Details for Patent: 8,039,451

Which drugs does patent 8,039,451 protect, and when does it expire?

Patent 8,039,451 protects EUCRISA and is included in one NDA.

Protection for EUCRISA has been extended six months for pediatric studies, as indicated by the *PED designation in the table below.

This patent has ninety-six patent family members in twenty-five countries.

Summary for Patent: 8,039,451

Title:	Boron-containing small molecules
Abstract:	This invention relates to compounds useful for treating fungal infections, more specifically topical treatment of onychomycosis and/or cutaneous fungal infections. This invention is directed to compounds that are active against fungi and have properties that allow the compound, when placed in contact with a patient, to reach the particular part of the skin, nail, hair, claw or hoof infected by the fungus. In particular the present compounds have physiochemical properties that facilitate penetration of the nail plate.
Inventor(s):	Stephen J. Baker, Tsutomu Akama, Carolyn Bellinger-Kawahara, Vincent S. Hernandez, Karin M. Hold, James J. Leyden, Kirk Maples, Jacob J. Plattner, Virginia Sanders, Yong-Kang Zhang
Assignee:	Anacor Pharmaceuticals LLC
Application Number:	US12/507,010
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 8,039,451
Patent Claim Types: see list of patent claims	Composition; Formulation; Compound;

United States Patent 8,039,451: Tavaborole Claim Scope, Exclusivity, and Patent Landscape

US Patent 8,039,451 protects tavaborole, the active ingredient in Kerydin 5% topical solution. Its independent claims cover the neutral compound and, separately, pharmaceutically acceptable salts. The patent also covers pharmaceutical formulations containing tavaborole or a covered salt with a pharmaceutically acceptable excipient. It does not, based on the claims provided, independently claim a method of treating onychomycosis, a particular concentration, a specific topical vehicle, a manufacturing process, or a dosage regimen.

The patent is the core composition-of-matter asset for tavaborole. Its principal commercial importance is that a generic applicant seeking to market tavaborole before patent expiry would need to address the compound claims and, depending on its formulation, the formulation claims.

What drug does United States Patent 8,039,451 protect?

US 8,039,451 protects 5-(4-cyanophenoxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaborole, the compound known generically as tavaborole.

Item	Information
Active ingredient	Tavaborole
Chemical name in the claims	5-(4-cyanophenoxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaborole
Product	Kerydin
Dosage form	Topical solution
FDA-approved strength	5%
Approved indication	Topical treatment of toenail onychomycosis caused by susceptible fungi
Original sponsor	Anacor Pharmaceuticals, Inc.
Current commercial ownership	Pfizer acquired Anacor in 2016
Patent	US 8,039,451
Patent issue date	October 18, 2011
Core patent type	Composition of matter and formulation
Statutory expiration	September 2, 2029, subject to any applicable term adjustment or regulatory extension

The patent title is generally identified as covering 5-substituted benzoxaboroles and their uses. The claims provided are narrower than a broad genus claim because they identify one specific substituted benzoxaborole rather than a Markush structure encompassing numerous substituents. [1]

How do claims 1 through 4 of US 8,039,451 work?

Claims 1 and 3 are composition claims. Claims 2 and 4 are formulation claims dependent on the corresponding composition claim.

Claim 1: neutral tavaborole

Claim 1 covers:

5-(4-cyanophenoxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaborole.

This is a direct compound claim. A product containing tavaborole in the claimed chemical form could fall within the literal scope of claim 1 regardless of whether it is sold as a topical solution, cream, gel, lacquer, suspension, or another dosage form.

The claim does not require:

• A particular drug concentration.
• A particular excipient.
• A particular route of administration.
• A particular indication.
• A particular dosage schedule.
• A particular particle size or polymorph, based on the claim language supplied.

Claim 2: formulation containing neutral tavaborole

Claim 2 requires:

1. A pharmaceutically acceptable excipient; and
2. The compound of claim 1.

This claim is narrower than claim 1 because it requires a pharmaceutical formulation. A formulation containing tavaborole and an excipient would potentially implicate claim 2. The claim does not specify the identity of the excipient, the physical form of the formulation, or the concentration.

The phrase “pharmaceutically acceptable excipient” is broad but functional. Common topical solvents, co-solvents, film-forming agents, stabilizers, penetration enhancers, and other inactive ingredients could qualify if used in a pharmaceutical formulation.

Claim 3: tavaborole and pharmaceutically acceptable salts

Claim 3 covers:

5-(4-cyanophenoxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaborole, or a pharmaceutically acceptable salt thereof.

