Macimorelin

Dosing from the Literature

Published for growth hormone: one 0.5 mg/kg test dose on the label for adults tested for growth hormone deficiency, single trial doses of 0.005–2.0 mg/kg in healthy adults, and 0.5–1.0 mg/kg a day for one week in 10 people with cancer cachexia (Macrilen label; Piccoli et al., 2007; Klaus et al., 2020; Herodes et al., 2023). Not published: any course longer than a week, or any trial of it for building muscle.

The table records doses as the label and each study gave them, by mouth unless noted. Every dose but the cachexia trial’s was a single dose; they are test and trial doses, not recommendations.

What It Is

Macimorelin is a small synthetic drug built like a modified peptide: two D-tryptophan units and one aminoisobutyric acid group joined in a chain by two peptide bonds (FDA summary review, 2017), written Aib-D-Trp-D-gTrp-CHO (Broglio et al., 2002). As the free base it is C26H30N6O3, 474.6 g/mol; the drug is its acetate salt, C28H34N6O5, 534.6 g/mol (PubChem; Macrilen label). The label classes it as a growth hormone secretagogue receptor agonist, also called a ghrelin receptor agonist (Macrilen label; FDA summary review, 2017). Its development codes were EP-1572, JMV-1843, ARD-07 and AEZS-130, and macimorelin is its international nonproprietary name (FDA substance registry).

Chemists at the University of Montpellier described it in 2003 as compound JMV 1843, one of a series built from an earlier compound, EP-51389: injected under the skin of rats it released more growth hormone than hexarelin, it worked by mouth in beagle dogs, it bound human pituitary receptors, and it was “selected for clinical studies” (Guerlavais et al., 2003). A University of Turin group, with the Montpellier chemists among its co-authors, had reported tests in two healthy young men in 2002, as EP1572: it raised growth hormone after an injection into a vein of 1.0 µg/kg and after oral doses as low as 0.06 mg/kg (Broglio et al., 2002). It was then developed as an oral test for growth hormone deficiency in adults, as ARD-07 by Ardana Biosciences and as AEZS-130 by Aeterna Zentaris (MacLean et al., 2009; Garcia et al., 2013; NCT00448747).

Its first Phase 3 began in 2007; its original sponsor, Ardana, halted it for financial reasons before it was restarted, and in 2008 Geref Diagnostic, the GHRH half of its comparison test (GHRH plus arginine), left the US market (NCT00448747; Garcia et al., 2013). FDA declined to approve the first application on November 5, 2014: the trial’s planned analysis had missed its goal, source records could not confirm some patients’ diagnoses, and one volunteer had a serious QT prolongation (FDA complete response letter, 2014). A new Phase 3 against the insulin tolerance test and a dedicated QT study followed, and FDA approved Macrilen on December 20, 2017, for the diagnosis of adult growth hormone deficiency, without referring it to an advisory committee (FDA approval letter, 2017; FDA summary review, 2017). Drugs@FDA lists it as a new molecular entity with orphan designation. The EU authorized it on January 11, 2019; it is now sold there as Ghryvelin (EMA medicines data, read October 4, 2026; COSCIENS, 2025).

Aeterna Zentaris licensed the US and Canadian rights to Strongbridge in January 2018; Novo Nordisk later marketed Macrilen in the US, and after Novo Nordisk’s license ended on May 23, 2023 the company wrote that US sales were “temporarily discontinued” until a relaunch with a new partner (Aeterna Zentaris, 2024). In August 2024 its Phase 3 in children failed its main goal (COSCIENS, August 27, 2024), and on July 23, 2026 FDA approved a label update saying diagnostic accuracy was not shown in children (FDA supplement approval letter, 2026; Macrilen label). The parent company, renamed COSCIENS Biopharma after a 2024 merger with Ceapro, stopped funding its German subsidiary Aeterna Zentaris GmbH, which holds the US application; the subsidiary filed for insolvency on March 23, 2026, and the parent expects to surrender its rights to Macrilen (COSCIENS, March 5, 2026; COSCIENS, 2026).

PubMed returns 48 records for “macimorelin” (October 4, 2026). By this page’s count, 27 report studies that gave it to people, animals or cells, or solved its structure on the receptor; the rest are reviews, computer-screening papers and articles that mention it. Searching its codes (EP1572, JMV-1843, AEZS-130, ARD-07) adds 4 more animal and tissue studies. One record is a 2026 heart-failure trial of an oral ghrelin-receptor agonist coded AC01, which PubMed indexes under macimorelin (Lund, Barandiarán Aizpurua et al., 2026). AC01 is a different compound: its developer says it was in-licensed from Helsinn (AnaCardio, June 25, 2026), the developers’ animal study identifies it as HM01, discovered by Helsinn (Lund, Hage et al., 2026), and a 2022 review of ghrelin-receptor drugs lists HM01 and macimorelin as separate compounds (Giorgioni et al., 2022). Neither the trial paper’s abstract nor its registration names macimorelin (NCT05642507), and the trial is not counted here.

Mechanism of Action

In people, the trials measured hormones and the drug in the blood (Klaus et al., 2020; Urwyler et al., 2021). The receptor, brain-cell and appetite findings come from a receptor structure, binding tests on human pituitary tissue and the cloned human receptor, brain slices from mice, and live mice (Wang et al., 2025; Guerlavais et al., 2003; Osterstock et al., 2010; Holubová et al., 2013; Pirnik et al., 2011).

