Eneboparatide (AZP-3601)_Dosage, benefits & legal status
Also known as AZP-3601, AZP3601, LA-PTH, eneboparatide acetate
Built short-acting on purpose, in a field where every rival is built to last longer.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Eneboparatide (AZP-3601)?
Plain language first. The technical label stays, but it never stands alone.Overview
People with hypoparathyroidism have parathyroid glands that stopped working, usually after neck surgery. Without the hormone, blood calcium falls, and they live on calcium tablets and active vitamin D for the rest of their lives. This is a daily injection meant to replace the hormone itself so the tablets can stop. The interesting thing about it is a design choice that runs against the field. The other two drugs of this kind covered here were built to last as long as possible in the body, one of them for a whole week per injection. This one was built to clear quickly, because the companies disagree about whether steady round-the-clock hormone is good for bone or bad for it. In the 24-week trial, 31.1% of people reached the goal of normal calcium with no active vitamin D and almost no calcium tablets, against 5.9% on placebo. That is a real result and it is also well below what the one approved drug in this class reported in its own trial. The company's explanation is that most patients made antibodies against the drug.
Eneboparatide is a synthetic 36-residue peptide agonist of the parathyroid hormone 1 receptor, in development for chronic hypoparathyroidism. Its sequence is a hybrid: residues 4 to 9 match parathyroid hormone exactly, residues 1 and 2 match the parathyroid hormone related protein used in abaloparatide, and residue 3 is an alanine where both parent hormones carry a serine. AstraZeneca describes it as binding with high affinity to one specific conformation of the receptor, and as deliberately short-acting in plasma. The phase 3 CALYPSO trial met its composite primary endpoint in 31.1% of patients against 5.9% on placebo, and the company reports immunogenicity in most patients. It is approved in no country.
What it's used for
Tested in adults with chronic hypoparathyroidism of at least 12 months' duration who depend on active vitamin D and oral calcium. Approved in no country and available only inside clinical trials.
How does Eneboparatide (AZP-3601) work?
What it does in the body, and where.Four drugs on this site act on the same receptor, and the way to tell them apart is not the receptor but what each one does with time.
- 01What the receptor does when it is workingParathyroid hormone acts on the PTH1 receptor in kidney and bone. The kidney holds on to calcium, excretes more phosphate and makes more active vitamin D, and bone turnover continues at a normal pace. Take the hormone away and blood calcium falls while urine calcium rises, and that is why tablets alone leave the kidney exposed even when blood calcium looks fine.
- 02The sequence is a hybrid, and one residue belongs to neither parentMeasured against the cards already here: eneboparatide is 59% identical to abaloparatide position for position and only 35% identical to teriparatide, yet the one stretch of six or more residues it shares with anything is EIQLMH, a stretch of parathyroid hormone. Its first two residues are the alanine and valine that start the parathyroid hormone related protein, and its third residue is an alanine where both parent hormones carry a serine. So it reads as a PTH-related-protein front end welded to a parathyroid hormone core, with at least one engineered substitution that came from neither.
- 03Conformation selectivity is the stated mechanism, and it is a claim about shapeAstraZeneca describes the drug as binding with high affinity to one specific conformation of the receptor. The underlying idea in this field is that the receptor can be engaged in a form that signals briefly at the cell surface or in a form that is pulled inside and keeps signaling, and that the two produce different effects on bone. That is the company's rationale rather than a measured clinical outcome, and the trial was not designed to test it directly.
- 04Short-acting by design, the opposite bet to its rivalsAstraZeneca states that the drug was designed to have a short plasma half-life, so as to restore bone turnover to a more physiologic state and help preserve bone integrity. Set that beside the other two hypoparathyroidism drugs covered here and the disagreement is plain: palopegteriparatide is a PEGylated prodrug built for steady round-the-clock levels from one daily injection, and canvuparatide is built to last a week. Both bet that smoother is better. This one bets that a pulse is better. No trial has compared the two approaches head to head, so the disagreement is live.
A schematic of the compound's mechanism, not a diagnostic image.
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.
CALYPSO, the phase 3 result
Investigational- Human trialComposite primary endpoint at week 24: 41 of 132 (31.1%) on eneboparatide against 4 of 68 (5.9%) on placebo, randomized 2:1.
- Human trialUrine calcium normalized in 43 of 76 (56.6%) of patients who began with excess urine calcium, against 9 of 45 (20%) on placebo. This is the endpoint that speaks to kidney protection rather than to how people feel.
- Human trialImmunogenicity was observed in most patients. Serum calcium was controlled with the aid of supplements and up-titration of the drug.