This claim expands coverage beyond the neutral compound to pharmaceutically acceptable salts. It is the broader composition claim within the supplied claim set.

The practical significance is substantial. A generic applicant cannot necessarily avoid claim 3 by converting tavaborole into a pharmaceutically acceptable salt. The salt must still be pharmaceutically acceptable and must correspond to the claimed tavaborole compound.

Claim 4: formulation containing tavaborole or a salt

Claim 4 covers a pharmaceutical formulation containing:

• Tavaborole; or
• A pharmaceutically acceptable salt of tavaborole; and
• A pharmaceutically acceptable excipient.

This claim reaches salt-based formulations that may not be covered by claim 2 if claim 2 is read as limited to the neutral compound.

What is the legal scope of the tavaborole composition claims?

The strongest part of the patent is the composition-of-matter protection in claims 1 and 3. Composition claims generally provide broader product-level protection than method claims because infringement can arise from making, using, selling, offering to sell, or importing the claimed compound, subject to the applicable statutory requirements.

A competitor could face infringement exposure even if it:

• Uses a different topical vehicle.
• Changes the concentration.
• Changes the container or applicator.
• Markets the product for a different antifungal use.
• Uses a different manufacturing route.
• Changes the excipient system.
• Uses a pharmaceutically acceptable salt covered by claim 3.

The claims supplied do not appear to require the marketed Kerydin formulation specifically. That distinction matters. A formulation design-around may avoid a narrow formulation claim, but it would not avoid the compound claims if the product still contains tavaborole.

What do the formulation claims protect?

The formulation claims protect pharmaceutical compositions containing tavaborole or a covered salt together with an excipient. They are not limited expressly to Kerydin’s 5% topical solution.

Formulations likely within the conceptual scope

Subject to claim construction and factual proof, the formulation claims could reach:

• Topical solutions.
• Topical gels.
• Creams and ointments.
• Nail lacquers.
• Suspensions.
• Other pharmaceutical dosage forms containing tavaborole and an excipient.

The claims do not expressly require treatment of nail disease. A formulation made for another pharmaceutical purpose could still satisfy the structural limitations.

Formulation design-around opportunities

A generic developer may seek to distinguish its product by arguing that:

• The product does not contain tavaborole.
• The active ingredient is not the claimed compound.
• The salt is not pharmaceutically acceptable.
• The product is not a pharmaceutical formulation.
• An alleged inactive ingredient is not an excipient.
• The formulation contains a chemically different derivative or prodrug.

These arguments would not necessarily defeat claims 1 or 3 if the product contains tavaborole itself. A vehicle change is therefore a weak design-around against the composition claims.

When does tavaborole lose patent and regulatory exclusivity?

Tavaborole’s principal US patent protection is expected to run through 2029, based on the ordinary 20-year term calculated from the relevant nonprovisional or international filing date. The FDA Orange Book identifies patent information associated with approved drug products, but the operative expiration date should be confirmed against the current Orange Book entry and the USPTO patent record. [2, 3]

Milestone	Date or period
Earliest priority date reported for the family	September 2, 2008
US patent issue	October 18, 2011
Kerydin FDA approval	July 7, 2014
Standard new chemical entity exclusivity	Five years from approval
NCE exclusivity end	July 7, 2019
Expected core patent expiry	September 2, 2029
Earliest ordinary generic entry point	After applicable patent and regulatory barriers expire, absent a successful challenge or settlement license

The five-year NCE period blocked submission of an ANDA for the same active ingredient during the first four years unless the ANDA included a Paragraph IV certification. That regulatory exclusivity period ended before the core patent term.

Patent expiration does not automatically guarantee immediate generic launch. A generic applicant may face:

• A 30-month stay triggered by patent litigation.
• Additional Orange Book-listed patents.
• Settlement restrictions.
• Regulatory review delays.
• Manufacturing validation and supply constraints.
• State-law or commercial launch considerations.

What is the Orange Book status of Kerydin and tavaborole?

Kerydin was approved under NDA 205816. As an approved small-molecule drug, its generic competitors would ordinarily use the abbreviated new drug application pathway rather than the biosimilar pathway. The relevant FDA regulatory issues are therefore ANDA filing, therapeutic equivalence, labeling, patent certification, and possible Paragraph IV litigation. [2]

The core Orange Book issue is whether US 8,039,451 remains listed for the approved product and whether any later patents covering the product or approved use are also listed. A listed composition patent creates a direct patent-certification issue for an ANDA applicant seeking approval before expiry.

