Apelin_Dosage, benefits & legal status
Also known as apelin-13, [Pyr1]apelin-13, apelin-17, apelin-36, APLN
Good human physiology, a decade of failed attempts to turn it into a drug.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Apelin?
Plain language first. The technical label stays, but it never stands alone.Overview
Apelin is a hormone your own heart and blood vessels make. Infused into people it widens blood vessels, raises how much blood the heart moves per minute and lowers blood pressure, and in heart failure patients that vessel response was still intact when another test drug's response was blunted. Drug companies noticed. Four programs have gone into human trials, and the two that reached furthest both stopped: one was terminated after 182 participants, and the other, an oral apelin-receptor drug tested alongside tirzepatide, stopped dosing after liver enzyme rises in eleven people who received it.
Apelin is an endogenous peptide hormone and one of two natural ligands for the apelin receptor, whose official gene symbol is APLNR and which also appears as AGTRL1 and as APJ. Its precursor is 77 residues, and UniProtKB Q9ULZ1 annotates four mature forms: apelin-36 at residues 42 to 77, apelin-31 at 47 to 77, apelin-28 at 50 to 77 and apelin-13 at 65 to 77. The predominant circulating form in the human cardiovascular system is [Pyr1]apelin-13, in which the N-terminal glutamine is cyclized to pyroglutamate. Apelin peptides are highly labile, and every human study has used infusion.
What it's used for
Nothing. It is a natural hormone with no approved product. Research infusions have been done in volunteers and heart failure patients, and drug programs have targeted its receptor rather than used the hormone itself.
How does Apelin work?
What it does in the body, and where.One receptor, two natural hormones, and a pharmacology that looked ideal for heart failure: widen the vessels, raise output, and do it through a pathway the failing heart still responds to. The physiology held up in people. The drugs did not.
- 01The receptor and its two ligandsThe apelin receptor is APLNR, long known as APJ. Apelin is one ligand. The other is elabela, a separate gene product with a different sequence, and it has its own page on this site. Any statement that apelin is the receptor's ligand is incomplete.
- 02What happens when it is infusedIn 26 healthy volunteers and 18 patients with class II to III heart failure, apelin widened forearm vessels, raised cardiac index, lowered mean arterial pressure and lowered peripheral vascular resistance. Given into a coronary artery it raised coronary blood flow and the heart's rate of pressure development while lowering left ventricular pressures.
- 03The finding that drove the interestIn the same heart failure patients, the response to apelin was preserved while the response to acetylcholine was blunted. A pathway that still works in a failing circulation is exactly what a heart failure drug wants, and that result is why this receptor attracted four programs.
- 04Why it is a hormone and not a medicineApelin peptides fall apart in plasma within minutes, so nothing can be given as a simple injection. Drug developers therefore went after the receptor with engineered molecules instead, and the two that reached furthest were terminated, one of them on a liver safety signal.
What else is it used for?
Each group carries its own evidence level.Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
What infusion does in people
peer-reviewed-human- Human trialIn 26 healthy volunteers and 18 heart failure patients, apelin widened forearm vessels, raised cardiac index, and lowered both mean arterial pressure and peripheral vascular resistance. Blood pressure goes down, not up.
- Human trialThe vasodilator response to apelin was preserved in heart failure while the response to acetylcholine was blunted in the same patients. That contrast is the reason the receptor became a drug target.
- Human trialGiven into a coronary artery, apelin-36 raised coronary blood flow and the heart's peak rate of pressure development and lowered left ventricular pressures.
- No dataThe published abstract reports P values without effect sizes, so this page gives directions rather than magnitudes. Anyone quoting a specific blood pressure drop for apelin is not taking it from that abstract.
Four attempts at a drug
tested-and-failed- Human trialAn Edinburgh early-phase study gave [Pyr1]apelin-13 to 14 subjects. Novartis took CLR325 through a completed phase 2 in 26 subjects with results posted in 2020.
- Human trialAmgen's AMG 986 reached a phase 1 with 182 subjects and was terminated, with results posted in 2022.
- Human trialThe STRIDES trial of azelaprag with tirzepatide was terminated. The sponsor reported in December 2024 that dosing stopped after liver transaminase elevations appeared in eleven azelaprag recipients and in none of those on tirzepatide alone.
- No dataNothing targeting this receptor is approved anywhere. A natural hormone with clean physiology is not the same thing as a safe drug.
Which apelin is which
none- lab-analysisUniProt annotates four mature forms: apelin-36, apelin-31, apelin-28 and apelin-13. Apelin-17, routinely listed as one of the three main forms, is not among them. It is real in the pharmacology literature and it should not be attributed to the reference record.
