Litigation Details for Anacor Pharmaceuticals, Inc. v. Lupin Limited (D. Del. 2018)

Anacor Pharmaceuticals, Inc. v. Lupin Limited (D. Del. 2018)

Docket	1:18-cv-01606-RGA	Date Filed	2018-10-17
Court	District Court, D. Delaware	Date Terminated	2020-09-11
Cause	35:271 Patent Infringement	Assigned To	Richard Gibson Andrews
Jury Demand	None	Referred To
Patents	7,582,621; 9,549,938; 9,566,289; 9,566,290; 9,572,823
Link to Docket	External link to docket

Details for Anacor Pharmaceuticals, Inc. v. Lupin Limited (D. Del. 2018)

Date Filed	Document No.	Description	Snippet	Link To Document
2018-10-17	108	Report and Recommendations	An ancestor to the patents-in-suit, U.S. Patent No. 7,582,621 (“the ’621 patent”), also claimed methods…of U.S. Patent Nos. 9,549,938, 9,566,289, 9,566,290, and 9,572,823 (collectively, the “patents-in- suit… While the IPR of the ʼ621 patent was pending, the patents-in-suit were being prosecuted before… the four patents-in-suit in early 2017 (before the PTAB’s IPR decision on the ʼ621 patent). Anacor listed…review of the patents-in-suit. The PTAB instituted review of all claims of all four patents-in-suit in	External link to document

Anacor Pharmaceuticals v. Lupin: Litigation Summary, Patent Analysis, and Generic Entry Risk

Last updated: August 16, 2026

Anacor Pharmaceuticals sued Lupin Limited in the U.S. District Court for the District of Delaware over Lupin's abbreviated new drug application for a generic version of Kerydin (tavaborole) topical solution, 5%. The case, No. 1:18-cv-01606-RGA, was a Hatch-Waxman patent action involving Orange Book-listed patents covering tavaborole topical formulations and treatment methods. The litigation did not produce a reported merits decision or claim-construction ruling. The case was later terminated, and publicly available docket materials do not disclose the material commercial terms of the resolution. [1]

What drug and ANDA were involved in Anacor v. Lupin?

The case concerned Kerydin, a topical antifungal product containing tavaborole 5% solution.

Item	Details
Branded product	Kerydin
Active ingredient	Tavaborole
Dosage form	Topical solution
Strength	5%
Indication	Treatment of toenail onychomycosis caused by susceptible fungi
NDA holder at launch	Anacor Pharmaceuticals
Later commercial owner	Pfizer, following its acquisition of Anacor
Generic applicant	Lupin Limited
Regulatory pathway	ANDA under the Hatch-Waxman Act
Court	U.S. District Court for the District of Delaware
Civil action	No. 1:18-cv-01606-RGA
Judge	Richard G. Andrews
Case type	Paragraph IV patent-infringement action

Kerydin was approved by the FDA in July 2014. Tavaborole is a small-molecule boron-containing antifungal agent. Because Lupin pursued an ANDA rather than a biologics application, the dispute involved generic substitution and Hatch-Waxman patent certification rules, not biosimilar interchangeability. [2]

What patents protected Kerydin in the Lupin litigation?

The asserted patent estate included U.S. Patent Nos. 9,192,662 and 9,566,238. Both patents were associated with tavaborole topical products and were listed in the FDA's Orange Book for Kerydin. [1, 3]

Patent	General subject matter	Relevance to Kerydin
U.S. 9,192,662	Tavaborole topical composition and formulation claims	Core product and formulation protection
U.S. 9,566,238	Additional tavaborole composition and treatment claims	Follow-on formulation and method protection

The patents were important because tavaborole's commercial value depended on a specific topical formulation capable of delivering the active ingredient to infected toenails. A generic applicant could avoid infringement by altering its formulation, concentration, excipients, or labeling, but those changes would have to remain consistent with FDA's ANDA requirements and the reference product's conditions of use.

The asserted portfolio did not create biologic-style manufacturing exclusivity. It was a small-molecule formulation estate. The principal barriers were the listed patents, FDA approval requirements, formulation development, and the need to establish pharmaceutical equivalence and bioequivalence or applicable comparative performance.

When did Kerydin lose regulatory exclusivity?

Kerydin's five-year new chemical entity exclusivity expired in 2019, based on its July 2014 approval. FDA regulatory exclusivity and patent protection operated on separate timelines.