The supplied claims do not establish the full Orange Book listing. Orange Book status must be evaluated from the current FDA product and patent tables, not from the patent claims alone.

Are there Paragraph IV challenges to tavaborole?

A generic applicant seeking approval before the listed patent expiry could file a Paragraph IV certification alleging that the patent is invalid, unenforceable, or not infringed. The certification would provide the NDA holder with a basis to sue within the statutory period and potentially trigger a 30-month FDA approval stay. [4]

The principal challenge targets would be:

• Anticipation of tavaborole.
• Obviousness based on benzoxaborole and antifungal prior art.
• Written description or enablement.
• Claim construction concerning the chemical identity of tavaborole.
• Salt coverage under claim 3.
• Formulation scope under claims 2 and 4.
• Patent-term or listing defects.

Because claims 1 and 3 identify a single active compound, an invalidity challenge would focus heavily on whether the exact compound was disclosed or rendered obvious by the prior art. A generic applicant would have limited value from a simple vehicle change if claims 1 and 3 remain enforceable.

What patent litigation affects tavaborole generic entry?

Publicly reported ANDA litigation has involved Anacor and generic-drug manufacturers, including Taro Pharmaceuticals, concerning Kerydin-related patent rights. The relevant litigation risk depends on the patents asserted, the ANDA formulation, the Paragraph IV certification, and the terms of any settlement or judgment.

The supplied claim set alone does not establish:

• The complete list of defendants.
• The filing dates of every complaint.
• Whether a final judgment invalidated or upheld each claim.
• The precise terms of any settlement.
• The authorized launch date for each generic applicant.

Those issues must be determined from the individual district-court docket, Federal Circuit decisions, settlement disclosures, and the current Orange Book record. A patent-family analysis should not treat an ANDA filing, litigation complaint, or settlement announcement as proof that the patent claims are invalid or unenforceable.

How strong is the US 8,039,451 patent estate?

The patent has strong product-level leverage but a limited claim architecture based on the supplied claims.

Strength factor	Assessment
Composition protection	Strong because claims 1 and 3 identify tavaborole directly
Salt protection	Meaningful under claim 3
Formulation protection	Moderate; broad excipient language but dependent on the active compound
Concentration protection	Not expressly present
Indication protection	Not expressly present
Method-of-use protection	Not present in the supplied claims
Manufacturing protection	Not present in the supplied claims
Vehicle-specific protection	Not expressly present
Design-around risk	Lower for the active compound; higher for formulations and non-tavaborole derivatives
Generic substitution risk	High after patent expiry or successful Paragraph IV challenge
Biosimilar risk	Not applicable

The patent’s commercial strength comes from the composition claims, not from the formulation claims. If a generic product contains tavaborole, changes to the delivery system may not avoid the core patent. Conversely, if the composition claims are invalidated or expire, the supplied formulation claims may offer less durable protection because they do not specify Kerydin’s exact excipient system or concentration.

Is there biosimilar risk for Kerydin?

No conventional biosimilar pathway applies. Tavaborole is a chemically synthesized small molecule, not a biologic. Competitive products would generally be filed as ANDAs under section 505(j) of the Federal Food, Drug, and Cosmetic Act.

The commercial threat is therefore generic substitution, not biosimilar interchangeability. The principal post-exclusivity risks are:

• AB-rated generic topical products.
• Pharmacy substitution.
• Price erosion.
• Multiple generic entrants.
• Private-label or authorized-generic competition.
• Loss of branded formulary leverage.

Which companies are relevant to the tavaborole competitive landscape?

The principal entities are:

Company	Role
Anacor Pharmaceuticals	Original developer and patent holder
Pfizer	Acquired Anacor and its associated assets
Sandoz/PharmaDerm	Commercialization participant associated with Kerydin
Taro Pharmaceuticals	Generic-drug company involved in reported Kerydin patent litigation
FDA	NDA approval, Orange Book listing, and ANDA review
USPTO	Patent examination, term adjustment, and maintenance records

The competitive market is distinct from the patent landscape. Other topical onychomycosis products, including efinaconazole and ciclopirox products, compete clinically and commercially but do not necessarily create direct patent overlap with tavaborole. Their patents and exclusivity periods should be analyzed separately.

What licensing deals affect tavaborole rights?