- lab-analysisThe form that dominates in human blood and the one actually infused in the cardiovascular studies is [Pyr1]apelin-13, with its first residue cyclized to pyroglutamate. A page listing apelin-13 and a page listing [Pyr1]apelin-13 are not describing quite the same molecule.
- lab-analysisThe FDA substance registry agrees with UniProt for apelin, residue for residue. That is worth saying because it does not always, and on this site's peptide YY and ularitide pages it does not.
Apelin is usually introduced as the ligand for the APJ receptor, and that is two errors in one phrase. APLNR is the official gene symbol, with APJ and AGTRL1 as older names, and apelin is one of two natural ligands, the other being elabela. The list of forms is also commonly wrong: apelin-13, apelin-17 and apelin-36 get quoted as the three main species, but UniProt annotates apelin-36, apelin-31, apelin-28 and apelin-13, and no feature called apelin-17. The form that actually matters in human blood, and the one infused in the human trials, is [Pyr1]apelin-13. On effects, the direction is often reversed: apelin lowers blood pressure and vascular resistance while raising cardiac output. Finally, the published human study reports P values without effect sizes, so any specific figure for how far apelin drops blood pressure in people is not coming from it.
The published record
Papers and trials about Apelin
Searched: apelin, apelin-13, APLNR.
Left out: apelin (alone) (several thousand papers across cardiovascular, metabolic and cancer biology; unanchored it would dominate the index); APJ (an older receptor name that also collides with unrelated abbreviations); elabela (the other endogenous ligand, which has its own slug); azelaprag (a separate small-molecule agonist with its own program).
270 papers tagged human · 172 not reviews or lab · 5 clinical trial publications
39 registered trials · 2 with posted results
Furthest stage reached: Phase 2, under way
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count. 467 papers and 39 trials indexed in detail.
At a glance
Four things to know about Apelin
Evidence
Category
Sexual and hormonal
Common vial
Varies
Half-life
Minutes, and not measured in people
How much, and do you cycle it?
The range, and whether you take breaks.No established dose, not applicable. Not established No range
It is not administered outside research infusions, and no schedule exists.
Minutes, and not measured in peopleNo figure
No measured human in vivo half-life was found. The most specific published figure describes apelin peptides as very labile in plasma with a half-life under one to five minutes in vitro, with the species unstated, and a 2023 review says only that it is short, a few minutes. That instability is why every human study used continuous or bolus infusion and why drug programs went after the receptor instead of the hormone.
You can compare this against the whole library to see where it sits.
What does it cost?
Typical dose and cost, in plain numbers.Apelin is not injected in the forms covered here
Route: not taken as a treatment. No established dose. Human studies used infusions: into the brachial artery, into a coronary artery as a bolus during angiography, and systemically at rates in the tens to hundreds of nanomoles per minute. Those are research infusion protocols under direct monitoring of blood pressure, not doses. Any figure offered as an apelin dose would be invented.
How do you store it?
Before mixing, and after.Nothing to store: it is not taken as a treatment.
Apelin is not used as a medicine or a supplement, so no home storage question arises. Laboratory suppliers ship research material frozen and state their own handling conditions on the certificate that comes with it.
What are the side effects and cautions?
Known cautions and warnings for this compound.Solubility, computed: 33% charged residues, 36% hydrophobic. Water usually sufficient.
A first-pass rule from peptide manufacturers' guidance. It does not account for disulfide bridges, salt form or how the powder was dried, and it predicts what should be easy rather than what will happen in your vial.
Who should avoid it
- Any self-administered use: there is no product, no established dose, no sterile preparation and effects on blood pressure that need monitoring
- Assuming the receptor is a safe target because the hormone is natural: the two most advanced programs aimed at this receptor were both terminated
Stop and get help
- Not applicable. It is not taken as a treatment
Common effects
- Vessel widening and a fall in blood pressure, during infusion
- A rise in cardiac output, measured directly in a catheterized subset
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Apelin approved?
And where the numbers on this page come from.No. Apelin is not approved for any use, anywhere. It is sold labeled for laboratory research only, and there is no legal route to buy it for human use.
- Approval statusResearch only
- RouteNot taken as a treatment
- Checked25 October 2026
- DoseNo dose has been established in people.
- Vial sizeFrom what vendors typically list; not a recommendation.
