United States Drug Patent 6,172,090: Claim Scope, Expiration, Orange Book Status, and Generic Entry Risk

U.S. Patent No. 6,172,090 protects the use of an insulin-sensitizing drug together with a biguanide to reduce adverse effects associated with diabetes treatment. Its commercially important embodiment is pioglitazone, or pioglitazone hydrochloride, administered with metformin. Claims 13, 16, and 17 are the most relevant to fixed-dose and separately administered pioglitazone-metformin products.

The patent is expired. It no longer creates a current U.S. patent barrier to generic pioglitazone-metformin products, although its historical claims were relevant to Paragraph IV litigation, product labeling, and the development of Actoplus Met and equivalent products. [1][2]

What does U.S. Patent 6,172,090 cover?

The patent covers a treatment method rather than a new chemical compound, tablet formulation, manufacturing process, or dosing schedule.

Claim 1 establishes the broadest category:

a diabetic patient;
an insulin sensitivity enhancer;
a biguanide;
administration of both active components; and
reduction of side effects associated with the active components.

The claim is drafted as a method of reducing side effects, but it requires administration of the two therapeutic classes. It does not expressly require a fixed-dose tablet, simultaneous administration, a specific dose, or a particular adverse event.

The claim structure is:

Claim group	Subject matter	Commercial significance
1	Insulin sensitivity enhancer plus biguanide for reducing side effects	Broad combination-treatment claim
2-9	Chemical and structural limitations on the insulin sensitivity enhancer	Narrows the genus toward thiazolidinedione compounds
10	Pioglitazone or its hydrochloride	Directly covers pioglitazone-based treatment
11	Phenformin, metformin, or buformin	Defines the biguanide class
12	Metformin specifically	Covers the principal commercial biguanide
13	Pioglitazone plus metformin	Core Actoplus Met combination claim
14	Troglitazone	Historical combination claim
15	Rosiglitazone or a pharmaceutically acceptable salt	Covers rosiglitazone plus a biguanide
16	The two agents mixed into an admixture	Supports a fixed-dose or premixed product
17	The agents administered separately	Covers coadministration without a fixed-dose combination

How broad is claim 1?

Claim 1 is broad in drug identity but narrower in therapeutic purpose.

It potentially reaches combinations involving:

pioglitazone;
rosiglitazone;
troglitazone;
other compounds falling within the claimed insulin-sensitizer class; and
phenformin, metformin, or buformin.

The claim does not require that the two agents be chemically combined. Claim 17 expressly covers independent administration. A patient receiving pioglitazone in one dosage form and metformin in another could therefore fall within the literal administration format described by the patent, assuming the claimed side-effect-reduction purpose is met.

The principal limitation is functional: the combination must be used to reduce side effects. A treatment directed only to improved glycemic control, without the claimed side-effect-reduction purpose, would present a narrower infringement theory under the claim language. In pharmaceutical method-of-use litigation, the intended purpose can depend on prescribing information, product labeling, physician instructions, and the circumstances of use.

What compounds are protected by claims 2 through 9?

Claims 2 through 9 define a chemical genus for the insulin sensitivity enhancer. The limitations include:

substituted hydrocarbon or heterocyclic groups;
pyridyl, oxazolyl, or thiazolyl groups;
optional alkyl, furyl, thienyl, phenyl, or naphthyl substituents;
a thiazolidinedione-related structure;
hydrogen or alkyl substitution at R1;
carbon, nitrogen, oxygen, or sulfur atoms in specified positions; and
optional pharmaceutically acceptable salts.

Claim 9 is the most specific structural genus before the expressly named compounds. It limits the compound to a heterocyclic-substituted structure, with specified values for m, n, X, A, R1, R2, L, and M.

Claim 10 then identifies pioglitazone or pioglitazone hydrochloride. This creates a direct species claim nested inside the broader chemical genus.

Claim 15 identifies rosiglitazone by chemical name. Claim 14 separately names troglitazone.

What is the significance of claim 7?

The supplied version of claim 7 is incomplete because the referenced partial formula and drawing are absent. Its scope cannot be determined solely from the text provided. The claim appears to limit a substituent designated R2 to hydrogen, alkyl, substituted hydroxyl, halogen, substituted acyl, nitro, or substituted amino groups.

The missing structural figure is material. It determines the position of R2 and the relationship between that substituent and the rest of the claimed molecule.

Does the patent cover pioglitazone and metformin?

Yes. Claim 13 expressly covers administration of pioglitazone or pioglitazone hydrochloride with metformin.

This is the patent's central commercial claim because:

pioglitazone is the insulin sensitivity enhancer;
metformin is the specified biguanide;
the combination was commercialized as a fixed-dose product; and
claims 16 and 17 address both mixed and separate administration.

Actoplus Met contains pioglitazone hydrochloride and metformin hydrochloride. The FDA-approved product is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes. [3]

The distinction between claim 13 and claims 16-17 matters:

Claim 13 focuses on the active ingredients and therapeutic combination.
Claim 16 covers an admixture, which is relevant to a single dosage form.
Claim 17 covers separate administration, which is relevant to co-packaged or separately prescribed products.

