The patent covers broad method-of-use claims for treating polycystic ovary syndrome (PCOS) and preventing or delaying type 2 diabetes in patients with gestational diabetes, hyperinsulinemia, insulin resistance, or "Syndrome X." Its principal commercial relevance is claim 8, which specifically covers troglitazone, and claims 11 and 12, which specifically cover pioglitazone and ciglitazone. The patent is expired and does not create a current U.S. barrier to generic or biosimilar entry.

United States Patent 5,602,133: PCOS Treatment Claims, Scope, Expiration, and Patent Landscape

What does U.S. Patent 5,602,133 cover?

U.S. Patent No. 5,602,133 is a method-of-treatment patent. The claims do not principally protect a new chemical entity, a particular tablet formulation, a manufacturing process, or a pharmaceutical composition independent of the indication.

The patent claims administering defined insulin-sensitizing compounds to patients for:

Treatment of polycystic ovary syndrome.
Prevention or delay of noninsulin-dependent diabetes mellitus in patients with gestational diabetes.
Prevention or delay of noninsulin-dependent diabetes mellitus in patients with Syndrome X.
Prevention or delay of noninsulin-dependent diabetes mellitus in patients with hyperinsulinemia or insulin resistance.

The patent's central technical concept is the use of thiazolidinedione-class and related insulin-sensitizing compounds in metabolic and reproductive disorders associated with insulin resistance. The claims extend across multiple chemical families, identified as Formulas I through X.

The patent's strongest commercial claim is claim 8 because it identifies a single compound: (+)-troglitazone, commercially known as troglitazone and formerly marketed as Rezulin.

How are the claims organized?

The 43 claims fall into four functional groups.

Claim group	Claims	Subject matter
PCOS treatment, Formula I	1-8	Broad genus through a specific troglitazone claim
PCOS treatment, Formulas II-X	9-20	Broad chemical genera, including pioglitazone and ciglitazone
Gestational diabetes	21-40	Prevention or delay of noninsulin-dependent diabetes
Syndrome X, hyperinsulinemia, insulin resistance	41-43	Formula I compounds for metabolic-risk populations

Claims 1, 9, and 13-20 are independent method claims. Claims 2-8 narrow claim 1. Claims 10-12 narrow claim 9. Claims 21, 29, and 33-40 repeat much of the earlier chemical coverage for the diabetes-prevention indication. Claims 41-43 narrow the indication but do not repeat the full multi-formula structure.

What does claim 1 protect?

Claim 1 covers a method of treating PCOS by administering a therapeutically effective amount of a Formula I compound in unit dosage form.

Formula I is a broad Markush structure. Its permitted variables include:

R1 and R2: hydrogen or C1-C5 alkyl.
R3: hydrogen, acyl, alkoxycarbonyl, aralkyloxycarbonyl, and related protecting or substituent groups.
R4 and R5: hydrogen, C1-C5 alkyl, C1-C5 alkoxy, or a C1-C4 alkylenedioxy group.
n: 1, 2, or 3.
W: methylene, carbonyl, or a substituted methine group.
Y and Z: oxygen or imino groups.
Pharmaceutically acceptable salts.

The claim therefore reaches a large family of insulin-sensitizing heterocyclic compounds rather than one commercial product. Its breadth is narrowed by several cumulative limitations:

The patient must be suffering from PCOS.
The compound must fall within Formula I.
The administration must involve a therapeutically effective amount.
The compound must be administered in unit dosage form.

A product could fall within the chemical genus but avoid infringement if the use is not for treating PCOS, if the active ingredient falls outside Formula I, or if the asserted method does not satisfy the unit-dosage limitation.

What is the scope of claims 2 through 8?

Claims 2 through 8 progressively narrow the Formula I coverage.

Claim	Limitation
2	Formula I compound mixed with a pharmaceutically acceptable excipient, diluent, or carrier
3	Y and Z are oxygen
4	W is methylene
5	n is 1
6	R1, R2, R4, and R5 are lower alkyl; R3 is hydrogen
7	Y and Z are oxygen, n is 1, and W is methylene
8	Specific (+)-troglitazone compound

Claims 3, 4, 5, and 6 each preserve substantial chemical breadth. Claim 7 creates a narrower structural subgenus. Claim 8 is a species claim directed to troglitazone.

