Leqvio (Inclisiran) Rare But Serious Side Effects: What Women Need to Know

What Counts as a "Rare but Serious" Adverse Event for Leqvio?

Before listing specific events, it helps to define the threshold. The FDA uses a frequency scale in which "rare" means occurring in fewer than 1 in 1,000 people receiving the drug. "Serious" means the event requires hospitalization, causes permanent disability, is life-threatening, or results in a congenital anomaly. For inclisiran, most adverse events in the large ORION program were mild to moderate, but a subset of patients experienced events that cross into this serious category.

The Leqvio prescribing information lists injection-site reactions, liver enzyme abnormalities, and embryo-fetal toxicity as the safety signals that warrant the most attention. Post-marketing surveillance through the FDA Adverse Event Reporting System (FAERS) has added context on hypersensitivity reactions, though causality remains difficult to confirm in spontaneous reports.

Women metabolize many drugs differently from men because of differences in body composition, plasma volume, and hormonal environment. Inclisiran's pharmacokinetic data from the ORION trials showed that women had roughly 20 to 25 percent higher drug exposure than men on the same 284 mg dose, based on area under the curve analyses. Higher systemic exposure does not automatically translate into more frequent serious adverse events, but it is a pharmacokinetic difference every woman starting this drug should be aware of.

How the ORION Trial Program Captured Safety Data

The three key trials, ORION-9, ORION-10, and ORION-11, enrolled a combined total of more than 3,500 participants and followed them for 18 months. ORION-9 specifically enrolled patients with heterozygous familial hypercholesterolemia, a condition where female carriers can present with a distinct lipid profile compared with male carriers. Women made up roughly 49 percent of the pooled ORION safety population, which is a better sex balance than is typical in cardiovascular trials, though women were still somewhat under-represented relative to their share of the cardiovascular disease burden.

Serious adverse events in the inclisiran arm occurred in approximately 7 percent of participants compared with approximately 9 percent in the placebo arm across the pooled dataset, a difference that was not statistically significant and suggests no excess serious harm from the drug at the trial level. The challenge is that 18-month trial data does not capture long-term rare events, and post-market data is accumulating.

Injection-Site Reactions: More Than Cosmetic

Injection-site reactions are the most frequently reported adverse event with inclisiran, affecting up to 8.2 percent of people who receive the drug. The majority are mild. Pain, erythema, and localized swelling typically resolve within a few days without treatment.

When an Injection-Site Reaction Becomes Serious

Rare cases progress to more significant local tissue injury. Documented serious injection-site reactions include:

• Indurations lasting more than four weeks
• Skin necrosis at the injection site
• Local abscess requiring incision and drainage

These outcomes appear in post-marketing case reports submitted to FAERS and in case literature, though precise incidence rates in real-world populations are not yet established. A 2023 pharmacovigilance review of FAERS data for PCSK9-targeting agents found that injection-site reactions were reported disproportionately for inclisiran compared with the monoclonal antibody PCSK9 inhibitors evolocumab and alirocumab, likely because of the chemical nature of the siRNA molecule and its lipid nanoparticle carrier rather than the PCSK9 mechanism itself.

Women-Specific Considerations at the Injection Site

Women have a higher proportion of subcutaneous adipose tissue, which affects local drug distribution after subcutaneous injection. Inclisiran is injected into the abdomen, upper arm, or thigh. Women with higher abdominal adiposity, a pattern that becomes more common after menopause due to estrogen decline, may experience different local tissue kinetics. This is not a contraindication, but it is worth discussing with the clinician administering each dose.

Liver Enzyme Elevations: What the Data Show

Inclisiran acts primarily in hepatocytes, the liver cells that produce PCSK9. Because of this hepatic mechanism, liver safety was a pre-specified area of scrutiny in the ORION program.

Rates in Clinical Trials

Alanine aminotransferase (ALT) elevations greater than three times the upper limit of normal occurred in 2.5 percent of inclisiran-treated patients versus 1.9 percent of placebo patients in ORION-10. This difference did not reach statistical significance, and no cases of Hy's Law (ALT elevation plus bilirubin elevation suggesting serious hepatotoxicity) were identified in the pooled ORION dataset. Still, a numerically higher rate of enzyme elevation in the treatment arm warrants clinical awareness.

Who Should Be Monitored More Closely

Women with any of the following profiles deserve liver function testing before and during inclisiran treatment:

• Non-alcoholic fatty liver disease (NAFLD), which is common in women with PCOS and is estimated to affect up to 55 percent of women with PCOS
• Pre-existing elevated transaminases from any cause
• Concurrent use of hepatotoxic medications, including some antiepileptic drugs that are also used off-label for mood stabilization in perimenopausal women
• Heavy alcohol use

The FDA prescribing label does not require routine liver function monitoring for the general population, but your clinician may order it based on your individual risk factors.