• Ghrelin receptor (GHSR-1a) agonist — The label says macimorelin releases growth hormone by activating growth hormone secretagogue receptors in the pituitary and hypothalamus (Macrilen label). Its developers reported that it binds human pituitary receptors and the cloned human GHS-R1a (Guerlavais et al., 2003). A 2025 cryo-electron microscopy study solved the receptor bound to macimorelin at 2.63 Å: it sits in a two-part pocket, and anamorelin, another approved agonist, bound the receptor more tightly (Wang et al., 2025).
• GHRH neurons and the pituitary — In brain slices from mice, the compound (as JMV1843, 10 nM) made growth-hormone-releasing-hormone (GHRH) neurons of the arcuate nucleus fire faster, as ghrelin did (Osterstock et al., 2010). The label says it acts downstream from the hypothalamus, releasing growth hormone stored in the pituitary, so deficiency caused by a recent hypothalamic lesion may be missed early (Macrilen label). In one adult with a homozygous variant of the ghrelin-receptor gene, growth hormone rose normally in an insulin tolerance test but not at all after macimorelin (Biagetti et al., 2023).
• Other pituitary hormones — In 28 healthy adults, ACTH, cortisol and prolactin rose for a short time, with no dose relationship (Klaus et al., 2020). In 28 other healthy volunteers, prolactin and free T4 rose and TSH fell, with no effect on ACTH, cortisol, LH or FSH (Urwyler et al., 2021). The two studies disagree on ACTH and cortisol. Copeptin, a marker of vasopressin, did not change (Urwyler et al., 2021), and neither oxytocin nor neurophysin-I rose (Sailer et al., 2021; Nikaj et al., 2026).
• More was not more — In 28 healthy adults, growth hormone peaks were similar after 0.5 and 1.0 mg/kg (31.9 and 37.8 ng/mL) and about half as high after 2.0 mg/kg (18.4 ng/mL), and blood levels of the drug rose less than in proportion to the dose (Klaus et al., 2020).
• Food and breakdown — In 16 healthy adults a meal about halved exposure: the area under the curve was 27.8 fasting and 13.7 with food (MacLean et al., 2009); the label gives a 55% lower peak and 49% lower exposure after a liquid meal. In a lab study with human liver microsomes, the enzyme CYP3A4 was the main one breaking it down, and the half-life after one 0.5 mg/kg dose in healthy adults is 4.1 hours (Macrilen label).
• Appetite circuits (mice) — In lean mice, 10 days of injections raised the hypothalamic appetite signals NPY and AgRP along with food intake (Holubová et al., 2013), and one 5 mg/kg injection under the skin switched on neurons in brain areas that govern feeding, as ghrelin did (Pirnik et al., 2011).
• QT interval — It lengthens the heart’s QT interval by about 11 msec through an unknown mechanism (Macrilen label); FDA’s reviewers wrote that the effect is not mediated through the hERG potassium channel (FDA summary review, 2017).

What the Research Shows

Most of its human research is about one use, testing the pituitary for growth hormone deficiency; the details are under Human Data. The rest is a one-week pilot in cancer cachexia (Herodes et al., 2023), hormone studies in volunteers (Urwyler et al., 2021) and animal and lab work.

• As a test in adults — Two Phase 3 trials, of about 100 and 157 adults, support the label (Garcia et al., 2013; Garcia et al., 2018). FDA’s reviewers concluded that a peak below 2.8 ng/mL “reliably rules in (or confirms)” deficiency and that the test “performs slightly less well at reliably ruling out” disease (FDA summary review, 2017). In a 2025 Delphi survey for the Growth Hormone Research Society, the adult panel treated the insulin tolerance test as the benchmark and reached consensus in favor of the macimorelin test (Arlien-Søborg et al., 2025).
• Body weight changes the reading — Peak growth hormone fell as body mass index rose in healthy controls (Garcia et al., 2013). In 37 adults tested at one center, the label’s 2.8 ng/mL cut-off classed 15 as deficient and a proposed 5.1 ng/mL cut-off classed 20; three of the five who differed had a low pre-test probability and a BMI above 35 (Yadav et al., 2026).
• As a test in children — In 24 children and teenagers, single doses of 0.25–1.0 mg/kg raised growth hormone with no macimorelin-related adverse events (Csákváry et al., 2021). The Phase 3 that followed, in 102 children, failed its main goal (COSCIENS, August 27, 2024), and the label now says diagnostic accuracy was not demonstrated (Macrilen label).
• Appetite, weight and muscle — In lean male mice, one injection of 0.01–10 mg/kg under the skin raised food intake up to five-fold, and 10 or 20 mg/kg a day for 10 days raised food intake and body weight (Holubová et al., 2013). In a 2-week mouse epilepsy study, 5 mg/kg into the abdomen twice a day did not significantly change food intake or body weight (Buckinx et al., 2021). In people, the only test of repeated doses was a one-week pilot in 15 people with cancer cachexia, with no significant change in weight, IGF-1, quality of life, handgrip strength or stair-climb power (Herodes et al., 2023). No study has measured muscle mass on it (PubMed and Europe PMC, searched October 4, 2026).
• Seizures (rodents) — In mice, it reduced seizure severity in two kindling models (Coppens et al., 2016; Buckinx et al., 2019), and 5 mg/kg into the abdomen twice a day for 2 weeks cut the number and length of seizures in a drug-resistant epilepsy model without changing how the disease developed (Buckinx et al., 2021). In rats, 330 µg/kg before pilocarpine did not change the seizures but limited some brain damage (Lucchi et al., 2013).
• Detection in sport — An anti-doping lab made a preliminary identification of 12 macimorelin metabolites in lab and rat experiments, the rats given single oral doses, and added the drug to screening and confirmation tests for human urine and blood (Lange et al., 2021).

