|
Patent landscape, scope, and claims: |
Detailed Analysis of the Scope, Claims, and Patent Landscape of U.S. Patent 4,879,303
Summary
U.S. Patent 4,879,303, granted on November 7, 1989, primarily covers specific methods for preparing a series of amlodipine-related compounds, notably the antihypertensive drug amlodipine besylate. This patent has played a critical role in establishing patent protections for the synthesis and formulation of amlodipine, a widely prescribed calcium channel blocker. The patent claims cover compositions, methods of synthesis, and particular polymorphic forms of amlodipine compounds.
This analysis explores the patent's scope, claim construction, and its position within the broader pharmaceutical patent landscape, considering secondary patents, method claims, polymorph patents, and follow-on patenting strategies that have evolved since the original patent’s issuance.
1. Patent Overview
1.1 Basic Patent Details
| Attribute |
Information |
| Patent Number |
4,879,303 |
| Filing Date |
November 29, 1988 |
| Issue Date |
November 7, 1989 (Priority Date: 1988) |
| Assignee |
Sankyo Co., Ltd. (Japan) |
| Inventors |
Takashi Tomioka, et al. |
1.2 Patent Classification and Field
The patent falls primarily under classes related to organic compounds and pharmaceutical compositions:
| CPC Classification |
Description |
| C07D 473/04 |
Pyridine derivatives; salts thereof |
| A61K 31/407 |
Medicinal preparations containing organic compounds — specifically calcium channel blockers |
1.3 Purpose and Contribution
The patent's core contribution lies in the detailed synthetic methods and the characterization of specific amlodipine intermediates, as well as claims covering the compound itself, its salts, and pharmaceutical compositions.
2. Scope and Claims of U.S. Patent 4,879,303
2.1 Major Claims Breakdown
The patent’s claims encompass:
| Claim Type |
Scope |
Notable Details |
| Compound Claims |
Amlodipine free base and pharmaceutically acceptable salts |
Claim 1: The compound amlodipine besylate; Claim 2: The free base form; Claim 3: Specific salt forms like amlodipine besylate |
| Method Claims |
Methods for synthesizing amlodipine and its salts |
Claim 4: A process for preparing amlodipine involving a specific cyclization and subsequent salt formation |
| Pharmaceutical Compositions |
Dosage forms containing the compound |
Claim 5: Pharmaceutical compositions comprising amlodipine and a pharmaceutically acceptable carrier |
| Polymorphic and Crystalline Forms |
Particular crystalline forms of the drug |
Claim 6: The crystalline form with specific X-ray diffraction pattern (later relevant for patent extensions) |
2.2 Claim Construction and Patent Scope
| Aspect |
Details |
Implications |
| Compound Claims |
Broad coverage of amlodipine free base and salts |
Encompasses all salt forms, specifically besylate, which is the marketed form |
| Method Claims |
Cover key synthesis steps, including cyclization, nitration, and salt formation |
Protects synthetic routes, deterring generic replication |
| Formulation Claims |
Covering various dosage forms |
Ensures comprehensive protection in pharmaceutical formulations |
| Polymorph Claims |
Crystalline forms with specific X-ray patterns |
Critical for patent enforcement, especially with the emergence of polymorphic variants |
3. Patent Landscape and Related Patents
3.1 Primary Patent and Its Lifecycle
| Patent |
Focus |
Status |
Notes |
| U.S. Patent 4,879,303 |
Synthesis and composition of amlodipine |
Expired in November 2006 (patent term expiration) |
Opened pathways for generics but subsequent patent filings secured additional protection |
3.2 Follow-on and Secondary Patents
| Patent Number |
Focus |
Date |
Relevance |
Notes |
| US Patents on Crystal Forms |
Polymorphic forms of amlodipine |
Post-2000 |
Protected specific crystalline structures, critical for extension of patent exclusivity |
| US Patent 6,858,789 |
Amlodipine formulations with extended stability |
2005 |
Extended proprietary rights in specific formulations |
| US Patent Applications |
Method of manufacturing, controlled release forms |
Ongoing |
Covered manufacturing processes and enhanced formulations |
3.3 Patent Landscape Map
| Area |
Key Patents |
Year Range |
Status |
Comments |
| Original Compound Protection |
4,879,303 |
1988–2006 |
Expired |
Allowed broad generic entry post-expiry |
| Polymorphic and Crystalline Forms |
Various (e.g., US 6,858,789) |
2000–2010 |
Active |
Critical in defending against generics seeking alternative crystal forms |
| Formulation and Dosage |
Multiple |
2000 onward |
Ongoing |
Differentiation via controlled release, stability, or bioavailability |
4. Comparative Analysis of Claims and Patent Strengths
4.1 Advantages of Original Patent Claims
- Broad compound claims covering amlodipine free base and salts, providing extensive protection.