What patent claims cover fixed-dose pioglitazone-metformin formulations?

U.S. Patent 6,172,090 is principally a combination-treatment patent. Claim 16 supports coverage of a product in which the insulin sensitizer and biguanide are mixed together, but the supplied claims do not define:

tablet hardness;
dissolution rate;
excipient identity;
release profile;
particle size;
coating;
bilayer construction;
manufacturing sequence; or
specific strength combinations.

The claims therefore do not function as a detailed formulation patent in the conventional pharmaceutical sense. A competitor could potentially avoid formulation-specific claims, if any existed in related patents, while still falling within the method claims during the patent term.

For fixed-dose combination products, patent analysis should separate four categories:

Patent category	Relevance to 6,172,090
Active-ingredient patent	Not the principal subject
Combination-use patent	Core subject
Fixed-dose formulation patent	Only indirectly implicated by claim 16
Manufacturing patent	Not apparent from the supplied claims
Method-of-use patent	Core subject, particularly claim 1 and claim 13

When did U.S. Patent 6,172,090 lose exclusivity?

The patent issued on January 9, 2001. Its term was governed by the modern 20-year patent term measured from the applicable U.S. nonprovisional filing date, subject to any patent-term adjustment or terminal disclaimer. [1][4]

Public patent records identify the patent as expired. Its term ended before the current generic market for pioglitazone-metformin products developed. Patent expiration eliminated the enforceable exclusionary right, but it did not eliminate historical relevance to:

abbreviated new drug application certifications;
Paragraph IV notices;
prior litigation;
licensing negotiations;
product-label strategy; and
freedom-to-operate analyses for earlier launches.

The patent should not be treated as a live blocking right in a current U.S. launch analysis.

What was the Orange Book status of the patent?

The FDA Orange Book identifies patents submitted by NDA holders for approved drug products and records patent-use codes and expiration information. [2]

For a combination product such as Actoplus Met, an Orange Book-listed method-of-use patent can affect ANDA approval through the Hatch-Waxman certification process. A generic applicant may need to certify that:

the listed patent has expired;
the applicant will not market before expiration;
the patent is invalid or not infringed; or
the patent is not relevant to the proposed product or labeling.

The practical effect depends on the patent listing, the associated use code, and whether the generic applicant uses a carve-out label under 21 U.S.C. § 355(j)(2)(A)(viii). [4]

Because U.S. Patent 6,172,090 is expired, it does not presently support a 30-month stay against approval of a new ANDA. Any current Orange Book entry should be read as historical listing information rather than a live regulatory exclusivity right.

Were there Paragraph IV challenges or patent litigation?

Combination-product patents commonly generate Paragraph IV activity when an ANDA applicant seeks approval before patent expiration. The relevant legal issue would have been whether a generic pioglitazone-metformin product infringed the method claims and whether those claims were valid.

For this patent, the most exposed claims would have been:

claim 13, because it expressly names pioglitazone and metformin;
claim 16, for a fixed-dose combination;
claim 17, for separate administration; and
claim 1, if the proposed labeling described side-effect reduction as part of the use.

Potential defenses would have included:

lack of infringement based on a label that omitted the claimed side-effect-reduction indication;
anticipation by prior combination-treatment disclosures;
obviousness based on known coadministration of insulin sensitizers and biguanides;
indefiniteness in the side-effect-reduction limitation;
written-description or enablement challenges against the broad genus; and
noninfringement based on a product containing a different insulin sensitizer.

The supplied record does not establish a complete litigation docket or settlement agreement history. The patent's expiration makes any historical litigation outcome less important to current market entry than the absence of an unexpired blocking patent.

How strong was the patent estate?

Claim strength

The estate had meaningful commercial value because claim 13 identified the exact pioglitazone-metformin combination. That specificity reduced chemical-scope disputes compared with the broader genus claims.

The estate also had structural breadth:

multiple insulin sensitizers;
multiple biguanides;
fixed-dose administration;
separate administration; and
pharmaceutically acceptable salts.

Its weaknesses were equally important:

the side-effect-reduction limitation may have complicated proof of infringement;
the claims did not define a particular adverse event;
the patent did not require a specific dose or dosage regimen;
the broad genus depended on the completeness and support of the underlying specification; and
troglitazone became commercially unusable after safety-related withdrawal, reducing the value of claim 14.

Commercial strength

Pioglitazone and metformin were the strongest commercial species. Phenformin and buformin had limited U.S. relevance, while troglitazone was withdrawn from the U.S. market because of hepatotoxicity concerns. Rosiglitazone was commercially important but faced substantial regulatory restrictions and safety scrutiny during part of the patent's life. [5][6]

The practical value of the estate was concentrated in pioglitazone-metformin treatment, not in the full chemical genus.