Human Data

Published: single-dose studies in healthy adults, two Phase 3 trials of it as a test for adult growth hormone deficiency, a single-dose study in children, hormone studies in healthy volunteers and a one-week pilot in cancer cachexia. Registered: six trials, all completed; three post results, and the children’s Phase 3 has neither posted nor published results (ClinicalTrials.gov, searched October 4, 2026).

• First doses in people (Broglio et al., 2002; Piccoli et al., 2007) — In two healthy young men, 1.0 µg/kg into a vein and oral doses as low as 0.06 mg/kg raised growth hormone (Broglio et al., 2002). In a Basel Phase 1, 36 healthy men took one oral dose of 0.005, 0.05 or 0.5 mg/kg or placebo, and a second part gave 0.2–0.5 mg/kg straight into the duodenum; drug levels rose quickly and with the dose, and growth hormone release was strong (Piccoli et al., 2007).
• Food, 16 adults (MacLean et al., 2009) — Eight men and eight women took 0.5 mg/kg once fasting and once with a test meal. Exposure was about twice as high fasting (area under the curve 27.8 against 13.7), the drug’s peak was 10.6 against 4.4 ng/mL, and growth hormone peaked at 37.1 ng/mL fasting against 13.0 ng/mL, later, with food.
• First Phase 3, against GHRH plus arginine (Garcia et al., 2013) — At 11 US centers, 53 adults with deficiency and 48 matched controls enrolled, and 50 with confirmed deficiency and the 48 controls were analyzed after 0.5 mg/kg; 43 patients and 10 controls also had the GHRH-plus-arginine test before Geref Diagnostic left the US market. Peak growth hormone averaged 2.36 ng/mL in patients and 17.71 ng/mL in controls. The authors’ cut point of 2.7 ng/mL gave 82% sensitivity and 92% specificity, and in those with both tests it separated patients from controls comparably to GHRH plus arginine (area under the ROC curve 0.99 against 0.94, P = .29). One control had a drug-related serious QT prolongation without symptoms that resolved within 24 hours. FDA later judged that the pre-specified analysis, a lower bound of the ROC area above 0.85, was not met, and that source records could not confirm some patients’ diagnoses (FDA complete response letter, 2014).
• Second Phase 3, against the insulin tolerance test (Garcia et al., 2018) — Adults with high, intermediate or low likelihood of deficiency and matched healthy controls took macimorelin (0.5 mg/kg) and the insulin tolerance test in random order (NCT02558829). By the label’s count, 157 had at least one test and 140 had both. With cut-offs of 2.8 ng/mL for macimorelin and 5.1 ng/mL for the insulin test, macimorelin agreed on 62 of the 66 people the insulin test cleared (negative agreement 94%) and flagged 55 of the 74 it called deficient, missing 19 (positive agreement 74%). In the intermediate- and low-likelihood groups, positive agreement was 61%, with a lower 95% bound of 43% (Macrilen label). One of 154 macimorelin tests failed, against 27 of 157 insulin tests (17.2%) in which blood sugar could not be driven low enough (Macrilen label). The trial needed the lower 95% confidence bound of positive agreement to reach 70%; it was 63% (FDA summary review, 2017). The paper reports 87% sensitivity and 96% specificity, and in a post hoc analysis a 5.1 ng/mL cut-off for both tests raised positive agreement to 82%; no serious adverse events were reported for macimorelin (Garcia et al., 2018). On retesting, results agreed in 31 of 34 people by the label’s count (91.2%) and in 97% of 33 in the paper.
• Re-analyses of the same trial (Garcia et al., 2021) — Age, BMI and sex did not meaningfully change the test’s performance, and of the cut-offs examined, 5.1 ng/mL gave 96% specificity and 92% sensitivity. The analysis was sponsored by Aeterna Zentaris, and employees of Aeterna Zentaris, Novo Nordisk and Strongbridge were among its authors.
• Single doses up to 4 times the label dose (Klaus et al., 2020; Lissy et al., 2021) — 28 healthy adults took 0.5, 1.0 or 2.0 mg/kg or placebo: 10 of 28 reported 19 adverse events, all mild or moderate, headache the most common drug-related one, and every dose lengthened QTcF by 10–11 ms (Klaus et al., 2020). In the thorough QT study, 60 healthy adults were randomized to take 2.0 mg/kg, placebo and moxifloxacin in turn, and 56 took all three: QTcF rose by a maximum of 9.61 ms at 4 hours, and the upper confidence bound passed the 10 ms regulatory threshold; 16 of 57 (28.1%) reported adverse events after macimorelin, headache in 8 (Lissy et al., 2021).
• Hormone studies in Basel (Urwyler et al., 2021; Sailer et al., 2021; Nikaj et al., 2026) — 28 healthy volunteers took 0.5 and then 0.75 mg/kg on two days: growth hormone rose but copeptin did not, so it offers no oral test for diabetes insipidus (Urwyler et al., 2021). In 25 volunteers given 0.75 mg/kg, oxytocin did not rise (Sailer et al., 2021), nor did neurophysin-I (Nikaj et al., 2026).
• Children (Csákváry et al., 2021; NCT04786873) — 24 children and teenagers aged 2 to under 18 with suspected deficiency took 0.25, 0.5 or 1.0 mg/kg once: no macimorelin-related adverse events, and growth hormone peaked at 37.5–52.5 minutes on average (Csákváry et al., 2021). The Phase 3 DETECT trial then gave 1.0 mg/kg on two occasions to 102 children aged 3–17 (the registry lists 101), compared with arginine and clonidine tests, and failed its main goal; the company reported a cut-off derived from the trial data of 25.59 ng/mL, against 7–10 ng/mL for existing tests, and suggested the comparison tests may have produced many false positives (COSCIENS, August 27, 2024). Aeterna Zentaris’s labeling text on DailyMed, posted in February 2026 before FDA approved the label’s pediatric section in July 2026, gives the lower 97.5% confidence bound of the ROC area as 0.66, short of the pre-specified 0.70, with 78.6% sensitivity and 67.9% specificity at that cut-off; the FDA-approved label does not carry these figures (DailyMed label, February 2026; Macrilen label). No results are posted or published.
• Cancer cachexia, one week (Herodes et al., 2023) — A randomized, double-blind, placebo-controlled pilot at two Veterans Affairs medical centers screened 9,129 patients and found 15 eligible: 8 were randomized to 0.5 mg/kg a day for 7 days and 5 to placebo (one in each arm stopped early), then 2 more were randomized to 1.0 mg/kg before the trial closed for poor enrollment (Herodes et al., 2023; NCT01614990). Changes in weight, IGF-1 and quality-of-life scores did not differ significantly from placebo. Of the goals set in advance, 2 on macimorelin and none on placebo gained at least 0.8 kg; 4 and 1 improved by at least 15% on a symptom scale, and 3 and 0 on a fatigue scale; no one met the IGF-1 goal; none of these differences was significant. On day 7, macimorelin recipients scored better on the symptom scale’s pain and fatigue items (P = 0.05 each), and test-meal calories were higher on macimorelin (1110 against 509 kcal, P = 0.03), but the change from the baseline test meal did not differ between the groups. The authors concluded that a week of daily macimorelin was safe and “numerically improved” weight and quality of life against placebo, and called for longer, larger studies (Herodes et al., 2023). No related adverse events were reported. Aeterna Zentaris supplied the drug, and one author was its employee.
• In practice (Yadav et al., 2026) — A review of 37 adults tested at one center found that the 5.1 ng/mL cut-off classed more people as deficient than 2.8 ng/mL (20 against 15), and leaving out the 90-minute sample changed no result.