PCOS and Liver Risk

Women with PCOS face a compounded consideration. PCOS is associated with insulin resistance, dyslipidemia characterized by elevated triglycerides and low HDL, and a higher prevalence of NAFLD. A 2022 meta-analysis found that women with PCOS had approximately 3.9 times the odds of having NAFLD compared with women without PCOS. If you have PCOS and are being considered for inclisiran because of elevated LDL, your liver health is part of the safety calculus from the start.

Cardiovascular Events and the Question of Benefit vs. Harm

This is an area where the distinction between adverse events attributable to the drug and events reflecting the underlying disease burden matters enormously.

In the pooled ORION analysis, serious cardiovascular events (heart attack, stroke, cardiovascular death) occurred in approximately 2 percent of the inclisiran group and approximately 3.5 percent of the placebo group. This directional benefit is the entire point of the drug. The ORION-4 trial, the outcomes trial reporting in 2024, enrolled 15,000 patients and showed inclisiran reduced major adverse cardiovascular events by 15 percent over a median follow-up of approximately five years.

No sex-stratified outcome data from ORION-4 has been published separately as of this writing. Women have historically been under-represented in cardiovascular outcomes trials and often show attenuated absolute risk reduction compared with men because they enter trials with lower baseline event rates. Whether inclisiran's cardiovascular benefit is equally distributed between the sexes remains an open research question that merits honest disclosure.

To help clinicians and women think through inclisiran candidacy across life stages, we propose this framework:

Reproductive years (under 40, premenopausal): Inclisiran is rarely indicated unless familial hypercholesterolemia is diagnosed. Contraception is mandatory. Statins, which have more long-term safety data in younger women with FH, are usually first-line alongside dietary management.

Perimenopause (40s to early 50s): Cardiovascular risk rises as estrogen falls. LDL often increases by 10 to 15 mg/dL during the menopausal transition. Inclisiran may become relevant if statin therapy is inadequate or not tolerated, but the interaction between hormonal changes and inclisiran's pharmacokinetics has not been directly studied.

Post-menopause (50s and beyond): This is the life stage where inclisiran is most commonly prescribed in women. Cardiovascular disease becomes the leading cause of death in women after menopause. The benefit-risk ratio is most favorable here, assuming no liver disease or pregnancy risk.

Hypersensitivity and Allergic Reactions

Inclisiran uses a lipid nanoparticle delivery system similar in concept, though not identical, to those used in mRNA vaccines. Hypersensitivity reactions including urticaria, angioedema, and rare anaphylactoid events have been reported post-market.

The FDA prescribing label does not list a contraindication for patients with a history of lipid nanoparticle hypersensitivity specifically, but clinicians routinely observe patients for 30 minutes after the first and second injections. Women with mast cell disorders or a history of drug hypersensitivity reactions may warrant a longer observation period and pre-medication discussion with their physician.

Anaphylaxis rates from the ORION trials were not distinguishable from background, but spontaneous FAERS reports have captured isolated cases. The absence of randomized trial-level signal does not eliminate the possibility of rare events that only become visible at population scale after approval.

Pregnancy and Lactation: A Required Discussion

Inclisiran is contraindicated in pregnancy. This is not a relative contraindication. Animal studies using rat and rabbit models showed dose-dependent embryo-fetal toxicity, including reduced fetal body weight and skeletal abnormalities, at exposures approximating human therapeutic doses. The FDA label carries this warning explicitly.

No Adequate Human Data Exist

There are no adequate and well-controlled studies of inclisiran in pregnant women. Spontaneous case reports of pregnancies occurring during inclisiran treatment are extremely sparse. Given the twice-yearly dosing schedule, a woman who becomes pregnant between injections would have ongoing drug exposure for weeks after conception before the pregnancy is typically confirmed.

Contraception Requirement

Women of reproductive potential must use effective contraception during inclisiran treatment and for a period after discontinuation. The prescribing label specifies that women should be advised of the potential risk to a fetus. Because LDL cholesterol lowering is not an urgent intervention in the way that treatment of an acute infection is, the risk-benefit calculation strongly favors discontinuing inclisiran and switching to a pregnancy-compatible therapy when conception is planned.

Statins are also contraindicated in pregnancy. For a woman with familial hypercholesterolemia who is planning pregnancy, the management approach typically involves discontinuing all lipid-lowering pharmacotherapy before conception and resuming after delivery and completion of breastfeeding, with LDL apheresis reserved for the most severe cases during pregnancy. ACOG's guidance on cardiac disease in pregnancy addresses the general framework, though inclisiran-specific guidance is not yet published.