How does this patent compare with pioglitazone and metformin compound patents?

Issue	U.S. 6,172,090	Pioglitazone compound patents	Metformin patents
Patent type	Combination method	Chemical compound and related uses	Chemical compound and formulations
Key product	Pioglitazone plus metformin	Pioglitazone products	Metformin products
Fixed-dose relevance	Claim 16	Usually indirect	Usually indirect
Separate administration	Expressly covered by claim 17	Generally not the focus	Generally not the focus
Current status	Expired	Core historical patents also expired or no longer blocking in the U.S.	Core historical patents expired
Generic impact	Historical combination barrier	Historical pioglitazone barrier	Historical metformin barrier

The combination patent was commercially distinct from the active-ingredient patents. A company could have freedom to market each ingredient individually while facing a separate combination-use patent during its term.

What generic launch risks exist today?

The direct risk from U.S. Patent 6,172,090 is no longer material because the patent is expired. Current launch analysis should instead examine:

FDA approval requirements for the proposed strength and dosage form;
bioequivalence for the fixed-dose product;
any unexpired formulation or process patents;
labeling carve-out requirements;
pediatric-exclusivity or regulatory-exclusivity records;
patent rights covering other combination products; and
state substitution and product-liability issues.

Biosimilar risk is not relevant. Pioglitazone and metformin are small-molecule drugs, so competing products proceed through the ANDA pathway rather than the biosimilar pathway under the Public Health Service Act.

What licensing deals affected the patent?

The patent was associated with Takeda's diabetes franchise and the development of pioglitazone combination products. The supplied claim record does not establish a separate third-party license, co-development agreement, or assignment that would alter the claim scope.

A licensing analysis must distinguish ownership from commercialization. A patent assignment or license would affect enforcement rights and royalties, but not the ordinary construction of claims 1-17.

What geographic coverage does the patent have?

U.S. Patent 6,172,090 provides rights only in the United States. It does not create direct protection in:

Europe;
Japan;
Canada;
China;
Australia; or
other jurisdictions.

International protection would require corresponding national or regional patents derived from the same priority filing. Foreign counterparts can have different claim scope, prosecution histories, expiration dates, supplementary protection certificates, and litigation outcomes.

Key Takeaways

U.S. Patent 6,172,090 is a combination-treatment patent, not primarily a compound or formulation patent.
Claim 13 directly covers pioglitazone or pioglitazone hydrochloride with metformin.
Claim 16 addresses mixed administration, including a fixed-dose combination.
Claim 17 covers separate administration of the two agents.
Claims 14 and 15 cover troglitazone and rosiglitazone combinations, respectively.
The patent's commercial value was concentrated in the pioglitazone-metformin combination.
The patent is expired and does not create a current U.S. patent barrier to generic entry.
Biosimilar analysis is inapplicable because both active ingredients are small molecules.
The missing structural figure in claim 7 prevents a complete construction of that dependent claim.
Current freedom-to-operate work should focus on later formulation, manufacturing, labeling, and combination-product patents.

FAQs

Is Actoplus Met still protected by U.S. Patent 6,172,090?

No. U.S. Patent 6,172,090 is expired. Historical Orange Book listing does not create current patent exclusivity.

Does claim 17 cover taking pioglitazone and metformin at different times?

The claim expressly covers independent administration, but infringement would depend on the product labeling, prescribed use, and whether the claimed side-effect-reduction purpose is practiced.

Does the patent cover metformin alone?

No. The claims require an insulin sensitivity enhancer in combination with a biguanide. Metformin monotherapy falls outside the claimed combination.

Is rosiglitazone covered by the patent?

Yes. Claim 15 identifies rosiglitazone, chemically named in the claim, when used with a biguanide under claim 1.

Can a generic manufacturer avoid the patent by using separate tablets?

During the patent term, separate tablets would not necessarily avoid infringement because claim 17 expressly covers independent administration. The patent's expiration removes that current obstacle.

References

United States Patent and Trademark Office. (2001). U.S. Patent No. 6,172,090, methods for reducing side effects of active components administered to diabetic patients.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2009). Actoplus Met prescribing information. Takeda Pharmaceuticals America, Inc.
Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355(j).
U.S. Food and Drug Administration. (2010). FDA drug safety communication: Ongoing evaluation of Avandia and cardiovascular risks.
U.S. Food and Drug Administration. (2011). Rezulin (troglitazone) information.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Japan	7-153500	Jun 20, 1995

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0861666	⤷ Start Trial	91298	Luxembourg	⤷ Start Trial
European Patent Office	0861666	⤷ Start Trial	300258	Netherlands	⤷ Start Trial
European Patent Office	0861666	⤷ Start Trial	SPC 038/2006	Ireland	⤷ Start Trial
European Patent Office	0861666	⤷ Start Trial	07C0006	France	⤷ Start Trial
European Patent Office	0861666	⤷ Start Trial	CA 2007 00001	Denmark	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,172,090

Summary for Patent: 6,172,090