RPB

Enlicitide

enlicitide decanoate, MK-0616

Cardiovascular & circulation
Awaiting medical reviewEN ES DE FR PT ZH+ Follow for updates

1What it is

Enlicitide is the most important proof-of-concept drug in modern peptide chemistry, and it is worth understanding even if cholesterol is not your interest. PCSK9 is a circulating protein that drags LDL receptors into the cell for destruction; block it and the liver keeps more receptors, which pulls LDL cholesterol out of the blood. Two monoclonal antibodies (alirocumab, evolocumab) and an siRNA (inclisiran) already do this, and all three must be injected — antibodies are large proteins and cannot survive the gut.

Enlicitide does the same job as a pill. It is a macrocyclic peptide: a peptide chain closed into a ring, which locks its shape, hides its backbone amide bonds from proteases, and gives it enough rigidity and shielding to cross the gut wall when formulated with an absorption enhancer. That combination — antibody-like target specificity with small-molecule oral dosing — is precisely what the macrocyclic peptide field has been promising for twenty years. Cross-link: cyclic peptide macrocycle drugs as a class (#250).

It is investigational. Three Phase 3 trials have reported, a large cardiovascular outcomes trial is ongoing, and nothing is approved.

2How it's thought to work

PCSK9 binding. The macrocycle binds PCSK9 at the surface that would otherwise contact the LDL receptor's EGF-A domain, blocking the interaction.
LDL receptor recycling preserved. Without PCSK9-driven degradation, LDL receptors return to the hepatocyte surface and continue clearing LDL particles from plasma.
Downstream. LDL-C falls, and with it non-HDL-C, apolipoprotein B and, to a lesser degree, Lp(a) — the same pattern as the injectable PCSK9 inhibitors.
Why the macrocycle is oral. cyclisation removes free N- and C-termini, constrains conformation, and allows intramolecular hydrogen bonding that shields polar groups. With a permeation enhancer in the tablet, enough drug crosses the intestinal epithelium to be useful. Oral bioavailability is still low in absolute terms — the dose is far larger than the equivalent injected antibody protein mass.
An oral macrocyclic PCSK9 inhibitor. PCSK9 marks the LDL receptor for destruction; caught by the ring, it cannot, so the receptor returns to the surface and goes on clearing LDL. The ring is what lets a molecule this size survive the gut.Schematic — not to scale

3What the research shows

LDL-C lowering in heterozygous familial hypercholesterolaemia

CORALreef HeFH randomised 303 adults with HeFH on stable statin therapy 2:1 to enlicitide 20 mg daily or placebo. LDL-C fell 59.4% versus placebo at week 24 (95% CI −65.6 to −53.2; p<0.001) and 61.5% at week 52. At week 24, non-HDL-C fell 53.0%, apolipoprotein B 49.1% and Lp(a) 27.5% versus placebo. Of enlicitide patients, 67.3% achieved both a ≥50% LDL-C reduction and an LDL-C below 55 mg/dL, versus 1.0% on placebo. Reductions appeared by week 4 (Merck Phase 3 report 2026; peer-reviewed publication †). [2][3]

LDL-C lowering in hypercholesterolaemia more broadly

CORALreef Lipids reported a comparable effect size and safety profile in a broader hypercholesterolaemia population. CORALreef AddOn studied enlicitide added to existing oral lipid-lowering therapy and was reported as positive, with enlicitide outperforming standard oral comparators (reported 2026) †.

Phase 2 dose-finding

A randomised Phase 2 trial across 6–30 mg daily doses reported LDL-C reductions of roughly 41–61% versus placebo at 8 weeks in adults at moderate to high cardiovascular risk, establishing the dose range (Ballantyne 2023, J Am Coll Cardiol). [1]
Not gradedpending

Cardiovascular outcomes

CORALreef Outcomes, enrolling over 14,500 participants, is the trial that will determine whether the LDL-C reduction translates into fewer heart attacks and strokes. Enrolment is complete; results are not available. Until it reports, the evidence is for a surrogate marker only — albeit one with unusually strong causal support from the rest of the LDL literature. Community use: essentially none documented. This is an investigational oral prescription drug with no self-directed use context.

4Reported side effects and interactions

Literature-reported

In CORALreef HeFH the safety profile was similar to placebo, with comparable rates of adverse events, serious adverse events and discontinuations (2.0% enlicitide versus 3.0% placebo). Across the programme, the reported pattern is gastrointestinal events consistent with the oral formulation and absorption enhancer rather than with PCSK9 inhibition itself †.

Community-reported

none; no community use exists.

