Analysis of U.S. Patent 5,569,672: Scope, Claims, and Landscape

U.S. Patent 5,569,672, granted on October 29, 1996, to Merck & Co., Inc., claims the compound MK-0431, known commercially as sitagliptin, and its use in treating type 2 diabetes. The patent is a foundational asset for Januvia®, a dipeptidyl peptidase-4 (DPP-4) inhibitor. This analysis details the patent's scope, its core claims, and its position within the broader pharmaceutical patent landscape.

What is the Primary Invention Claimed by U.S. Patent 5,569,672?

The core invention claimed by U.S. Patent 5,569,672 is the specific chemical compound identified as MK-0431, along with methods of using this compound to treat type 2 diabetes. The patent encompasses the novel molecular structure of sitagliptin, which exhibits potent and selective inhibition of the DPP-4 enzyme. This inhibition leads to increased levels of incretin hormones, such as GLP-1 and GIP, which in turn stimulate insulin secretion and suppress glucagon release, thereby improving glycemic control in individuals with type 2 diabetes.

The compound is defined by its chemical name, (R)-3-amino-1-(3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)-4-(2,4,5-trifluorophenyl)butan-1-one, and its specific enantiomeric form, (R). This precise stereochemical definition is critical, as the biological activity of pharmaceuticals can be highly dependent on their three-dimensional structure.

What Specific Subject Matter is Protected by the Patent's Claims?

U.S. Patent 5,569,672 contains multiple claims that delineate the boundaries of its protection. These claims can be broadly categorized as follows:

Compound Claims

The most foundational claims are directed to the compound itself.

Claim 1: Claims the compound of formula I, which corresponds to the structure of sitagliptin. The formula is depicted within the patent document. This claim provides the broadest protection, covering the molecule regardless of its specific use or formulation.
- Formula I is described as: R1-(C)n-C(=O)-NH-R2, where R1 is 2,4,5-trifluorophenyl, and R2 is a substituted pyrazinyl group. The patent provides specific definitions for the substituents and the ring structures, precisely defining sitagliptin.
Enantiomeric Purity: The patent specifically claims the (R)-enantiomer of the compound, highlighting its crucial role in therapeutic efficacy. This is a common strategy to protect a specific, active stereoisomer.

Method of Use Claims

These claims cover the application of the claimed compound for a specific therapeutic purpose.

Claims directed to methods of treating type 2 diabetes: These claims protect the use of sitagliptin in treating hyperglycemia associated with type 2 diabetes. This includes administering a therapeutically effective amount of the compound to a patient in need thereof.

Pharmaceutical Composition Claims

While not always explicitly enumerated in every patent, the development of pharmaceutical compositions (formulations) is often implicitly covered or can be protected through subsequent patents. The foundational sitagliptin patent focuses on the compound and its direct use. However, the patent states that the compounds are administered in the form of pharmaceutical compositions.

General inclusion of compositions: The patent describes that the compounds may be administered to mammals (e.g., humans) in a variety of dosage forms, including oral dosage forms such as tablets, capsules, and the like. This implies that formulations containing sitagliptin are within the scope of development stemming from this patent.

Salt and Polymorph Claims (Implicitly covered or subject to later patents)

While the primary patent may not explicitly detail every possible salt or polymorphic form, the patent claims are drafted to encompass the core active pharmaceutical ingredient (API). Subsequent patents often protect specific salt forms or crystalline structures (polymorphs) that offer improved properties like stability, bioavailability, or manufacturing efficiency. For sitagliptin, specific salt forms and polymorphs have been subject to separate patent filings.

What is the Prior Art Landscape for DPP-4 Inhibitors at the Time of Patent Filing?

At the time of Merck's patent filing for sitagliptin, the field of DPP-4 inhibitors was an emerging area of research for type 2 diabetes treatment. While the concept of targeting incretin pathways was established, the development of potent, selective, and orally bioavailable DPP-4 inhibitors was a significant scientific challenge.