The evidence meter on the Macimorelin card reads “Human pilots”, not “Approved drug”: it counts published human data for the use on its tag, muscle and growth hormone, and macimorelin’s approval is for a one-dose diagnostic test, not for raising growth hormone over time or building muscle. Its two adult Phase 3 trials tested it as that test (Garcia et al., 2013; Garcia et al., 2018). Its randomized studies of growth hormone release gave single doses to healthy adults (Piccoli et al., 2007; Klaus et al., 2020), and the one trial of repeated doses, a one-week pilot in 15 people with cancer cachexia, found no significant difference from placebo (Herodes et al., 2023).

Reconstitution & Storage

There is nothing to inject. Macrilen comes as 60 mg of macimorelin (68 mg of the acetate) in white to off-white granules in an aluminum pouch, one pouch per box; on the label, a healthcare professional dissolves the granules in 120 mL of water, giving 0.5 mg/mL, and the person being tested drinks the volume that matches their weight (Macrilen label).

• Storage — The label keeps the pouches refrigerated at 2–8 °C and has the mixed solution used within 30 minutes, with any left over discarded (Macrilen label). FDA’s reviewers found that the stability data supported a 48-month shelf life at 2–8 °C (FDA summary review, 2017). The EU product is also kept refrigerated, in its package, away from light and moisture, and its label gives an unopened sachet a shelf life of 4 years (Ghryvelin EU label).
• Food — Much less is absorbed with a meal (MacLean et al., 2009); the label’s test follows at least 8 hours of fasting (Macrilen label).
• Products outside the label — A chemical supplier lists macimorelin acetate as a research reagent, for research use only, and says it does not sell to patients (catalog read October 4, 2026). No study has tested such a product in people, and no analysis of one turned up in the PubMed searches for this page.

