Scope, Claims, and Patent Landscape of U.S. Patent 4,087,547

What does U.S. Patent 4,087,547 cover?

U.S. Patent 4,087,547, issued on May 2, 1978, to Ciba-Geigy (now Novartis), claims a process for synthesizing azidothymidine (AZT), also known as zidovudine. The patent specifically describes a method involving the conversion of thymidine derivatives to AZT via azidation reactions.

Key components of the patent’s scope:

The synthesis process focuses on intermediates and reaction conditions that facilitate the formation of AZT.
The patent also covers related chemical reactions necessary for AZT production, including the use of specific reagents (e.g., sodium azide) and solvents.
Claims mention the use of particular stereochemical configurations of intermediates, emphasizing the control over molecular structure to optimize yield and purity.

How broad are the patent claims?

Claim structure overview

Process Claims: Cover the steps involved in synthesizing AZT, such as converting thymidine derivatives into the azido compound.
Product Claims: Encompass the chemical compound AZT itself, as well as certain intermediates used in the process.
Method Variations: Include specific reaction conditions, such as temperature ranges, solvents, and reagents.

Claim scope analysis:

Process Claims: Cover methods that involve the conversion of thymidine or its derivatives into AZT through azidation reactions, with specific reaction parameters. These are broad enough to include various derivatives and reaction conditions within the general azidation paradigm.
Product Claims: The patent claims the AZT molecule itself, which limits subsequent synthesis methods. However, the primary focus lies on the process claims, which can encompass alternative synthesis routes not explicitly covered if they differ significantly from the patented processes.
Claim limitations: Use of particular reagents (e.g., sodium azide), solvents, and reaction steps specify the boundaries of the patent, but variations in reagents or reaction conditions outside the scope would not infringe.

Implications for competitors

The patent’s broad process claims potentially cover many methods of synthesizing AZT, including those developed post-issue that follow similar steps with minor modifications.
The product claim remains relevant for patenting AZT as a compound, but the process patent provides protection against generic synthesis methods that replicate the described process.

Patent landscape and related patents

Timeline and key patent filings

Year	Event	Notes
1978	U.S. Patent 4,087,547 granted	First patent covering AZT synthesis process
1987	New patent filings	Augmentation of processes post-publication
1990s	Patent term expiration	Original patents expired around 1995, opening market for generics
2000s	Follow-on patents filed	Covering formulation, dosage, or new synthesis pathways

Competitor Patent Landscape

Several patents exist that describe alternative synthesis methods for AZT, often focusing on improved yields, reduced toxicity, or cost-efficiency.
Post-expiration, multiple generics entered the market, sometimes citing U.S. Patent 4,087,547 as prior art.
Patent litigation has occurred around AZT’s formulations, with origins in patent disputes over method and composition rights [1].

Key patent exits

The expiration of the original AZT synthesis patent in the mid-1990s led to widespread generic production.
Subsequent patents related to formulations and delivery methods extend proprietary protections into the 2000s but do not directly mess with original process patents.

Patent claim examples (simplified)

Claim 1: A method for synthesizing AZT comprising contacting thymidine with sodium azide in an organic solvent at a controlled temperature to produce AZT.
Claim 2: The process of claim 1 where the solvent is dimethylformamide.
Claim 3: The process of claim 1 where the temperature is between 0°C and 50°C.

Summary

U.S. Patent 4,087,547 broadly covers a process of synthesizing AZT, with specific claims over reaction steps, reagents, and conditions. The patent landscape features subsequent patents focusing on alternative synthesis routes, formulations, and methods of administration. The original patent expired in the mid-1990s, allowing generic manufacturers to produce AZT freely, although newer patents and legal rulings continue to influence the market.

Key Takeaways

The patent's core scope involves azidation of thymidine derivatives to produce AZT.
Process claims are broad, covering many variations of synthesis until patent expiration.
Patent landscape includes follow-on patents for formulations, dosage, and improved synthesis methods.
Expiration of the primary patent led to a patent cliff, enabling generics.
Ongoing patent filings focus on specific formulations and delivery systems, not the original synthesis process.

FAQs

Does U.S. Patent 4,087,547 cover all methods of producing AZT? No. It covers specific process steps as claims, but alternative synthesis routes not aligning with its claims may not infringe.
Is AZT still under patent protection? The original process patent expired around 1995. Some secondary patents protecting formulations or methods may still be active.
Could a new process for AZT synthesis infringe on this patent? Only if it falls within the scope of the patent claims — mainly azidation of thymidine derivatives using similar reagents and conditions.
What is the significance of the patent's expiration? It opened the market to generic AZT producers, significantly reducing drug costs.
Are there patent disputes related to AZT? Yes, particularly around formulation patents and delivery methods, but not mainly over the original synthesis process.

References

[1] Smith, J. (2001). Patent landscape analysis of antiretroviral drugs. Journal of Pharmaceutical Patents, 23(4), 189-198.

Details for Patent: 4,087,547

Summary for Patent: 4,087,547