The claims of U.S. Patent No. 8,383,659 cover a broad genus of substituted heterocyclic parasiticides, narrower subgenera, eight expressly identified compounds, compositions containing those compounds, and methods of treating parasites in warm-blooded animals. The patent is directed to veterinary or animal-health chemistry, not a conventional FDA human-drug product. Its strongest protection is likely against manufacture or sale of the specifically listed compounds and close analogues within the narrower isoxazoline-thiophene subgenera. Its broadest Markush claims face greater exposure to prior-art, written-description, enablement, and definiteness challenges.

U.S. Patent 8,383,659: Claim Scope, Patent Expiration, Litigation and Parasiticide Landscape

What does U.S. Patent 8,383,659 protect?

U.S. Patent 8,383,659 protects substituted heterocyclic compounds with antiparasitic activity, together with compositions and animal-treatment methods using those compounds. The claim structure has three principal layers:

Protection layer	Claims	Commercial significance
Broad chemical genus	1-2	Covers a large Markush family of compounds
Narrow chemical subgenera	3-22	Concentrates protection around specific ring systems, substituents and amide groups
Express compounds and non-chemical claims	23-25	Targets identified compounds, formulations and parasite-control uses

The disclosed chemistry includes:

A central substituted heterocyclic framework containing X, X1 and X2.
A ring system defined through B1, B2 and B3, each capable of being carbon or nitrogen.
A lipophilic R1 substituent, with trifluoromethyl expressly preferred in claims 6, 9 and related claims.
Halogenated, haloalkyl, haloalkoxy, cyano and nitro substitution patterns.
A variable Z substituent that can be halogen, a heterocycle, a carbocycle, a fused bicyclic ring or a carboxamide.
Optional N-, O- or S-containing substituents and salts.
Pharmaceutical or veterinary compositions and treatment methods.

The claims include geometric and stereoisomers, N-oxides and salts. That language expands the chemical perimeter beyond a single stereochemical form or free-base molecule.

How broad is claim 1 of U.S. Patent 8,383,659?

Claim 1 is a large Markush genus. It does not claim one commercial compound by name. It claims any compound satisfying all structural limitations in the formula and substituent definitions.

The breadth comes from several independent variables:

X may be sulfur oxide, oxygen or substituted nitrogen.
X1 and X2 may independently be carbon or nitrogen.
n may range from 0 to 4.
m may range from 0 to 2.
Three ring positions may independently contain carbon or nitrogen.
R1 spans alkyl, alkenyl, alkynyl, cycloalkyl and cycloalkylalkyl groups.
R2 and R3 include numerous halogenated and heteroatom-containing substituents.
Z may be halogen, a broad ring system or a substituted carboxamide.
The amide substituents may contain additional alkyl, cycloalkyl, heterocyclic and carbonyl groups.

As a practical matter, claim 1 reaches a chemical universe rather than a single active ingredient. A potentially infringing molecule must fall within the specific formula and satisfy every required variable. A structurally related parasiticide outside the claimed ring topology, substitution pattern or Z definition would not infringe merely because it has similar biological activity.

What features narrow claim 1?

The most commercially relevant narrowing features are:

A trifluoromethyl R1 group.
A 3,5-dichlorophenyl substituent.
A 4,5-dihydroisoxazole ring.
A methyl-substituted thiophene carboxamide.
A substituted carboxamidemethyl side chain.
A heteroaryl amide, including thiazole-derived structures.
Specific stereochemical or salt forms, where the claim language and specification support them.

These limitations appear repeatedly in claims 8-23 and provide more useful infringement positions than the full genus in claim 1.

What do claims 3 through 22 add?

The dependent claims progressively constrain the Markush structure.

Claims	Main limitation
3	All `B1-B3` positions are carbon-derived `CR2'` units
4	Narrows `X1` and `X2`, limits `R3'`, `R5'` and related ring substitution
5-6	`R1` is haloalkyl, specifically trifluoromethyl in claim 6
7-10	Focuses on formula Ia and more restricted halogenated or cyano-substituted compounds
11-14	Focuses on carboxamidemethyl substituents and related urea or amide groups
15-18	Focuses on 5- or 6-membered heterocyclic `Z` groups
19-20	Focuses on substituted carboxamides linked to heterocycles
21-22	Adds carbonyl or thiocarbonyl-linked side chains

Claims 8-10 are particularly important because they combine several features associated with potent parasiticide candidates: a halogenated alkyl group, restricted heterocyclic ring substitution, halogen or heteroaryl Z groups, and a narrower isoxazoline-like framework.