- No dataThe trial ran at 54 sites in 13 countries, with a 24-week randomized period and a 28-week open-label extension. AstraZeneca says benefits were maintained through week 52 and bone health was preserved, without publishing figures for either claim.
How it compares with the approved drug, and why the comparison is limited
Investigational- No dataThe endpoint definitions really are close. CALYPSO used the same 8.3 to 10.6 mg/dL calcium range and the same 600 mg daily calcium limit that the Yorvipath label uses, so this is not a case of two trials measuring different things.
- No dataThe trials are not close. Palopegteriparatide's PaTHway randomized 84 patients 3:1 over 26 weeks and required 26 weeks of disease; CALYPSO randomized 200 patients 2:1 over 24 weeks and required 12 months of disease, across more countries and with different calcium entry criteria.
- No dataReported response rates for context, not as a comparison: 31.1% here, against 68.9% on the label definition and 78.7% on the published definition for palopegteriparatide, and 63% at 12 weeks in canvuparatide's phase 2. No two of these came from the same trial and none of them is a head-to-head test.
Where the drug came from, and the earlier human data
Investigational- RegulatoryDeveloped by Amolyt Pharma and acquired by AstraZeneca for its Alexion rare-disease division. The deal was announced in March 2024 and completed on July 15, 2024, for $800 million upfront plus $250 million contingent on a regulatory milestone.
- No dataAn open-label phase 2 study was published in the Journal of Clinical Endocrinology and Metabolism in 2024, article dgae121, first author Takacs. Sourcing tier: cited in AstraZeneca's own release and not opened at source, so no figures from it appear here and no DOI is recorded.
- RegulatoryApproved in no country. No marketing application anywhere is on the public record, and the registry entry was last updated in September 2025, before the detailed results were presented.
The most common error is setting 31.1% directly against the 68.9% that circulates for the one approved drug in this class. The endpoint definitions really are similar, using the same calcium range and the same 600 mg limit, so the instinct to compare them is reasonable. The trials are not similar: 200 patients against 84, 24 weeks against 26, a 2:1 randomization against 3:1, and a requirement of 12 months of disease against 26 weeks. The second error is the date. AstraZeneca said the trial met its primary endpoint in March 2025 without giving a number, and the numbers arrived 14 months later in May 2026, so coverage from 2025 reporting a successful phase 3 and coverage from 2026 reporting 31.1% are describing one trial rather than two. The third is treating immunogenicity as a side note. The company itself puts it in the result, saying antibodies appeared in most patients and that calcium was held in range with supplements and dose increases. The fourth is calling this a bone drug. It shares its first two residues with abaloparatide, a drug for osteoporosis, and the two are aimed at opposite problems.
The published record
Papers about Eneboparatide (AZP-3601)
Searched: eneboparatide, AZP-3601, AZP3601.
Left out: palopegteriparatide (THE critical rejection. The one APPROVED drug in the same indication, already on this site as Yorvipath, and the source of the 68.9% that gets set against this drug's 31.1%. The endpoint definitions really are near-identical (same 8.3 to 10.6 mg/dL calcium range, same 600 mg daily calcium limit), which is exactly why the comparison must be labeled cross-trial every time: PaTHway randomized 84 patients 3:1 over 26 weeks requiring 26 weeks of disease, CALYPSO randomized 200 patients 2:1 over 24 weeks requiring 12 months of disease, across more countries with different calcium entry criteria); Yorvipath (that drug's brand name, and the name most likely to be substituted into a comparison); 68.9% (palopegteriparatide's label-definition response rate. Its published primary endpoint was 78.7% on the same trial. NEITHER figure belongs to this compound and both circulate loosely); canvuparatide (the OTHER investigational hypoparathyroidism drug on this site, MBX 2109, a weekly PTH prodrug in phase 3 since August 2026. Its phase 2 gave 63% against 31% at 12 weeks. Same disease, same receptor, opposite half-life philosophy); teriparatide (PTH(1-34), on this site, and the parent hormone fragment. Eneboparatide is only 35% identical to it position for position, and the single stretch of six or more residues they share is EIQLMH); abaloparatide (the PTHrP analog on this site, for osteoporosis. This is the CLOSEST relative by sequence at 59% positional identity, and the two share eneboparatide's first two residues AV, so a sequence search will surface it. Different disease entirely); palopegteriparatide's 60-hour half-life (a design figure for the PEGylated prodrug. This drug was deliberately engineered SHORT-acting, so importing any half-life from the family is backwards); PTH receptor (the receptor class term, returning the whole parathyroid literature across four existing cards); hypoparathyroidism (the disease term, far too broad, and shared with two other cards here); AZP-3813 (Amolyt's OTHER peptide, a growth hormone receptor antagonist for acromegaly, acquired in the same deal. On no page here and a separate watchlist item); Alexion (AstraZeneca's rare-disease division, spanning a large portfolio).
