Esperion Therapeutics v. Micro Labs: NEXLETOL Bempedoic Acid Patent Case Dismissed Without Prejudice
Esperion Therapeutics asserted three patents covering its bempedoic acid drug NEXLETOL against generic entrant Micro Labs in New Jersey federal court. After 369 days of litigation, all claims and counterclaims were dismissed without prejudice under Rule 41, with each party bearing its own costs — leaving the door open for future proceedings.
NEXLETOL Patent Fight Ends Without Prejudice After a Year of Litigation
Esperion Therapeutics, Inc., the developer and marketer of NEXLETOL (bempedoic acid), filed this Hatch-Waxman patent infringement action on 8 May 2024 in the U.S. District Court for the District of New Jersey against Micro Labs USA, Inc. and its parent Micro Labs Limited. The complaint asserted three U.S. patents — US11760714B2, US11926584B2, and US11613511B2 — each covering aspects of bempedoic acid, the first-in-class ATP-citrate lyase inhibitor approved for LDL-C reduction in cardiovascular risk patients.
The case concluded on 12 May 2025 when the parties filed a stipulated dismissal under Fed. R. Civ. P. 41(a)(1)(A)(ii). All claims and counterclaims were dismissed without prejudice, with each party required to bear its own costs, fees, and expenses. A without-prejudice dismissal carries no preclusive effect — Esperion retains the right to re-assert the same patents against Micro Labs in a future action, and Micro Labs’s invalidity or non-infringement counterclaims were equally extinguished without a merits ruling.
The 369-day duration suggests the parties reached an accommodation before the case progressed to claim construction or summary judgment, stages that typically trigger significant cost escalation in pharmaceutical patent litigation. Whether the resolution reflects a confidential licensing arrangement, a formulation change by Micro Labs, or a strategic reassessment by Esperion is not disclosed in the public record. The without-prejudice posture means competitive dynamics between NEXLETOL and Micro Labs’s ANDA product remain unresolved as a matter of law.
Filing to Case Dismissed in 369 days
369 days — typical ANDA patent cases in D.N.J. often extend 2–3 years before trial
Dismissed without prejudice: what the stipulated exit means for both parties
Rule 41 stipulated dismissal — no merits decided
Under Fed. R. Civ. P. 41(a)(1)(A)(ii), parties may jointly dismiss an action by filing a signed stipulation. A without-prejudice dismissal under this rule has no res judicata effect — the same claims can be re-filed in a future action. No court adjudication of infringement, validity, or enforceability of the three bempedoic acid patents occurred here.
No merits rulingThe record is silent on whether a settlement drove the exit
A dismissal ‘without prejudice’ means Esperion preserves the right to sue Micro Labs again on the same patents. A dismissal ‘with prejudice’ would have barred re-filing. The stipulation specifies without prejudice, but the public record does not disclose whether the parties entered a confidential license, consent decree, or commercialisation agreement alongside the dismissal — a common structure in Hatch-Waxman resolutions.
Re-filing rights preservedEsperion retains all three patents fully enforceable
Because the dismissal carries no merits ruling, US11760714B2, US11926584B2, and US11613511B2 remain valid and enforceable on their face. Esperion can assert them in future proceedings — against Micro Labs or any other ANDA filer targeting NEXLETOL. The absence of a court ruling also means no adverse claim construction or invalidity finding enters the public record.
Patents remain intactMicro Labs’s path to market remains legally uncertain
Micro Labs obtained no court ruling confirming non-infringement or invalidity of the asserted patents — findings that would have cleared a regulatory pathway under Hatch-Waxman. Without a favourable merits outcome or a disclosed licence, the commercial viability of Micro Labs’s generic bempedoic acid product remains contingent on factors not visible in the public record. The without-prejudice posture means litigation risk persists.
Market path unresolvedFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Esperion Therapeutics, Inc. | Company | Pharmaceutical innovator and marketer of NEXLETOL — holder of US11760714B2, US11926584B2, and US11613511B2Search in Eureka ↗ |
| Defendant | Micro Labs | Individual | Generic pharmaceutical manufacturer seeking ANDA approval for bempedoic acid tabletsSearch in Eureka ↗ |
| Co-Defendant | Micro Labs Limited | Individual | Search in Eureka ↗ |
| Plaintiff counsel | Jessica K. Formichella | Attorney | Counsel for Esperion Therapeutics, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Katelyn O’Reilly | Attorney | Counsel for Esperion Therapeutics, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Liza M. Walsh | Attorney | Counsel for Esperion Therapeutics, Inc.Search in Eureka ↗ |
| Plaintiff law firm | Walsh Pizzi O’Reilly Falanga LLP | Law Firm | Representing Esperion Therapeutics, Inc.Search in Eureka ↗ |
| Defendant counsel | James S. Richter | Attorney | Counsel for Micro LabsSearch in Eureka ↗ |
| Defendant law firm | MIDLIGE RICHTER LLC | Law Firm | Representing Micro LabsSearch in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | New Jersey District CourtSearch in Eureka ↗ |
Official order — verbatim text
The stipulated dismissal under Rule 41(a)(1)(A)(ii) is a procedural exit agreed by both parties — it carries no judicial finding on infringement, validity, or claim scope. The ‘without prejudice’ designation is legally significant: it preserves Esperion’s right to re-assert all three patents and prevents Micro Labs from invoking claim preclusion in any future proceeding. The each-party-bears-own-costs clause suggests neither side extracted a clear concession from the other, at least on the public record.