Exclusivity or protection	Approximate timing	Commercial effect
FDA approval	July 2014	Kerydin entered the U.S. market
Five-year NCE exclusivity	Through approximately July 2019	Blocked submission of a standard ANDA during the initial period, subject to statutory exceptions
Four-year Paragraph IV restriction	Through approximately July 2018	Allowed ANDA filing only under specified patent-certification rules
Orange Book patent term	Extended beyond NCE exclusivity	Determined whether an approved generic could launch
Hatch-Waxman 30-month stay	Triggered by timely patent litigation after a Paragraph IV notice	Temporarily restricted FDA approval of the ANDA

The Lupin case was filed in 2018, before the end of the five-year NCE period. That timing allowed the patent dispute to proceed while regulatory exclusivity and listed-patent issues overlapped. The ultimate launch date would have depended on the settlement, court disposition, patent expiry, or another statutory approval pathway.

Was Lupin's ANDA a Paragraph IV challenge?

Yes. The action was filed as a Hatch-Waxman infringement case arising from Lupin's ANDA and its Paragraph IV certification concerning Kerydin patents. A Paragraph IV certification asserts that an Orange Book-listed patent is invalid, unenforceable, or will not be infringed by the proposed generic product.

The certification creates an artificial act of infringement under 35 U.S.C. § 271(e)(2). The branded company can then sue before commercial launch. If the suit is filed within the statutory period after receiving the ANDA notice, FDA approval may be stayed for up to 30 months, subject to earlier termination or modification under the statute. [4]

The public record does not establish that Lupin prevailed on invalidity, noninfringement, or unenforceability. There was no reported final merits judgment in Lupin's favor.

What was the litigation timeline?

Date or period	Event
July 2014	FDA approved Kerydin for toenail onychomycosis
2016	Pfizer acquired Anacor Pharmaceuticals
2018	Lupin filed an ANDA for generic tavaborole topical solution
September 2018	Anacor filed Civil Action No. 1:18-cv-01606-RGA in Delaware
2018-2019	Pleadings and Hatch-Waxman case-management activity proceeded
Later proceeding	The action was terminated without a reported merits opinion
Current status	Closed litigation; no public trial judgment identified

The docket does not provide a reported claim-construction opinion, summary-judgment decision, or trial verdict. The record also does not establish a publicly disclosed damages award. The case therefore provides limited judicial guidance on the construction or validity of the asserted tavaborole claims.

What was the litigation status and settlement outcome?

The case is closed. Its termination indicates that the parties resolved or otherwise disposed of the action without a reported merits adjudication. Publicly available court records do not disclose the key commercial provisions of the resolution, including:

• Whether Lupin received a license to launch before patent expiry;
• Whether the parties agreed to a fixed launch date;
• Whether the agreement included a supply arrangement;
• Whether Pfizer or Anacor granted Lupin a covenant not to sue;
• Whether the agreement included acceleration provisions tied to another generic entrant;
• Whether the Federal Trade Commission received a filed agreement under the Medicare Modernization Act.

No reported opinion establishes that the asserted patents were invalid, unenforceable, or not infringed. The absence of a merits judgment means the case should not be treated as a judicial rejection of the Kerydin patent estate.

What Orange Book patents covered Kerydin?

The principal Orange Book-listed patents associated with Kerydin were U.S. Patent Nos. 9,192,662 and 9,566,238. Orange Book listing is commercially significant because it gives an ANDA applicant a formal patent-certification framework and allows the NDA holder to invoke Hatch-Waxman litigation procedures. [3]

Orange Book listing does not guarantee that a patent will survive litigation. It establishes the patent's regulatory relevance. Generic applicants can challenge the listing through a Paragraph IV certification, or they can certify that approval will be delayed until patent expiry through a Paragraph III certification.

The listed patents were formulation-oriented rather than limited to a broad chemical composition covering every possible tavaborole use. That distinction matters. A formulation patent can be vulnerable to a design-around if the generic can achieve the required product performance with different excipients or manufacturing conditions. The practical strength of the estate depended on claim scope, prosecution history, infringement proof, and the feasibility of an alternative formulation.

How strong was the Anacor patent estate?

The estate had moderate commercial strength but limited publicly demonstrated litigation strength.

Factors supporting the estate

1. Kerydin had a specific topical formulation and a defined FDA-approved indication.
2. The patents extended protection beyond the five-year NCE period.
3. Orange Book listing created a direct mechanism for delaying generic approval.
4. A formulation-centered estate can protect the commercial product even when basic compound protection is weaker or nearing expiry.
5. The product's topical delivery profile made formulation performance relevant to regulatory approval and infringement analysis.