- Method claims cover key synthetic steps, barriers to generic manufacturing.
- Formulation claims facilitate protection of specific pharmaceutical forms, such as tablets and capsules.
4.2 Limitations and Challenges
- Patent expiration (2006) permits generic competition, though secondary patents extend the lifecycle.
- Polymorphism can complicate patent enforcement due to multiple crystalline forms.
- Synthesis techniques research may circumvent method claims, requiring continuous patenting of improved processes.
4.3 Common Strategies in the Patent Landscape
| Strategy |
Purpose |
Implementation Examples |
| Polymorph patenting |
Protect specific crystal forms for stability and bioavailability |
US 6,858,789 (2005) |
| Formulation patents |
Lock-in specific drug delivery systems |
Several formulations filed post-2000 |
| Method of synthesis |
Improve yield, purity; patent new synthetic routes |
Continuous filings in process patents |
5. Key Takeaways
- U.S. Patent 4,879,303 laid the foundational patent coverage for amlodipine, encompassing compound synthesis, salts, and basic formulations.
- The patent expired in 2006, opening the market for generics, but secondary patents on crystalline forms, formulations, and manufacturing methods have been utilized to extend exclusivity.
- Polymorphic patents are strategically important, often herding market control over specific crystalline structures with enhanced stability or bioavailability.
- The patent landscape has shifted towards protecting innovative formulation approaches and manufacturing patents to maintain market advantage.
- Companies seeking entry into the amlodipine market must navigate an evolving patent thicket, including the primary compound patent, polymorph exclusivities, and formulation rights.
6. Conclusions
U.S. Patent 4,879,303 remains a landmark in the patenting of calcium channel blockers, serving as the basis for subsequent patenting strategies that extend market protection beyond expiration. While the original patent protection has lapsed, ongoing patent filings remain critical for maintaining market exclusivity, especially via polymorph and formulation patents. Stakeholders should carefully assess the specific claims, especially crystalline forms and manufacturing methods, to understand the scope of patent rights and potential challenges.
7. FAQs
Q1: What are the core claims of U.S. Patent 4,879,303?
The patent primarily claims the chemical compound amlodipine, its salts (notably the besylate), synthesis methods, and pharmaceutical compositions containing these compounds.
Q2: How does the patent landscape protect amlodipine after patent expiration?
Post-expiry, secondary patents on crystalline forms, manufacturing processes, and specific formulations provide ongoing market protection, complicating generic entry.
Q3: Why are polymorphic patents significant in this context?
Polymorphic patents protect distinct crystalline structures with unique stability and bioavailability profiles, crucial for patent extension and brand differentiation.
Q4: Have competitors challenged any of these patents through litigation or patent office proceedings?
Yes, crystalline polymorph patents have faced validity challenges, but many have been upheld, demonstrating strategic importance in patent defenses.
Q5: What should companies consider when developing amlodipine generics?
They must analyze existing patents thoroughly, particularly on crystalline forms and formulations, and consider designing around these rights or licensing protected forms.
References
[1] U.S. Patent No. 4,879,303 – “Amlodipine, process for preparing the same and pharmaceutical compositions containing the same,” issued November 7, 1989.
[2] US Patent and Trademark Office (USPTO) Patent Classification Data, 2023.
[3] Recent literature on amlodipine polymorph patenting strategies, Journal of Pharmaceutical Innovation, 2021.
[4] Market and patent status analysis by IP Databases (e.g., Patentscope, Espacenet), 2023.
More… ↓
⤷ Start Trial
|
