US Patent 6,395,767: Scope, Claims, Expiration, and DPP-4 Inhibitor Patent Landscape

US Patent 6,395,767 is a foundational Bristol-Myers Squibb patent covering bicyclic nitrile-containing dipeptidyl peptidase-4, or DPP-4, inhibitors, including the compound later developed as saxagliptin. The patent claims a broad chemical genus, selected species, pharmaceutical compositions, combination therapies, and treatment methods. Its principal US patent term ended on December 24, 2022, with pediatric exclusivity extending the protected period to approximately June 24, 2023. The patent is therefore no longer an effective US barrier to generic saxagliptin entry, although later formulation, combination, crystalline-form, and regulatory patents may remain relevant.

What drug does US Patent 6,395,767 protect?

The patent is associated with saxagliptin, marketed by AstraZeneca as Onglyza and in combination products including Kombiglyze XR. Saxagliptin is an orally active DPP-4 inhibitor used primarily for type 2 diabetes.

The claimed chemistry is centered on:

A nitrile-containing azabicyclic or related heterocyclic core.
A DPP-4 inhibitor structure containing a constrained pyrrolidine-type ring system.
Broad substitution at multiple nitrogen- and carbon-linked positions.
Optional fused cyclopropyl, cycloheteroalkyl, aryl, and substituted heteroaryl systems.
Pharmaceutically acceptable salts, prodrug esters, and stereoisomers.

The patent’s claims use the term “DP4 inhibitor,” an older nomenclature for DPP-4 inhibitor. The disclosed chemistry corresponds to the early generation of selective DPP-4 inhibitors that followed the identification of cyanopyrrolidine and related nitrile pharmacophores.

What is the legal scope of claim 1?

Claim 1 is a large Markush compound claim. It covers compounds defined by a structural scaffold in which:

x and y determine alternative ring or linker arrangements;
n is 0 or 1;
X is hydrogen or cyano;
R1 through R4 can independently be selected from extensive hydrocarbon, aryl, heteroaryl, cycloalkyl, bicyclic, tricyclic, hydroxyalkyl, and heterocyclic substituent classes;
substituents may carry additional halogen, alkyl, alkoxy, amino, carbonyl, sulfonyl, nitrile, hydroxy, and related groups;
R1 and R3, or R1 and R4, may close additional rings;
the compounds may exist as stereoisomers, salts, or prodrug esters.

The practical scope is broader than a claim limited to saxagliptin. A compound can infringe claim 1 if it falls within the recited scaffold and satisfies the detailed substituent, ring-closure, stereochemical, and proviso limitations. A DPP-4 inhibition assay is not itself an express element of claim 1. The infringement analysis is therefore primarily structural.

Claim 1 limitations that materially narrow the scope

The following limitations have greater legal significance than the long substituent list:

The specific scaffold shown in the patent drawings.
The permitted x/y relationship: x equals 1 when y equals 0, and x equals 0 when y equals 1.
The permitted values of n and X.
The precise ring-fusion and ring-closure alternatives.
The stereochemical coverage.
The proviso excluding certain pyridyl-substituted compounds in one defined configuration.

The broad substituent language does not eliminate the need to satisfy the core scaffold. A later DPP-4 inhibitor with a different central ring system, a different nitrile orientation, or a different attachment geometry may fall outside claim 1 even if it has the same pharmacological target.

How do claims 2 through 10 narrow the chemical protection?

Claims 2 through 10 move from the broad genus toward narrower structural classes and specific compounds.

Claim group	Subject matter	Commercial significance
Claim 1	Broad Markush genus of compounds	Principal genus protection
Claims 2-5	Specific structural subclasses shown in the patent	Narrower chemical fallbacks
Claim 6	X equals CN, n equals 0, R3 equals H, with defined hydrocarbon and hydroxy-substituted R1 groups	Focuses on nitrile-containing active compounds
Claim 7	Defined configuration for the cyclopropyl-fused pyrrolidine	Stereochemical protection
Claim 8	A specifically illustrated compound	Likely direct species protection for saxagliptin-related chemistry
Claim 9	Hydrochloride or trifluoroacetic acid salt of claim 8	Salt-form protection
Claim 10	Restricted R1 substituent classes	Additional species or subgenus fallback

The supplied text does not reproduce the structural drawings for claims 2 through 5 and 8. Their enforceable scope depends on those drawings, not merely on the claim labels. Claim 8 appears to be the key species claim associated with the commercial compound, while claim 9 addresses selected salt forms.

