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

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

Docket		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
Parties	LUPIN PHARMACEUTICALS, INC.
Patents	7,582,621; 9,549,938; 9,566,289; 9,566,290; 9,572,823
Attorneys	Aryeh N. Feinstein
Firms	Shaw Keller LLP
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				External link to document
2018-10-17	1		of U.S. Patent No. 9,459,938 (“the ’938 patent”); U.S. Patent No. 9,566,289 (“the ’289 patent”); U.S. …. Patent No. 9,566,290 (“the ’290 patent”); and U.S. Patent No. 9,572,823 (“the ’823 patent”). These…the ’938 patent, the ’290 patent, the ’823 patent, or claims 1–5 or 7–15 of the ’289 patent. …the ’938 patent, the ’290 patent, the ’823 patent, or claims 1–5 or 7–15 of the ’289 patent. …the ’289 patent; claims 2, 5–6, 8, and 11–12 of the ’290 patent; and claim 2 of the ’823 patent.	External 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
2018-10-17	4		Commissioner of Patents and Trademarks for Patent/Trademark Number(s) 9,459,938 B2; 9,566,289 B2; 9,566,290… 11 September 2020 1:18-cv-01606 835 Patent - Abbreviated New Drug Application(ANDA) None	External link to document

Anacor Pharmaceuticals v. Lupin Limited, 1:18-cv-01606: Litigation Summary and Patent Analysis

Last updated: August 12, 2026

Anacor Pharmaceuticals, Inc. sued Lupin Limited in the U.S. District Court for the District of Delaware after Lupin filed an abbreviated new drug application seeking approval for a generic version of Kerydin, the topical antifungal product containing tavaborole. The case concerned patents listed for Kerydin and was brought under the Hatch-Waxman framework following Lupin’s Paragraph IV certification. The litigation was resolved through a stipulated dismissal, and the public docket does not disclose the commercial terms of the parties’ settlement. [1]

What drug and patents were involved in Anacor Pharmaceuticals v. Lupin?

The case involved Kerydin, a topical solution containing 5% tavaborole for the treatment of toenail onychomycosis. The product was developed by Anacor and approved by the U.S. Food and Drug Administration in July 2014 under NDA 205479. Pfizer acquired Anacor in 2016, but the litigation was filed in Anacor’s name. [2][3]

What is Kerydin and how does tavaborole work?

Tavaborole is a boron-containing antifungal compound. It inhibits fungal leucyl-tRNA synthetase, an enzyme required for protein synthesis. Kerydin is applied once daily to the affected toenail and surrounding skin.

Product	Active ingredient	Dosage form	FDA indication	NDA holder at approval
Kerydin	Tavaborole 5%	Topical solution	Toenail onychomycosis	Anacor Pharmaceuticals
Kerydin approval	FDA approval in 2014	10 mL and 15 mL presentations	Patients with fungal toenail infection	Anacor, later acquired by Pfizer

Which patents protected Kerydin?

The principal patent associated with Kerydin was U.S. Patent No. 7,582,621. The patent covers oxaborole compounds, including tavaborole, and uses of those compounds as antifungal agents. The Orange Book also identified later patents associated with Kerydin’s composition and method-of-use coverage. [2][4]

The relevant patent estate can be summarized as follows:

Patent	General subject matter	Relevance to Kerydin
U.S. Patent No. 7,582,621	Oxaborole compounds and antifungal uses	Core compound and therapeutic protection
Later Kerydin-listed patents	Product, formulation, or method-of-use claims	Potential barriers to ANDA approval and commercial launch
FDA exclusivity	New chemical entity and other regulatory exclusivities	Separate from patent protection

Public patent databases and Orange Book records should be read together because a patent’s listed expiration date may differ from the practical date on which a generic can launch. Patent-term adjustment, pediatric exclusivity, statutory stays, settlement provisions, and the scope of surviving claims can affect the commercial timeline.

Why did Anacor sue Lupin under the Hatch-Waxman Act?

