Last updated: July 7, 2026
Endo Pharmaceuticals Inc. sued Perrigo UK FINCO Limited Partnership (and related parties) in the District of Delaware for alleged infringement in connection with a proposed generic product. The case number is 1:19-cv-00437. The dispute centers on Orange Book-listed patents for the reference product and typical Hatch-Waxman infringement theories that hinge on the scope of the asserted claims, claim construction, and any jurisdictional or procedural defenses.
What is Endo Pharmaceuticals Inc. v. Perrigo UK FINCO Limited Partnership, 1:19-cv-00437 about?
The case is a Hatch-Waxman patent infringement action filed by Endo in the District of Delaware against Perrigo UK FINCO Limited Partnership. These suits generally follow FDA submission timing where the generic challenger files an ANDA with Paragraph IV certifications and the brand owner asserts infringement of one or more patents listed for the reference listed drug (RLD) in FDA’s Orange Book. (Case docket is the controlling record; see cited court entry.) [1]
What claims and theories are typically asserted in this posture?
Hatch-Waxman actions in the same procedural posture as 1:19-cv-00437 usually include:
- Direct infringement under 35 U.S.C. § 271(a) for manufacture, use, sale, or importation in the United States by or on behalf of the ANDA applicant.
- Induced infringement and/or contributory infringement under 35 U.S.C. §§ 271(b)-(c), depending on how the complaint is pled.
- Administrative-triggered damages exposure tied to the launch “at risk” timeline and any settlement or consent-judgment terms, if reached. [1]
What patents are usually at issue in Endo vs. generic challengers?
In Endo’s generic patent litigations, asserted patents commonly cover one or more of the following Orange Book categories:
- Formulation and composition-of-matter (drug substance compositions; excipient systems; active plus defined ratios; polymorphs).
- Method-of-use (indications, patient populations, dosing regimens, or therapeutic effects).
- Dosage form and manufacturing constraints (including controlled-release or extended-release design choices).
Patent identities are determined by the complaint’s list of asserted Orange Book patents and claim numbers, which is reflected on the docket and in the pleadings. [1]
What patents protect the Orange Book-listed Endo product in 1:19-cv-00437?
Patent protection is tied to the Orange Book listings for the RLD that the ANDA applicant referenced in the Paragraph IV notice. In litigation, Endo typically asserts specific Orange Book patents and specific claim sets. The docket for 1:19-cv-00437 is the authoritative source for:
- The asserted patent list
- The patent claim numbers
- The infringement contentions framework and any claim construction positions [1]
How do courts identify “the Orange Book patents” in these cases?
Typically:
- Endo alleges infringement of the patents listed in the Orange Book for the RLD.
- Perrigo responds with invalidity and non-infringement defenses tied to the proposed generic product and the claim scope.
- If there are co-defendants or related corporate entities, the caption ties to the applicant and/or marketing entity responsible for the ANDA. [1]
When does Endo v. Perrigo lose exclusivity and how do patent expirations drive the litigation?
In ANDA Paragraph IV litigation, exclusivity timelines drive practical leverage:
- If an asserted patent is scheduled to expire before the anticipated commercial launch, the case often narrows toward non-infringement/invalidity outcomes or settlement economics.
- If exclusivity or patent protection extends beyond the launch window, the litigation supports delayed entry unless a settlement shortens the barrier.
The exact expiration dates for the asserted patents must be taken from the patents asserted in the complaint for 1:19-cv-00437. Those dates govern whether the case is “bet-the-company” on claim validity or an economic dispute over launch timing. [1]
What outcomes matter most for generic launch timing?
The decision tree in Hatch-Waxman is typically:
- Non-infringement ruling: immediate or early launch becomes viable if no other stay-triggering patents remain.
- Invalidity ruling: entry proceeds after any remaining statutory barriers are resolved.
- Settlement: often includes an agreed “carve-out” launch date, royalties, or stipulations tied to remaining patents.
- Dismissal on procedural grounds: can lead to re-filing dynamics depending on notice and venue issues. [1]
What is the litigation timeline for 1:19-cv-00437 and what procedural milestones occurred?
The controlling timeline is the District of Delaware docket. For accurate sequencing, the key milestones include:
- Filing date and initial complaint
- Answer and affirmative defenses
- Claim construction schedule (Markman)
- Motions practice (dismissals, summary judgment)
- Trial or dispositive rulings
- Any settlement, stipulation, or consent judgment entry
- Post-judgment appeals or termination notices
For 1:19-cv-00437, the docket is the authoritative ledger for those events. [1]
Why procedural posture affects patent-strategy analysis
- Claim construction can shift infringement risk without changing validity.
- Joinder of parties, amended complaints, or narrowing of asserted claims can reflect early assessment of which patents are stronger or weaker.
- Settlement entries often include confidential terms, but the court docket typically records dismissals or consent judgments that signal the end-state. [1]
How strong is Endo’s patent estate against Perrigo in 1:19-cv-00437?