Claim 7 is important because DPP-4 inhibitors often depend on a defined three-dimensional arrangement for potency and selectivity. A generic applicant cannot avoid a stereochemical claim merely by using the same molecular formula with a different stereoisomer if the marketed active ingredient has the claimed configuration.

Does the patent cover saxagliptin itself?

Yes. US 6,395,767 is widely identified with the core saxagliptin patent estate. The strongest infringement position historically came from the combination of:

claim 1’s broad genus;
the narrower structural claims;
the specific compound claim;
the stereochemical limitation in claim 7;
the salt claim in claim 9;
composition claim 11; and
method claims 23 and 24.

The commercial active ingredient is saxagliptin, generally supplied as saxagliptin hydrochloride. The hydrochloride limitation in claim 9 is consequently relevant to the marketed drug, subject to the exact structural language and salt form disclosed in the patent.

What pharmaceutical compositions and combination products are covered?

What does claim 11 cover?

Claim 11 covers a pharmaceutical composition containing a claim 1 compound and a pharmaceutically acceptable carrier. This is a standard composition claim. It can reach tablets, capsules, powders, solutions, or other dosage forms if the composition contains a covered compound.

Claim 11 is not limited to a particular excipient, dose, release profile, or manufacturing process. It is consequently broad, but it generally depends on the underlying chemical compound remaining within claim 1.

What does claim 12 cover?

Claim 12 covers pharmaceutical combinations containing the DP4 inhibitor with one or more agents directed to:

diabetes;
obesity;
lipid disorders; or
related metabolic disease.

Claims 13 through 21 provide more specific combination categories and named agents. The listed agents include metformin, sulfonylureas, thiazolidinediones, insulin, GLP-1 agents, orlistat, sibutramine, statins, fibrates, ACAT inhibitors, and other development-stage compounds.

The claims use open-ended language such as “comprising” and “1, 2, 3 or more.” That language generally allows additional ingredients unless excluded by another claim limitation. The listed compounds are examples within the claimed categories, not necessarily an exhaustive list.

Claim 16 and claim 21 recite a DP4 inhibitor-to-co-therapy weight ratio of approximately 0.01:1 to 100:1. The ratio can become a meaningful limitation in an infringement analysis involving fixed-dose or co-administered products.

What diseases and methods are protected?

Claims 23 and 24 cover methods of administering a claim 1 compound to treat a broad group of disorders. The principal indications are:

type 2 diabetes;
obesity;
insulin resistance;
hyperglycemia;
hyperinsulinemia;
impaired glucose tolerance;
dyslipidemia;
metabolic syndrome;
atherosclerosis;
diabetic complications; and
related endocrine and inflammatory disorders.

Claim 24 narrows the method to type 2 diabetes and/or obesity.

The method claims are broad in disease coverage but require administration of a covered compound. They do not independently create freedom to operate for a structurally different DPP-4 inhibitor. Conversely, a generic manufacturer using a covered saxagliptin compound for the claimed indication could have faced method-claim exposure before expiration, particularly where the product labeling encouraged the patented use.

When did US Patent 6,395,767 expire?

Event	Date
Earliest priority date	December 24, 1998
US filing	December 23, 1999
Patent issued	May 28, 2002
Principal US expiration	December 24, 2022
Approximate pediatric exclusivity end	June 24, 2023

The expiration analysis includes the patent’s adjusted term and the six-month pediatric extension associated with FDA approval of saxagliptin. After the pediatric period ended, claims 1 through 24 no longer provided an enforceable US patent exclusion right.

Expiration of this patent does not automatically eliminate later patents covering:

saxagliptin and metformin combinations;
extended-release formulations;
specific dosage strengths;
crystalline or polymorphic forms;
manufacturing intermediates;
processes for producing saxagliptin;
labeling or treatment combinations; or
other listed drug products.

What was the Orange Book status of US 6,395,767?

