The story of PCSK9 is an archetypal chapter from the precision medicine book of successes. It opens with the discovery of rare genetic variants that naturally lower PCSK9 activity, showing how well lowering low-density lipoprotein cholesterol (LDL-C) protects against cardiovascular disease. That discovery leads to a renaissance in lipid management, with monoclonal antibodies, RNA-based therapies, and experimental gene-editing methods to permanently silence the gene. The latest advance in delivering PCSK9-inhibiting therapies is perhaps also the simplest: a pill.
Last week, the FDA approved Merck’s once-daily oral PCSK9 inhibitor LIPFENDRA (enlicitide), making it the first pill to target one of cardiovascular medicine’s most validated therapeutic pathways. In two pivotal Phase III studies, enlicitide reduced placebo-adjusted LDL-C by as much as 60% in adults with hypercholesterolemia, including those with heterozygous familial hypercholesterolemia (HeFH), when added to diet and exercise.
Seth S. Martin, MD, professor and preventive cardiologist at Johns Hopkins, believes cheaper, oral PCSK9 inhibition—a 30-day supply of LIPFENDRA costs $315 compared to injectable PCSK9 inhibitors that cost $500-$600 per month—could help expand the use of one of cardiology’s most effective therapeutic strategies.
“I see oral PCSK9 inhibition as a meaningful advance that can help build on momentum in this regard by expanding the options available to patients and clinicians,” Martin told Inside Precision Medicine. “Having a once-daily oral medication as an option can significantly broaden the use of PCSK9-targeted therapy. The more options we have, the better positioned we are to collaborate with our patients in finding treatment approaches that work and close gaps in care.”
The approval could solve one of preventive cardiology’s biggest problems: implementing highly effective LDL-lowering therapies. “Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death, and elevated LDL-C is one of its most important modifiable drivers,” Martin said. “If we’re going to knock ASCVD off the top of that list, we’ll need to scale up the use of effective LDL-C-lowering therapies to consistently hit LDL-C goals that we set in our 2026 ACC/AHA/Multisociety Dyslipidemia Guideline.”
Molecular innovation meets medicinal chemistry
Enlicitide is a macrocyclic peptide that binds PCSK9 with high affinity while remaining orally bioavailable—a feat many researchers once considered unattainable.
“For years, many medicinal chemists believed it simply wasn’t possible to develop an oral molecule that could inhibit the PCSK9–LDL receptor interaction the way monoclonal antibodies do,” Christie Mitchell Ballantyne, MD, chief of cardiology at Baylor College of Medicine and an investigator in the enlicitide clinical development program, told Inside Precision Medicine. “This isn’t a conventional small molecule. It’s a macrocyclic peptide, and developing it required extraordinary chemistry.”
The challenge went beyond finding a PCSK9-binding molecule. Ballantyne said it took multiple rounds of innovation to optimize the lead compound for oral absorption, metabolic stability, and scalable manufacturing after screening massive macrocyclic libraries. With these manufacturing advances, which may be as important as molecular design, Merck was able to introduce enlicitide at a lower price than injectable PCSK9 inhibitors and even some oral LDL-lowering therapies by simplifying chemical synthesis, potentially overcoming one of the main barriers to the drug class’s use.
Two Phase III CORALreef studies supported FDA approval. In the 2,904-patient CORALreef Lipids trial, adults with hypercholesterolemia at high cardiovascular risk had a placebo-adjusted 56% LDL reduction at 24 weeks, increasing to 60% with revised post hoc data handling that excluded biologically implausible baseline LDL-C values. Enlicitide also reduced non-high-density lipoprotein (HDL) cholesterol by 54% and apolipoprotein B by 50%. The 303-patient CORALreef HeFH study produced similarly robust findings, with placebo-adjusted LDL reductions of 59% alongside significant decreases in non-HDL cholesterol and ApoB.
Overall, Ballantyne said, the Phase III program largely confirmed what decades of PCSK9 biology had led researchers to expect, lining up remarkably well with what has been seen from monoclonal antibodies.
Karol Watson, MD, PhD, professor of medicine/cardiology at the David Geffen School of Medicine at UCLA and co-director of the UCLA Program in Preventive Cardiology, expects the trial to validate what decades of LDL biology have consistently suggested, while emphasizing that definitive evidence still matters. “Based on everything we’ve learned over the last several decades, I think it’s very reasonable to expect that those LDL reductions will translate into fewer cardiovascular events,” Watson told Inside Precision Medicine. “But we’ll let the outcomes trial give us the definitive answer.”
For example, although LDL-C is one of medicine’s most extensively validated surrogate biomarkers, regulators appropriately distinguish between lowering cholesterol and demonstrating reductions in heart attacks, strokes, and cardiovascular death.
Merck’s ongoing CORALreef Outcomes trial aims to answer that question directly. The study has enrolled more than 14,500 high-risk patients and is evaluating whether enlicitide reduces major cardiovascular events in addition to lowering LDL-C. Ballantyne noted that investigators continue collecting long-term safety and efficacy data through both the outcomes trial and extension studies.
Making prevention practical
PCSK9 inhibitors have reduced LDL-C by roughly 60% and lowered cardiovascular events for nearly a decade. Yet despite strong clinical evidence, they remain substantially underused in routine practice. The reasons have been familiar: high initial prices, burdensome insurance requirements, physician inertia, and patient reluctance to begin lifelong injectable therapy for a condition that causes no immediate symptoms.
“The challenge has never really been whether PCSK9 inhibition works,” Ballantyne said. “These have been excellent drugs. But they’ve had an access problem.”