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Side Effects & Risks

• Common reactions (label) — In 154 adults given 0.5 mg/kg in the Phase 3: altered taste 4.5% (7 people); dizziness, headache and fatigue 3.9% each; nausea and hunger 3.2% each; diarrhea and upper respiratory infection 1.9% each; feeling hot, heavy sweating, nasopharyngitis and slow heart rate (sinus bradycardia) 1.3% each (Macrilen label). In the first Phase 3, the unflavored solution tasted unpleasant to 66.7% of patients and 57.4% of controls (Garcia et al., 2013).
• QT prolongation — In 28 healthy adults, every single dose from 0.5 to 2.0 mg/kg lengthened QTcF by 10–11 ms (Klaus et al., 2020), and 2.0 mg/kg lengthened it by up to 9.61 ms in the thorough QT study in healthy adults (Lissy et al., 2021). In the first Phase 3, one control had an asymptomatic QT prolongation with T-wave changes that the paper reports as drug-related and serious (serious because the volunteer was hospitalized as a precaution); it resolved within 24 hours, and the volunteer had stopped citalopram, a drug FDA has linked to QT prolongation, 7 days earlier (Garcia et al., 2013). FDA wrote that the drug could not be excluded as its cause and asked for a thorough QT study (FDA complete response letter, 2014). FDA’s reviewers describe the serious QT event in the original application: a morbidly obese control, 365 lbs, given a relatively high absolute dose, whose QTc rose by 61 milliseconds to 501 (FDA summary review, 2017). The label advises against using it with drugs that prolong the QT interval and lists antipsychotics, moxifloxacin and class IA and III antiarrhythmics among them (Macrilen label). The EU label calls for caution in people with a proarrhythmic condition, and says that in long QT syndrome or after torsades de pointes its use may only be considered in a cardiovascular clinical unit (Ghryvelin EU label).
• Wrong results — Strong CYP3A4 inducers can lower its blood levels and give a false positive; growth hormone treatment and drugs that affect growth hormone release can distort the result; and a recent hypothalamic lesion can give a false negative (Macrilen label). Its performance is not established above a BMI of 40, and there were too few people aged 65 and over to judge them (Macrilen label).
• Other hormones — Prolactin rose after a dose in two studies, and ACTH and cortisol in one of them (Klaus et al., 2020; Urwyler et al., 2021).
• In children and in cancer cachexia — No macimorelin-related adverse events in 24 children (Csákváry et al., 2021); Aeterna Zentaris’s February 2026 labeling text on DailyMed, not the FDA-approved July 2026 label, says safety in 126 pediatric patients was consistent with that in adults (DailyMed label, February 2026; Macrilen label). No related adverse events in the one-week cachexia pilot (Herodes et al., 2023).
• Pregnancy, cancer and fertility — No data in pregnancy and no animal reproduction studies; no long-term cancer studies in rodents and no fertility studies; it did not cause mutations in bacterial and mouse-cell tests (Macrilen label).
• What has not been tested — Use for more than 7 days, use to raise growth hormone over time, and any effect on muscle mass (Herodes et al., 2023; PubMed and Europe PMC, searched October 4, 2026).
• WADA — Prohibited at all times: the 2026 Prohibited List names macimorelin under S2.2.4, growth hormone releasing factors, among “growth hormone secretagogues (GHS) and their mimetics [e.g. anamorelin, capromorelin, ibutamoren (MK-677), ipamorelin, lenomorelin (ghrelin), macimorelin and tabimorelin]” (World Anti-Doping Agency, 2026). Detection methods for urine and blood are published (Lange et al., 2021).

Bloodwork & Monitoring

Macrilen is itself a blood test of the pituitary. What its label lists, and what the trials measured:

• The test (label) — Growth hormone in blood drawn 30, 45, 60 and 90 minutes after the dose; a maximum below 2.8 ng/mL confirms adult growth hormone deficiency (Macrilen label). The EU label uses the 45, 60 and 90 minute samples and the same cut-off (Ghryvelin EU label). At one center, leaving out the 90-minute sample changed no result in 37 adults (Yadav et al., 2026).
• Before the test (label) — The label lists missing sex hormones, thyroid hormone and glucocorticoid replaced, growth hormone treatment stopped at least a week before, strong CYP3A4 inducers and drugs that change growth hormone release washed out, and at least 8 hours of fasting (Macrilen label).
• Heart rhythm — The first Phase 3 recorded ECGs before and 60 minutes after the dose (Garcia et al., 2013), and the QT studies measured QTcF at set times after dosing (Klaus et al., 2020; Lissy et al., 2021). The EU label says ECG checks before and 1, 2, 4 and 6 hours after the dose may be indicated in people with kidney or liver impairment or a proarrhythmic condition (a past heart attack, heart failure or a QTc above 500 ms), and that in long QT syndrome or after torsades de pointes its use may only be considered in a cardiovascular clinical unit (Ghryvelin EU label).
• Safety labs in the trials — Blood count and metabolic panel at screening and after the study, and IGF-1 (Garcia et al., 2013); blood count, metabolic panel, urinalysis, ECG and IGF-1 in the cachexia pilot (Herodes et al., 2023).
• Which tests fit a given person — A question for a licensed healthcare provider. This page can’t answer it.

Commonly Stacked With

No study has tested macimorelin in combination with another compound on this site (PubMed and Europe PMC, searched October 4, 2026). In the first Phase 3, the patients who needed other hormones replaced had been on stable replacement for at least 3 months, most often sex steroids (87%), thyroxine (85%) and glucocorticoids (62%) (Garcia et al., 2013). In its trials it was compared with other growth hormone tests, each given as a separate test in a crossover, not combined: GHRH plus arginine (Garcia et al., 2013), the insulin tolerance test (Garcia et al., 2018) and, in children, arginine and clonidine (NCT04786873). The label has missing sex hormones, thyroid hormone and glucocorticoid replaced before the test, and lists drugs that can distort the result or add to its QT effect, growth hormone itself among them (Macrilen label).