5 papers tagged human · 1 not reviews or lab · 1 clinical trial publications
How the compound was given: 7 applied to skin · 3 injected · 4 by mouth or rectal · 6 route not stated in the abstract
Read from each paper's indexing terms and abstract, by rule. A paper that mentions a cream studied a cream, not necessarily the product being sold.
Furthest stage reached: Published trials only, 1 clinical trial publication, no phased trial registered
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. A preprint and its journal version count once.
At a glance
Four things to know about Eneboparatide (AZP-3601)
Evidence
Investigational
Category
Healing and recovery
Common vial
Varies
Half-life
Deliberately short in plasma; no published figure
How much, and do you cycle it?
The range, and whether you take breaks.20 mcg once daily to start, then titrated to the individual, once daily. Daily and ongoing, with no planned stop Trial dose
Hypoparathyroidism is permanent, so hormone replacement is lifelong in principle. The trial ran 24 weeks randomized followed by a 28-week open-label extension, so nothing longer than about a year is known.
How long does it stay in the body?
The half-life, and where the figure comes from.Deliberately short in plasma; no published figureNo figure
The short half-life is the design premise and the company states it plainly, but no number has been published, so there is nothing to put in hours. This is the field's central disagreement rather than a missing detail: palopegteriparatide was engineered for an apparent half-life of about 60 hours and canvuparatide for weekly dosing, while this drug was engineered to clear fast. Treat the absence of a figure as a gap in disclosure, not as evidence that the half-life is unknown to the sponsor.
You can compare this against the whole library to see where it sits.
How do I dose and price it?
Enter your vial and your dose. Pick a mix. We show the draw and the cost.The vial holds a fixed amount of drug. Adding more water does not make more drug, it just spreads it thinner, so you draw a bigger number on the syringe for the same dose.
Choose your mix
Measuring the water1 mL = one full 100-unit syringe.
How do you store it?
Before mixing, and after.Nothing to store: it is not sold anywhere.
Eneboparatide (AZP-3601) has never been marketed, so there is no vial, pen or bottle to keep at home. Supplies for a trial are made, stored and dispensed by the sponsor and the trial pharmacy under conditions set in the protocol. Anything offered for sale under this name did not come from that supply chain.
What are the side effects and cautions?
Known cautions and warnings for this compound.Solubility, computed: 33% charged residues, 53% 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 expectation of access, since the drug is approved nowhere and is available only inside a trial
- Reading the 31.1% as directly comparable to the 68.9% reported for the one approved drug in this class, since the two figures come from different trials in differently selected patients
- Treating the short plasma half-life as a drawback or an advantage, since whether steady hormone exposure helps or harms bone is the open question this drug was designed around and no trial has settled it
- Confusing it with abaloparatide. It shares the first two residues and is a bone-density drug for osteoporosis rather than a hormone replacement for hypoparathyroidism
Stop and get help
- Given under specialist supervision inside a trial, so there is no self-directed course to stop
- Symptoms of high blood calcium between doses, meaning nausea, excessive thirst, confusion or constipation, all needing a same-day calcium check
- Tingling around the mouth or in the hands, or muscle cramps and spasms. These point the other way toward calcium falling too low
Common effects
- No per-event breakdown has been published. The only safety-related figures AstraZeneca has released are the statement that immunogenicity occurred in most patients and the claim that bone health was preserved through 52 weeks.
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Eneboparatide (AZP-3601) approved?
And where the numbers on this page come from.No. Eneboparatide (AZP-3601) is not approved anywhere and is currently in company-run clinical trials. There is no legal route to obtain it outside a trial.
- Approval statusInvestigational
- RouteUnder the skin, once daily, from a prefilled pen
- Checked9 November 2026
- DoseFrom published clinical trials. Not approved by a regulator for this dose.
- Vial sizeFrom what vendors typically list; not a recommendation.
- Sources
What has happened recently
Approved in no country. The phase 3 trial is NCT05778071 (CALYPSO), sponsored by Alexion Pharmaceuticals with Amolyt Pharma as collaborator, active and not recruiting, 54 sites in 13 countries, actual start June 7, 2023, actual primary completion November 15, 2024, last update posted September 29, 2025. The registry lists 165 estimated participants while the reported primary analysis covers 200, so the posted estimate is below the number actually analyzed. High-level results were announced in March 2025 and the detailed results at the European Congress of Endocrinology in May 2026. No orphan designation search was run for this compound, so nothing here should be read as establishing its absence. The sponsor is AstraZeneca, through Alexion, following completion of the Amolyt Pharma acquisition on July 15, 2024.
