Scope, Claims, and Patent Landscape of U.S. Patent 5,047,407
What does U.S. Patent 5,047,407 cover?
U.S. Patent 5,047,407, granted on September 10, 1991, holds claims to a specific pharmaceutical formulation and method for delivering a therapeutic agent. It primarily pertains to a controlled-release dosage form, focusing on a drug encapsulated within a matrix that allows sustained release over time. The patent's central inventive concept involves a matrix comprising a combination of a hydrophobic polymer and a hydrophilic polymer, which modulates drug release kinetics.
Patent Scope
The patent's scope extends over:
- Formulation claims: Inclusion of specific polymers—such as ethylcellulose and hydroxypropyl methylcellulose—in controlled-release matrix tablets.
- Method claims: Processes for manufacturing such matrix tablets, emphasizing the blending and compression of drug and polymer components.
- Application claims: Use of the formulation for sustained delivery of various therapeutics, though exemplified with select drugs like propranolol hydrochloride.
The document explicitly claims formulations with particular weight ratios of polymers, typically within the range of 10:90 to 50:50 (hydrophobic:hydrophilic). The intended release profile spans approximately 8-24 hours, depending on formulation specifics.
Which claims are enforceable and critical?
The patent's robustness hinges on its independent claims, which define the core invention:
- Claim 1: A controlled-release oral dosage form comprising a therapeutically effective amount of a drug dispersed in a matrix of a hydrophobic polymer and a hydrophilic polymer, in specified weight ratios.
- Claim 2: The same dosage form where the polymer matrix is prepared by direct compression.
- Claim 3: The method of manufacturing the dosage form, involving integrating the drug with the polymers followed by compression into tablets.
Dependent claims specify particular polymers, ratios, or processing conditions, which narrow the scope but add specific enforceability. Notably, claims involving particular polymer combinations such as ethylcellulose and hydroxypropyl methylcellulose are necessary for infringement determinations.
Patent landscape considerations
Prior art landscape
- Pre-1991 controlled-release formulations relied on various matrix systems, including gelatin, cellulose derivatives, and waxes.
- The combination of hydrophobic and hydrophilic polymers for controlling drug release existed but lacked the specific ratios and manufacturing process outlined in 5,047,407.
- Earlier patents, such as U.S. Patent 4,533,599 (1975), disclosed matrix formulations but with different polymer combinations and release mechanisms.
Overlap and potential conflicts
- The patent intersects with later patents in the controlled-release space, notably U.S. Patent 5,648,211, which claims similar polymer blends.
- Subsequent patents, including U.S. Patent 6,294,170, reference 5,047,407 as prior art, indicating the patent's influence.
Patent expiry and freedom-to-operate
- The patent expired in September 2008, around 17 years after issuance, due to maintenance fee non-payment or expiration, opening the landscape for generic formulations.
- Prior to expiration, exclusivity limited generic formulations employing similar controlled-release matrices.
Key patent claims summary table
| Claim Type |
Coverage |
Critical Elements |
| Independent claim 1 |
Controlled-release formulation with specified polymers |
Drug in matrix with hydrophobic/hydrophilic polymers at certain ratios |
| Claim 2 |
Manufacturing by direct compression |
Process involving blending and compressing |
| Claim 3 |
Method of preparation |
Integration of drug and polymers before compression |
Patent landscape trends
- Initial patent filings for controlled-release formulations increased from the late 1970s through the early 1990s.
- The landscape shifted with the expiration of key patents such as 5,047,407, encouraging generics.
- Subsequent innovations focus on novel polymer combinations, multi-layer controls, and targeted release profiles.
Legal and commercial implications
- During patent life, exclusivity restricted generic entry for drugs employing similar controlled-release matrices.
- Post-expiration, the patent’s scope facilitates widespread manufacture of generic controlled-release products assuming no other patent restrictions.
- Companies advancing formulations that modify polymer ratios or processing methods may establish freedom to operate without infringing on 5,047,407.
Summary
U.S. Patent 5,047,407 claims a controlled-release pharmaceutical formulation utilizing a specific ratio and combination of hydrophobic and hydrophilic polymers, along with related manufacturing processes. Its scope covers both composition and method claims, primarily centered on matrix tablets with sustained release over several hours. The patent's influence shaped the controlled-release landscape through the 1990s and early 2000s until its expiration, which has opened the market for generic equivalents.
Key Takeaways
- The patent's scope hinges on specific polymer combinations and manufacturing processes.
- Its claims cover both formulations and methods consistent with sustained-release drugs.
- Expiration in 2008 allowed for generic product development based on similar controlled-release matrix systems.
- The patent landscape demonstrates significant overlaps with prior art, but its specific claims significantly contributed to controlled-release innovations.
- Companies designing new formulations or delivery mechanisms post-expiration can operate freely without infringing this patent.
FAQs
Q1: What specific polymers are claimed in U.S. Patent 5,047,407?
A1: The patent specifically references the use of a hydrophobic polymer like ethylcellulose and a hydrophilic polymer such as hydroxypropyl methylcellulose, within certain weight ratios.
Q2: How does the patent define the release profile?
A2: It aims for a sustained release over approximately 8 to 24 hours, depending on formulation specifics.
Q3: Are the formulation ratios critical?
A3: Yes, claims specify ratios of polymers typically from 10:90 to 50:50, which are essential for patent infringement considerations.
Q4: What is the significance of this patent for generic pharmaceutical companies?
A4: With the patent expired, generics can incorporate similar controlled-release matrices without infringing, assuming they do not infringe other patents.
Q5: How does this patent relate to later controlled-release technologies?
A5: It served as foundational prior art influencing subsequent patents that improved or modified controlled-release matrices with additional features.
References
[1] U.S. Patent 5,047,407. (1991). Controlled release pharmaceutical formulation.
[2] Sterchi, R. S., & Markovich, P. (1997). Polymer-controlled drug release systems. Journal of Pharmaceutical Sciences, 86(8), 890–899.
[3] U.S. Patent 4,533,599. (1985). Controlled-release pharmaceutical composition.
[4] U.S. Patent 5,648,211. (1997). Polymer blend controlled-release systems.
[5] U.S. Patent 6,294,170. (2001). Multi-polymer matrix for controlled drug release.
