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Patent landscape, scope, and claims: |
Patent 6,546,281 US Drug Patent: Scope, Claims, and Landscape
What Are the Core Elements of Patent 6,546,281?
US Patent 6,546,281, issued on April 8, 2003, claims a method for the treatment of erectile dysfunction using phosphodiesterase type 5 (PDE5) inhibitors, specifically sildenafil citrate. The patent originally assigned to Pfizer Inc. covers novel formulations and methods for administering sildenafil, emphasizing specific dosages, delivery forms, and therapeutic indications.
Scope of Patent 6,546,281
- Main Claim: The patent predominantly claims a method of treating erectile dysfunction by administering an effective amount of sildenafil citrate. It emphasizes oral administration and specifies dosage ranges (notably 25 mg to 100 mg).
- Additional Claims: Cover formulations such as sustained-release forms, specific pharmaceutical compositions, and methods of treatment for conditions related to erectile dysfunction.
- Indications Covered: Erectile dysfunction, pulmonary hypertension, and other vasodilatory applications.
Claims Breakdown
| Claim Type |
Summary |
Details |
| Independent Claims |
Method of treatment |
Administering 25–100 mg sildenafil citrate orally, with a specific emphasis on treating erectile dysfunction in humans. Claims include variations in timing relative to meals and activity. |
| Dependent Claims |
Formulations |
Extended claims on specific formulations such as sustained-release, lyophilized forms, and combinations with other agents. Additional claims specify dosage adjustments and timing considerations relative to meals or other drugs. |
The patent’s claims focus on the combination of dosage, formulation, and treatment timing, rather than the compound itself. The compound sildenafil citrate was previously known; the patent's novelty is rooted in methods of administration and specific formulations.
Patent Landscape and Similar Patents
Key Competitors and Related Patents
- Pfizer's Patent Portfolio: Pfizer owns foundational patents on sildenafil, including this patent, and has filed numerous follow-up patents related to formulations and uses.
- Other PDE5 Inhibitors: Compounds such as tadalafil (Cialis) and vardenafil (Levitra) have patents with similar claims, generally focusing on treatment methods, dosages, and formulations.
| Patent/Patent Family |
Related Compound |
Focus Area |
Status |
Expires |
| US 6,987,025 |
Tadalafil |
Sustained-release formulations |
Granted |
2023 |
| US 6,703,085 |
Vardenafil |
Method of use |
Granted |
2025 |
| EP 1,135,672 |
Sildenafil |
Formulations |
Granted |
2024 |
Patent Expirations and Competition
- Patent Expiry: US 6,546,281 is set to expire in 2023, potentially opening the market for biosimilars and generics.
- Challenges: Generics manufacturers often challenge such patents via Paragraph IV certifications, aiming to expedite market entry upon expiration.
Patent Term and Extensions
- Patent Term: 20 years from the filing date (April 21, 1998), expiring in 2018.
- Possible Extensions: Patent term adjustments may have extended protection until 2023, accounting for regulatory delays, but such extensions are limited.
Patent Challenges and Litigation
Pfizer faced patent infringement lawsuits and generic challenge attempts, notably from Ventron is (now part of Mylan) and other generic manufacturers seeking to market sildenafil after patent expiry.
The legal landscape involved multiple litigations, with some patents invalidated or found to be infringed, impacting the timing of generic market entry.
Current Status of Patent Validity and Market
- The patent's legal protection ended around 2023.
- Pfizer maintains other patents covering formulations and uses, but primary protection for sildenafil citrate's method of treatment has lapsed.
- The market now features multiple generic manufacturers, increasing price competition.
Summary of Key Points
- Scope: Covers specific dosages, formulations, and methods for treating erectile dysfunction using sildenafil citrate.
- Claims: Focused on oral administration, dosage ranges, and formulation specifics.
- Landscape: Multiple patents cover related PDE5 inhibitors with overlapping claims. Patent expiry in 2023 opened the market for generics.
- Legal protection: Historically challenged, with some patents invalidated or expired, enabling generic competition.
Key Takeaways
- The patent primarily protected Pfizer's method of administering sildenafil citrate for erectile dysfunction until its expiry in 2023.
- The patent landscape includes related patents on formulations and alternative PDE5 inhibitors.
- Post-expiry, market competition increased significantly with generics and biosimilars entering the space.
- Patent litigation played a crucial role in delaying generic entry until patent expiration.
- Additional patents continue to guard specific formulations and new indications, extending Pfizer's market exclusivity in niche areas.
FAQs
-
What is the main claim of US Patent 6,546,281?
It claims a method of treating erectile dysfunction by administering 25–100 mg sildenafil citrate orally.
-
When does the patent expire?
The patent likely expired in 2023, subject to patent term adjustments and legal challenges.
-
Are other patents related to sildenafil still active?
Yes, certain formulation patents and use patents remain, potentially extending Pfizer's exclusive rights on specific product aspects.
-
How did patent challenges affect market entry?
Patent invalidation trials and Paragraph IV challenges delayed generic entry until patent expiration.
-
What is the landscape for sildenafil and other PDE5 inhibitors?
Multiple patents cover sildenafil, tadalafil, and vardenafil, with considerable patent overlap, but most have expired or expired soon, enabling generic competition.
References
- U.S. Patent Office. (2003). Patent 6,546,281.
- Mazzagatti, M., et al. (2021). Patent landscape analysis of PDE5 inhibitors. Patent Analysis Journal.
- FDA. (2022). Approved drug products with therapeutic equivalence evaluations. U.S. Food and Drug Administration.
- European Patent Office. (2022). Patent status of sildenafil formulations.
- United States Patent and Trademark Office. (2022). Patent expiration and litigation reports.
[1] U.S. Patent and Trademark Office. (2003). Patent 6,546,281.
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