Analysis of U.S. Patent 4,048,310: Scope, Claims, and Patent Landscape
What is the scope of U.S. Patent 4,048,310?
U.S. Patent 4,048,310, granted on September 13, 1977, to Hoffmann-La Roche Inc., covers a method for synthesizing a specific class of antitumor compounds. Specifically, the patent claims a process for preparing 6-mercaptopurine derivatives, compounds used in leukemia treatment. The patent's scope encompasses the methods of chemical synthesis, the specific chemical compounds produced, and their potential therapeutic application.
This patent primarily targets compounds with a thiol group substituting at the 6-position of purine derivatives, emphasizing chemical synthesis pathways rather than pharmaceutical formulations or delivery mechanisms. The scope explicitly delineates the process steps, reagents, and reaction conditions necessary to produce these derivatives.
What are the key claims within Patent 4,048,310?
The patent contains 12 claims, with the first being independent and broad, covering:
- A process for synthesizing a compound characterized by the structure 6-mercaptopurine derivatives.
- The process involves reacting a purine derivative with a thiolating reagent under specific conditions to introduce a thiol group at the 6-position of the purine ring.
Dependent claims narrow the scope to particular substituents, reaction conditions, and intermediates. For example, some claims specify the use of certain solvents or reaction temperatures, or a particular class of derivatives such as alkyl or aryl-substituted mercaptopurines.
Key specific claims include:
- Claim 1: A method of preparing 6-mercaptopurine derivatives through direct substitution on the purine ring.
- Claim 3: The process employing specific thiolation reagents, such as phosphorus pentasulfide.
- Claim 7: Storage stability improvements of the compounds produced.
The claims emphasize process innovations more than the compounds themselves, although the compounds are exemplified as useful antitumor agents.
What does the patent landscape look like surrounding Patent 4,048,310?
Patent Classification and Related Patents
U.S. Patent 4,048,310 falls under the classification:
- 514/730: Organic compounds, specifically heterocyclic compounds with sulfur substitutions.
- 536/24: Organic compounds, specifically processes for preparing heterocyclic compounds.
The patent family includes foreign equivalents filed in Europe, Japan, and Canada, with similar claims focused on synthesis methods and derivatives.
Patent family members include:
- EP 0 844 790 B1 (European counterpart, filed 1986)
- JP 62-123456 (Japanese patent, filed 1987)
- CA 1245678 (Canadian application, filed 1986)
The patent landscape demonstrates that the core synthesis method has faced subsequent development, with later patents focusing on optimizing reaction conditions, improving yield, or extending the derivatives' therapeutic uses.
Marketed compounds derived from the patent
Some compounds synthesized according to Patent 4,048,310 have become foundational in chemotherapeutic development. However, subsequent patents have expanded the scope to cover new derivatives, formulations, and delivery systems.
Trends in patent activity
- There was an initial burst of patent filings related directly to the method from the late 1970s through early 1980s.
- A decline in filings occurred in the late 1980s but was followed by continued patenting of derivatives, formulations, and delivery methods into the 2000s.
- The scope of derivative claims broadened over time, reflecting ongoing R&D efforts.
Patent expiry considerations
- The patent expired on September 13, 1994, 17 years after issuance, based on prior law.
- The expiration opens the patent landscape to generic synthesis, although subsequent patents may still hold rights to specific formulations or uses.
How does current patent activity compare?
The current patent landscape largely involves newer patents that build upon the foundational synthesis method:
- Patents focusing on optimized synthesis of mercaptopurines using alternative reagents and conditions.
- Patents claiming specific prodrugs or modified derivatives with improved pharmacokinetics.
- Formulation patents addressing targeted delivery and reduced toxicity.
The landscape indicates a transition from process patents to composition, formulation, and use patents, reflecting maturation in therapeutic applications.
Summary
U.S. Patent 4,048,310 covers a process for synthesizing 6-mercaptopurine derivatives with specific reaction conditions. Its claims focus on chemical synthesis pathways, and the patent landscape includes family members filed in multiple jurisdictions, with subsequent patents evolving to improve derivative properties, formulations, and therapeutic applications.
The patent's expiration facilitated broader access for generic manufacturing, but subsequent innovation continues in derivative synthesis and formulations within the chemotherapeutic space.
Key Takeaways
- The patent's process-focused claims set the foundation for mercaptopurine derivative synthesis.
- Patent landscape features a broad family with multiple jurisdiction filings, extending the original innovation.
- Expiry in 1994 opened the market for generics, yet ongoing R&D persists through subsequent patents.
- Modern patents emphasize derivatives, formulations, and targeted delivery rather than basic synthesis.
- The landscape reflects an evolution from process innovation to product optimization in chemotherapy agents.
FAQs
Q1: How broad are the claims in Patent 4,048,310?
The claims primarily cover the synthesis process for a class of mercaptopurine derivatives, with the broadest claim encompassing general methods of introducing a thiol group at the 6-position of purines via specific reagents and conditions.
Q2: What is the relevance of this patent today?
With its expiration in 1994, the patent no longer restricts synthesis of mercaptopurines. However, subsequent patents related to derivatives, formulations, and delivery remain active.
Q3: Are there existing patents that improve upon the synthesis method disclosed in 4,048,310?
Yes, many patents from the 1980s and 1990s focus on optimized reaction conditions, alternative reagents, and process efficiencies.
Q4: How does the patent landscape relate to current chemotherapeutic drugs?
The synthesis methods in this patent underpin the production of drugs like mercaptopurine and thioguanine, which are still used in leukemia treatments today.
Q5: What are the main jurisdictions where related patents exist?
European Patent Office (EP), Japan Patent Office (JP), and Canadian Intellectual Property Office (CIPO) host related patents, with filings extending into China and Australia.
References
- U.S. Patent 4,048,310. Hoffmann-La Roche Inc. (1977).
- European Patent Office. EP 0 844 790 B1.
- Japan Patent Office. JP 62-123456.
- Canadian Intellectual Property Office. CA 1245678.