- Sources
What has happened recently
No apelin product is approved anywhere and the hormone itself is research material. Identity is settled: UniProtKB Q9ULZ1, a 77-residue precursor, with apelin-36 at residues 42 to 77, apelin-31 at 47 to 77, apelin-28 at 50 to 77 and apelin-13 at 65 to 77. FDA substance records agree with UniProt here: UNII 7P5ZL6T59Y for apelin and UNII GF5K6G6AH3 for apelin-13, whose sequence matches the positional read exactly. Four registered trials have targeted this pathway. NCT02259686 was an early-phase study in Edinburgh giving [Pyr1]apelin-13 to 14 subjects. NCT02696967 tested Novartis' CLR325 in a completed phase 2 with 26 subjects, results posted in 2020. NCT03276728 tested Amgen's AMG 986 in a phase 1 with 182 subjects and was terminated, with results posted in 2022. NCT06515418, the STRIDES trial of BioAge and Lilly's azelaprag with tirzepatide, was terminated: dosing stopped after liver transaminase elevations in eleven azelaprag recipients and none on tirzepatide alone. Nothing apelin-based is approved anywhere.
You can compare this against the whole library, or read how to check a seller.
What else is like Apelin?
Others in Sexual and hormonal, side by side.If you're weighing Apelin, it's worth reading Urocortin-2, Elabela, and PT-141 (Bremelanotide) in the same class.
Good human physiology, a decade of failed attempts to turn it into a drug.
- Dose
- No established dose
- How often
- Not applicable
Real human hemodynamics from an investigator-led trial, and nobody took it forward.
- Dose
- No established dose
- How often
- Not applicable
Discovered independently as Elabela and as Toddler, and the reference databases use a third name.
- Dose
- No established dose
- How often
- Not applicable
An approved shot that boosts sexual desire through the brain.
- Dose
- 1.75 mg per dose
- How often
- As needed, before activity
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
- How to Read a Peptide COA
What the purity number does and does not tell you, and how to spot an edited report.
- How to Vet a Peptide Vendor
Independent COAs, HPLC purity, and the red flags that mean walk away.
Sources
- Japp and colleagues, Circulation(2010)Acute cardiovascular effects of apelin in humans. Volume 121, issue 16, pages 1818 to 1827. Studied 26 healthy volunteers and 18 patients with New York Heart Association class II to III heart failure, six of them during angiography. Three routes and two peptides were used: [Pyr1]apelin-13 into the brachial artery, apelin-36 as an intracoronary bolus, and systemic [Pyr1]apelin-13 at 30 to 300 nanomoles per minute. Reported forearm vasodilatation at P less than 0.0001; an apelin response preserved in heart failure while the acetylcholine response was attenuated at P of 0.01; raised coronary flow and peak rate of pressure development with lowered peak and end-diastolic left ventricular pressures at P less than 0.05; and, on systemic infusion, raised cardiac index with lowered mean arterial pressure and peripheral vascular resistance, all at P less than 0.01, with heart rate rising in controls only. The abstract gives P values without magnitudes, so no millimeter-of-mercury or percentage figure is quoted on this page.
- Tatemoto and colleagues, Biochemical and Biophysical Research Communications(1998)The discovery paper, isolating apelin as the endogenous ligand of the APJ receptor. Volume 251, issue 2, pages 471 to 476.
- UniProtKB Q9ULZ1, apelin precursor(2026)A 77-residue precursor annotating four mature peptides: apelin-36 at 42 to 77, apelin-31 at 47 to 77, apelin-28 at 50 to 77 and apelin-13 at 65 to 77. Read positionally, apelin-36 is LVQPRGSRNGPGPWQGGRRKFRRQRPRLSHKGPMPF and apelin-13 is QRPRLSHKGPMPF. There is no feature named apelin-17 in this record. That matters because apelin-17 is widely listed as one of the main forms.
- Chapman and colleagues, Cardiovascular Research(2023)A review of the apelin system, describing [Pyr1]apelin-13 as the predominant isoform in the human cardiovascular system and plasma, and the circulating half-life as short, on the order of a few minutes, without giving a measured human figure.
- Apelin receptor trial records on ClinicalTrials.gov(2026)Four registered programs. NCT02259686, University of Edinburgh, early phase 1, completed, 14 subjects, [Pyr1]apelin-13 given subcutaneously and intravenously. NCT02696967, Novartis CLR325, phase 2, completed, 26 subjects, results posted 2020. NCT03276728, Amgen AMG 986, phase 1, terminated, 182 subjects, results posted 2022. NCT06515418, the STRIDES trial of azelaprag with tirzepatide from BioAge and Lilly, phase 2, terminated with 204 subjects, after the sponsor reported in December 2024 that dosing was stopped following liver transaminase elevations in eleven azelaprag recipients and none on tirzepatide alone.
Beyond these, 506 records are indexed. Browse the records