Anacor sued after receiving notice that Lupin had submitted an ANDA containing a Paragraph IV certification. A Paragraph IV certification alleges that a listed patent is invalid, unenforceable, or will not be infringed by the proposed generic product.

The complaint asserted that Lupin’s ANDA product would infringe Kerydin-related patents. Filing the action within the statutory period triggered the Hatch-Waxman 30-month stay, generally preventing FDA approval of the ANDA for up to 30 months unless the court issued an earlier decision or another statutory event ended the stay. [1][5]

What was Lupin’s legal position?

Lupin’s ANDA certification placed the validity, enforceability, and infringement of the asserted patents in dispute. Typical defenses in this setting include:

• Noninfringement based on the formulation or manufacturing process.
• Invalidity for anticipation or obviousness.
• Lack of written description or enablement.
• Improper patent listing or an attack on the scope of the listed claims.
• Noninfringement of method-of-use claims based on the proposed labeling.

The public docket does not provide a reported merits opinion resolving these defenses. The case therefore did not establish a precedential determination that the asserted Kerydin patents were valid, enforceable, or infringed by Lupin’s product.

What was the procedural history of Anacor v. Lupin?

The case was filed in the District of Delaware under case number 1:18-cv-01606. The action was assigned to Judge Richard G. Andrews. The complaint followed Lupin’s ANDA filing and Paragraph IV notice concerning a generic tavaborole product. [1]

Key litigation timeline

Date or period	Event
July 2014	FDA approved Kerydin for toenail onychomycosis
2016	Pfizer acquired Anacor
2018	Lupin submitted an ANDA with a Paragraph IV certification
2018	Anacor filed suit in the District of Delaware
Litigation period	Patent infringement, validity, and ANDA approval issues were placed before the court
Final disposition	The action was terminated through a stipulated dismissal
Public result	No reported trial judgment or appellate merits decision

The docket reflects a negotiated resolution rather than a final adjudication. The settlement terms, including any authorized launch date, royalty arrangement, license, or restrictions on Lupin’s product, were not made public in the reported court record.

What was the settlement outcome?

The parties ended the litigation through a stipulated dismissal. The dismissal eliminated the pending infringement action but did not produce a published opinion addressing the asserted claims.

Did the settlement permit Lupin to launch a generic?

The public case record does not establish the precise date or conditions of any Lupin launch. A Hatch-Waxman settlement can permit an ANDA applicant to enter before patent expiration, subject to conditions such as:

• A negotiated entry date.
• A license under the asserted patents.
• Royalty payments.
• Restrictions on manufacturing or distribution.
• A contingent launch tied to another generic entrant.
• A covenant not to sue.

The docket in this matter does not publicly set out those commercial provisions. The dismissal alone should not be treated as proof that Lupin was immediately authorized to market its product.

Did the parties file a Federal Trade Commission settlement notice?

Hatch-Waxman settlements involving pharmaceutical patent disputes may be subject to filing requirements under the Medicare Modernization Act. Public settlement notices can identify whether the agreement contains a payment, exclusive supply arrangement, or other restriction. The court docket’s dismissal does not by itself disclose the full agreement.

What was the Orange Book status of Kerydin?

Kerydin was listed in the FDA Orange Book as a prescription topical drug. Orange Book listings identified patents that Anacor or its successor asserted against generic applicants. The listing status was relevant because Lupin’s Paragraph IV certification created the statutory basis for the infringement action. [2]

How does an Orange Book listing affect generic entry?

An Orange Book patent listing does not guarantee that the patent will survive a validity challenge. It creates a framework for:

1. A generic applicant to certify against the listed patent.
2. The NDA holder to bring an infringement action.
3. FDA approval to be stayed for the statutory period.
4. The parties to litigate or settle before the stay expires.

The commercial effect depends on the asserted claims. A compound patent generally creates a broader barrier than a narrow method-of-use patent. A formulation patent can matter when the ANDA product uses the same concentration, solvent system, delivery vehicle, or application method.

What generic entry risks existed for Kerydin?