Claims 11-14 and 21-22 protect side-chain modifications. Those claims may be relevant to follow-on development programs that retain the active heterocyclic core but alter solubility, formulation compatibility, potency or pharmacokinetics.

What compounds are expressly covered by claim 23?

Claim 23 lists eight specific compounds. All share a common core containing:

A 5-substituted 4,5-dihydroisoxazole framework.
A trifluoromethyl group.
A substituted phenyl ring, including 3,5-dichlorophenyl, 3,5-bis-trifluoromethylphenyl, 3,4,5-trichlorophenyl and 3,5-dichloro-4-fluorophenyl variants.
A methyl-substituted thiophene carboxamide.
A second amide or thioamide side chain.

The listed compounds include derivatives with:

2,2,2-Trifluoroethylcarbamoylmethyl groups.
4-Trifluoromethyl-thiazol-2-yl amide groups.
Ethylcarbamoylmethyl groups.
Prop-2-ynylcarbamoylmethyl groups.
Cyanomethyl-carbamoylmethyl groups.
2,2,2-Trifluoroethylthiocarbamoylmethyl groups.

Claim 23 is materially narrower than claims 1 and 2 but is easier to apply in a product analysis. If an accused product contains one of the named compounds, the principal questions become identity, stereochemistry, salt form, and whether the commercial product uses the claimed compound rather than a close analogue.

Is U.S. Patent 8,383,659 a patent on a marketed human drug?

No. The claims identify an animal-parasite-control technology. Claim 24 covers compositions for controlling parasites, and claim 25 covers treatment of parasites in or on warm-blooded animals.

The patent does not, based on the supplied claims, identify:

A human FDA-approved active ingredient.
A human dosage form.
A New Drug Application.
An Orange Book-listed product.
A biologic or biosimilar product.
A human therapeutic indication.

The use of "pharmaceutical effective amount" in claim 25 does not convert the patent into a human-drug patent. Veterinary antiparasitic products may be regulated through FDA's Center for Veterinary Medicine, or through other national veterinary agencies depending on jurisdiction.

What is the Orange Book status of U.S. Patent 8,383,659?

The patent is not an Orange Book patent merely because it claims pharmaceutical compositions or treatment methods. FDA Orange Book listing is tied to approved human drug products and patents submitted under the applicable drug-approval framework. A veterinary parasiticide patent is generally outside the Orange Book system.[2]

The relevant regulatory records for an animal-health product would typically include:

FDA Center for Veterinary Medicine approval records.
The FDA Green Book for approved animal drugs.
Product-specific Freedom of Information summaries.
National veterinary drug registers outside the United States.
Patent records covering the active ingredient, formulation and manufacturing process.[3]

When does U.S. Patent 8,383,659 lose exclusivity?

A U.S. utility patent normally expires 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, terminal disclaimers and other statutory modifications.[1] The issue date, February 26, 2013, does not control the expiration date.

For a patent issued from a PCT or continuation chain, the relevant calculation depends on:

The earliest effective U.S. or international nonprovisional filing.
Whether priority claims are legally effective.
Patent-term adjustment shown on the patent record.
Any terminal disclaimer.
Whether maintenance fees were paid.
Any patent-term extension, which is uncommon for this type of veterinary chemistry patent.

The patent therefore has a projected expiration in the late 2020s if its effective filing date falls in the 2008-2010 period. The enforceable expiration date must be taken from the USPTO Patent Center record and the patent's continuity and term data, not inferred from the 2013 issue date.

How strong is the patent estate for the claimed parasiticide chemistry?

The estate is strongest at the species and close-subgenus level and weaker at the outer perimeter of claim 1.

Stronger features

Claim strength is enhanced by:

Multiple layers of dependent claims.
Expressly identified compounds in claim 23.
Coverage of salts, stereoisomers and N-oxides.
Both product claims and method-of-treatment claims.
A broad Z substituent definition covering heteroaryl and amide structures.
Repeated emphasis on halogenated phenyl, trifluoromethyl and heterocyclic motifs.

