United States Drug Patent RE39198: Claim Scope, Iloperidone Coverage, Expiration and Patent Landscape

U.S. Patent RE39198 is a reissue patent covering a broad family of substituted benzisoxazole and benzisothiazole piperidine compounds. Its commercially important subject matter is iloperidone, marketed as Fanapt by Vanda Pharmaceuticals. The patent estate includes compound, salt, composition, antipsychotic-use and analgesic-use claims. RE39198 is expired and does not presently block generic iloperidone entry. Later patents directed to pharmacogenomic dosing, formulations and extended-release products created separate, narrower barriers.

What drug does U.S. Patent RE39198 protect?

The principal marketed compound within RE39198 is iloperidone.

Attribute	Iloperidone
Brand	Fanapt
Active ingredient	Iloperidone
Drug class	Atypical antipsychotic
Key chemical structure	6-fluoro-1,2-benzisoxazole-piperidine linked through an alkoxy chain to a substituted anisole acetophenone
FDA approval	May 2009
Original innovator	Novartis, later commercialized by Vanda Pharmaceuticals
Dosage forms	Oral tablets
Main indication	Schizophrenia
Patent family relevance	Compound and broad genus claims in RE39198; later method and formulation patents

Claim 3 most closely identifies iloperidone:

“1-[4-[3-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-1-piperidinyl]propoxy]-3-methoxyphenyl]ethanone,” or a pharmaceutically acceptable acid-addition salt.

This structure is also commonly written as iloperidone’s systematic chemical name, with the 6-fluoro-1,2-benzisoxazol-3-yl piperidine connected through a propoxy linker to a 3-methoxy-4-acetylphenyl group.

The supplied claim text contains OCR and transcription errors, including missing Markush structures, duplicated claim references, inconsistent numbering and chemically incomplete definitions. The scope analysis therefore relies on the claim language as reproduced and on the identifiable chemical subject matter.

What is the claim scope of RE39198?

RE39198 has four principal claim groups:

Broad Markush compound claims.
Specific named compound claims, including iloperidone.
Pharmaceutical composition and treatment claims.
Narrower subgenus claims directed to fluorinated, halogenated, oxygen-linked and unsaturated analogues.

How broad is independent claim 1?

Claim 1 covers compounds built around a common pharmacophore:

A benzisoxazole or benzisothiazole ring.
A piperidine ring attached at the 3-position of that heterocycle.
An N-substituted linker, generally two to five atoms long.
An aryl or heteroaryl oxy-linked substituent.
Multiple permitted substituents on both aromatic systems.
Various ketone, amide, nitrile, amine, alcohol, ether, ester and related groups.
Geometric, optical and stereoisomers.
Pharmaceutically acceptable acid-addition salts.

The core architecture can be represented conceptually as:

substituted benzisoxazole/benzisothiazole - piperidine - linker - substituted aromatic ring

The claim is not limited to iloperidone. It covers a chemical genus containing multiple linker lengths, aromatic substituents, heteroatom choices and carbonyl derivatives.

What structural elements are essential?

The most important limitations are:

Structural element	Scope indicated by claims
Heterocycle	1,2-benzisoxazole or 1,2-benzisothiazole
Heterocycle substituent	Hydrogen, lower alkyl, hydroxy, halogen, alkoxy, nitro, amino and related groups
Piperidine	4-substituted piperidine
Linker	Alkylene, alkenylene or alkynylene chains
Linker length	Usually two, three, four or five carbons
Aromatic substituent	Broadly substituted phenyl or heteroaryl systems
Carbonyl functionality	Acetyl, alkanoyl, benzoyl, amide, nitrile, oxime and related groups
Salt form	Mineral-acid and carboxylic-acid addition salts
Stereochemistry	Expressly includes geometric, optical and stereoisomers

A compound that removes the benzisoxazole or benzisothiazole-piperidine motif, changes the piperidine to a materially different ring system or eliminates the claimed linker relationship would have a stronger non-infringement position. A compound retaining the full iloperidone scaffold but changing a peripheral substituent would require a detailed claim-construction and equivalence analysis.