Kerydin faced several distinct entry risks.

Compound-patent risk

The core oxaborole patent was the most important part of the estate because a valid, enforceable compound patent can block products containing tavaborole regardless of minor formulation differences. If the asserted claims covered tavaborole itself or a broad genus that included tavaborole, a noninfringement strategy would be difficult.

Formulation risk

A generic applicant can attempt to design around formulation claims by changing excipients, solvent ratios, packaging, or manufacturing conditions. That strategy is less effective if the listed claims cover the active ingredient in a broad composition or claim the concentration and dosage form used by the reference product.

Method-of-use risk

Kerydin’s indication was specific: treatment of toenail onychomycosis. Method-of-use claims can create litigation exposure even when the generic applicant proposes a narrower label. The practical risk depends on whether the relevant use is induced by the proposed labeling, physician prescribing patterns, or product marketing.

Regulatory exclusivity

FDA regulatory exclusivity is separate from patent protection. Kerydin received new chemical entity exclusivity associated with its 2014 approval. That exclusivity restricted approval of certain competing applications for a statutory period, but it did not extend the patent term. [2][5]

When did Kerydin lose exclusivity?

Kerydin’s regulatory exclusivity expired before the end of its patent estate. The initial five-year new chemical entity period associated with the 2014 approval generally ended in 2019, subject to the specific FDA exclusivity coding and any applicable extensions. Patent protection continued independently based on the expiration dates of the listed patents. [2]

Patent expiration versus regulatory exclusivity

Protection	Function	Relevance to Kerydin
NCE exclusivity	Restricts certain FDA approvals	Ended before the core patent term
Orange Book patents	Support infringement litigation against ANDA applicants	Primary source of post-exclusivity protection
30-month stay	Delays FDA approval after timely patent litigation	Applies to qualifying Paragraph IV litigation
Patent-term adjustment or extension	May move the effective expiration date	Must be confirmed from the patent record

The core patent term should be evaluated using the USPTO patent record and the FDA Orange Book rather than relying on the nominal 20-year term calculated from the earliest filing date. [2][4]

How strong was Anacor’s patent estate?

Anacor’s estate was commercially meaningful because it combined a core oxaborole patent with product-specific Orange Book listings. Its strongest feature was the potential breadth of compound protection. The estate’s weakness was timing: Kerydin entered the market in 2014, while the principal generic challenge arose after regulatory exclusivity had ended and while the product’s commercial opportunity was dependent on the remaining patent term.

Patent-strength assessment

Factor	Assessment
Core active-ingredient protection	Strongest potential barrier if the asserted claims covered tavaborole directly
Formulation protection	Dependent on claim scope and the generic’s excipient profile
Method-of-use protection	Vulnerable to label-scope and induced-infringement arguments
Litigation leverage	Meaningful because the case triggered the statutory approval stay
Trial certainty	Limited because the case settled without a merits ruling
Long-term durability	Dependent on surviving patent expiration and any later generic approvals

The settlement prevented the court from testing the patent estate against Lupin’s invalidity and noninfringement defenses. Investors and licensing counterparties should therefore avoid treating the dismissal as a validation of the patents.

What litigation affected Kerydin’s generic competition?

Anacor and Pfizer pursued patent litigation against multiple generic applicants seeking approval for tavaborole products. These cases typically arose after ANDA filings with Paragraph IV certifications and were concentrated in the District of Delaware.

The competitive landscape included generic drug manufacturers evaluating:

• Whether to challenge the core compound patent.
• Whether to pursue a formulation design-around.
• Whether to accept a delayed launch under settlement.
• Whether to rely on a permitted carve-out from the Kerydin indication.
• Whether to launch at risk after patent expiration or an adverse court ruling.

The Lupin action is therefore best viewed as one component of a broader Kerydin patent-challenge program, rather than as an isolated dispute.

What commercial exposure did Kerydin create?