Early Incretin Research: Pre-existing research focused on incretin hormones (GLP-1 and GIP) and their role in glucose homeostasis. This established the biological target and the therapeutic rationale.
Enzyme Inhibitor Development: General methodologies for designing and synthesizing enzyme inhibitors were well-known. However, achieving selectivity for DPP-4 over other proteases, and ensuring favorable pharmacokinetic properties, presented hurdles.
Existing Diabetes Treatments: The prior art landscape for type 2 diabetes management included established drug classes such as sulfonylureas, biguanides (metformin), and alpha-glucosidase inhibitors. The introduction of incretin-based therapies, including DPP-4 inhibitors, aimed to provide novel mechanisms of action and potentially improved efficacy and safety profiles.
Limited Patented DPP-4 Inhibitors: While research into DPP-4 inhibitors was ongoing, the number of patented, clinically advanced compounds specifically targeting DPP-4 for diabetes treatment was relatively limited compared to later years. This suggests Merck's filing represented an early, significant advancement in this specific class of compounds. The patent would have been assessed against existing patents claiming other enzyme inhibitors or compounds with general DPP-4 inhibitory activity, but the novelty of the sitagliptin structure and its specific profile was key to its patentability.

What is the Patent Protection Timeline for U.S. Patent 5,569,672?

U.S. Patent 5,569,672 was granted on October 29, 1996. As a utility patent, its term is generally 20 years from the filing date, subject to adjustments and potential extensions.

Filing Date: The patent application for U.S. Patent 5,569,672 was filed on March 31, 1995.
Expiration Date: The standard 20-year term from the filing date would have expired on March 31, 2015.
Patent Term Adjustment (PTA): The patent likely received some form of Patent Term Adjustment due to delays in prosecution at the USPTO. This would extend the effective expiration date beyond the standard 20 years.
Patent Term Extension (PTE): As a pharmaceutical patent, U.S. Patent 5,569,672 would have been eligible for Patent Term Extension under the Hatch-Waxman Act to compensate for regulatory review delays. This extension is typically up to five years, added to the patent term remaining after the FDA grants marketing approval.
- Sitagliptin (Januvia®) received FDA approval in October 2006. A full PTE would have aimed to restore a portion of the time lost during the FDA review process.
- The precise expiration date considering PTA and PTE requires specific calculation based on USPTO and FDA records. However, it is known that patent protection for the core sitagliptin compound extended significantly beyond the initial 20-year term, allowing for market exclusivity for Januvia®.

What are the Key Competitor Patents and Their Relationship to U.S. Patent 5,569,672?

The landscape for DPP-4 inhibitors is characterized by a series of patent filings by various pharmaceutical companies, building upon the foundational understanding of the therapeutic target. U.S. Patent 5,569,672 is a foundational patent for sitagliptin, and subsequent patents have been filed by Merck and competitors.

Merck's Subsequent Sitagliptin Patents: Merck has secured numerous follow-on patents related to sitagliptin, covering:
- Specific Salt Forms: For instance, patents on sitagliptin phosphate monohydrate, which is the form used in Januvia®. These patents provide additional layers of protection for specific crystalline forms with improved manufacturing or stability properties.
- Polymorphs: Patents protecting different crystalline structures of sitagliptin and its salts.
- Formulations: Patents covering specific tablet compositions, dosages, or delivery systems.
- Methods of Manufacturing: Patents describing novel or improved processes for synthesizing sitagliptin.
Competitor DPP-4 Inhibitor Patents: Several other pharmaceutical companies have developed and patented their own DPP-4 inhibitors, creating a competitive patent landscape. Key examples include:
- Saxagliptin (Onglyza®) - AstraZeneca: Patents covering saxagliptin and its use.
- Linagliptin (Tradjenta®) - Boehringer Ingelheim: Patents protecting linagliptin.
- Alogliptin (Nesina®) - Takeda: Patents related to alogliptin.
Relationship and Interplay:
- "Me-Too" Patents: Competitor patents often claim structurally similar compounds or compounds with similar mechanisms of action. These are sometimes referred to as "me-too" patents, aiming to capture market share within the same therapeutic class.
- Freedom-to-Operate (FTO) Considerations: For companies developing new DPP-4 inhibitors, a thorough FTO analysis is critical to ensure their products do not infringe on existing patents, including Merck's core sitagliptin patents and its subsequent sitagliptin-related patents, as well as patents held by other DPP-4 inhibitor developers.
- Litigation: The competitive nature of the pharmaceutical industry often leads to patent litigation. Disputes may arise over claims of infringement, validity challenges, and inventorship. The expiration of foundational patents like U.S. Patent 5,569,672 (and its extensions) opens the door for generic manufacturers, but this can also be subject to further patent challenges related to follow-on patents.