For Ballantyne, the promise of enlicitide came through while taking a look at the CORALreef safety data, where findings closely mirrored the placebo. Adverse event-related discontinuation rates were similar across treatment groups, while diarrhea and dizziness occurred infrequently.
“When I review a placebo-controlled trial, one of the first things I examine is whether patients discontinue therapy more often than placebo,” Ballantyne said. “If discontinuation rates are similar, that’s generally very good news because it tells you patients can tolerate the medication.”
Watson believes oral therapy addresses one of those barriers by giving physicians another option for patients who hesitate when injections enter the conversation. “Having an oral PCSK9 inhibitor is a really important step forward because it gives us another option for patients who just don’t want an injectable medication,” she said. “Many patients do perfectly well with injections, but for others it’s a real barrier. Sometimes they put off starting treatment, and sometimes they never start it at all. If we can offer a pill instead, I think we’ll be able to get more patients on effective therapy sooner.”
That flexibility may be especially valuable for patients with established cardiovascular disease or HeFH who remain above guideline-recommended LDL targets despite maximally tolerated statins and ezetimibe. “We now have another way to lower LDL cholesterol without asking patients to make the jump to an injectable if they’re reluctant,” Watson said.
Still, Watson cautions against assuming an oral formulation will automatically solve the adherence problem. “An oral medication has the potential to improve adherence for some patients because many people would rather take a pill than give themselves an injection,” she said. “But we have to remember another group of patients hates taking daily medications, so they will prefer an every 2-week injectable.”
Keith C. Ferdinand, MD, professor of medicine at the Tulane University School of Medicine and the Tulane Heart & Vascular Institute, shares that assessment. “Undertreatment is widespread and common,” Ferdinand told Inside Precision Medicine. “PCSK9 inhibitor uptake has been poor, but probably due to early access barriers and costs. But generic high-intensity statins, costing much less, are underutilized, and most ASCVD patients do not obtain a [cholesterol target of <70 mg/dL]. If an oral PCSK9 inhibitor has cost barriers, uptake will be poor and may not increase goal attainment.”
For Ferdinand, introducing another effective drug is only part of the solution. Measuring whether clinicians actually achieve LDL targets may be equally important. “Oral PCSK9 inhibitors may be costly and underutilized,” he said. “A performance measure of goal attainment would have to overcome therapeutic inertia. Clinicians need a report card on their care and outcomes and respond to high LDL-C. Widespread coverage with easy prior authorization is key.”
A new chapter for PCSK9—and precision medicine
The arrival of the first oral PCSK9 inhibitor also comes as cardiovascular medicine enters another transformative era. Several investigational gene-editing therapies are designed to permanently disable PCSK9 after a single treatment, raising the possibility that lifelong cholesterol management could eventually become a one-time intervention.
At first glance, the technologies appear to compete. Ballantyne sees them as addressing different clinical needs. “The numbers you’re seeing are on top of statin therapy,” he said. “Patients didn’t stop their statins—they received gene editing in addition to their daily medication.” That context changes the comparison. “If you’re still taking a pill every day,” Ballantyne said, “and you could instead take a pill that combines a statin with an oral PCSK9 inhibitor, that’s another way of thinking about the problem.”
Rather than viewing oral therapy and gene editing as mutually exclusive, he expects cardiovascular prevention to evolve into a spectrum of treatment options. Most patients may continue using inexpensive oral medications, while one-time genetic interventions could eventually serve carefully selected populations for whom lifelong adherence is particularly challenging or extraordinarily high LDL levels warrant more aggressive intervention. Ballantyne believes the field will ultimately determine which patients benefit most from each approach based on durability, safety, cost, practicality, and patient preference rather than assuming a single technology will replace all others.
After all, PCSK9 remains the target that human genetics first illuminated more than two decades ago. What is changing is how clinicians and patients may choose to intervene. “The more options we have, the better positioned we are to collaborate with our patients in finding treatment approaches that work and close gaps in care,” Ballantyne said. “If oral PCSK9 inhibitors help more patients initiate treatment, stay on therapy, and achieve guideline-recommended LDL-C levels, they can meaningfully improve cardiovascular disease prevention over the next several years and beyond.”
Whether enlicitide ultimately becomes transformative will depend on factors extending well beyond medicinal chemistry. “This has the potential to be more than just another cholesterol-lowering drug,” Watson said. “Whether it becomes truly practice-changing will depend on several things: cost, access, and whether clinicians are comfortable incorporating it into routine care.”
Watson expects the cardiovascular outcomes data to determine just how broadly clinicians embrace the therapy. “Given what we know about LDL-C as a causal driver of atherosclerotic cardiovascular disease and given the amount of LDL lowering this drug produces, I’d be surprised if we didn’t see cardiovascular benefit,” she said. “If those outcome data are positive, I think this could become another really valuable tool in our toolbox. I don’t see it replacing statins or ezetimibe, but I do see it helping many more high-risk patients actually reach their LDL goals.”
For Ballantyne, however, the approval represents something even larger than another effective lipid-lowering therapy. “It’s a remarkable science story,” he said. “You start with human genetics, then monoclonal antibodies, then RNA therapies, now macrocyclic peptides. It’s another example of how understanding biology can lead to entirely new therapeutic approaches.”
For patients who continue to struggle to reach recommended LDL targets despite existing therapies, that story has now produced something both novel and reassuringly familiar: a once-daily pill.
The post Jagged Little Pill: With Merck’s Oral PCSK9 Inhibitor, Does LDL-C Care Change? appeared first on Inside Precision Medicine.
