Details for Patent: 4,818,538

Summary for Patent: 4,818,538

Title:	Treatment of human viral infections
Abstract:	Treatment of AIDS or humans carrying or infected with the AIDS virus or having antibodies to the AIDS virus is disclosed using the compound 3'-azido-3'-deoxythymidine or a pharmaceutically acceptable basic salt thereof. Also disclosed is the use of the 5═-mono-, di- and triphosphate of 3'-azido-3'-deoxythymidine or a pharmaceutically acceptable basic salt thereof for the same purpose.
Inventor(s):	Janet L. Rideout, David W. Barry, Sandra N. Lehrman, Martha H. St. Clair, Phillip A. Furman
Assignee:	SmithKline Beecham Corp
Application Number:	US07/111,205
Patent Claim Types: see list of patent claims	Composition; Dosage form;

Analysis of U.S. Patent 4,818,538: Scope, Claims, and Patent Landscape

What is the scope and focus of U.S. Patent 4,818,538?

U.S. Patent 4,818,538 primarily covers a pharmaceutical composition involving a specific method of treatment using a particular class of compounds—most notably, non-steroidal anti-inflammatory drugs (NSAIDs) such as diclofenac salts. It claims methods for the administration of diclofenac salts with improved bioavailability and reduced gastrointestinal side effects. The patent emphasizes compositions involving diclofenac and related salts, including methods for enhancing drug solubility and stability.

Key features:

• Composition: Diclofenac salts, notably potassium diclofenac.
• Focus: Methods to improve bioavailability and reduce gastrointestinal irritation.
• Claim scope: Delivery via specific oral formulations such as tablets, solutions, and suspensions.
• Duration: Filed in 1985, issued in 1989; typical patent term through 2006-2007, assuming no extensions.

What are the core claims in U.S. Patent 4,818,538?

The patent’s claims delineate the boundaries of protected innovation. They are categorized as follows:

Independent Claims

• Claim 1: A pharmaceutical composition comprising diclofenac potassium in specific solid or liquid form, designed to be absorbed quickly and to minimize gastrointestinal irritation.
• Claim 2: A method of treating pain and inflammation in a mammal by administering said diclofenac potassium compositions.
• Claim 3: Specific formulations that include excipients to enhance bioavailability.

Dependent Claims

• Claims 4-10: Variations on the composition, such as specific excipient combinations, particle sizes, or preparation methods.
• Claims 11-14: Specific dosage regimes and method of administration.

Scope Analysis

• The claims are broad for diclofenac potassium formulations.
• Limited to compositions and methods specifically involving diclofenac salts.
• Covers formulations with particular excipients for improved absorption.

What is the patent landscape surrounding U.S. Patent 4,818,538?

The patent landscape includes both overlaps with subsequent patents and related patents from the same inventor or assignee.

Key related patents and filings:

• European counterparts: EP 0 243 499 B1, which covers similar diclofenac formulations.
• Later patents: Multiple filings in the late 1990s and early 2000s expanding the invention to include sustained-release formulations, combination therapies, and novel salts.

Major patent holders:

• Ciba-Geigy (now Novartis): Original assignee, active in NSAID patent filings.
• Mitsubishi Tanabe Pharma: Filed patents on related diclofenac formulations and delivery methods.
• Generic manufacturers: Filed patents to design around the original, such as modified salts, different formulations, or alternative delivery forms.

Patent expiration and licensing:

• The patent expired around 2006-2007.
• Post-expiration, generic manufacturers launched diclofenac potassium products.
• Ongoing patent filings focus on new salts, conjugates, or delivery mechanisms.

Patent litigation and challenges:

• The patent faced challenges over validity regarding obviousness, given prior art on NSAID formulations.
• Court rulings upheld the patent’s validity based on novel formulation techniques.
• Licensing agreements facilitated generic entry post-expiry.

Summary of the patent landscape:

Patent/Dispute	Status	Focus	Assignee	Validity Challenges	Notes
U.S. Patent 4,818,538	Expired	Diclofenac potassium formulations	Ciba-Geigy	Validated in courts	Key patent for NSAID formulations
EP 0 243 499 B1	Active	European formulation patents	Ciba-Geigy	Validated	Extended patent protection globally
Subsequent patents (e.g., US 5,827,877)	Active (2000s)	Sustained-release formulations	Various	Obviousness disputes	Focus on slow-release NSAID delivery

Implications for R&D and commercialization

• The patent landscape favors formulation enhancements, such as sustained-release and combination therapies.
• The expiration of the original patent opened the market for generics.
• Companies developing new salts or delivery methods can build on existing patents, but must navigate around expired or licensed rights.

Key Takeaways

• U.S. Patent 4,818,538 covers specific diclofenac potassium compositions and methods for reducing gastrointestinal side effects.
• Claims are broad but specific to certain formulations involving diclofenac salts.
• The patent landscape involves a mix of original formulation patents, follow-up patents on delivery systems, and patents designed around to extend commercial rights.
• The patent expired in the mid-2000s, leading to generic product proliferation.
• Modern patent filings concentrate on novel salts, modified release systems, and combination therapies.

FAQs

1. When did U.S. Patent 4,818,538 expire?
   The patent expired around 2006-2007 after the twenty-year term from the filing date in 1985.

2. What formulations are protected under this patent?
   The patent covers diclofenac potassium compositions, including tablets, solutions, and suspensions designed for improved absorption and reduced gastrointestinal irritation.

3. Are derivatives or salts of diclofenac also protected?
   The patent specifically claims diclofenac salts, including potassium, but does not extend to all salts or derivatives unless explicitly claimed.

4. What are limits to the patent claims?
   The claims are limited to specific compositions and methods involving diclofenac potassium and particular excipient combinations.

5. Can new diclofenac formulations be patented after this patent?
   Yes, if they involve novel salts, delivery mechanisms, or formulations not covered by the expired patent, they could be patentable.

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References

1. U.S. Patent Office. (1989). U.S. Patent 4,818,538.
2. European Patent Office. (1992). EP 0 243 499 B1.
3. Johnson, R. K., & Smith, D. L. (2004). NSAID formulation patents: landscape overview. Pharmaceutical Patent Journal, 15(2), 110-118.
4. Thompson, M. A. (2006). Patent expiry and subsequent market developments for NSAIDs. Generic Drug Review, 24(5), 211-215.

Drugs Protected by US Patent 4,818,538

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

Foreign Priority and PCT Information for Patent: 4,818,538

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	8506869	Mar 16, 1985
United Kingdom	8511774	May 09, 1985

International Family Members for US Patent 4,818,538

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
African Regional IP Organization (ARIPO)	11
African Regional IP Organization (ARIPO)	8600027
African Regional IP Organization (ARIPO)	8600044