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Related Compounds

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References

1. Aeterna Zentaris GmbH. MACRILEN (macimorelin) for oral solution. Prescribing information, revised 07/2026 (supplement S-005; initial US approval 2017). accessdata.fda.gov/drugsatfda_docs/label/2026/205598s005lbl.pdf. Read October 4, 2026.
2. Aeterna Zentaris GmbH. MACRILEN (macimorelin acetate) granule, for solution. Structured product label on DailyMed, set ID aeb30f1a-4815-47ae-a2cb-b6b4e26372e1, version 3, published February 19, 2026, marked “Revised: MM/YYYY” (section 8.4, Pediatric Use, and the pediatric safety statement in section 6.1). Posted after the company submitted supplement S-005 on January 23, 2026 and before FDA approved it on July 23, 2026; the FDA-approved label of July 2026 carries a two-sentence section 8.4 and no pediatric statement in section 6.1. dailymed.nlm.nih.gov. Read October 4, 2026.
3. U.S. Food and Drug Administration. Drugs@FDA, NDA 205598 (MACRILEN; Aeterna Zentaris): original approval December 20, 2017 (type 1, new molecular entity; orphan); labeling supplement S-003, November 27, 2019; efficacy supplement S-005, July 23, 2026 (priority; orphan); product 001, macimorelin acetate equivalent to 60 mg base per pouch, marketing status “Discontinued.” openFDA drug/drugsfda, data of October 2, 2026. api.fda.gov/drug/drugsfda.json?search=application_number:NDA205598. Read October 4, 2026.
4. FDA. NDA 205598 approval letter to Aeterna Zentaris, Inc., agent for Aeterna Zentaris GmbH, December 20, 2017 (not referred to an advisory committee). accessdata.fda.gov/drugsatfda_docs/appletter/2017/205598Orig1s000ltr.pdf. Read October 4, 2026.
5. FDA. NDA 205598 complete response letter, November 5, 2014 (Drug Approval Package, Other Action Letters). accessdata.fda.gov/drugsatfda_docs/nda/2017/205598Orig1s000OtherActionLtrs.pdf. Read October 4, 2026.
6. FDA, Center for Drug Evaluation and Research. Division Director Summary Review, NDA 205598, Macrilen (macimorelin), 2017. accessdata.fda.gov/drugsatfda_docs/nda/2017/205598Orig1s000SumR.pdf. Read October 4, 2026.
7. FDA. NDA 205598/S-005 supplement approval letter, July 23, 2026 (pediatric labeling under the Best Pharmaceuticals for Children Act; section 8.4). accessdata.fda.gov/drugsatfda_docs/appletter/2026/205598Orig1s005ltr.pdf. Read October 4, 2026.
8. FDA. National Drug Code Directory: Macrilen, NDC 58844-130 (Aeterna Zentaris GmbH; marketing start January 29, 2018; no end date) and NDC 0169-1401 (Novo Nordisk; marketing start January 31, 2022; marketing end February 28, 2027); macimorelin acetate bulk ingredient, NDC 59162-0001. openFDA drug/ndc, data of October 2, 2026. Read October 4, 2026.
9. National Library of Medicine. PubChem: macimorelin, CID 9804938 (C26H30N6O3, 474.6 g/mol), and macimorelin acetate, CID 71526737 (C28H34N6O5, 534.6 g/mol). pubchem.ncbi.nlm.nih.gov. Read October 4, 2026.
10. FDA. Global Substance Registration System: macimorelin, UNII 8680B21W73 (INN and USAN; codes AEZS-130, ARD-07, D-87575, EP-1572, JMV-1843; CAS 381231-18-1). gsrs.ncats.nih.gov. Read October 4, 2026.
11. Guerlavais V, Boeglin D, Mousseaux D, Oiry C, et al. New active series of growth hormone secretagogues. J Med Chem. 2003;46(7):1191-1203. PMID: 12646029. DOI: 10.1021/jm020985q.
12. Broglio F, Boutignon F, Benso A, Gottero C, et al. EP1572: a novel peptido-mimetic GH secretagogue with potent and selective GH-releasing activity in man. J Endocrinol Invest. 2002;25(8):RC26-RC28. PMID: 12240910. DOI: 10.1007/BF03345096.
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19. Lissy M, Demmel V, Sachse R, Ammer N, Kelepouris N, Ostrow V. Thorough QT/QTc Study Evaluating the Effect of Macimorelin on Cardiac Safety Parameters in Healthy Participants. Clin Pharmacol Drug Dev. 2021;10(5):494-501. PMID: 32961034. DOI: 10.1002/cpdd.872.
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23. Csákváry V, Ammer N, Bagci EB, Bolshova OV, et al. Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Macimorelin in Children with Suspected Growth Hormone Deficiency: An Open-Label, Group Comparison, Dose-Escalation Trial. Horm Res Paediatr. 2021;94(7-8):239-250. PMID: 34438400. DOI: 10.1159/000519232.
24. Herodes M, Anderson LJ, Shober S, Schur EA, et al. Pilot clinical trial of macimorelin to assess safety and efficacy in patients with cancer cachexia. J Cachexia Sarcopenia Muscle. 2023;14(2):835-846. PMID: 36860137. DOI: 10.1002/jcsm.13191.