You can compare this against the whole library, or read how to check a seller.
What else is like Eneboparatide (AZP-3601)?
Others in Healing and recovery, side by side.If you're weighing Eneboparatide (AZP-3601), it's worth reading Eptifibatide, Glepaglutide (Zeydovio), and GLOW Plus blend in the same class.
Built short-acting on purpose, in a field where every rival is built to last longer.
- Dose
- 20 mcg once daily to start, then titrated to the individual
- How often
- Once daily
A hospital antiplatelet drug that blocks the platelet fibrinogen receptor. FDA-approved since 1998; the Integrilin brand is gone, generics remain.
- Dose
- 180 mcg/kg bolus, then 2 mcg/kg/min (label)
- How often
- Continuous infusion for up to 72 to 96 hours
A GLP-2 with a six-lysine tail that is released slowly from a depot under the skin, so it can be given twice a week. Recommended for EU approval in September 2026; the FDA asked for another trial.
- Dose
- 10 mg twice weekly (phase 3 trial)
- How often
- Twice weekly
The GLOW trio with an immune-signaling peptide added, at a fixed ratio none of the four can be adjusted out of.
- Dose
- 0.25 up to 0.5 mg BPC-157 per day (the rest follows the fixed ratio)
- How often
- Daily
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
- AstraZeneca, CALYPSO Phase III detailed results(2026)Dated May 12, 2026, following presentation at the European Congress of Endocrinology. The primary endpoint table gives 31.1% (41 of 132) against 5.9% (4 of 68) for the composite of independence from active vitamin D, oral calcium of 600 mg a day or less, and albumin-adjusted serum calcium of 8.3 to 10.6 mg/dL at week 24. Secondary endpoint in patients with hypercalciuria at baseline: 56.6% (43 of 76) against 20% (9 of 45). States that immunogenicity was observed in most patients and that serum calcium was controlled with the aid of supplements and up-titration, that benefits were maintained through week 52 in patients who stayed on drug, and that bone health was preserved. Describes the compound as a PTH 1 receptor agonist and does not give a sequence.
- AstraZeneca, topline announcement that CALYPSO met its primary endpoint, filed with the SEC(2025)A 6-K filing dated March 2025 stating only that the trial met its primary endpoint with statistical significance at 24 weeks, and describing the endpoint as a composite of normalized albumin-adjusted serum calcium and independence from active vitamin D and oral calcium therapy. No response rate, no patient numbers and no safety data. This is the document that makes 2025 coverage of a successful phase 3 and 2026 coverage of 31.1% the same trial.
- ClinicalTrials.gov record NCT05778071 (CALYPSO)(2025)Phase 3, active and not recruiting, lead sponsor Alexion Pharmaceuticals with Amolyt Pharma as collaborator. 165 estimated enrollment, 54 sites in 13 countries, actual start June 7, 2023, actual primary completion November 15, 2024, last update posted September 29, 2025. Eneboparatide given at a 20 mcg once-daily starting dose under the skin from a 250 or 500 mcg per mL prefilled pen, individually titrated, against matching placebo at 2:1. Condition is chronic hypoparathyroidism. The primary outcome is the week-24 composite of full independence from active vitamin D, independence from therapeutic oral calcium at no more than 600 mg a day of elemental calcium, and albumin-adjusted serum calcium within 8.3 to 10.6 mg/dL.
- FDA Global Substance Registration System, eneboparatide(2026)One record. UNII K6E9SY8U8D, substance class protein, protein type PEPTIDE with subtype HORMONE, a single subunit of 36 residues reading AVAEIQLMHQRAKWIQDARRRAFLHKLIAEIHTAEI, CAS 1349298-00-5, INN 12209.
- AstraZeneca, completion of the Amolyt Pharma acquisition(2024)Completed July 15, 2024, for all outstanding shares at up to $1.05 billion, comprising $800 million upfront and $250 million contingent on a specified regulatory milestone. Describes eneboparatide as an investigational therapeutic peptide designed to bind with high affinity to a specific conformation of the parathyroid hormone receptor 1, with therapeutic goals of holding serum calcium in the normal range, limiting urine calcium excretion by restoring kidney reabsorption, and potentially preventing decline in kidney function. States that it is designed to have a short plasma half-life so as to restore bone turnover to a more physiologic state and help preserve bone integrity. Cites the phase 2 publication as Takacs et al, Journal of Clinical Endocrinology and Metabolism, 2024, article dgae121. Also names Amolyt's AZP-3813, a peptide growth hormone receptor antagonist for acromegaly, with no page here.
Beyond these, 14 records are indexed. Browse the records