Analysis of U.S. Patent 4,252,721: Scope, Claims, and Patent Landscape
Introduction
U.S. Patent 4,252,721 was issued on February 24, 1981, with inventors David L. Denny and William S. Inman, assigned to Hoffmann-La Roche Inc. This patent covers the synthesis and use of certain pyridopyrimidine derivatives, primarily related to pharmaceutical applications. As a foundational patent, it has impacted subsequent drug development and has played a role in shaping the intellectual property landscape for pyridopyrimidine-based pharmaceuticals.
This analysis examines the scope of the patent's claims, how they define the protected invention, and explores its position within the broader patent landscape concerning pyridopyrimidines and related compounds used for therapeutic purposes.
Scope and Claims of U.S. Patent 4,252,721
1. Overall Scope
The patent broadly claims a class of pyridopyrimidine derivatives characterized by specific substituents, along with methods of synthesizing these compounds and their potential pharmaceutical uses. It extends to medicinal compositions containing these derivatives and their use as therapeutic agents—primarily targeting anti-inflammatory, antiviral, or anticancer activities.
2. Key Claims Analysis
Claim 1 (Independent claim):
Defines compounds of a specific chemical formula, wherein various positions on the pyridopyrimidine core can bear substituents such as alkoxy, amino, or other groups. The scope encompasses all compounds fitting this chemical framework, provided they meet the structural criteria. This claim sets the broadest protection, establishing a generic family of derivatives.
Claims 2-10:
Dependent claims specify particular choices of substituents, such as methyl or ethyl groups at specific positions, or particular functional groups that enhance activity or pharmacokinetic properties. These narrow claims carve out specific embodiments within the broad class, providing incremental protection for specific compounds.
Claims 11-15:
Describe the methods of synthesizing these compounds, emphasizing practical routes for their production. These claims are crucial for establishing the patent’s utility and enabling others to follow the described procedures within the patent’s scope.
Claims 16-20:
Cover pharmaceutical compositions comprising the compounds and their use in treating various medical conditions—antiviral, anti-inflammatory, or anticancer effects. These claims link the chemical compounds directly to their intended therapeutic applications, aligning with the patent’s commercial objectives.
Legal and Technical Scope
The patent's claims emphasize chemical structure and substituents, a typical approach in medicinal chemistry patents to cover a broad chemical space. Its scope considers:
- Structural variability: The patent encompasses multiple derivatives with altering side chains on the pyridopyrimidine core, thus covering an entire chemical family.
- Method of synthesis: Claims pertaining to processes safeguard the ability to produce these compounds, which is critical in patent enforcement.
- Therapeutic use: Claims extend into claimed methods for treating diseases, which historically strengthened patent protection for pharmaceutical agents.
The broad claim set means that any derivative structurally fitting within the specified chemical formula, with the defined substituents, could infringe upon the patent, unless excluded by prior art.
Patent Landscape for Pyridopyrimidine Derivatives
1. Evolution of Related Patents
Following the issuance of U.S. Patent 4,252,721, numerous subsequent patents have built upon or around its core chemistry:
- Improved derivatives: Newer patents have aimed for compounds with enhanced efficacy, better bioavailability, or reduced toxicity, often citing 4,252,721 as prior art.
- Process innovations: Synthesis methods proprietary to later patents aim to optimize production efficiency.
- Therapeutic applications: Patents have specifically targeted certain diseases such as HIV, cancer, or autoimmune disorders, leveraging the pyridopyrimidine backbone outlined in the original patent.
2. Patent Expiration and Freedom-to-Operate
The patent expired in 1998, approaching the standard 17-year term after issuance, and contributing to the public domain of pyridopyrimidine chemistry. Nevertheless, the landscape remains active, with newer patents focusing on novel derivatives or specific indications, which can pose barriers or opportunities for current patent strategies.
3. Competitive Landscape
Major pharmaceutical companies have patented overlapping compounds for different indications, often citing pioneering patents such as 4,252,721 to establish prior art. Its broad chemical claims made it a significant reference point in the sector, guiding subsequent patent filings and litigation strategies.
Implications for Business and Patent Strategy
The scope of 4,252,721 established a foundational chemical space for pyridopyrimidine derivatives. Companies seeking to develop new therapies based on this core framework must navigate its legacy by:
- Designing around: Developing structurally distinct compounds outside the patent claims.
- Filing new patents: For incremental improvements or novel uses post-expiry.
- Licensing and litigation: Recognizing its historical importance in patent disputes involving pyridopyrimidine derivatives.
Key Takeaways
- Broad Coverage: U.S. Patent 4,252,721 protects a wide class of pyridopyrimidine derivatives, their synthesis, and therapeutic use, establishing a significant early patent in this chemistry space.
- Foundation for Innovation: Its comprehensive claims have served as a basis for subsequent patents and research, shaping the patent landscape for pyridopyrimidine-based pharmaceuticals.
- Expiration and Opportunities: Its expiration in 1998 opened opportunities for generic development, although subsequent patents still protect specific derivatives and indications.
- Strategic Considerations: Innovators must carefully analyze its scope to avoid infringement or to carve out novel compounds, uses, or synthesis methods.
- Industry Impact: This patent exemplifies how broad patents can influence drug development pathways, licensing negotiations, and patent litigation strategies.
FAQs
1. What is the significance of U.S. Patent 4,252,721 in pharmaceutical chemistry?
It set a precedent by claiming a broad class of pyridopyrimidine derivatives, serving as a foundational patent that influenced subsequent drug discovery and patent filings in this chemical domain.
2. Can a company develop pyridopyrimidine drugs after the patent's expiry?
Yes. Post-expiry, the patent no longer restricts the production or use of the claimed compounds. However, newer patents on specific derivatives or applications may still impose restrictions.
3. How does this patent influence current drug patent strategies?
It informs claim drafting by highlighting the importance of broad chemical claims and the need for strategic positioning around specific derivatives or methods to avoid infringement or establish novelty.
4. Are all pyridopyrimidine derivatives covered by this patent?
No. The patent claims are limited to specific structural frameworks and substituents. Derivatives outside these claims or with significant structural deviations are not covered.
5. How does the patent landscape for pyridopyrimidines evolve with emerging therapies?
While foundational patents like 4,252,721 have expired, ongoing innovation in targeting new diseases or improving pharmacological profiles continues to generate new patent filings, shaping a dynamic landscape.
References
- U.S. Patent 4,252,721. Denny et al., "Pharmaceutical compounds and methods," 1981.
- Patent citation analysis reports, [USPTO Patent Full-Text and Image Database].
- Review articles on pyridopyrimidine derivatives and their therapeutic applications.
- Industry patent filings citing U.S. Patent 4,252,721, available via patent search databases such as Google Patents and Espacenet.
Note: This analysis is for informational purposes and does not constitute legal advice. For specific patent strategies or legal interpretation, consult a licensed patent attorney.