Class-level considerations. very low achieved LDL-C has been extensively studied with injectable PCSK9 inhibitors and has not produced the cognitive, hormonal or haemorrhagic harms that were feared; that reassurance carries across mechanistically but has not been separately established for this drug over long periods.

Theoretical. oral peptide formulations with permeation enhancers raise questions about local gastrointestinal tolerability and about variability of absorption with food and with co-administered drugs. Dosing instructions for oral peptides are typically strict for this reason (compare semaglutide (#3) oral, which requires fasting and a small volume of water).

Interactions. no major established interactions reported; absorption-related interactions with food and with other oral medicines are the expected area of concern and should be read from the final label †.

Markers researchers commonly monitor

These follow the CORALreef protocols and standard lipid management:

MarkerWhy it's watched
LDL-Cthe primary endpoint and the point of the drug; measured at baseline, week 4 (when the effect appears) and periodically after.
Non-HDL-C and apolipoprotein Bbetter measures of total atherogenic particle burden than LDL-C alone, and both reported in the trials.
Lp(a)reduced by roughly a quarter in CORALreef HeFH; relevant because few oral drugs move it at all.
Triglycerides and HDL-Ccompleting the lipid panel.
Liver enzymes (ALT/AST)routine with lipid-lowering therapy, and relevant to any new oral agent.
Creatine kinaseonly if muscle symptoms arise; PCSK9 inhibition is not myotoxic, but background statins are.
Fasting glucose and HbA1cstatins modestly raise diabetes risk; PCSK9 inhibitors have not shown this, and it is worth baseline data.
Cardiovascular eventsthe outcome that matters, and the reason CORALreef Outcomes exists.

Free for everyone. Safety information is never behind a paywall.

5Formulation and administration context

An oral tablet taken once daily, formulated as the decanoate salt with a permeation enhancer to achieve intestinal absorption. There is no injection, no and no self-preparation step. Administration conditions relative to food and other medicines are a defined part of oral peptide dosing and will be set by the approved label; nothing here should be treated as instruction. Investigational material only at the time of review.

6Commonly studied alongside

Statins (as background therapy in every trial), ezetimibe and bempedoic acid as oral comparators or add-ons, and the injectable PCSK9-targeting agents alirocumab, evolocumab and inclisiran as the established alternatives. Cross-link: cyclic peptide macrocycle drugs as a class (#250), eptifibatide, pegcetacoplan and zilucoplan as other cyclic or constrained peptide drugs already approved.

Informational cross-links. Not stack recommendations.

7Regulatory status by region

RegionStatus (checked —)
United StatesNot FDA-approved; investigational. Phase 3 data from CORALreef HeFH, Lipids and AddOn reported; sponsor plans to share data with regulators worldwide †
European UnionNot authorised; investigational
United KingdomNot licensed
AustraliaNot approved
South AfricaNot registered
SportNot prohibited by WADA; lipid-lowering drugs are not on the prohibited list. A non-approved substance may still raise S0 questions for athletes — check the current list

8Open questions

  • Whether LDL-C reduction with this agent reduces cardiovascular events — CORALreef Outcomes will answer this.
  • How variable oral absorption is in practice, and how much food and co-medication affect it.
  • Long-term gastrointestinal tolerability of a daily permeation-enhanced oral peptide.
  • Whether an oral option changes adherence enough to shift population LDL control, which is the real public-health argument for it.
  • Whether the macrocyclic peptide approach now extends to other targets previously thought to need antibodies.

9References

  1. 1Ballantyne CM et al. (2023). Phase 2b randomized trial of the oral PCSK9 inhibitor MK-0616. J Am Coll Cardiol. PubMed · DOI
  2. 2Merck (2026). CORALreef HeFH Phase 3 results: enlicitide decanoate in adults with heterozygous familial hypercholesterolemia (company report; peer-reviewed publication to be confirmed). PubMed
  3. 3Merck (2026). CORALreef Lipids and CORALreef AddOn Phase 3 results (company reports). PubMed
  4. 4Johns DG et al. (2023). Orally bioavailable macrocyclic peptide that inhibits binding of PCSK9 to the low-density lipoprotein receptor. Circulation. PubMed · DOI
  5. 5Tucker TJ et al. (2021). A series of novel, highly potent, and orally bioavailable next-generation tricyclic peptide PCSK9 inhibitors. J Med Chem. PubMed · DOI
  6. 6Sabatine MS et al. (2017). Evolocumab and clinical outcomes in patients with cardiovascular disease (FOURIER). NEJM — class outcome benchmark. PubMed · DOI

References are being resolved to PubMed/DOI identifiers; links search PubMed for the citation until then.

† Being confirmed by our reviewers against current sources.

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11Page history

31 Oct 2026Profile published — awaiting medical review

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