25. Yadav P, Hamrahian AH, Salvatori R. Real-world diagnostic performance of the macimorelin stimulation test in the diagnosis of adult growth hormone deficiency. Pituitary. 2026;29(2). PMID: 41793495. DOI: 10.1007/s11102-026-01654-0.
26. Biagetti B, Valenzuela I, Campos-Martorell A, Campos B, et al. Contribution of Dynamic and Genetic Tests for Short Stature Diagnosing: A Case Report. Diagnostics (Basel). 2023;13(13):2259. PMID: 37443653. DOI: 10.3390/diagnostics13132259.
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28. Wang RL, Sun J, Liu H, Guo SM, et al. Molecular recognition of two approved drugs Macimorelin and Anamorelin by the growth hormone secretagogue receptor. Acta Pharmacol Sin. 2025;46(11):2998-3008. PMID: 40542284. DOI: 10.1038/s41401-025-01606-7.
29. Osterstock G, Escobar P, Mitutsova V, Gouty-Colomer LA, et al. Ghrelin stimulation of growth hormone-releasing hormone neurons is direct in the arcuate nucleus. PLoS One. 2010;5(2):e9159. PMID: 20161791. DOI: 10.1371/journal.pone.0009159.
30. Holubová M, Spolcová A, Demianová Z, Sýkora D, et al. Ghrelin agonist JMV 1843 increases food intake, body weight and expression of orexigenic neuropeptides in mice. Physiol Res. 2013;62(4):435-444. PMID: 23590608. DOI: 10.33549/physiolres.932488.
31. Pirnik Z, Bundziková J, Holubová M, Pýchová M, et al. Ghrelin agonists impact on Fos protein expression in brain areas related to food intake regulation in male C57BL/6 mice. Neurochem Int. 2011;59(6):889-895. PMID: 21843570. DOI: 10.1016/j.neuint.2011.08.001.
32. Coppens J, Aourz N, Walrave L, Fehrentz JA, et al. Anticonvulsant effect of a ghrelin receptor agonist in 6Hz corneally kindled mice. Epilepsia. 2016;57(9):e195-e199. PMID: 27378373. DOI: 10.1111/epi.13463.
33. Buckinx A, Van Den Herrewegen Y, Pierre A, Cottone E, et al. Differential Effects of a Full and Biased Ghrelin Receptor Agonist in a Mouse Kindling Model. Int J Mol Sci. 2019;20(10):2480. PMID: 31137460. DOI: 10.3390/ijms20102480.
34. Buckinx A, Pierre A, Van Den Herrewegen Y, Guenther E, et al. Translational potential of the ghrelin receptor agonist macimorelin for seizure suppression in pharmacoresistant epilepsy. Eur J Neurol. 2021;28(9):3100-3112. PMID: 34157194. DOI: 10.1111/ene.14992.
35. Lucchi C, Curia G, Vinet J, Gualtieri F, et al. Protective but not anticonvulsant effects of ghrelin and JMV-1843 in the pilocarpine model of Status epilepticus. PLoS One. 2013;8(8):e72716. PMID: 24015271. DOI: 10.1371/journal.pone.0072716.
36. Lange T, Thomas A, Görgens C, Bidlingmaier M, et al. Comprehensive insights into the formation of metabolites of the ghrelin mimetics capromorelin, macimorelin and tabimorelin as potential markers for doping control purposes. Biomed Chromatogr. 2021;35(6):e5075. PMID: 33458843. DOI: 10.1002/bmc.5075.
37. Lund LH, Barandiarán Aizpurua A, Bollano E, Braun O, et al. Safety, pharmacokinetics, and exploratory efficacy of the oral ghrelin receptor agonist AC01 in heart failure with reduced ejection fraction (GOAL-HF1): a randomised, double-blind, placebo-controlled, phase 1b/2a study. Lancet. 2026;408(10551):248-262. PMID: 42341796. DOI: 10.1016/S0140-6736(26)00904-9. (Registration: ClinicalTrials.gov NCT05642507, sponsor AnaCardio AB.)
38. Lund LH, Hage C, Carlström M, Champéroux P, et al. The Orally Available Ghrelin Receptor-Agonist AC01 Improves Systolic Function in HFrEF Mice and Nonhuman Primates. JACC Basic Transl Sci. 2026;11(8):101635. PMID: 42485931. DOI: 10.1016/j.jacbts.2026.101635.
39. Giorgioni G, Del Bello F, Quaglia W, Botticelli L, et al. Advances in the Development of Nonpeptide Small Molecules Targeting Ghrelin Receptor. J Med Chem. 2022;65(4):3098-3118. PMID: 35157454. DOI: 10.1021/acs.jmedchem.1c02191.
40. AnaCardio AB. AnaCardio’s Phase 1b/2a GOAL-HF1 study in patients with heart failure and reduced ejection fraction (HFrEF) published in The Lancet. Press release, June 25, 2026 (AC01 “in-licensed from Helsinn”). anacardio.com. Read October 4, 2026.
41. Aeterna Zentaris Inc. Annual report (Form 20-F) for the year ended December 31, 2023, filed March 27, 2024: the January 16, 2018 license and assignment agreement with Strongbridge Ireland Limited; Novo Nordisk’s license, rights regained May 23, 2023, and US sales “temporarily discontinued”; the January 4, 2017 announcement on the confirmatory Phase 3; Israeli approval. sec.gov/Archives/edgar/data/1113423/000149315224011401/form20-f.htm. Read October 4, 2026.
42. COSCIENS Biopharma Inc. Annual report (Form 20-F) for the year ended December 31, 2024, filed April 9, 2025: launch countries in Europe; approval in the Republic of Korea on September 7, 2023. sec.gov/Archives/edgar/data/1113423/000164117225003456/form20-f.htm. Read October 4, 2026.