Troglitazone is structurally consistent with the Formula I limitations and is the claim most closely connected to an identifiable commercial drug. It is also the claim most vulnerable to a prior-art challenge based on the compound's earlier disclosure, known antidiabetic activity, and the obviousness of applying an insulin sensitizer to insulin-resistant PCOS.

Does claim 8 cover troglitazone?

Yes. Claim 8 expressly covers:

"(+)-5-[[4-[(3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)methoxy]phenyl]methyl]-2,4-thiazolidinedione."

That compound is troglitazone, the active ingredient formerly marketed by Parke-Davis and Warner-Lambert as Rezulin.

Claim 8 requires:

The patient has PCOS.
The compound is administered in a therapeutically effective amount.
The compound is administered in unit dosage form.

The claim does not require a particular dose, dosing frequency, tablet strength, excipient, brand, route of administration, or clinical endpoint. Claim 2, by contrast, requires admixture with an excipient, diluent, or carrier. A commercial tablet would ordinarily satisfy the formulation limitation in claim 2, but claim 8 itself is directed to the administration of the specified compound in unit dosage form.

What do claims 9 through 20 protect?

Claims 9 through 20 cover additional chemical families used to treat PCOS.

Claim 9 recites Formula II. Claims 11 and 12 identify pioglitazone and ciglitazone, respectively. The claim structure is significant because it moves beyond a single Formula I family and attempts to cover a broader portfolio of known insulin-sensitizing compounds.

Pioglitazone and ciglitazone claims

Claim 11 covers pioglitazone for PCOS. Pioglitazone was later commercialized as Actos by Takeda. Claim 12 covers ciglitazone, an earlier thiazolidinedione compound that was not commercialized as a major FDA-approved product.

Claims 13 through 20 cover additional structural classes through Formulas III-X. The provided claim text does not identify commercial compounds for every formula. These claims are best understood as genus claims directed to additional thiazolidinedione-like, heterocyclic, and insulin-sensitizing structures.

The breadth of claims 13-20 is materially different from claims 8, 11, and 12:

Claims 8, 11, and 12 identify specific compounds.
Claims 13-20 use extensive structural definitions.
The latter claims may cover numerous compounds with no commercial history.
Infringement depends on mapping the accused active ingredient to the applicable formula and proving the PCOS treatment method.

What do claims 21 through 43 protect?

Claims 21 through 43 do not concern PCOS. They address diabetes-risk reduction and insulin-resistance conditions.

Gestational diabetes claims

Claims 21-40 cover preventing or delaying the onset of noninsulin-dependent diabetes mellitus in a host suffering from gestational diabetes.

The claim families parallel claims 1-20:

Claims 21-28: Formula I.
Claims 29-32: Formula II, including pioglitazone and ciglitazone.
Claims 33-40: Formulas III-X.

These claims are method claims for a prevention indication. They do not claim treatment of established type 2 diabetes. The patient population is defined by gestational diabetes, and the claimed outcome is prevention or delay of later noninsulin-dependent diabetes.

Syndrome X and insulin-resistance claims

Claim 41 covers Formula I compounds for preventing or delaying noninsulin-dependent diabetes in a host suffering from Syndrome X.

Claim 42 addresses concomitant hyperinsulinemia.

Claim 43 addresses insulin resistance characterized by:

Hyperinsulinemia.
Failure to respond to exogenous insulin.

Claims 41-43 are narrower than claim 1 as to patient condition but remain broad as to the Formula I compound genus.

When did U.S. Patent 5,602,133 expire?

U.S. Patent 5,602,133 issued on February 11, 1997. Because the application was filed under the pre-Uruguay Round Agreement Act patent-term regime, the ordinary term was generally 17 years from grant, subject to patent-term adjustment, terminal disclaimers, or other statutory modifications. On that basis, the patent term ended in February 2014. The patent is no longer enforceable.

Event	Date or status
Patent issued	February 11, 1997
Ordinary pre-URAA term	17 years from grant
Expected ordinary expiration	February 11, 2014
Current enforceability	Expired
Current Paragraph IV relevance	None for this patent
Current biosimilar relevance	None

The patent cannot presently support an injunction, damages claim for post-expiration activity, or a current generic-entry challenge under the Hatch-Waxman patent-certification framework.

What is the Orange Book status of U.S. Patent 5,602,133?

U.S. Patent 5,602,133 is not a current Orange Book barrier to generic approval.

The Orange Book lists patents submitted by approved drug applicants for approved drug products. A method-of-use patent directed to PCOS may be relevant to a drug's use but does not automatically become an Orange Book-listed patent. Listing also depends on the relationship between the patent claims, the approved labeling, and the drug product identified in the applicable New Drug Application.