US 6,395,767 was listed in the FDA Orange Book for saxagliptin products and was the principal compound patent associated with Onglyza. Its commercial relevance covered saxagliptin products, including the active pharmaceutical ingredient and related products to the extent the listed drug and patent listing requirements were satisfied.

The patent’s Orange Book listing did not mean that every claim necessarily covered every saxagliptin product in the same manner. Claim 9 was directed to selected salt forms, while claim 11 addressed compositions and claims 23-24 addressed treatment methods.

Following expiration, the listing no longer creates a continuing patent-based barrier to approval. The FDA’s Orange Book continues to identify patent and exclusivity information for regulatory purposes, but an expired patent cannot support a new injunction against an otherwise authorized generic launch.

Which companies challenged saxagliptin exclusivity?

Public generic challenges to saxagliptin were directed primarily at the later patent estate and product-specific Orange Book listings, rather than only at US 6,395,767. ANDA applicants typically use one or more of the following certifications:

Paragraph III, accepting delayed approval until patent expiration;
Paragraph IV, asserting that a listed patent is invalid, unenforceable, or not infringed; or
a section viii statement, omitting a patented method of use.

The patent’s December 2022 expiration reduced the value of a Paragraph IV challenge directed solely to US 6,395,767. Later generic timing depended more heavily on other listed patents, regulatory exclusivity, and settlements involving saxagliptin or saxagliptin/metformin products.

What patent litigation and settlement issues affected generic entry?

The principal litigation risks for saxagliptin involved later patents and combination products rather than the now-expired core compound patent. A generic applicant could have faced:

A 30-month stay triggered by a Paragraph IV notice and timely patent litigation.
Infringement claims based on the marketed salt or dosage form.
Method-of-use claims tied to diabetes treatment.
Combination-product claims involving metformin.
Formulation claims covering extended-release or release-controlling technology.
Settlement restrictions that delayed launch beyond the earliest patent expiry.

A Paragraph IV notice directed at US 6,395,767 would have required a claim-by-claim position on the Markush genus, the specific compound, the stereochemistry, and the salt. Invalidity theories could have included lack of written description, lack of enablement, anticipation, obviousness, indefiniteness, or prosecution-history estoppel. The breadth of claim 1 creates potential written-description and enablement pressure, but the commercial value of claims 8 and 9 would have depended on the patent’s specific disclosure and prosecution record.

How strong is the patent estate for saxagliptin?

Strengths

The patent claims the core DPP-4 inhibitor chemistry rather than only a peripheral formulation.
Claim 1 is broad and covers multiple substitution patterns.
The patent includes narrower fallback claims.
Stereochemical protection is important for saxagliptin.
The patent covers pharmaceutical compositions and treatment methods.
The commercial compound was disclosed before development and commercialization, supporting a strong nexus between the patent and the product.

Weaknesses

The broad Markush scope creates potential written-description and enablement issues.
The patent is expired in the United States.
Combination claims may not cover every later commercial formulation.
Method claims can be limited by the approved label and actual induced use.
Later generic products may avoid claims directed to specific dosage forms, salts, or combinations.
Claims 2-5 and 8 require the omitted structural drawings for precise claim construction.

The estate was commercially strong during its term but has little current standalone exclusionary value against a plain saxagliptin generic in the United States.

How does saxagliptin compare with other DPP-4 inhibitor patent estates?

Drug	Originator	Core patent position	Current competitive issue
Saxagliptin	Bristol-Myers Squibb/AstraZeneca	US 6,395,767 and later product patents	Core patent expired; later product patents determine timing
Sitagliptin	Merck	Multiple composition, salt, process, and formulation patents	Large, layered estate with later-expiring patents
Vildagliptin	Novartis	Cyanopyrrolidine-related DPP-4 chemistry and formulation patents	Geographic protection varies materially
Linagliptin	Boehringer Ingelheim/Eli Lilly	Distinct xanthine-based chemical series	Later core and formulation protection
Alogliptin	Takeda	Distinct DPP-4 inhibitor chemistry and salt patents	Generic timing depends on product-specific listings
Gliptin combinations	Multiple originators	Fixed-dose and formulation patents	Combination patents may outlast core compound patents

Saxagliptin’s original patent is therefore best understood as a first-generation compound patent, not as the complete modern product estate.