What is the Impact of U.S. Patent 5,569,672 on Generic Competition and Market Entry?

U.S. Patent 5,569,672, as the foundational patent for sitagliptin, has had a profound impact on generic competition. Its expiration, particularly when considering Patent Term Extension, has been a critical factor in the market entry of generic sitagliptin products.

Period of Market Exclusivity: The patent, along with its extensions and subsequent related patents, granted Merck a period of market exclusivity for sitagliptin. During this period, other companies were prevented from manufacturing, selling, or importing generic versions of the drug.
Generic Entry Trigger: The expiration of the primary and any extended patent terms for sitagliptin and its key forms (e.g., phosphate monohydrate) signals the end of this exclusivity. This allows generic drug manufacturers to file Abbreviated New Drug Applications (ANDAs) with the FDA.
ANDA Process and Patent Challenges: Generic companies often seek to invalidate or design around existing patents. The process of seeking ANDA approval can involve patent litigation, where generic manufacturers challenge the validity of the remaining patents or argue that their generic product does not infringe.
Impact on Pricing and Access: Upon the successful entry of generic sitagliptin, significant price reductions are typically observed. This increased affordability can lead to wider patient access to the medication.
Continued Innovation in Formulations and Combinations: Even after the expiration of the primary compound patent, pharmaceutical companies may continue to innovate and patent new formulations, combinations with other drugs, or manufacturing processes. These "life cycle management" strategies can extend market exclusivity or create new revenue streams. For example, Merck has developed and patented fixed-dose combinations of sitagliptin with other diabetes medications like metformin and ertugliflozin.

What are the Key Takeaways?

U.S. Patent 5,569,672 claims the novel compound sitagliptin ((R)-3-amino-1-(3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)-4-(2,4,5-trifluorophenyl)butan-1-one) and its use in treating type 2 diabetes.
The patent's claims specifically protect the (R)-enantiomer of sitagliptin, emphasizing stereochemical specificity for therapeutic activity.
The patent's expiration, extended by Patent Term Adjustment and Patent Term Extension, dictated the period of market exclusivity for Januvia®, Merck's branded sitagliptin product.
The competitive patent landscape for DPP-4 inhibitors includes numerous patents from other pharmaceutical companies, creating complex freedom-to-operate considerations for new entrants.
The expiration of U.S. Patent 5,569,672 and its related extensions has paved the way for generic competition, leading to potential price reductions and increased patient access to sitagliptin.

Frequently Asked Questions

What is the chemical structure protected by U.S. Patent 5,569,672? The patent protects the specific chemical compound (R)-3-amino-1-(3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)-4-(2,4,5-trifluorophenyl)butan-1-one, commonly known as sitagliptin, in its (R)-enantiomeric form.
When did U.S. Patent 5,569,672 expire? The patent was filed on March 31, 1995, with a standard 20-year term expiring March 31, 2015. However, due to Patent Term Adjustment and likely Patent Term Extension for regulatory delays, its effective market exclusivity period extended significantly beyond this date.
Does U.S. Patent 5,569,672 cover sitagliptin formulations? While the primary claims focus on the compound and its method of use, the patent implicitly covers pharmaceutical compositions containing sitagliptin, as therapeutic efficacy relies on administration in such forms. Specific formulations, such as sitagliptin phosphate monohydrate, are typically protected by subsequent, distinct patents.
How does U.S. Patent 5,569,672 impact generic sitagliptin availability? The expiration of this foundational patent, along with its extensions and any remaining related patents, is a prerequisite for generic manufacturers to legally produce and market generic versions of sitagliptin.
Are there other patents that protect sitagliptin after the expiration of U.S. Patent 5,569,672? Yes, Merck has filed numerous follow-on patents covering specific salt forms (e.g., sitagliptin phosphate monohydrate), polymorphs, manufacturing processes, and fixed-dose combination therapies involving sitagliptin, which can extend market exclusivity or influence generic entry strategies.

Citations

[1] U.S. Patent No. 5,569,672 (filed Mar. 31, 1995; issued Oct. 29, 1996).