Several factors limit the patent's Orange Book significance:

Troglitazone was withdrawn from the U.S. market in 2000 because of serious hepatotoxicity.
Pioglitazone was approved for type 2 diabetes, not PCOS.
The patent's PCOS indication was not the principal FDA-approved labeling for pioglitazone.
The patent has expired.
An expired patent cannot delay an ANDA approval through a current 30-month stay.

A generic applicant seeking approval for pioglitazone would evaluate the Orange Book patents listed for the approved product and labeling, not rely on this expired PCOS patent as a present regulatory obstacle. FDA approval of a PCOS indication would require separate clinical and regulatory support because PCOS treatment is not established merely by the patent's claim language.

Were Paragraph IV challenges relevant?

Paragraph IV challenges would have been legally relevant while the patent was unexpired and if the patent had been listed for an applicable approved drug product.

A Paragraph IV certification asserts that an Orange Book-listed patent is invalid, unenforceable, or not infringed. For this patent, likely challenge theories would have included:

Anticipation based on earlier disclosure of the claimed compounds.
Obviousness based on known insulin sensitizers and known PCOS-associated insulin resistance.
Lack of written description for the full breadth of Formulas I-X.
Lack of enablement for the large number of chemical entities and broad disease indications.
Indefiniteness in terms such as "therapeutically effective amount," "host," "lower alkyl," and broad disease-condition language.
Noninfringement based on an accused drug falling outside the specified formula.
Noninfringement based on the approved indication not being PCOS or the claimed diabetes-prevention population.

There is no current Paragraph IV exposure because the patent has expired.

What patent litigation affects U.S. Patent 5,602,133?

The supplied record does not establish a reported federal litigation history, a settlement agreement, a consent judgment, or a license involving U.S. Patent 5,602,133. The patent's present legal status is controlled by expiration, regardless of any historical prosecution or dispute.

No current litigation risk arises from the patent itself. Historical litigation research would require review of PACER, USPTO prosecution records, assignment documents, and FDA patent-listing records. No current enforceable claim remains available for assertion.

What formulation patents are protected by the patent?

The patent has limited formulation coverage.

Claim 2 and claim 10 require the active compound to be administered in admixture with a pharmaceutically acceptable excipient, diluent, or carrier. These limitations describe conventional pharmaceutical compositions but do not specify:

Tablet coating.
Particle size.
Polymorph.
Salt form beyond acceptable salts.
Dissolution profile.
Controlled release.
Bioavailability enhancement.
Specific excipient ratios.
Manufacturing parameters.

The claims therefore do not operate as strong formulation patents. They are method claims in which the formulation language narrows how the active ingredient is administered. A later formulation patent covering a specific pioglitazone polymorph, tablet architecture, controlled-release system, or manufacturing process would be legally distinct.

How strong is the patent estate?

The patent has high historical breadth but low current commercial strength.

Factor	Assessment
Chemical breadth	High in claims 1, 9, and 13-20
Species coverage	Clear for troglitazone, pioglitazone, and ciglitazone
Formulation protection	Limited
Method-of-use breadth	High
Written-description risk	Potentially significant for broad Markush genera
Enablement risk	Potentially significant across ten formulas and multiple indications
FDA linkage	Limited
Current enforceability	None
Generic-entry risk today	None
Biosimilar risk today	None

The broad claim architecture creates substantial historical validity and claim-construction issues. A genus covering many structurally diverse compounds may be challenged if the specification does not adequately disclose representative species, synthesis, pharmacology, and utility across the full scope.

The PCOS indication also raises an obviousness question. If the prior art disclosed insulin resistance in PCOS and the compounds were already known insulin sensitizers, a challenger could argue that the claimed treatment was an expected therapeutic application. The patent's best defense would have been evidence of unexpected clinical effects, such as improved ovulation, reduced androgen levels, or improved insulin sensitivity in PCOS patients.

How does this patent compare with competing drug patent estates?

U.S. Patent 5,602,133 should be distinguished from core compound and product patents.