Factors limiting the estate

1. Tavaborole is a small molecule, so the product did not receive biologic exclusivity or manufacturing-process protection comparable to complex biologics.
2. Generic applicants could investigate formulation alternatives.
3. Method-of-use claims may be limited by the scope of the approved label and induced-infringement evidence.
4. A settlement without a merits judgment left patent validity and enforceability unresolved.
5. The commercial value of Kerydin was exposed to generic substitution after regulatory exclusivity ended.

The most defensible conclusion is that the estate was commercially meaningful but not judicially validated in this case.

What formulations were protected by the Kerydin patents?

The asserted patents were directed to tavaborole topical compositions and related use claims. Kerydin's approved dosage form was a 5% topical solution applied to the affected toenails.

Formulation-related issues likely included:

• Tavaborole concentration;
• Solvent and excipient selection;
• Physical stability;
• Delivery through the nail plate;
• Product viscosity and application properties;
• Container and closure compatibility;
• Manufacturing controls affecting uniformity;
• Labeling for toenail onychomycosis.

The core litigation question was whether Lupin's proposed ANDA product would practice the claimed formulation limitations. The answer would depend on the exact ANDA composition and the interpretation of each claim element. ANDA litigation generally limits discovery of the generic product to the proposed product and related manufacturing information, rather than requiring proof based on speculative future products.

Did method-of-use patents create additional risk?

Yes. Method-of-use claims can create a separate infringement theory when a generic label directs use for the patented indication.

For Kerydin, the relevant use was treatment of toenail onychomycosis. A generic applicant may attempt a section viii statement that omits a patented indication, but that strategy is less effective when the patented use is central to the reference product's approved labeling or when the proposed label still encourages the patented use.

Method-of-use patent risk depends on:

• The exact wording of the claims;
• The approved and proposed labels;
• Whether the use is carved out;
• Prescriber behavior;
• Evidence of inducement;
• Whether the formulation claims independently cover the generic product.

Because Kerydin was approved for a narrow dermatological indication, label design and product-use instructions were likely important parts of the risk analysis.

Which companies challenged or could challenge Kerydin patents?

Lupin was the defendant in this action. Other generic manufacturers could have pursued their own ANDA strategies, including Paragraph III or Paragraph IV certifications, depending on the timing and status of the Orange Book patents.

The principal competitive groups were:

Company group	Strategy
Anacor/Pfizer	Enforce Orange Book patents and protect Kerydin sales
Lupin	Seek ANDA approval and challenge listed patents
Other generic companies	Potentially file later ANDAs or rely on a first-filer's patent resolution
Contract manufacturers	Provide formulation or manufacturing capacity, subject to confidentiality and IP controls

The public record for this case does not establish a separate successful generic launch by another company resulting from a judgment against the asserted patents.

What generic entry risks existed after the case closed?

The principal generic-entry scenarios were:

Early negotiated entry

If Lupin obtained a license under a settlement, it could launch before the latest patent expiry on an agreed date. Such agreements often include acceleration rights if another generic launches earlier, but the public record does not disclose whether those provisions existed here.

Entry after patent expiry

Lupin could launch after expiration of the relevant Orange Book patents, assuming FDA approval and resolution of any remaining regulatory issues.

Entry after patent invalidation or noninfringement

A merits victory by Lupin could have removed or reduced the patent barrier. No such reported decision appears in the case record.

Entry by another applicant

A separate ANDA applicant could create independent litigation and potentially alter the commercial timing. A settlement with one generic does not automatically resolve the rights of all other applicants.

Formulation design-around

A generic could seek approval for a formulation that does not infringe the asserted claims. That approach carries technical and regulatory risk because the product must still satisfy the applicable ANDA requirements.

How did Anacor v. Lupin affect revenue exposure?

Kerydin's revenue exposure was concentrated in the U.S. topical antifungal market. The product had no biologic manufacturing moat and faced the standard price erosion risk associated with small-molecule generic entry.

Risk factor	Revenue impact
End of NCE exclusivity	Permitted greater generic development activity
Paragraph IV litigation	Could delay generic approval or launch
Settlement-based entry	Could establish a fixed date for revenue erosion
Multiple generic entrants	Increased probability of rapid price compression
Limited product differentiation	Reduced protection against substitution
Formulation complexity	Could slow, but not necessarily prevent, generic competition

A first generic entrant typically has greater pricing leverage than later entrants. A settlement that permits one generic to launch before full patent expiry can reduce branded revenue earlier than a complete patent win, while preserving some period of market exclusivity.