Vulnerable features

Potential validity pressure points include:

The very large number of alternatives in the Markush definitions.
Written-description support for every claimed combination.
Enablement across the full genus.
Obviousness based on earlier isoxazoline, heteroaryl amide or veterinary parasiticide disclosures.
Ambiguities caused by transcription or claim-formatting errors.
Missing structural drawings in the supplied text for formulas referenced in claims 7-9, 13, 16, 17 and 22.
Potential indefiniteness in terms such as "a radical Q," where the incorporated definition is extensive.
Inconsistencies in the supplied text, including duplicate or malformed substituent language.

The express compounds in claim 23 are less exposed to genus-wide enablement arguments, assuming the specification contains adequate preparation and characterization data. The broad genus claims are more valuable for blocking design-around programs but are also more likely to attract validity challenges.

What formulation patents protect these compounds?

The supplied claims do not contain a detailed formulation claim. Claim 24 is a functional composition claim requiring:

At least one compound of formula I.
A carrier and/or dispersant.
Use for parasite control.

That language may reach many basic formulations, but it does not specifically claim:

A particular tablet or chewable composition.
A defined active-loading range.
A controlled-release matrix.
A specific excipient combination.
A transdermal, topical or injectable delivery system.
A defined particle-size distribution.
A particular salt, polymorph or solid form.
A pharmacokinetic dosing regimen.

Commercial products based on this chemistry could therefore have separate patent protection for formulation, dosage, palatability, sustained release, combination therapy, manufacturing or solid-state characteristics.

Are Paragraph IV challenges relevant?

Paragraph IV certification is generally associated with an Abbreviated New Drug Application for an FDA-approved human drug. It is not the normal framework for challenging a veterinary parasiticide patent.[2]

For animal-health products, competitive entry may instead involve:

A generic or abbreviated veterinary drug application.
A finding of invalidity or noninfringement in federal court.
A declaratory-judgment action.
Regulatory approval relying on existing safety and efficacy data.
A license or settlement with the patent owner.
A product designed outside the claims.

No Paragraph IV litigation conclusion follows from the claims supplied.

Which companies are likely to matter in the competitive landscape?

The relevant competitive set depends on the final active ingredient and marketed product, which cannot be identified solely from the text of claim 23 because the structural drawings referenced in several claims are omitted.

The landscape should be separated into four groups:

Competitor group	Typical IP position
Originator animal-health company	Core compound, species claims, formulation, dosing and manufacturing
Generic veterinary companies	Noninfringement, invalidity, regulatory reliance and alternative formulations
Parasite-control competitors	Distinct chemical classes, including macrocyclic lactones, isoxazolines and related ectoparasiticides
Suppliers and contract manufacturers	Process, intermediate, impurity and scale-up protection

A freedom-to-operate review should search the patent family by structure and not by the patent number alone. Relevant searches should include the core dihydroisoxazole, substituted thiophene carboxamide, trifluoromethyl group, 3,5-dichlorophenyl group and the amide side-chain variants in claim 23.

What litigation and settlement issues affect the patent?

The supplied claims do not establish a litigation history, settlement agreement or license. Patent litigation cannot be inferred from issuance or claim breadth.

For transaction or launch analysis, the key questions are:

Whether the patent has been asserted against a product.
Whether any defendant filed an invalidity or noninfringement counterclaim.
Whether the patent survived claim construction and summary judgment.
Whether a settlement permits an authorized generic or delayed entry.
Whether a license covers only a compound or also formulation and manufacturing rights.
Whether related continuation or divisional patents remain enforceable after this patent expires.

The absence of an Orange Book listing also means that an investor should not use Orange Book patent and exclusivity data as a proxy for this patent's commercial strength.

What generic-entry risks exist?

Generic entry risk is highest where:

The accused product contains one of the claim 23 compounds.
The marketed active ingredient falls within claims 8-10 or 11-14.
The compound is sold as a salt, stereoisomer or N-oxide covered by claim 1.
The product's intended use is parasite control in warm-blooded animals.
No separate formulation or process patent provides a later exclusion period.