Drug	Commercial status	Primary patent relevance
Troglitazone	Withdrawn in 2000	Compound and product patents historically important; this patent added PCOS method coverage
Pioglitazone	FDA-approved for type 2 diabetes	Core compound, salt, formulation, and labeling patents were more commercially significant than the PCOS method patent
Ciglitazone	Development compound	Historical research compound; limited current commercial exposure
Rosiglitazone	FDA-approved for type 2 diabetes	Separate compound and product patent estate; not specifically identified in the supplied claims
Metformin	FDA-approved insulin-sensitizing agent	Chemically and legally outside the claimed Formula I-X families unless a specific formula were shown to encompass it

The patent does not cover all PCOS therapies. It does not claim metformin, oral contraceptives, gonadotropins, aromatase inhibitors, GLP-1 receptor agonists, or antiandrogen therapies as such.

What generic launch scenarios existed?

Before expiration, the principal scenarios were:

A generic or innovator seeking a PCOS indication could face method-of-use issues if the patent were listed and the product labeling induced the claimed use.
A generic seeking only a type 2 diabetes indication could potentially avoid the PCOS method claims through a skinny-label strategy, subject to inducement and labeling facts.
A pioglitazone manufacturer could challenge claim 11 on validity or noninfringement grounds.
A troglitazone manufacturer would have faced separate regulatory and safety barriers because Rezulin was withdrawn.
After expiration, any remaining method-of-use restriction disappeared.

Current commercial exposure is therefore driven by other active or historical product patents, regulatory exclusivities, safety restrictions, and market demand, not by U.S. Patent 5,602,133.

What geographic coverage does the patent have?

The patent grants rights only in the United States. It does not establish protection in:

Europe.
Japan.
Canada.
Australia.
China.
India.
Any other jurisdiction.

Foreign counterparts would require separate publication and family analysis. U.S. expiration does not determine the status of corresponding foreign patents, although most corresponding rights would also be expected to have expired given the age of the patent family.

Key Takeaways

U.S. Patent 5,602,133 is a broad method-of-use patent, not a core compound or formulation patent.
Claims 1-20 target PCOS treatment using multiple insulin-sensitizing chemical families.
Claim 8 specifically covers troglitazone.
Claims 11 and 12 specifically cover pioglitazone and ciglitazone.
Claims 21-43 address diabetes prevention or delay in gestational diabetes, Syndrome X, hyperinsulinemia, and insulin resistance.
Claims 2 and 10 provide only limited formulation narrowing through conventional excipient language.
The patent issued February 11, 1997 and expired in February 2014 under the applicable pre-URAA term.
It is not a current Orange Book, Paragraph IV, generic-entry, or biosimilar barrier.
No current litigation or settlement exposure is established for the expired patent.
Historical validity issues would have centered on obviousness, written description, enablement, and the breadth of the Markush formulas.
Current competitive and revenue exposure rests on separate drug-specific patent estates and FDA-approved labeling.

Frequently Asked Questions

Does U.S. Patent 5,602,133 claim pioglitazone for PCOS?

Yes. Claim 11 specifically identifies pioglitazone as a Formula II compound for treating PCOS.

Does the patent cover metformin for PCOS?

No specific claim identifies metformin. The claims are directed to compounds falling within Formulas I-X, and metformin is not identified in the provided claims as a covered species.

Could an expired PCOS patent block an FDA-approved pioglitazone generic?

No. An expired patent cannot presently block approval or support a 30-month stay. Other listed patents or regulatory requirements could still affect approval timing.

Does claim 8 cover all troglitazone formulations?

Claim 8 covers administering the specified troglitazone compound in unit dosage form for PCOS. It does not independently require a particular excipient or formulation architecture. Claim 2 adds conventional excipient, diluent, or carrier language.

Does the patent create biosimilar risk?

No. Troglitazone, pioglitazone, and ciglitazone are small molecules, not biologics. Biosimilar law is not the applicable pathway, and the patent has expired.

References

U.S. Patent No. 5,602,133. (1997). Treatment of polycystic ovarian syndrome and prevention of noninsulin-dependent diabetes mellitus. United States Patent and Trademark Office.
United States Code, Title 35, § 154. (2024). Contents and term of patent; provisional rights.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
U.S. Food and Drug Administration. (2000). FDA public health advisory: Rezulin (troglitazone) withdrawal. Center for Drug Evaluation and Research.
U.S. Food and Drug Administration. (2018). Small business assistance: Frequently asked questions on the Orange Book. Center for Drug Evaluation and Research.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	198045	⤷ Start Trial
Austria	303147	⤷ Start Trial
Austria	376829	⤷ Start Trial
Austria	489952	⤷ Start Trial
Australia	1770997	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,602,133

Summary for Patent: 5,602,133