Analysis of U.S. Patent 4,436,741: Scope, Claims, and Patent Landscape
What is the scope of U.S. Patent 4,436,741?
U.S. Patent 4,436,741 was issued on March 6, 1984, to Abbott Laboratories. It covers a formulation and process for the sustained release delivery of theophylline, a bronchodilator used in asthma treatment. The patent claims to improve therapeutic efficacy by controlling drug release over an extended period, reducing dosing frequency.
The patent's scope centers on:
- Drug formulation: The use of a specific matrix comprising hydrophilic polymers that regulate the dissolution of theophylline.
- Manufacturing process: Methods of preparing controlled-release theophylline tablets, primarily involving blending, compression, or coating techniques.
- Extended-release mechanisms: The use of polymers such as hydroxypropyl methylcellulose (HPMC) and polyethylene glycol (PEG) to modify release kinetics.
The patent's claims are narrowly focused on specific formulations containing particular polymer compositions and processing methods designed for sustained drug release over extended timeframes.
What are the main claims of U.S. Patent 4,436,741?
The patent comprises 12 claims, with Claim 1 being the broadest. The core of Claim 1 states:
"A controlled-release oral dosage form comprising theophylline dispersed in a hydrophilic matrix comprising hydroxypropyl methylcellulose and polyethylene glycol, wherein the dosage form provides a substantially zero-order release rate of theophylline over a predetermined period."
Other claims specify:
- Variations in polymer ratios (e.g., HPMC to PEG ratios of 80:20 to 20:80).
- The form of the formulation (e.g., tablets, capsules).
- Specific processing steps, such as compression parameters or coating techniques.
- Inclusion of optional excipients that do not alter the release characteristics significantly.
The claims are defense-oriented, aiming to protect specific formulations and manufacturing methods that achieve sustained theophylline release.
How does the patent landscape look for related drugs and formulations?
Patent Families and Subsequent Patents
The scope of Patent 4,436,741 has influenced subsequent patents in the field of sustained-release respiratory drugs. Key points include:
- Related drug patents: Several patents have cited or built upon this patent, focusing on alternative polymers, drug combinations, or delivery technologies for theophylline and other bronchodilators.
- Litigation and licensing: Abbott Laboratories has maintained rights over the patents, with licensing agreements in place for extending or modifying formulations.
- Competitor filings: Companies such as GlaxoSmithKline and Boehringer Ingelheim have filed patents with similar claims around sustained release formulations of similar or related drugs, often with narrower claims to avoid infringement.
Patent expiration impact
Patent 4,436,741 expired in 2001, opening the field for generic formulations and alternative technologies. This expiration resulted in:
- Generic entry: Multiple generics introduced post-2001, utilizing formulations similar to those claimed in the patent.
- Innovation: Development of new controlled-release formulations using different polymers like ethylcellulose or new manufacturing techniques not covered by the original patent.
Patent landscape mapping
| Patent Type |
Focus Area |
Year of Application |
Status |
Assignee |
| Original Patent |
Sustained-release theophylline formulation |
1982 |
Expired 2001 |
Abbott Laboratories |
| Follow-up Patents |
Modified formulations, manufacturing processes |
1983-1995 |
Active or expired |
Various (GSK, Boehringer) |
| New Formulation Patents |
Alternative polymers, combinations |
2002-2010 |
Active |
Multiple entities |
Overall, the patent landscape transitioned from the original formulation patent to a broader array of formulations and delivery technologies, with increased competition post-expiration.
What are the implications for current R&D and investment?
- The expiration of Patent 4,436,741 has led to extensive generic competition.
- Innovators focus on formulations using non-infringing polymers, such as ethylcellulose or novel excipients, to develop new extended-release products.
- Patent filings remain active around delivery devices, combination therapies, and targeted release systems, indicating ongoing innovation in the space.
Key Takeaways
- U.S. Patent 4,436,741 covers specific sustained-release formulations of theophylline using HPMC and PEG, with claims narrowly tailored around composition and manufacturing.
- The patent's expiration in 2001 has led to broad generic adoption and diversified patent filings, emphasizing alternative polymers and technologies.
- Current patent activity is concentrated on delivering more sophisticated or targeted controlled-release systems, often avoiding existing claims.
- The patent landscape reflects both the limitations of specific claims and the ongoing evolution of controlled-release drug delivery.
FAQs
1. Does Patent 4,436,741 cover all sustained-release theophylline formulations?
No, it specifically covers formulations containing hydroxypropyl methylcellulose and polyethylene glycol, with particular manufacturing methods.
2. Can companies develop new theophylline formulations without infringing this patent?
Yes. They can use different polymers (e.g., ethylcellulose), alternative delivery systems, or novel manufacturing processes.
3. Are there ongoing patents related to this patent?
Yes, especially patents related to alternative polymers, delivery devices, and combination therapies filed after 2001.
4. How does the patent landscape influence generic drug development?
Post-expiration, numerous generics have entered the market, utilizing formulations similar to the original patent claims.
5. What are current R&D trends for sustained-release respiratory drugs?
Focus on targeted release systems, non-polymer-based matrices, and combination formulations to improve efficacy and patient compliance.
References
[1] United States Patent and Trademark Office. (1984). U.S. Patent 4,436,741.
[2] Mazer, N., & Forges, T. (2010). Patent landscape review for sustained-release formulations. Journal of Pharmaceutical Innovation, 5(2), 78-89.
[3] Li, X., et al. (2015). Advances in controlled-release drug delivery systems. International Journal of Pharmaceutics, 478(1), 723-735.
