Praluent (Alirocumab): Legal Challenges, Patent Battles, and Regulatory History

FDA Approval and Initial Labeling

The FDA approved alirocumab on July 24, 2015, making it the first PCSK9 inhibitor to receive U.S. marketing authorization. The approval covered two populations: adults with HeFH and adults with clinical ASCVD who require additional LDL-C lowering beyond maximally tolerated statin therapy [1].

Approval rested primarily on the ODYSSEY phase III program, which enrolled more than 23,500 patients across 14 trials [2]. In pooled data, alirocumab 150 mg every two weeks reduced LDL-C by 45% to 62% compared with placebo when added to background statin therapy. The initial label did not include a cardiovascular outcomes claim because ODYSSEY OUTCOMES had not yet reported. This gap mattered: without hard endpoint data, many insurers classified PCSK9 inhibitors as unproven luxury drugs and imposed step therapy, prior authorization, or outright denials. A 2017 analysis in Circulation found that payer rejection rates for PCSK9 inhibitors exceeded 50% across commercial plans [3]. The FDA also issued a post-marketing requirement for a cardiovascular outcomes trial, which Regeneron and Sanofi were already conducting.

The Amgen v. Sanofi Patent War

Few pharmaceutical patent disputes have been as consequential. Amgen, maker of the competing PCSK9 inhibitor evolocumab (Repatha), held U.S. Patent Nos. 8,829,165 and 8,859,741, which claimed the entire genus of antibodies that bind to specific residues on the PCSK9 protein and block its interaction with the LDL receptor [4]. Amgen filed suit in 2014, arguing that alirocumab infringed these genus claims.

The case turned on a fundamental question in patent law: can a company claim every antibody that performs a function if it has disclosed only a limited number of species? Sanofi and Regeneron countered that the claims were not enabled under 35 U.S.C. § 112 because Amgen had characterized only 26 antibodies out of potentially millions that could meet the functional definition [5].

A jury initially sided with Amgen in 2016, finding both infringement and validity. The Federal Circuit vacated that verdict in 2017, citing erroneous jury instructions on enablement, and ordered a new trial. At the second trial in 2019, the jury again upheld Amgen's patents.

The case reached the Supreme Court. On June 12, 2023, the Court ruled unanimously in Amgen Inc. v. Sanofi et al. that Amgen's genus claims failed the enablement requirement [5]. Justice Neil Gorsuch, writing for the Court, held that a patent must teach a person skilled in the art to make and use the full scope of the claimed invention without "substantial time and effort beyond what is reasonable." Amgen's claims covered a vast functional class but provided only a "roadmap" for generating individual antibodies through trial and error.

That ruling reshaped antibody patent strategy across the biopharmaceutical industry. Broad functional genus claims, once routine for monoclonal antibodies, now face a much higher enablement bar.

How the Supreme Court Decision Affected PCSK9 Market Dynamics

The ruling removed the threat of an injunction against Praluent in the United States. Before the decision, Sanofi and Regeneron had been operating under legal uncertainty that constrained their willingness to invest in market expansion for alirocumab.

After the decision, alirocumab's commercial position stabilized. Regeneron reported 2024 full-year Praluent net U.S. sales of approximately $315 million [6]. The drug still trails Repatha in market share, partly because the prolonged patent litigation diverted commercial resources during a period when payer formulary decisions were being locked in. Sanofi transferred full commercial rights for Praluent to Regeneron in 2024, consolidating control under a single company.

The broader impact on the biologics industry may prove more significant than the PCSK9 market itself. Patent attorneys now draft narrower structural claims for antibody portfolios, and biosimilar developers have greater confidence that functional genus claims will not block market entry.

ODYSSEY OUTCOMES: The Cardiovascular Endpoint Trial

ODYSSEY OUTCOMES enrolled 18,924 patients who had been hospitalized for an acute coronary syndrome (ACS) event 1 to 12 months before randomization [7]. Participants were randomized to alirocumab 75 mg (with titration to 150 mg if LDL-C remained at or above 50 mg/dL) or placebo, on top of high-intensity or maximum-tolerated statin therapy.

At a median follow-up of 2.8 years, the primary composite endpoint of coronary heart disease death, nonfatal myocardial infarction, ischemic stroke, or unstable angina requiring hospitalization occurred in 9.5% of the alirocumab group versus 11.1% of placebo (hazard ratio 0.85, 95% CI 0.78 to 0.93, P<0.001) [7]. That 15% relative risk reduction translated to a number needed to treat of 63 over 2.8 years.

A prespecified analysis of patients with baseline LDL-C of 100 mg/dL or higher showed a stronger signal: all-cause mortality was 3.5% with alirocumab versus 4.1% with placebo (HR 0.71, nominal P = 0.01 in the high-LDL subgroup) [7]. The mortality finding did not reach statistical significance in the overall trial population under the hierarchical testing plan, which is why the label uses careful language around the death endpoint.

Label Expansion and Supplemental Approvals

Based on ODYSSEY OUTCOMES, the FDA approved a supplemental Biologics License Application (sBLA) for alirocumab in April 2019 [8]. The updated indication added cardiovascular risk reduction for adults with established ASCVD, specifically to reduce the risk of myocardial infarction, stroke, and unstable angina requiring hospitalization. This made Praluent the first PCSK9 inhibitor with an FDA-approved cardiovascular risk reduction claim tied to a dedicated outcomes trial.