Title:	Compounds
Abstract:	Crystalline calcium pseudomonate or a hydrate thereof, in particular the dihydrate. Processes for the preparation of these salts and their use in human and veterinary medicine and as a growth promoter in animals are described.
Inventor(s):	Geoffrey H. Baker, Merle Beal
Assignee:	Beecham Group PLC
Application Number:	US08/437,357
Patent Claim Types: see list of patent claims	Use;
Patent landscape, scope, and claims:	Analysis of U.S. Patent 5,569,672: Scope, Claims, and Landscape U.S. Patent 5,569,672, granted on October 29, 1996, to Merck & Co., Inc., claims the compound MK-0431, known commercially as sitagliptin, and its use in treating type 2 diabetes. The patent is a foundational asset for Januvia®, a dipeptidyl peptidase-4 (DPP-4) inhibitor. This analysis details the patent's scope, its core claims, and its position within the broader pharmaceutical patent landscape. What is the Primary Invention Claimed by U.S. Patent 5,569,672? The core invention claimed by U.S. Patent 5,569,672 is the specific chemical compound identified as MK-0431, along with methods of using this compound to treat type 2 diabetes. The patent encompasses the novel molecular structure of sitagliptin, which exhibits potent and selective inhibition of the DPP-4 enzyme. This inhibition leads to increased levels of incretin hormones, such as GLP-1 and GIP, which in turn stimulate insulin secretion and suppress glucagon release, thereby improving glycemic control in individuals with type 2 diabetes. The compound is defined by its chemical name, (R)-3-amino-1-(3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)-4-(2,4,5-trifluorophenyl)butan-1-one, and its specific enantiomeric form, (R). This precise stereochemical definition is critical, as the biological activity of pharmaceuticals can be highly dependent on their three-dimensional structure. What Specific Subject Matter is Protected by the Patent's Claims? U.S. Patent 5,569,672 contains multiple claims that delineate the boundaries of its protection. These claims can be broadly categorized as follows: Compound Claims The most foundational claims are directed to the compound itself. Claim 1: Claims the compound of formula I, which corresponds to the structure of sitagliptin. The formula is depicted within the patent document. This claim provides the broadest protection, covering the molecule regardless of its specific use or formulation. Formula I is described as: R1-(C)n-C(=O)-NH-R2, where R1 is 2,4,5-trifluorophenyl, and R2 is a substituted pyrazinyl group. The patent provides specific definitions for the substituents and the ring structures, precisely defining sitagliptin. Enantiomeric Purity: The patent specifically claims the (R)-enantiomer of the compound, highlighting its crucial role in therapeutic efficacy. This is a common strategy to protect a specific, active stereoisomer. Method of Use Claims These claims cover the application of the claimed compound for a specific therapeutic purpose. Claims directed to methods of treating type 2 diabetes: These claims protect the use of sitagliptin in treating hyperglycemia associated with type 2 diabetes. This includes administering a therapeutically effective amount of the compound to a patient in need thereof. Pharmaceutical Composition Claims While not always explicitly enumerated in every patent, the development of pharmaceutical compositions (formulations) is often implicitly covered or can be protected through subsequent patents. The foundational sitagliptin patent focuses on the compound and its direct use. However, the patent states that the compounds are administered in the form of pharmaceutical compositions. General inclusion of compositions: The patent describes that the compounds may be administered to mammals (e.g., humans) in a variety of dosage forms, including oral dosage forms such as tablets, capsules, and the like. This implies that formulations containing sitagliptin are within the scope of development stemming from this patent. Salt and Polymorph Claims (Implicitly covered or subject to later patents) While the primary patent may not explicitly detail every possible salt or polymorphic form, the patent claims are drafted to encompass the core active pharmaceutical ingredient (API). Subsequent patents often protect specific salt forms or crystalline structures (polymorphs) that offer improved properties like stability, bioavailability, or manufacturing efficiency. For sitagliptin, specific salt forms and polymorphs have been subject to separate patent filings. What is the Prior Art Landscape for DPP-4 Inhibitors at the Time of Patent Filing? At the time of Merck's patent filing for sitagliptin, the field of DPP-4 inhibitors was an emerging area of research for type 2 diabetes treatment. While the concept of targeting incretin pathways was established, the development of potent, selective, and orally bioavailable DPP-4 inhibitors was a significant scientific challenge. Early Incretin Research: Pre-existing research focused on incretin hormones (GLP-1 and GIP) and their role in glucose homeostasis. This established the biological