US11760714B2, US11926584B2 & US11613511B2 — Bempedoic Acid Compositions and Methods
The three asserted patents — US11760714B2 (application US17/577829), US11926584B2 (application US18/297846), and US11613511B2 (application US17/742728) — protect bempedoic acid, an ATP-citrate lyase (ACL) inhibitor used to lower LDL cholesterol. Bempedoic acid works upstream of statins in the cholesterol biosynthesis pathway and is specifically activated in the liver, reducing the muscle-related side effects associated with statins. NEXLETOL received FDA approval in 2020 and represents a commercially significant cardiovascular asset for Esperion.
The layered patent portfolio — with applications spanning different filing windows — is consistent with a lifecycle management strategy designed to extend exclusivity on a first-in-class mechanism. For generic manufacturers, a Paragraph IV challenge requires contesting all three patents simultaneously, each potentially at different expiry dates. For competitors developing ACL inhibitors or combination therapies in the LDL-lowering space, the breadth of the portfolio across compositions and methods creates meaningful freedom-to-operate exposure that this litigation’s inconclusive resolution does not diminish.
Should your team run an FTO against NEXLETOL’s bempedoic acid patent estate?
Any pharmaceutical company developing an ACL inhibitor, a bempedoic acid generic, or a combination product incorporating bempedoic acid should treat Esperion’s three-patent portfolio as a live enforcement risk. The without-prejudice dismissal here confirms that Esperion is willing to litigate and that the patents have not been invalidated or narrowed by any court ruling. R&D teams reformulating bempedoic acid or designing structurally related ACL inhibitors face unresolved claim scope across all three patents.
PatSnap Eureka’s FTO Search Agent allows product and IP teams to map claim coverage across US11760714B2, US11926584B2, and US11613511B2 simultaneously — including prosecution history analysis and prior art mapping. Because no Markman order has construed these claims, Eureka’s AI-assisted claim parsing provides the most operationally current FTO baseline available. Teams can also set automated alerts for new ANDA filings or continuation patents in Esperion’s bempedoic acid family.
Run a freedom-to-operate analysis on US11760714B2 to assess your product’s exposure
Run FTO in Eureka →Similar Hatch-Waxman Bempedoic Acid and Cardiovascular Drug Patent Cases
Cases involving ANDA challenges to branded cardiovascular small-molecule drugs in the D.N.J., including related bempedoic acid and LDL-lowering therapy patent disputes.
What this case signals for the bempedoic acid and cardiovascular drug IP landscape
Three-patent ANDA suits resolved without prejudice often signal off-record licensing activity — or a strategic pause ahead of re-engagement.
Without-prejudice exits in ANDA cases typically reflect off-record deal-making
When a branded pharmaceutical company dismisses an ANDA suit without prejudice after less than a year, it rarely signals capitulation. The more common driver is a confidential licence or entry-date agreement that is not required to be disclosed under Hatch-Waxman. Competitors and investors should treat this resolution as strategically ambiguous rather than a green light for generic market entry.
Three-patent coverage on bempedoic acid raises the cost of generic challenge
Esperion’s assertion of three patents — spanning different application numbers and filing years — suggests a layered IP strategy around NEXLETOL. Any ANDA filer seeking a Paragraph IV certification against all three patents faces compounding litigation exposure. The dismissal here does not reduce that structural barrier for future generic entrants; the patents remain listed and enforceable.
Esperion v Micro — key questions answered
Esperion asserted three patents: US11760714B2, US11926584B2, and US11613511B2, all covering aspects of bempedoic acid — the active ingredient in NEXLETOL. The case was filed in the District of New Jersey on 8 May 2024 as a Hatch-Waxman infringement action triggered by Micro Labs’s ANDA filing.
A dismissal without prejudice under Rule 41 carries no preclusive effect. Esperion retains the right to re-assert US11760714B2, US11926584B2, and US11613511B2 against Micro Labs in a future action. No finding of infringement, non-infringement, or invalidity was made, so the legal positions of both parties are reset to pre-litigation status.
No. The without-prejudice dismissal did not constitute a ruling that Micro Labs’s ANDA product does not infringe Esperion’s patents or that the patents are invalid. Micro Labs obtained no judicial clearance for market entry. Whether a confidential licence or entry-date agreement was reached is not disclosed in the public record.
The public record does not explain the commercial rationale. Common drivers in Hatch-Waxman cases of this duration include: a confidential licence granting Micro Labs an authorised generic or delayed entry date; a formulation change by Micro Labs that mooted the infringement claims; or a strategic decision by Esperion to pause litigation pending portfolio reinforcement. Each party bearing its own costs suggests a negotiated resolution rather than capitulation.
Bempedoic acid is a first-in-class ATP-citrate lyase (ACL) inhibitor that lowers LDL cholesterol by acting upstream of statins in the hepatic cholesterol biosynthesis pathway. Marketed as NEXLETOL by Esperion, it is FDA-approved for LDL-C reduction in adults with heterozygous familial hypercholesterolaemia or established cardiovascular disease. Its differentiated mechanism and commercial uptake make its patent estate a high-value enforcement target.
PatSnap Eureka searches patents and litigation data to answer instantly.