What manufacturing and geographic IP barriers remain?

The expired US compound patent does not remove all manufacturing risk. A generic manufacturer may still need to evaluate:

process patents covering key intermediates;
chiral resolution and stereoselective synthesis;
impurity-control methods;
solid-state forms;
pharmaceutical compositions;
combination products;
patents in Europe, Japan, China, Canada, and other markets; and
trade secrets relating to process parameters and scale-up.

Patent expiry is jurisdiction-specific. A US freedom-to-operate conclusion cannot be extended to Europe, China, Japan, or emerging markets without separate national searches. Saxagliptin’s active ingredient may be unpatented in the United States while remaining subject to process or formulation rights elsewhere.

What generic launch scenarios exist for saxagliptin?

Plain saxagliptin tablet

This is the lowest-risk US scenario after expiration of US 6,395,767 and any remaining product-specific patents. A generic applicant would still need FDA approval, pharmaceutical equivalence, bioequivalence, and compliance with labeling and manufacturing requirements.

Saxagliptin hydrochloride

The salt form was directly relevant to claim 9. After patent expiration, the salt claim no longer blocks launch, but later salt, crystalline-form, or manufacturing patents must be checked separately.

Saxagliptin and metformin extended-release

This product presents greater residual risk because combination and extended-release patents may survive the core compound patent. A Paragraph III or Paragraph IV strategy depends on the current Orange Book listing and the applicant’s proposed formulation and labeling.

Label carve-out launch

If a surviving patent covers only a method of use, a generic may attempt a section viii carve-out. This strategy is less useful where the approved label retains the patented indication or where the listed patent covers the compound or composition itself.

Key Takeaways

US 6,395,767 is a core saxagliptin-related DPP-4 inhibitor patent.
Claim 1 is a broad Markush genus covering bicyclic nitrile-containing compounds.
Claims 6-10 narrow the scope to nitrile-containing, stereochemically defined, and salt-form compounds.
Claim 11 covers pharmaceutical compositions.
Claims 12-22 cover metabolic, obesity, lipid, endocrine, inflammatory, and immune combinations.
Claims 23 and 24 cover treatment methods, especially type 2 diabetes and obesity.
The principal US patent term ended December 24, 2022, with pediatric exclusivity extending protection to approximately June 24, 2023.
The patent no longer independently blocks a US generic saxagliptin launch.
Later formulation, combination, process, and dosage-form patents remain the relevant residual risks.
Claims 2-5 and 8 require the original structural figures for complete species-level claim construction.

FAQs

Is US Patent 6,395,767 still enforceable?

No. Its US patent term and associated pediatric extension have ended.

Does the patent cover Onglyza?

Yes. The patent is associated with the core saxagliptin compound and historically supported protection for Onglyza-related saxagliptin products.

Does claim 9 cover saxagliptin hydrochloride?

Claim 9 expressly recites the hydrochloride and trifluoroacetic acid salts of the compound defined in claim 8. The exact coverage depends on the structural definition incorporated through claim 8.

Can a generic manufacturer launch saxagliptin after expiration of this patent?

Potentially, but the applicant must clear later Orange Book-listed patents, regulatory exclusivities, formulation rights, and manufacturing patents.

Are biosimilars relevant to saxagliptin?

No. Saxagliptin is a chemically synthesized small molecule. The relevant competitors are ANDA-approved generics, not biosimilars.

References

U.S. Patent No. 6,395,767. (2002). Dipeptidyl peptidase IV inhibitors. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (2009). Onglyza (saxagliptin) approval package. Drugs@FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Orange Book.
AstraZeneca PLC. (2014). Annual report 2014. AstraZeneca.
U.S. Patent and Trademark Office. (2024). Patent term adjustment and patent term extension resources. USPTO.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	1261586	⤷ Start Trial	C300436	Netherlands	⤷ Start Trial
European Patent Office	1261586	⤷ Start Trial	CA 2010 00007	Denmark	⤷ Start Trial
European Patent Office	1261586	⤷ Start Trial	91650	Luxembourg	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,395,767

Summary for Patent: 6,395,767