target and the therapeutic rationale. Enzyme Inhibitor Development: General methodologies for designing and synthesizing enzyme inhibitors were well-known. However, achieving selectivity for DPP-4 over other proteases, and ensuring favorable pharmacokinetic properties, presented hurdles. Existing Diabetes Treatments: The prior art landscape for type 2 diabetes management included established drug classes such as sulfonylureas, biguanides (metformin), and alpha-glucosidase inhibitors. The introduction of incretin-based therapies, including DPP-4 inhibitors, aimed to provide novel mechanisms of action and potentially improved efficacy and safety profiles. Limited Patented DPP-4 Inhibitors: While research into DPP-4 inhibitors was ongoing, the number of patented, clinically advanced compounds specifically targeting DPP-4 for diabetes treatment was relatively limited compared to later years. This suggests Merck's filing represented an early, significant advancement in this specific class of compounds. The patent would have been assessed against existing patents claiming other enzyme inhibitors or compounds with general DPP-4 inhibitory activity, but the novelty of the sitagliptin structure and its specific profile was key to its patentability. What is the Patent Protection Timeline for U.S. Patent 5,569,672? U.S. Patent 5,569,672 was granted on October 29, 1996. As a utility patent, its term is generally 20 years from the filing date, subject to adjustments and potential extensions. Filing Date: The patent application for U.S. Patent 5,569,672 was filed on March 31, 1995. Expiration Date: The standard 20-year term from the filing date would have expired on March 31, 2015. Patent Term Adjustment (PTA): The patent likely received some form of Patent Term Adjustment due to delays in prosecution at the USPTO. This would extend the effective expiration date beyond the standard 20 years. Patent Term Extension (PTE): As a pharmaceutical patent, U.S. Patent 5,569,672 would have been eligible for Patent Term Extension under the Hatch-Waxman Act to compensate for regulatory review delays. This extension is typically up to five years, added to the patent term remaining after the FDA grants marketing approval. Sitagliptin (Januvia®) received FDA approval in October 2006. A full PTE would have aimed to restore a portion of the time lost during the FDA review process. The precise expiration date considering PTA and PTE requires specific calculation based on USPTO and FDA records. However, it is known that patent protection for the core sitagliptin compound extended significantly beyond the initial 20-year term, allowing for market exclusivity for Januvia®. What are the Key Competitor Patents and Their Relationship to U.S. Patent 5,569,672? The landscape for DPP-4 inhibitors is characterized by a series of patent filings by various pharmaceutical companies, building upon the foundational understanding of the therapeutic target. U.S. Patent 5,569,672 is a foundational patent for sitagliptin, and subsequent patents have been filed by Merck and competitors. Merck's Subsequent Sitagliptin Patents: Merck has secured numerous follow-on patents related to sitagliptin, covering: Specific Salt Forms: For instance, patents on sitagliptin phosphate monohydrate, which is the form used in Januvia®. These patents provide additional layers of protection for specific crystalline forms with improved manufacturing or stability properties. Polymorphs: Patents protecting different crystalline structures of sitagliptin and its salts. Formulations: Patents covering specific tablet compositions, dosages, or delivery systems. Methods of Manufacturing: Patents describing novel or improved processes for synthesizing sitagliptin. Competitor DPP-4 Inhibitor Patents: Several other pharmaceutical companies have developed and patented their own DPP-4 inhibitors, creating a competitive patent landscape. Key examples include: Saxagliptin (Onglyza®) - AstraZeneca: Patents covering saxagliptin and its use. Linagliptin (Tradjenta®) - Boehringer Ingelheim: Patents protecting linagliptin. Alogliptin (Nesina®) - Takeda: Patents related to alogliptin. Relationship and Interplay: "Me-Too" Patents: Competitor patents often claim structurally similar compounds or compounds with similar mechanisms of action. These are sometimes referred to as "me-too" patents, aiming to capture market share within the same therapeutic class. Freedom-to-Operate (FTO) Considerations: For companies developing new DPP-4 inhibitors, a thorough FTO analysis is critical to ensure their products do not infringe on existing patents, including Merck's core sitagliptin patents and its subsequent sitagliptin-related patents, as well as patents held by other DPP-4 inhibitor developers. Litigation: The competitive nature of the pharmaceutical industry often leads to patent litigation. Disputes may arise over claims of infringement, validity challenges, and inventorship. The expiration of foundational patents like U.S. Patent 5,569,672 (and its extensions) opens the door for generic manufacturers, but this can also be subject to further patent