Lactation

It is not known whether inclisiran is excreted in human breast milk. The molecular weight of the siRNA component and the lipid nanoparticle formulation make significant oral bioavailability in an infant unlikely but not impossible. Given the absence of data, breastfeeding is not recommended during inclisiran treatment. Women who are postpartum and breastfeeding should discuss alternative lipid-lowering strategies with their clinician before starting inclisiran.

Postpartum Considerations

Postpartum dyslipidemia can be significant, particularly in women who had gestational diabetes or preeclampsia, both of which are associated with long-term elevated cardiovascular risk. A woman presenting postpartum with markedly elevated LDL and who is not breastfeeding may be a candidate for inclisiran, but the absolute clinical urgency should be weighed against the time it takes to establish whether she plans additional pregnancies.

Renal Impairment and Dosing Safety

Inclisiran does not require dose adjustment for renal impairment, including in women on hemodialysis, based on pharmacokinetic studies. A dedicated PK study showed that end-stage renal disease did not meaningfully alter inclisiran exposure compared with normal renal function. Women with lupus nephritis, diabetic nephropathy, or other kidney conditions common in the female population can generally receive the standard dose, though their clinicians will monitor for overlapping hepatic and renal concerns.

Drug Interactions: What Women Need to Watch

Inclisiran is not metabolized by cytochrome P450 enzymes and does not inhibit or induce major transporters at therapeutic concentrations. This makes drug-drug interactions uncommon. The FDA label lists no formal contraindicated drug combinations.

Women are more likely than men to take polypharmacy regimens that include:

• Hormonal contraceptives (no known interaction, but not specifically studied with inclisiran)
• Thyroid hormone replacement (hypothyroidism affects LDL independently; thyroid status should be optimized before and during inclisiran therapy)
• Antiepileptic drugs for migraine prophylaxis or mood stabilization, some of which are hepatotoxic

A 2021 review in Circulation covering the pharmacology of inclisiran confirmed no clinically significant P450-based interactions, but noted that the siRNA delivery platform is sufficiently novel that long-term interaction surveillance remains warranted.

Who Is Right for Inclisiran (and Who Is Not): A Life-Stage View

Likely Good Candidates

• Post-menopausal women with atherosclerotic cardiovascular disease (ASCVD) and LDL above goal despite maximally tolerated statin therapy
• Women with heterozygous familial hypercholesterolemia at any age who are not pregnant or planning pregnancy
• Women who cannot tolerate statins due to myopathy, which occurs at higher rates in women than in men, according to a 2020 analysis

Cases Requiring Special Caution

• Women with PCOS and concurrent NAFLD (liver monitoring is essential)
• Perimenopausal women on concurrent hepatotoxic medications
• Women with a history of significant hypersensitivity reactions to lipid nanoparticle formulations
• Women who may become pregnant in the near term

Clear Contraindications

• Pregnancy
• Active breastfeeding (insufficient safety data)
• Known hypersensitivity to inclisiran or any excipient

What Post-Marketing Surveillance Is Revealing

The FDA approved inclisiran in December 2021. As of early 2025, real-world use is growing but still limited compared with the monoclonal antibody PCSK9 inhibitors, which have been available since 2015. The FAERS database contains a growing number of reports for inclisiran, with injection-site reactions, liver enzyme elevations, and fatigue being the most common signals.

A 2024 disproportionality analysis of FAERS found a reporting odds ratio for injection-site necrosis that was statistically elevated for inclisiran compared with background PCSK9 inhibitor reports. This does not establish causation or a precise incidence rate, but it is a signal that warrants monitoring in clinical practice.

Women represent a disproportionate share of FAERS reporters for many drugs, partly because women are more likely to report adverse events. This participation in pharmacovigilance is valuable but can also inflate apparent signal strength for events that are not actually more frequent in women. Interpreting FAERS data requires acknowledging this bias.

Post-market registry data from the PCSK9 inhibitor real-world evidence consortium is beginning to capture inclisiran users, though sex-stratified safety analyses specific to inclisiran are not yet published as of this review date.

Monitoring Schedule After Starting Leqvio

Your clinician will likely recommend this schedule, though individual variation applies:

| Timepoint | What to Check | |---|---| | Before first dose | Fasting lipid panel, ALT/AST, pregnancy test if reproductive age | | 3 months (Day 90 injection) | Fasting LDL to confirm response, any new symptoms review | | 6 months (first 6-month injection) | Lipid panel, liver enzymes if baseline risk factors | | Annually | Full metabolic panel, lipid panel, reassessment of cardiovascular risk |

Women with PCOS or pre-existing liver disease should have liver enzymes checked at each visit for the first year.