Anacor entered commercial arrangements for Kerydin before Pfizer acquired Anacor. Commercialization rights associated with Sandoz or PharmaDerm are distinct from ownership of US 8,039,451. Pfizer’s acquisition of Anacor transferred control of Anacor’s intellectual-property portfolio and product assets to Pfizer. [5]

A commercial license may allocate:

• US commercialization rights.
• Canadian or international rights.
• Manufacturing responsibilities.
• Milestone payments.
• Royalty obligations.
• Patent enforcement authority.
• Rights to generic settlements.

A commercialization agreement does not itself change the patent’s expiration date or expand the literal claim scope.

What generic launch scenarios exist for tavaborole?

The principal scenarios are:

Launch after patent expiry

A generic applicant completes FDA review and launches after the relevant patent barriers expire. This is the lowest litigation-risk scenario and the most likely basis for broad market entry.

Paragraph IV challenge

A generic applicant challenges US 8,039,451 before expiry. The sponsor may sue, triggering a possible 30-month stay. Launch timing then depends on litigation outcome, settlement terms, or court-authorized entry.

Authorized generic

The brand owner or its licensee may supply a generic-labeled product before or after patent expiry. This can reduce the commercial impact of an independent generic launch.

Formulation design-around

A competitor may develop a non-tavaborole product or a derivative that does not satisfy the composition claims. A vehicle-only change is less likely to avoid the compound claims.

Key Takeaways

• US 8,039,451 is the core tavaborole patent associated with Kerydin.
• Claims 1 and 3 provide direct composition-of-matter protection.
• Claim 3 extends coverage to pharmaceutically acceptable salts.
• Claims 2 and 4 cover formulations containing tavaborole or a covered salt plus a pharmaceutically acceptable excipient.
• The supplied claims do not expressly cover a treatment method, concentration, specific vehicle, manufacturing process, or dosage regimen.
• Tavaborole is subject to the ANDA pathway, not the biosimilar pathway.
• The key generic risk is a Paragraph IV challenge or entry after the expected September 2029 patent expiry.
• The patent’s strongest commercial feature is product-level protection against any formulation containing tavaborole.
• Formulation-only protection is less important than the composition claims because the supplied formulation claims do not identify Kerydin’s precise vehicle or strength.
• Anacor was the original developer; Pfizer acquired Anacor, while Sandoz/PharmaDerm participated in commercialization and Taro has been associated with reported ANDA litigation.

FAQs About US 8,039,451 and Tavaborole

Does US 8,039,451 cover Kerydin 5% solution?

Yes. Kerydin contains tavaborole, the compound identified in claims 1 and 3. Its pharmaceutical solution formulation also falls within the general subject matter of claims 2 and 4, subject to the legal requirements for infringement.

Can a generic avoid US 8,039,451 by using a cream instead of a solution?

Not necessarily. A different vehicle may affect the formulation claims, but it would not avoid claims 1 and 3 if the cream contains tavaborole or a covered pharmaceutically acceptable salt.

Does the patent claim treatment of toenail fungus?

The claims provided do not contain a method-of-use claim. They claim the compound and pharmaceutical formulations containing it.

Are tavaborole salts protected separately from tavaborole?

Yes. Claim 3 expressly includes pharmaceutically acceptable salts of the claimed tavaborole compound, and claim 4 covers formulations containing those salts.

What is the principal invalidity risk for the patent?

The principal risk is a prior-art or obviousness challenge directed to the exact tavaborole structure. The formulation claims may also face narrower enablement, construction, or noninfringement disputes depending on the competing product.

References

1. United States Patent and Trademark Office. (2011). US Patent No. 8,039,451, 5-substituted benzoxaboroles and uses thereof.
2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
3. United States Patent and Trademark Office. (2024). Patent Center: US Patent No. 8,039,451.
4. U.S. Food and Drug Administration. (2017). Guidance for industry: 180-day exclusivity for generic drug products.
5. Pfizer Inc. (2016). Pfizer completes acquisition of Anacor Pharmaceuticals.

Drugs Protected by US Patent 8,039,451

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Anacor Pharms Inc	EUCRISA	crisaborole	OINTMENT;TOPICAL	207695-001	Dec 14, 2016		RX	Yes	Yes	8,039,451*PED				Y

International Family Members for US Patent 8,039,451

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	2343304		CA 2020 00022	Denmark
European Patent Office	2343304		301049	Netherlands
European Patent Office	2343304		LUC00157	Luxembourg
European Patent Office	2343304		PA2020524	Lithuania
European Patent Office	2343304		122020000038	Germany
European Patent Office	2343304		2020C/531	Belgium