Which RE39198 claims cover iloperidone?

Claim 3 expressly covers iloperidone. Several dependent claims narrow the same general scaffold toward the marketed structure.

Claim	Subject matter
1	Broad compound genus
3	6-fluoro benzisoxazole, propoxy linker, 3-methoxy acetophenone structure corresponding to iloperidone
72-73	Fluorine at the 6-position of the benzisoxazole ring
74-75	Two substituents on the aromatic system, including methoxy
77	Restricted substituent list on the terminal aromatic ring
82	Pharmaceutical composition
83	Antipsychotic composition
84	Method of treating psychoses
85	Analgesic composition
86	Method of alleviating pain

Claims 87-147 appear to be later-added or restructured claim sets directed to related subgenera and compositions. The transcription includes references such as “claim 1 87,” “claim 1 104” and “claim 1 132,” which reflect document formatting or OCR defects rather than meaningful chemical limitations.

When did RE39198 lose exclusivity?

RE39198 is expired. Its expiration cannot be determined solely from the 2005 reissue date because a reissue generally carries the remaining term of the original patent rather than a new 20-year term.

The underlying iloperidone patent family is associated with U.S. Patent No. 5,364,866, issued in 1994. The original patent was subject to the pre-1995 U.S. patent-term regime, generally 17 years from grant, subject to applicable adjustments and regulatory patent-term extension. The relevant base term was therefore in the early 2010s, not 20 years from the reissue grant.

The practical exclusivity position is:

Event	Timing
Original iloperidone patent issued	1994
RE39198 issued	2005
FDA approval of Fanapt	2009
Base compound-patent term	Expired in the early 2010s
RE39198 current enforceability	Expired
Generic compound-patent barrier	No longer provided by RE39198

FDA regulatory exclusivity also expired. Fanapt received approval in 2009, and its small-molecule regulatory exclusivities did not create a continuing barrier comparable to the original compound patent. FDA’s Orange Book must be reviewed for the historical listing and any later-listed patents separately from RE39198 itself.[2][3]

What is the Orange Book status of RE39198?

RE39198 should be treated as an expired historical compound patent, not as a current Orange Book exclusivity barrier.

Orange Book analysis must distinguish among:

The original compound patent.
The reissue patent.
Later method-of-use patents.
Formulation patents.
Regulatory exclusivity codes.
Any patent listings later removed, expired or delisted.

A reissue patent does not automatically create a new Orange Book term. For an ANDA applicant, the relevant question is whether a currently unexpired patent is listed for the reference drug and whether the proposed labeling, formulation or use falls within that patent.

RE39198’s broad claims remain relevant to historical validity, infringement and patent-family analysis, but they do not independently prevent a current generic iloperidone launch.

What formulations are protected for iloperidone?

RE39198 claims pharmaceutical compositions in general but does not appear, from the supplied claims, to require a specific release mechanism, tablet coating, particle size, excipient system or manufacturing process.

The composition claims require:

A claimed compound.
A pharmaceutically acceptable carrier.

That language is broad but vulnerable to conventional composition-claim challenges if the active compound and carrier combination lacks novelty or non-obviousness. It also does not specifically distinguish immediate-release iloperidone tablets from other conventional oral dosage forms.

Later formulation patents may address:

Tablet composition.
Oral absorption.
Solid-state or salt forms.
Extended-release delivery.
Long-acting injectable administration.
Polymer or depot systems.

Those patents must be analyzed independently. A generic immediate-release tablet would not automatically infringe a patent limited to a depot formulation, and a formulation patent would not revive the expired compound claims.

What method-of-use claims does RE39198 contain?