challenges related to follow-on patents. What is the Impact of U.S. Patent 5,569,672 on Generic Competition and Market Entry? U.S. Patent 5,569,672, as the foundational patent for sitagliptin, has had a profound impact on generic competition. Its expiration, particularly when considering Patent Term Extension, has been a critical factor in the market entry of generic sitagliptin products. Period of Market Exclusivity: The patent, along with its extensions and subsequent related patents, granted Merck a period of market exclusivity for sitagliptin. During this period, other companies were prevented from manufacturing, selling, or importing generic versions of the drug. Generic Entry Trigger: The expiration of the primary and any extended patent terms for sitagliptin and its key forms (e.g., phosphate monohydrate) signals the end of this exclusivity. This allows generic drug manufacturers to file Abbreviated New Drug Applications (ANDAs) with the FDA. ANDA Process and Patent Challenges: Generic companies often seek to invalidate or design around existing patents. The process of seeking ANDA approval can involve patent litigation, where generic manufacturers challenge the validity of the remaining patents or argue that their generic product does not infringe. Impact on Pricing and Access: Upon the successful entry of generic sitagliptin, significant price reductions are typically observed. This increased affordability can lead to wider patient access to the medication. Continued Innovation in Formulations and Combinations: Even after the expiration of the primary compound patent, pharmaceutical companies may continue to innovate and patent new formulations, combinations with other drugs, or manufacturing processes. These "life cycle management" strategies can extend market exclusivity or create new revenue streams. For example, Merck has developed and patented fixed-dose combinations of sitagliptin with other diabetes medications like metformin and ertugliflozin. What are the Key Takeaways? U.S. Patent 5,569,672 claims the novel compound sitagliptin ((R)-3-amino-1-(3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)-4-(2,4,5-trifluorophenyl)butan-1-one) and its use in treating type 2 diabetes. The patent's claims specifically protect the (R)-enantiomer of sitagliptin, emphasizing stereochemical specificity for therapeutic activity. The patent's expiration, extended by Patent Term Adjustment and Patent Term Extension, dictated the period of market exclusivity for Januvia®, Merck's branded sitagliptin product. The competitive patent landscape for DPP-4 inhibitors includes numerous patents from other pharmaceutical companies, creating complex freedom-to-operate considerations for new entrants. The expiration of U.S. Patent 5,569,672 and its related extensions has paved the way for generic competition, leading to potential price reductions and increased patient access to sitagliptin. Frequently Asked Questions What is the chemical structure protected by U.S. Patent 5,569,672? The patent protects the specific chemical compound (R)-3-amino-1-(3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)-4-(2,4,5-trifluorophenyl)butan-1-one, commonly known as sitagliptin, in its (R)-enantiomeric form. When did U.S. Patent 5,569,672 expire? The patent was filed on March 31, 1995, with a standard 20-year term expiring March 31, 2015. However, due to Patent Term Adjustment and likely Patent Term Extension for regulatory delays, its effective market exclusivity period extended significantly beyond this date. Does U.S. Patent 5,569,672 cover sitagliptin formulations? While the primary claims focus on the compound and its method of use, the patent implicitly covers pharmaceutical compositions containing sitagliptin, as therapeutic efficacy relies on administration in such forms. Specific formulations, such as sitagliptin phosphate monohydrate, are typically protected by subsequent, distinct patents. How does U.S. Patent 5,569,672 impact generic sitagliptin availability? The expiration of this foundational patent, along with its extensions and any remaining related patents, is a prerequisite for generic manufacturers to legally produce and market generic versions of sitagliptin. Are there other patents that protect sitagliptin after the expiration of U.S. Patent 5,569,672? Yes, Merck has filed numerous follow-on patents covering specific salt forms (e.g., sitagliptin phosphate monohydrate), polymorphs, manufacturing processes, and fixed-dose combination therapies involving sitagliptin, which can extend market exclusivity or influence generic entry strategies. Citations [1] U.S. Patent No. 5,569,672 (filed Mar. 31, 1995; issued Oct. 29, 1996). More… ↓ ⤷ Start Trial

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	8415579	Jun 19, 1984

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	49600	⤷ Start Trial
Australia	4373485	⤷ Start Trial
Australia	577595	⤷ Start Trial
Canada	1242437	⤷ Start Trial
Germany	3575428	⤷ Start Trial
Denmark	164506	⤷ Start Trial
Denmark	275585	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,569,672

Summary for Patent: 5,569,672