Inclisiran is a cholesterol-lowering medication that works by silencing the gene responsible for producing a protein called PCSK9 in the liver. Unlike older PCSK9-targeting drugs that intercept the protein after it’s already made, inclisiran stops the protein from being produced in the first place. The result is a roughly 50% reduction in LDL cholesterol with just two injections per year after the initial dosing period.
The Role of PCSK9 in Cholesterol
To understand inclisiran, you need to understand the problem it solves. Your liver removes LDL cholesterol from your bloodstream using receptors on the surface of liver cells. These receptors grab onto LDL particles, pull them inside the cell, and break them down. After doing their job, the receptors normally recycle back to the cell surface to grab more LDL.
PCSK9 is a protein that interferes with this recycling. It binds to LDL receptors and tags them for destruction, so instead of returning to the surface, the receptors get broken down along with the cholesterol. Fewer receptors on the surface means less LDL gets cleared from your blood, and your cholesterol levels rise. People with naturally high PCSK9 activity tend to have higher LDL, while rare genetic variants that reduce PCSK9 are linked to lower LDL and lower heart disease risk. That’s what made PCSK9 such an attractive drug target.
How Inclisiran Silences PCSK9 Production
Inclisiran belongs to a class of drugs called small interfering RNAs (siRNAs). These are short, synthetic strands of genetic material designed to intercept and destroy a specific messenger RNA before it can be used to build a protein. In this case, the target is the messenger RNA that carries instructions for making PCSK9.
Here’s the step-by-step process. After injection, inclisiran travels to the liver, where a sugar molecule attached to the drug acts as a homing signal. Liver cells have receptors that recognize this sugar and pull the drug inside. Once in the cell, inclisiran’s double-stranded RNA gets loaded into a protein complex called RISC, which is part of the cell’s natural gene-silencing machinery. The RISC complex then uses one strand of inclisiran as a template to find and bind to matching PCSK9 messenger RNA. When it locks on, it cuts the messenger RNA apart, preventing it from ever being translated into the PCSK9 protein.
The key advantage of this approach is durability. The RISC complex isn’t used up when it destroys one messenger RNA molecule. It can go on to find and destroy additional copies, which is why a single dose keeps working for months. Inclisiran remains active in the liver for several months after each injection, continuously suppressing new PCSK9 production.
How It Differs From Other PCSK9 Drugs
Before inclisiran, the two available PCSK9 inhibitors (evolocumab and alirocumab) were monoclonal antibodies. These work at a completely different stage in the process. Instead of preventing PCSK9 from being made, antibodies circulate in the bloodstream and physically bind to PCSK9 protein after it’s already been released by the liver. By latching onto PCSK9, the antibodies block it from attaching to LDL receptors, keeping those receptors safe to continue clearing cholesterol.
Both approaches ultimately achieve the same goal: protecting LDL receptors so they can remove more cholesterol from the blood. But the practical differences matter. Monoclonal antibodies break down relatively quickly in the body, so they require injections every two to four weeks. Inclisiran’s gene-silencing mechanism lasts much longer, which is why maintenance dosing is only needed twice a year. For people who find frequent injections burdensome, this is a meaningful distinction. The LDL reductions are comparable between the two approaches.
How Much It Lowers Cholesterol
In pooled data from major clinical trials involving patients with atherosclerotic cardiovascular disease, inclisiran reduced LDL cholesterol by about 52% compared to placebo over 18 months. That level of reduction held steady with continued twice-yearly dosing. Long-term data from the ORION-3 extension study showed that PCSK9 levels remained suppressed by 62% to 78% over four years, with consistent cholesterol lowering throughout.
These reductions are on top of whatever benefit patients were already getting from statins. Inclisiran is approved specifically as an add-on to maximally tolerated statin therapy, not as a replacement for it.
Dosing Schedule
Inclisiran is given as a subcutaneous injection, typically in a healthcare provider’s office. The schedule is straightforward: a first injection on day one, a second injection at three months, and then one injection every six months from that point forward. The three-month loading dose allows the drug to reach full suppression of PCSK9 more quickly than waiting a full six months between the first two doses.
This twice-yearly schedule is one of the most distinctive features of the drug. Compared to daily pills or biweekly injections, it removes much of the adherence burden that makes long-term cholesterol management difficult for many people.
Who It’s Approved For
The FDA approved inclisiran (sold as Leqvio) for adults with two specific conditions who need additional LDL lowering beyond what statins and other oral therapies can achieve. The first is heterozygous familial hypercholesterolemia, a genetic condition that causes very high cholesterol from birth. The second is clinical atherosclerotic cardiovascular disease, meaning people who have already had a heart attack, stroke, or been diagnosed with blocked arteries.
Current guidelines from the American College of Cardiology and American Heart Association give inclisiran a “reasonable to use” recommendation for adults whose LDL remains at or above 100 mg/dL despite maximally tolerated statin therapy, with or without ezetimibe. For very high-risk patients, the guidelines also position inclisiran as an option for those who can’t tolerate or access the monoclonal antibody alternatives, or who strongly prefer less frequent dosing.
Side Effects
The most common side effect is a reaction at the injection site, occurring in about 8% of patients compared to 2% with placebo. These reactions include pain, redness, and rash at the spot where the injection was given. They’re generally mild and rarely lead to stopping treatment. Only 0.2% of patients in clinical trials discontinued inclisiran because of injection site reactions.
Joint pain (arthralgia) occurred in 5% of patients versus 4% with placebo, and bronchitis in 4% versus 3%. Beyond these, the overall safety profile in trials was similar to placebo. Because inclisiran acts specifically inside liver cells and targets a single messenger RNA, it doesn’t have the broad systemic effects that some other injectable therapies carry.
What’s Still Unknown
Inclisiran clearly lowers LDL cholesterol, but whether that translates into fewer heart attacks and strokes hasn’t been proven yet in a dedicated outcomes trial. The ORION-4 trial, a large randomized study following participants for a median of five years, is expected to report results in late 2026. Its primary endpoint is the rate of major cardiovascular events, including heart attack, stroke, and death from coronary heart disease. Until those results arrive, the case for inclisiran rests on the well-established relationship between lower LDL levels and lower cardiovascular risk, rather than direct proof from the drug itself.