSizeStudiesPeopleStudies list
Hormone Levels

10 preclinical studies support this finding. Primarily preclinical evidence.

Improves (the measure goes up)Moderate effect10 studies

Studies that measured hormone levels

Seizure Activity

3 preclinical studies support this finding. Primarily preclinical evidence.

Improves (the measure goes down)Small effect3 studies

Studies that measured seizure activity

Key findings

  • GH Deficiency DiagnosisGrowth Hormone DeficiencyImproves (the measure goes up)
  • Diagnostic SafetyGrowth Hormone DeficiencyImproves (the measure goes up)
  • GH Stimulation ResponseGrowth Hormone DeficiencyImproves (the measure goes up)

Safety notes in the studies

  • No hypoglycemia risk unlike ITT.

Studies cited

23 studies from PubMed

  1. Molecular recognition of two approved drugs Macimorelin and Anamorelin by the growth hormone secretagogue receptor.Acta pharmacologica Sinica, 2025 · PMID 40542284
  2. Macimorelin Acetate for the Diagnosis of Childhood-onset Growth Hormone DeficiencyJ Clin Endocrinol Metab, 2023 · PMID 36694890
  3. Pilot clinical trial of macimorelin to assess safety and efficacy in patients with cancer cachexiaInvest New Drugs, 2023 · PMID 36860137
  4. Diagnosis and testing for growth hormone deficiency across the ages: a global view of the accuracy, caveats, and cut-offs for diagnosis.Endocrine connections, 2023 · PMID 37052176
  5. Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Macimorelin in Children with Suspected Growth Hormone Deficiency: An Open-Label, Group Comparison, Dose-Escalation TrialHorm Res Paediatr, 2021 · PMID 34438400
  6. Current concepts of the diagnosis of adult growth hormone deficiency.Reviews in endocrine & metabolic disorders, 2021 · PMID 32959175
  7. Growth hormone deficiency in adults with Cushing's disease.Best practice & research. Clinical endocrinology & metabolism, 2021 · PMID 33272904
  8. Translational potential of the ghrelin receptor agonist macimorelin for seizure suppression in pharmacoresistant epilepsy.European journal of neurology, 2021 · PMID 34157194
  9. Sensitivity and specificity of the macimorelin test for diagnosis of AGHDEndocr Connect, 2020 · PMID 33320108
  10. Safety, tolerability, pharmacokinetics, and pharmacodynamics of macimorelin in healthy adults: Results of a single-dose, randomized controlled studyGrowth Horm IGF Res, 2020 · PMID 32325373
  11. Thorough QT/QTc Study Evaluating the Effect of Macimorelin on Cardiac Safety Parameters in Healthy ParticipantsClin Pharmacol Drug Dev, 2020 · PMID 32961034
  12. Growth hormone secretagogues: history, mechanism of action, and clinical developmentJCSM Rapid Commun, 2020 · PMID 30725920
  13. An update on the diagnosis of growth hormone deficiencyIndian J Endocrinol Metab, 2019 · PMID 31638606
  14. Adult growth hormone deficiency: clinical advances and approaches to improve adherence.Expert review of endocrinology & metabolism, 2019 · PMID 31721610
  15. Macimorelin as a Diagnostic Test for Adult GH DeficiencyJ Clin Endocrinol Metab, 2018 · PMID 29860473
  16. An update on the diagnosis of growth hormone deficiency.Discoveries (Craiova, Romania), 2018 · PMID 32309600
  17. Anticonvulsant effect of a ghrelin receptor agonist in 6Hz corneally kindled mice.Epilepsia, 2016 · PMID 27378373
  18. The macimorelin-stimulated growth hormone test for adult growth hormone deficiency diagnosis.Expert review of molecular diagnostics, 2014 · PMID 24834478
  19. Macimorelin (AEZS-130)-Stimulated Growth Hormone (GH) Test: Validation of a Novel Oral Stimulation Test for the Diagnosis of Adult GH DeficiencyJ Clin Endocrinol Metab, 2013 · PMID 23559086
  20. Protective but not anticonvulsant effects of ghrelin and JMV-1843 in the pilocarpine model of Status epilepticus.PloS one, 2013 · PMID 24015271
  21. Ghrelin stimulation of growth hormone-releasing hormone neurons is direct in the arcuate nucleus.PloS one, 2010 · PMID 20161791
  22. New active series of growth hormone secretagogues.Journal of medicinal chemistry, 2003 · PMID 12646029
  23. Growth Hormone Stimulation Tests in Assessing Adult Growth Hormone Deficiency.2000 · PMID 27809446