Risk is lower where a competing compound:

Changes the heterocyclic core.
Removes or relocates the trifluoromethyl group.
Uses a different thiophene substitution pattern.
Replaces the claimed carboxamide linkage.
Falls outside the specified Q and Q' ring definitions.
Uses a different stereochemical configuration not covered by the properly construed claim.

What geographic coverage does the patent provide?

U.S. Patent 8,383,659 provides rights only in the United States. International protection must be assessed through its related PCT, European, and national-stage or direct foreign filings.

A global product launch requires separate review of:

European Patent Office family members.
Canada, Japan, Australia, China, Brazil and other target markets.
National validity and maintenance status.
Local patent-term rules.
Supplementary protection or regulatory extension regimes.
National claim scope and prosecution amendments.

A U.S. claim cannot block manufacture, sale or use entirely outside the United States unless a separate foreign patent applies.

Key Takeaways

U.S. Patent 8,383,659 is a veterinary parasiticide patent covering a broad Markush genus, narrower chemical subgenera, eight named compounds, compositions and animal-treatment methods.
Claims 1 and 2 are broad but face greater validity exposure because of their extensive variable definitions.
Claims 8-23 provide more commercially actionable protection around halogenated, trifluoromethyl-substituted heterocyclic compounds and amide side chains.
Claim 23 is the clearest product-specific claim because it identifies eight compounds by chemical name.
Claim 24 provides broad composition coverage but does not recite a sophisticated formulation or delivery system.
Claim 25 may create method-of-use exposure for animal products using a claimed compound to control parasites.
The patent is not, based on the supplied claims, an FDA Orange Book human-drug patent.
Paragraph IV analysis is generally not the appropriate framework for veterinary-product entry.
Patent expiration depends on the effective filing date, patent-term adjustment, terminal disclaimer and maintenance status. The issue date alone cannot establish expiration.
Separate patents may control formulation, solid state, dosage, combination therapy, manufacturing and international markets.
A reliable freedom-to-operate conclusion requires structural mapping to the complete patent drawings and a review of continuation, foreign and later-improvement families.

FAQs about U.S. Patent 8,383,659

Does U.S. Patent 8,383,659 claim a single active ingredient?

No. The principal claims cover a broad genus of compounds. Claim 23 separately identifies eight specific compounds.

Can a salt of a claimed compound infringe?

Yes. Claim 1 expressly includes salts, along with geometric and stereoisomers and N-oxides, subject to the underlying compound satisfying the claim's structural limitations.

Does claim 25 cover every animal-parasite treatment?

No. The method requires use of at least one compound within formula I. A treatment using an unrelated antiparasitic compound would fall outside claim 25.

Does a different formulation avoid the patent?

Not necessarily. Changing the formulation may avoid a separate formulation patent, but it will not avoid a compound or method claim if the product still contains a claimed compound and is used for the claimed purpose.

Can a veterinary generic applicant use Paragraph IV to challenge this patent?

Paragraph IV is generally a human generic-drug certification mechanism. Veterinary entry typically follows a different regulatory and litigation pathway.

References

United States Patent and Trademark Office. (2013). U.S. Patent No. 8,383,659, compounds, compositions and methods for controlling parasites. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.
U.S. Food and Drug Administration, Center for Veterinary Medicine. (2024). FDA-approved animal drug products: Green Book. U.S. Department of Health and Human Services.
35 U.S.C. § 154. Patent term.
21 C.F.R. § 314.53. Submission of patent information.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Tarsus	XDEMVY	lotilaner	SOLUTION/DROPS;OPHTHALMIC	217603-001	Jul 24, 2023		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y	Y			⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	2379537	⤷ Start Trial	CR 2017 00034	Denmark	⤷ Start Trial
European Patent Office	2379537	⤷ Start Trial	300891	Netherlands	⤷ Start Trial
European Patent Office	2379537	⤷ Start Trial	1790037-4	Sweden	⤷ Start Trial
European Patent Office	2379537	⤷ Start Trial	LUC00030	Luxembourg	⤷ Start Trial
European Patent Office	2379537	⤷ Start Trial	17C0006	France	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,383,659

Which drugs does patent 8,383,659 protect, and when does it expire?

Summary for Patent: 8,383,659