Strength in these actions is measured by:
- Whether asserted claims are narrow or broad and whether they map to a generic design-around space.
- Prior art burden for invalidity.
- Claim construction vulnerability for functional limitations.
- Whether Endo’s asserted claims overlap with known generic industry design choices (formulation, release profile, or dosing schema).
The specific assessment for 1:19-cv-00437 requires the asserted patents and claims listed in the complaint and the court’s construction outcomes as reflected on the docket. [1]
What generic entry risks exist for Perrigo if Endo’s asserted claims are construed narrowly?
If a court construes key limitations narrowly, Perrigo’s product may fall outside infringement scope even if validity arguments remain unsettled. Common risk patterns include:
- Generic formulation differences that avoid a claimed ratio, particle size, or release characteristic.
- Method-of-use limitations that require specific patient conditions or dosing steps not performed as described in the ANDA labeling.
Again, the infringement mapping is anchored to the asserted claim elements in 1:19-cv-00437. [1]
How does Perrigo’s proposed ANDA design-around strategy factor into the case?
In ANDA litigation, generic challengers often pivot on:
- Non-infringement by engineering around composition-of-matter limitations.
- Invalidation arguments that focus on obviousness combinations or anticipation based on prior patents and publications.
- Labeling-based non-infringement for method-of-use claims where the ANDA’s proposed labeling fails to instruct the infringing method.
The actual design-around positions are contained in infringement contentions, invalidity contentions, and claim construction briefing on the docket. [1]
What patent litigation outcomes usually lead to settlement or consent judgment in these disputes?
These cases commonly settle at one of three inflection points:
- After Markman (claim construction) changes the infringement profile.
- After summary judgment on select claims.
- During expert discovery once damages exposure and remaining claim strength are clearer.
The docket for 1:19-cv-00437 is the source for the actual end outcome (trial verdict, dismissal, settlement, or consent judgment). [1]
What is the FDA Orange Book status and Paragraph IV posture for this dispute?
The FDA posture in these cases is usually:
- Perrigo submitted an ANDA referencing an Endo RLD.
- Perrigo filed Paragraph IV certifications challenging one or more Orange Book patents.
- Endo sued within the statutory window to trigger the 30-month stay (or extend entry restrictions if the case remains active past the initial stay window).
Orange Book status and the exact patents certified under Paragraph IV are reflected by:
- The Orange Book entries tied to the RLD
- The notice letter and complaint’s asserted patent list
- The FDA procedural timeline on the ANDA side
The exact Orange Book patent identifiers for 1:19-cv-00437 are determined by the complaint and docket filings. [1]
What regulatory pathway is impacted by 1:19-cv-00437?
The regulatory impact is typically:
- ANDA is delayed by the statutory stay if the case is timely filed and falls within the Hatch-Waxman stay mechanics.
- If a settlement is reached, the stay may be lifted by court dismissal or consent judgment, depending on settlement terms.
The practical consequence for Perrigo is whether it can launch at risk, after lift of the stay, or only after expiration of the relevant patents. [1]
Key takeaways
- Endo Pharmaceuticals Inc. v. Perrigo UK FINCO Limited Partnership (1:19-cv-00437, District of Delaware) is a Hatch-Waxman patent infringement dispute tied to Orange Book-listed patents and a generic ANDA Paragraph IV posture. [1]
- The litigation’s leverage points are patent claim scope (especially via Markman), remaining asserted claims after any amendments, and whether the outcome preserves a statutory entry barrier. [1]
- Any assessment of strength, expiration-driven strategy, or launch risk must be anchored to the asserted patent list and claim numbers from the 1:19-cv-00437 docket and pleadings. [1]
FAQs
1) What court heard Endo Pharmaceuticals Inc. v. Perrigo UK FINCO Limited Partnership, 1:19-cv-00437?
The case is in the District of Delaware under case number 1:19-cv-00437. [1]
2) What legal framework governs infringement allegations in this type of case?
Hatch-Waxman patent infringement under 35 U.S.C. §§ 271 and the ANDA Paragraph IV litigation process tied to Orange Book patents. [1]
3) How is “at-risk” launch affected by these lawsuits?
Generic entry is typically stayed while the litigation is active and can be delayed by the statutory 30-month stay mechanics unless it is lifted through dismissal, settlement, or court outcomes. [1]
4) Do settlements appear on the public docket in a way that signals the practical outcome?
Yes. Docket entries usually include dismissal, stipulation, or consent-judgment filings that mark the procedural end-state. [1]
5) Where do patent numbers and claim lists come from for this specific action?
From the complaint and asserted-claims listings reflected in the 1:19-cv-00437 docket and associated filings. [1]
References
- United States District Court for the District of Delaware. Endo Pharmaceuticals Inc. v. Perrigo UK FINCO Limited Partnership, No. 1:19-cv-00437 (docket).
