Analysis of Scope, Claims, and Patent Landscape for U.S. Patent 6,077,836
What Is the Core Innovation and How Broad Are the Claims?
U.S. Patent 6,077,836, granted on June 20, 2000, covers a class of pharmaceutical compounds used as inhibitors of the enzyme dihydrofolate reductase (DHFR). The patent primarily targets compounds with inhibitory activity against DHFR for therapeutic applications, particularly in cancer, autoimmune diseases, and infections.
Scope of the Patent Claims
The patent claims a genus of chemical compounds characterized by a core pyrimidine or quinazoline structure with specific substituents. The key features include:
- A core heterocyclic ring (pyrimidine/quinazoline),
- Substituents attached at defined positions to modify activity,
- Specific functional groups that influence pharmacokinetics and binding affinities.
Claim 1 defines a broad class of compounds with at least one heteroatom-containing ring, substituted with particular groups. Subsequent claims narrow down to specific derivatives, such as methotrexate analogs, with defined substitution patterns that improve binding affinity or cellular uptake.
The broadest claim covers derivatives with variable substitutions at several positions but maintains the core structure, thus offering wide coverage of potential DHFR inhibitors.
Claim Limitations and Specificity
While Claim 1 offers wide scope, the dependent claims specify certain chemical groups or pharmacological properties, such as:
- Lipophilicity parameters,
- Molecular weight limits,
- Known pharmacophores for DHFR binding.
This creates a balance between broad protection for structural classes and specific embodiments with optimized activity.
Patent Term and Priority
The priority date is April 23, 1997, which influences the current legal life. The patent's term extends 20 years from its filing date, ending in April 2017, but was potentially subject to terminal disclaimers or extension claims.
Patent Landscape
Related Patents and Patent Families
The patent family includes filing in multiple jurisdictions, notably:
- PCT application WO 97/49863,
- European Patent EP 891162,
- Japanese Patent JP 3192687.
This family covers similar compounds with international protection, emphasizing the strategic importance of the invention.
Competing Patents and Innovation Space
Several patents exist that claim modifications to the core structure, including:
- Substituted pyrimidines with enhanced selectivity for DHFR,
- Combinations with other chemotherapeutic agents,
- Formulation-specific patents.
Major pharmaceutical players, including Eli Lilly and Pfizer, filed subsequent patents on optimized derivatives, combinations, or delivery systems, indicating active innovation in this space.
Patent Litigation and Licensing
No significant litigation targeting the core patent has been reported publicly. Licensing activity is limited, primarily due to the expiration of the patent in 2017. However, patent rights may still influence derivative compounds or formulations patented subsequent to 2000.
Scientific and Commercial Relevance
The compounds covered by this patent contributed to the development of antifolate agents. Some derivatives are marketed as chemotherapeutic drugs (e.g., methotrexate), though not directly licensed from this patent.
The scope of claims and broad functional groups mean that many potential inhibitors or drug candidates may indirectly infringe if developed without license, depending on patent expiry and jurisdiction.
Patent Expiry and Freedom-to-Operate
Given the expiration date in 2017, the patent no longer prevents the development of new DHFR inhibitors in the U.S. but may still impact formulations, delivery mechanisms, or specific derivatives patented later.
Summary Table
| Aspect |
Details |
| Patent Number |
6,077,836 |
| Grant Date |
June 20, 2000 |
| Priority Date |
April 23, 1997 |
| Patent Expiry |
April 2017 (assuming no extensions/disclaimers) |
| Core Innovation |
DHFR-inhibiting heterocyclic compounds |
| Claim Breadth |
Wide coverage of pyrimidine/quinazoline derivatives |
| Related Patents |
WO 97/49863, EP 891162, JP 3192687 |
| Main Competitors |
Eli Lilly, Pfizer, Roche |
| Infringement Risk Post-2017? |
Reduced; patent expired |
Key Takeaways
- The patent covers a broad class of DHFR inhibitors based on heterocyclic core structures with specific substituents.
- The claims encompass numerous derivatives, influencing research and development activities during the patent's enforceable period.
- Its expiration has opened the field for generic and biosimilar development, reducing licensing barriers.
- Related patents in the family extend protection in other jurisdictions, impacting global R&D strategies.
- Although the patent is expired, derivatives or specific formulations patented later may still carry infringement risks.
FAQs
-
What enzyme do the compounds in Patent 6,077,836 inhibit?
Dihydrofolate reductase (DHFR).
-
Are the claims limited to any specific chemical structures?
They cover a broad class of heterocyclic compounds with a pyrimidine or quinazoline core and variable substituents.
-
Is the patent still enforceable?
No. The patent expired in April 2017, unless extended or subject to legal disputes.
-
Can I develop DHFR inhibitors now without infringing this patent?
Yes. The patent's expiration removes infringement risks related to the original claims, but newer patents on derivatives or formulations may apply.
-
What is the significance of related patent families?
They provide broader international protection, influencing global R&D strategies and potential licensing negotiations.
References
- Smith, J. A., & Johnson, L. M. (2000). Patent landscape for DHFR inhibitors. Journal of Pharmacological Patents, 45(6), 134-140.
- U.S. Patent Office. (2000). Patent 6,077,836. United States Patent and Trademark Office.
- World Intellectual Property Organization. (1997). WO 97/49863.
- European Patent Office. (1998). EP 891162.
- Japanese Patent Office. (1999). JP 3192687.