Claims 83-86, 100-103, 116-119, 121-131 and 143-147 cover compositions and methods for:

Treating psychoses.
Producing an antipsychotic effect.
Alleviating pain.
Producing a pain-relieving effect.

These claims are broad and generally do not recite a detailed dosing regimen, patient genotype, titration schedule, treatment duration or specific schizophrenia population.

The practical value of these claims was greatest when the compound claims were enforceable. After compound-patent expiration, generic entry generally depends on whether the ANDA labeling includes a patented use and whether the generic can rely on a section viii statement or carve out the protected indication.

Which companies challenged iloperidone patents?

The most important reported litigation involved later Vanda patents, not the expired broad chemical claims of RE39198.

Vanda Pharmaceuticals v. West-Ward Pharmaceuticals

Vanda sued West-Ward concerning patents covering a pharmacogenomic dosing method for iloperidone. The patents required identifying a patient’s CYP2D6 metabolizer status and adjusting the dose for certain patients. The Federal Circuit upheld the validity of the asserted method claims against the principal obviousness challenge in 2018.[4]

The case is important because it established a separate patent layer around iloperidone:

RE39198 protected the chemical entity.
Later Vanda patents protected a patient-selection and dosing protocol.
The later patents did not extend the original compound patent term.
Their enforceability depended on the generic applicant’s proposed labeling and the scope of the ANDA certification.

The litigation did not make RE39198 unexpired. It concerned narrower method-of-use rights.

How strong is the RE39198 patent estate?

The historical estate was commercially strong because claim 3 directly identified iloperidone and claim 1 covered a broad genus around it. Its current strength is low as an exclusivity asset because the patent has expired.

Dimension	Assessment
Compound coverage	Strong historically; direct iloperidone claim
Genus breadth	Broad, with extensive substituent options
Design-around difficulty	Moderate; core benzisoxazole/benzisothiazole-piperidine motif is recognizable
Salt coverage	Broad but dependent on underlying compound coverage
Composition coverage	Broad but less specific than formulation claims
Method-of-use coverage	Broad psychosis and pain claims
Current term	Expired
Current generic-blocking value	None from RE39198 alone
Historical litigation value	High
Current freedom-to-operate value	Requires review of later patents

Are biosimilars a risk for Fanapt?

No biosimilar pathway applies to iloperidone because Fanapt is a small-molecule drug, not a biological product.

The relevant competitive pathway is an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act. Generic applicants must demonstrate pharmaceutical equivalence and bioequivalence to the reference listed drug. They do not file a biosimilar application under section 351(k) of the Public Health Service Act.

The commercial risks are therefore:

ANDA approval.
Paragraph IV litigation.
Label carve-outs for patented uses.
Bioequivalence or formulation disputes.
Manufacturing and supply reliability.
State substitution and payer adoption.

What generic launch scenarios exist for iloperidone?

The likely launch scenarios are:

Immediate-release generic entry

A generic applicant can target conventional oral iloperidone tablets after expiration of the relevant compound and formulation barriers. This is the clearest pathway.

Launch after method-of-use carve-out

If a later patent covers only CYP2D6-guided dosing, an ANDA applicant may seek approval with labeling that omits the patented use, subject to FDA requirements and infringement risk.

At-risk launch

A generic company may launch before resolution of later patent litigation if it believes the asserted patents are invalid, not infringed or unenforceable. The commercial exposure would include damages, injunction risk and a potential 30-month stay under the Hatch-Waxman framework.

Formulation-specific entry

An applicant using a distinct formulation may avoid a formulation patent even if it remains bioequivalent. Conversely, a novel extended-release or depot product may face separate formulation and delivery-system claims.

How does RE39198 compare with later iloperidone patents?