The case record does not provide a disclosed settlement payment, launch date, royalty, or revenue forecast. Those terms cannot be inferred from the docket's termination alone.

Is biosimilar risk relevant to Kerydin?

No. Kerydin is a small-molecule drug approved under an NDA. Its competitive threat is generic substitution through the ANDA pathway, not biosimilar competition under the Public Health Service Act.

The relevant questions are:

• Whether the ANDA is approved;
• Whether the generic product is therapeutically equivalent;
• Whether listed patents remain enforceable;
• Whether the generic can launch under a settlement or after patent expiry;
• How many generic applicants enter the market.

How does Kerydin's patent estate compare with a biologic patent estate?

Kerydin's estate was narrower in several respects.

Issue	Kerydin	Typical biologic
Approval pathway	NDA/ANDA	BLA/351(k)
Competitive product	Generic	Biosimilar or interchangeable biosimilar
Core protection	Formulation, use, and compound patents	Composition, formulation, process, assay, and manufacturing patents
Regulatory exclusivity	NCE and related NDA exclusivity	Biologic exclusivity periods
Manufacturing barrier	Generally lower	Often materially higher
Substitution	Governed by generic substitution rules	Depends on interchangeability designation and state law

Kerydin could be commercially protected by formulation patents, but the product lacked the technical manufacturing barriers often associated with biologics.

What is the current business and legal takeaway?

Anacor Pharmaceuticals v. Lupin is a closed Hatch-Waxman case involving generic tavaborole 5% topical solution. Lupin's Paragraph IV challenge triggered patent litigation, but the case ended without a reported merits decision. The asserted Kerydin patents remained commercially relevant during the litigation, while their ultimate validity and infringement status were not adjudicated in the public record.

For diligence purposes, the case should be classified as:

• A Paragraph IV ANDA challenge;
• A formulation- and method-of-use patent dispute;
• A terminated case without a public merits ruling;
• A settlement or other disposition with undisclosed commercial terms;
• A generic-entry risk event for Kerydin;
• A small-molecule generic case, not a biosimilar dispute.

Key Takeaways

• Anacor sued Lupin in Delaware over an ANDA for generic Kerydin, or tavaborole 5% topical solution.
• The case involved U.S. Patent Nos. 9,192,662 and 9,566,238.
• The litigation arose from Lupin's Paragraph IV patent certifications.
• Kerydin's five-year NCE exclusivity ended approximately in 2019.
• The case closed without a reported claim-construction decision, trial verdict, or invalidity judgment.
• Publicly available materials do not disclose the material terms of the parties' resolution.
• The patent estate was centered on topical formulation and treatment claims.
• Generic, rather than biosimilar, competition was the relevant commercial risk.
• The litigation's termination should not be treated as a judicial determination that the asserted patents were invalid or not infringed.

FAQs About Anacor Pharmaceuticals v. Lupin

Was Lupin allowed to launch generic tavaborole?

The public docket does not establish the precise launch date or whether Lupin received an early-entry license. Case termination alone does not prove that Lupin launched or obtained immediate FDA approval.

Did Pfizer own the Kerydin patents when the case was filed?

Pfizer had acquired Anacor Pharmaceuticals in 2016. The lawsuit was filed in Anacor's name, while Pfizer was the parent company associated with the acquired business and Kerydin rights.

Did the case invalidate U.S. Patent No. 9,192,662?

No reported merits judgment in the case invalidated the patent. The action ended without a public judicial ruling resolving validity.

Could another generic company challenge Kerydin after the Lupin case?

Yes. A separate ANDA applicant could pursue its own certification and litigation strategy. The resolution with Lupin would not automatically bind unrelated generic applicants.

Did Kerydin have patent protection for its manufacturing process?

The cited litigation centered on patents associated with tavaborole compositions and uses. The public record does not establish a separate manufacturing-process patent injunction or a manufacturing-specific judgment in this action.

References

1. U.S. District Court for the District of Delaware. (2018). Anacor Pharmaceuticals, Inc. v. Lupin Limited, No. 1:18-cv-01606-RGA. PACER/Court docket records.

2. U.S. Food and Drug Administration. (2014). Kerydin (tavaborole) topical solution, 5%: Prescribing information and approval materials. FDA.

3. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

4. U.S. House of Representatives, Office of the Law Revision Counsel. (n.d.). 35 U.S.C. § 271(e)(2) and § 355(j): Patent certifications and ANDA litigation. United States Code.