Kerydin was a branded topical antifungal product with revenue exposure to generic substitution after patent and regulatory barriers weakened. The principal commercial risks were:

1. Loss of exclusivity after the NCE period.
2. Paragraph IV challenges by multiple ANDA applicants.
3. Price erosion after the first generic launch.
4. Reduced reimbursement and pharmacy substitution.
5. Limited differentiation for a once-daily topical product if generic products were therapeutically substitutable.

The value of the patent estate depended on whether settlement agreements delayed generic entry and whether those agreements preserved meaningful exclusivity beyond the basic Orange Book expiration date.

Did Anacor v. Lupin create a precedent for later patent disputes?

No. The case did not produce a reported claim-construction order, summary-judgment decision, trial verdict, or appellate ruling addressing the validity or infringement of the Kerydin patents. Its importance was procedural and commercial: Lupin’s Paragraph IV filing created litigation and delayed potential FDA approval while the parties negotiated a resolution.

What manufacturing and intellectual-property barriers applied to tavaborole generics?

Tavaborole generics faced more than patent claims. The active pharmaceutical ingredient contains boron and requires controlled synthesis, purification, characterization, and impurity management. A generic applicant also had to demonstrate pharmaceutical equivalence and meet FDA requirements for a topical solution.

Potential barriers included:

• Replication of the reference formulation.
• Control of impurities and degradation products.
• Stability of the topical solution.
• Container-closure compatibility.
• Manufacturing-process confidentiality.
• Formulation patent claims.
• FDA comparative requirements for topical products.

These manufacturing issues do not replace patent protection, but they can increase development cost and delay approval even after a patent challenge is resolved.

What is the business significance of the Lupin dismissal?

The dismissal confirms that the dispute ended without a public merits judgment. It does not disclose whether Lupin received a license, agreed to a delayed entry, paid royalties, or abandoned its ANDA strategy. The key diligence issue is therefore the relationship between the dismissal, the applicable Orange Book patent terms, and any later FDA approval or commercial launch by Lupin or another applicant.

Key Takeaways

• Anacor sued Lupin in Delaware after Lupin filed a Paragraph IV ANDA challenge to Kerydin, a 5% tavaborole topical solution.
• The case was filed as 1:18-cv-01606 and assigned to Judge Richard G. Andrews.
• The asserted patent estate included U.S. Patent No. 7,582,621 and later Kerydin-related Orange Book listings.
• The litigation triggered the Hatch-Waxman approval stay.
• The case ended through stipulated dismissal rather than a reported merits decision.
• Public filings do not disclose the settlement’s launch date, royalty terms, or other commercial provisions.
• Kerydin’s FDA regulatory exclusivity ended before the full patent estate, leaving patent litigation as the principal barrier to generic entry.
• The dismissal does not establish that the asserted patents were valid, enforceable, or infringed.

FAQs About Anacor Pharmaceuticals v. Lupin

Was Anacor Pharmaceuticals acquired by Pfizer before the Lupin litigation?

Yes. Pfizer acquired Anacor in 2016. The 2018 complaint was filed in Anacor’s name in connection with Kerydin.

What condition did Kerydin treat?

Kerydin treated fungal infection of the toenails, medically known as toenail onychomycosis.

Was Lupin’s generic tavaborole product approved by the FDA?

The litigation docket alone does not establish the final FDA approval or commercial launch status of Lupin’s ANDA product.

Did the court rule that U.S. Patent No. 7,582,621 was valid?

No reported decision in the identified action resolved the validity of the patent. The case ended by stipulated dismissal.

Are tavaborole products biologics subject to biosimilar competition?

No. Tavaborole is a small-molecule active ingredient. Competition proceeds through the ANDA generic-drug pathway, not the biosimilar pathway under the Public Health Service Act.

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 docket records.

2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

3. U.S. Food and Drug Administration. (2014, July 7). FDA approves new treatment for toenail fungus. FDA.

4. United States Patent and Trademark Office. (2009). U.S. Patent No. 7,582,621, oxaborole compounds and uses thereof. USPTO Patent Center.

5. Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355(j).