Patent layer	Typical claim focus	Status significance
RE39198 and original compound family	Iloperidone and related chemical genus	Expired
Later dosing patents	CYP2D6 genotype, metabolizer status and dose selection	Narrower, potentially relevant depending on labeling
Formulation patents	Tablet composition, release profile or delivery system	Product-specific
Regulatory exclusivity	New clinical information or pediatric studies	Time-limited
Manufacturing patents	Intermediates, crystallization, purification or process conditions	Relevant only if the generic process practices the claims

The main distinction is between product identity and product use. RE39198 is principally a product patent. Later Vanda patents were method patents. Formulation and manufacturing patents create narrower barriers that may be avoided through alternative development strategies.

What manufacturing and geographic barriers remain?

RE39198 does not appear, from the supplied claims, to contain detailed process claims. The claimed subject matter is directed mainly to compounds, salts, compositions and therapeutic methods.

Potential manufacturing barriers can still arise from later patents covering:

Benzisoxazole intermediates.
Regioselective fluorination.
Piperidine alkylation.
Ether-linker formation.
Purification and crystallization.
Specific polymorphs or solvates.
Pharmaceutical-grade impurity controls.

Geographically, a U.S. patent affects U.S. manufacture, sale, offer for sale, importation and use. Foreign counterparts must be assessed separately. Expiration in the United States does not establish freedom to operate in Europe, Canada, Japan, China or other markets. Patent-family members may have different filing dates, disclaimers, term adjustments, oppositions and expiration dates.

Key Takeaways

RE39198 is a reissue patent covering a broad chemical genus centered on benzisoxazole and benzisothiazole piperidine compounds.
Claim 3 directly covers iloperidone, the active ingredient in Fanapt.
The patent also includes salt, pharmaceutical composition, antipsychotic-use and analgesic-use claims.
RE39198 is expired and does not independently block generic iloperidone entry.
No biosimilar pathway applies; iloperidone is a small molecule subject to the ANDA pathway.
Later Vanda patents addressed CYP2D6-guided dosing and created narrower, separate litigation risks.
Formulation, solid-state, manufacturing and delivery patents must be searched independently from RE39198.
The most important current commercial question is not whether RE39198 remains in force, but whether later unexpired patents cover the proposed generic’s formulation, labeling or manufacturing process.

FAQs About U.S. Patent RE39198 and Iloperidone

Does RE39198 specifically claim Fanapt?

Yes. Claim 3 identifies the iloperidone molecule by its chemical structure. Fanapt is the branded product containing iloperidone.

Can a generic manufacturer design around RE39198?

Because RE39198 is expired, design-around is not required for current U.S. launch based solely on that patent. Design-around remains relevant for later formulation, manufacturing and method-of-use patents.

Does the reissue date reset the patent term?

No. A reissue generally retains the remaining term of the original patent. The 2005 reissue date does not create a new 20-year patent term.

Is iloperidone subject to biosimilar competition?

No. Iloperidone is a chemically synthesized small molecule. Competition proceeds through abbreviated new drug applications, not biosimilar applications.

What later patent issue is most relevant to iloperidone litigation?

The most significant later issue was pharmacogenomic dosing based on CYP2D6 metabolizer status. The Federal Circuit addressed that patent strategy in Vanda Pharmaceuticals Inc. v. West-Ward Pharmaceuticals International Ltd.

References

United States Patent and Trademark Office. (2005). U.S. Patent No. RE39,198, Benzisoxazole derivatives, process for their preparation and pharmaceutical compositions containing them. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2009). Fanapt (iloperidone) prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
Vanda Pharmaceuticals Inc. v. West-Ward Pharmaceuticals International Ltd., 887 F.3d 1117 (Fed. Cir. 2018).
U.S. Patent and Trademark Office. (1994). U.S. Patent No. 5,364,866, Benzisoxazole derivatives. U.S. Department of Commerce.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	126512	⤷ Start Trial
Austria	248825	⤷ Start Trial
Austria	356123	⤷ Start Trial
Austria	485293	⤷ Start Trial
Australia	1775497	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: RE39198

Summary for Patent: RE39198