43. COSCIENS Biopharma Inc. Annual report (Form 20-F) for the year ended December 31, 2025, filed March 25, 2026: insolvency filings of Aeterna Zentaris GmbH and Zentaris IVF GmbH on March 23, 2026; rights to Macrilen expected to be surrendered; the 2024 merger with Ceapro. sec.gov/Archives/edgar/data/1113423/000149315226012703/form20-f.htm. Read October 4, 2026.
44. COSCIENS Biopharma Inc. COSCIENS Biopharma Inc. Announces Top-Line Results of Phase 3 DETECT-Trial for the Diagnosis of Childhood-Onset Growth Hormone Deficiency. Press release, August 27, 2024 (Form 6-K, Exhibit 99.1). sec.gov/Archives/edgar/data/1113423/000149315224033937/ex99-1.htm. Read October 4, 2026.
45. COSCIENS Biopharma Inc. COSCIENS Provides Strategic Update. Press release, March 5, 2026 (Form 6-K, Exhibit 99.1). sec.gov/Archives/edgar/data/1113423/000149315226009018/ex99-1.htm. Read October 4, 2026.
46. European Medicines Agency. Medicines data: Ghryvelin (previously Macimorelin Aeterna Zentaris), EMEA/H/C/004660, authorised, marketing authorisation January 11, 2019, holder Atnahs Pharma Netherlands B.V., additional monitoring; Adlumiz (anamorelin), refused November 16, 2017. ema.europa.eu (medicines data table, timestamp October 4, 2026). Read October 4, 2026.
47. European Medicines Agency. Ghryvelin (macimorelin) 60 mg granules for oral suspension in sachet: product information (EU/1/18/1337/001; first authorisation January 11, 2019). ema.europa.eu/en/documents/product-information/ghryvelin-epar-product-information_en.pdf. Read October 4, 2026.
48. ClinicalTrials.gov. Registrations of macimorelin: NCT00377377 (Phase 1, healthy men, University Hospital Basel, completed 2006), NCT00448747 (Phase 3 against GHRH plus arginine, 101, completed 2011, results posted), NCT01614990 (Phase 2 pilot in cancer cachexia, 15, completed 2021, results posted), NCT02558829 (Phase 3 against the insulin tolerance test, 157, completed 2016, results posted), NCT03844217 (copeptin study, 28 healthy volunteers, completed 2019) and NCT04786873 (DETECT, Phase 3 in children, 101, completed June 13, 2024, no results posted). clinicaltrials.gov, API v2. Read October 4, 2026.
49. Code of Federal Regulations. 21 CFR 216.23, Bulk drug substances that can be used to compound drug products in accordance with section 503A of the Federal Food, Drug, and Cosmetic Act, and 21 CFR 216.24, Drug products withdrawn or removed from the market for reasons of safety or effectiveness. ecfr.gov. Read October 4, 2026.
50. 21 U.S.C. 353a, Pharmacy compounding (section 503A of the Federal Food, Drug, and Cosmetic Act), subsection (b)(1). law.cornell.edu/uscode/text/21/353a. Read October 5, 2026.
51. FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act (categories 1–3). Updated May 14, 2026. fda.gov/media/94155/download.
52. FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503B of the Federal Food, Drug, and Cosmetic Act (categories 1–3). Updated March 21, 2025. fda.gov/media/94164/download.
53. World Anti-Doping Agency. Prohibited List 2026 (in effect January 1, 2026). S2.2.4, Growth hormone releasing factors: “growth hormone secretagogues (GHS) and their mimetics,” naming macimorelin. wada-ama.org.
54. Searches of October 4, 2026: PubMed, “macimorelin” (48 records; 27 report studies of macimorelin itself; the AC01 trial is indexed under macimorelin and not counted); PubMed, EP1572, JMV-1843, AEZS-130, ARD-07, Macrilen or Ghryvelin (53 records, 4 more studies of the compound); Europe PMC, “macimorelin” (216 hits); PubMed and Europe PMC, macimorelin with sermorelin, GHRH, tesamorelin, CJC-1295, ipamorelin, ibutamoren (MK-677), GHRP-2, GHRP-6, hexarelin, anamorelin, somatropin or testosterone (no study of a combination); ClinicalTrials.gov, “macimorelin” and its codes (six registrations, all completed); FDA warning-letter index, “macimorelin” and “Macrilen” (no letters); a chemical-supplier catalog listing macimorelin acetate for research use only (supplier not named). Searches of October 5, 2026, on AC01’s identity: PubMed, “HM01 AND ghrelin” (18 records) and HM01 with macimorelin or its codes (0 records); Europe PMC, “HM01” with macimorelin or JMV 1843 (2 hits, both reviews).

Related Research

• GHRP-2Pralmorelin — approved in Japan as a one-dose growth hormone test
• AnamorelinOral ghrelin-receptor agonist — cancer cachexia
• MK-677Ibutamoren — oral ghrelin-receptor agonist, never approved
• SermorelinGHRH fragment — Geref and Geref Diagnostic, withdrawn