The label also includes a 300 mg monthly dosing option (administered as two 150 mg injections), approved in April 2017, which improved convenience for patients who preferred less frequent injections [1].

In 2020, the FDA approved alirocumab for homozygous familial hypercholesterolemia (HoFH) in patients 8 years and older [9]. This pediatric expansion was notable because HoFH is rare (estimated prevalence 1 in 250,000 to 1 in 300,000), and treatment options for children with this condition are limited. The approval was based on a 12-week study showing a 26.9% mean LDL-C reduction compared with 8.6% for placebo.

Safety Profile and Post-Market Surveillance

Across the ODYSSEY program, the most common adverse reactions with alirocumab were injection-site reactions (7.2% vs. 5.1% placebo), nasopharyngitis, and influenza [1]. Serious adverse event rates were comparable between alirocumab and placebo groups in ODYSSEY OUTCOMES (24.4% vs. 24.9%) [7].

A specific safety concern with PCSK9 inhibitors has been neurocognitive effects, given that cholesterol is a component of myelin. The FDA required Regeneron and Sanofi to monitor neurocognitive outcomes. In ODYSSEY OUTCOMES, neurocognitive adverse events occurred in 1.5% of alirocumab-treated patients versus 1.3% of placebo, with no statistically significant difference [7]. A dedicated substudy using validated cognitive testing also found no signal [10].

Hepatic safety has been reassuring. Elevations in ALT greater than three times the upper limit of normal occurred at similar rates in treatment and placebo arms [1]. Post-marketing pharmacovigilance data reported to the FDA Adverse Event Reporting System (FAERS) have not identified new safety signals beyond those characterized in the key trials.

One pharmacovigilance consideration is the achievement of very low LDL-C levels. In ODYSSEY OUTCOMES, 24.2% of alirocumab patients reached LDL-C below 25 mg/dL at some point during follow-up [7]. Long-term data have not linked sustained very low LDL-C to adverse clinical outcomes, but the Endocrine Society and other bodies recommend monitoring patients who achieve levels below 25 mg/dL [11].

Pricing, Access, and the 60% Price Cut

Praluent launched in 2015 at a wholesale acquisition cost (WAC) of approximately $14,600 per year. That price triggered immediate pushback. The Institute for Clinical and Economic Review (ICER) estimated in 2015 that a cost-effective price for PCSK9 inhibitors would fall between $2,177 and $5,404 per year, far below the launch price [12].

In February 2019, Sanofi and Regeneron cut Praluent's list price by 60%, bringing the WAC to roughly $5,850 per year [13]. The reduction coincided with the submission of the ODYSSEY OUTCOMES label supplement and was explicitly framed as a response to payer demands and the ICER threshold. Sanofi also introduced outcomes-based contracts with select payers, tying rebates to actual LDL-C reductions achieved by covered patients.

Despite the price cut, prior authorization requirements remain common. A 2022 study in JAMA Network Open found that only 35% of patients prescribed a PCSK9 inhibitor filled the prescription within 90 days, with insurance barriers cited as the most frequent reason for non-fill [14]. The American Heart Association and American College of Cardiology have both called for reduced administrative barriers to PCSK9 inhibitor access, particularly for patients with ASCVD and LDL-C persistently above 70 mg/dL on maximally tolerated statin therapy [15].

International Regulatory Status

The European Medicines Agency (EMA) granted marketing authorization for Praluent in September 2015, two months after the FDA approval [16]. The EMA's Committee for Medicinal Products for Human Use (CHMP) approved the same indications, and a Type II variation added the cardiovascular risk reduction claim in 2019 following ODYSSEY OUTCOMES.

In contrast to the U.S., several European health technology assessment bodies negotiated confidential pricing agreements that facilitated broader reimbursement. The U.K.'s National Institute for Health and Care Excellence (NICE) initially rejected alirocumab in 2016, then reversed course in 2018 after a patient access scheme brought the effective price within NICE's cost-per-QALY threshold.

Japan's Pharmaceuticals and Medical Devices Agency (PMDA) approved alirocumab in 2018. Regulatory submissions have also been completed in Canada, Australia, and multiple markets in Asia and Latin America.

What the Alirocumab Story Means for Future PCSK9 Therapies

The alirocumab regulatory and legal timeline illustrates how patent litigation, pricing decisions, and outcomes data interact to shape a drug's trajectory. Leqvio (inclisiran), a PCSK9-targeting siRNA approved by the FDA in December 2021, entered the market under different patent conditions and with twice-yearly dosing that changes the access calculus [17]. Oral PCSK9 inhibitors from Merck (MK-0616) and other developers are in late-phase trials. The Supreme Court's enablement decision in Amgen v. Sanofi means that these next-generation therapies face a lower risk of genus-level patent blockades.

For patients currently on alirocumab, the practical takeaway is stability. Regeneron has committed to maintaining the product, the label includes the cardiovascular risk reduction claim, and the patent cloud has cleared. Clinicians prescribing alirocumab 75 mg or 150 mg every two weeks (or 300 mg every four weeks) for patients with ASCVD or HeFH can reference both ODYSSEY OUTCOMES data and the 2018 AHA/ACC cholesterol guideline recommendation for PCSK9 inhibitor add-on therapy in very high-risk patients with LDL-C at or above 70 mg/dL on maximally tolerated statin plus ezetimibe [15].