United States Patent 6,025,389: Calcium Mupirocin Cream Claims, Expiration, and Patent Landscape

US 6,025,389 covers a specific topical calcium mupirocin cream formulation and methods of treating bacterial infection with that formulation. The patent issued February 15, 2000, and its standard 20-year term expired in January 2017, based on the January 21, 1997 effective U.S. filing date. The patent therefore does not create a current U.S. patent barrier to generic calcium mupirocin cream development.

The claims are narrow composition claims. They require the listed ingredients, approximate concentrations, and a topical pharmaceutical or veterinary composition. The method claims do not independently cover mupirocin treatment. They are limited to applying the patented formulation.

What does US Patent 6,025,389 protect?

The patent protects a water-in-oil or emulsion-type topical composition containing calcium mupirocin, mineral oil, polyethylene glycol monocetyl ether, fatty alcohols, preservatives, xanthan gum, and purified water.

Core claim limitations

Element	Claim requirement
Calcium mupirocin	About 2.4% by weight
Mineral oil USP	About 50.9% by weight
Polyethylene glycol monocetyl ether	About 6% by weight
Stearyl alcohol	About 3.5% by weight
Cetyl alcohol	About 3.5% by weight
Phenoxyethanol	About 0.5% by weight
Benzyl alcohol	About 1% by weight
Xanthan gum	About 0.2% by weight
Purified water	About 32% by weight
Composition type	Pharmaceutical or veterinary composition
Disease use	Treatment of bacterial infection
Narrower active form	Calcium mupirocin dihydrate

The stated percentages total approximately 100%. Claim 1 uses the transition term “comprising,” which generally permits additional ingredients unless they materially alter the claimed composition or defeat another claim limitation. The claim nonetheless requires every listed component in approximately the claimed amount.

How do the four issued claims differ?

Claim 1: Formulation claim

Claim 1 is the principal composition claim. A potentially infringing product would need to contain:

Calcium mupirocin;
Each of the eight specified excipient components;
The claimed approximate concentration for each component; and
A pharmaceutical or veterinary use.

A product containing calcium mupirocin but omitting xanthan gum, benzyl alcohol, or polyethylene glycol monocetyl ether would not literally satisfy claim 1. The same is true for a formulation using materially different quantities.

The claim does not expressly require a cream, ointment, tube, package size, pH, viscosity, particle size, manufacturing process, or treatment site. Those characteristics may be relevant to infringement analysis, but they are not explicit claim limitations.

Claim 2: Treatment method using the claim 1 composition

Claim 2 covers applying a therapeutically effective amount of the claim 1 composition to a subject requiring treatment for bacterial infection.

The method is narrower than a general method-of-use claim for mupirocin. It requires use of the complete formulation claimed in claim 1. A physician or patient using a different mupirocin formulation would not literally practice claim 2.

Claim 3: Dihydrate limitation

Claim 3 narrows claim 1 by requiring the calcium mupirocin to be calcium mupirocin dihydrate. It retains all formulation limitations from claim 1.

Claim 3 provides a more specific product claim than claim 1, but it does not expand the protected formulation space. A formulation using an anhydrous or different solid form could fall outside the literal scope of claim 3, subject to the facts and any doctrine-of-equivalents analysis.

Claim 4: Treatment method using the dihydrate formulation

Claim 4 narrows claim 2 and requires application of the claim 3 composition. It is the most specific method claim in the patent.

How strong is the patent estate for the calcium mupirocin cream?

The U.S. patent estate is narrow in claim scope and expired in 2017. During its term, the patent could have been commercially significant because the claims track a finished dosage-form composition rather than only the active ingredient.

Scope strengths

The patent had several practical strengths during its enforceable period:

It claimed the complete commercial-style formulation rather than an isolated laboratory intermediate.
It included multiple excipients that could make design-around development more difficult.
It included both product claims and treatment-method claims.
The “about” language may have provided some tolerance around the stated percentages.
The “comprising” language may have allowed additional excipients in an accused product.

Scope weaknesses

The claims also had substantial design-around vulnerabilities:

The formulation required a relatively specific excipient combination.
Every listed ingredient was a potential point of noninfringement.
The claims did not broadly cover all topical mupirocin creams.
The claims did not cover mupirocin calcium as a chemical compound generally.
The claims did not expressly claim a manufacturing process.
The method claims depended on use of the narrowly defined composition.

A competitor could seek a noninfringing formulation by changing one or more excipients, replacing mineral oil, modifying the emulsifier system, eliminating xanthan gum, using a different preservative system, or materially changing the concentration profile.

When did US 6,025,389 expire?

US 6,025,389 expired in January 2017 under the ordinary patent-term calculation based on its January 21, 1997 U.S. filing date. The patent issued in 2000, but the relevant term was generally measured from the effective nonprovisional filing date rather than the issue date under the post-1995 U.S. patent-term regime. [1]

Event	Date
Effective U.S. filing date	January 21, 1997
Patent issued	February 15, 2000
Standard 20-year expiration	January 21, 2017
Current status	Expired

The expiration date should be distinguished from FDA exclusivity. Patent expiration permits patent-based generic entry, but FDA approval, labeling, manufacturing, and product-specific regulatory requirements remain separate issues.

What was the FDA and Orange Book status?

US 6,025,389 was associated with the Bactroban Cream product containing mupirocin calcium. Bactroban Cream was approved under an NDA for topical treatment of bacterial skin infections, including impetigo-related indications reflected in product labeling. [2]

The Orange Book historically listed patent information for approved mupirocin calcium products. Orange Book listing does not itself prove that every formulation or method claim is valid or enforceable. It identifies patents submitted by the NDA holder and provides the regulatory patent reference used in the abbreviated approval process. [3]

FDA pathway

For a generic calcium mupirocin cream, the likely regulatory pathway is an abbreviated new drug application under section 505(j) of the Federal Food, Drug, and Cosmetic Act, assuming the reference product and dosage form support an ANDA pathway. The applicant would generally need to address:

Pharmaceutical equivalence;
Active ingredient and salt form;
Dosage form and route;
Strength;
Inactive ingredients;
Product quality and microbiological controls;
Bioequivalence or comparative performance requirements; and
Listed patents and exclusivities.

The product is a small-molecule topical drug. It is not a biologic and does not use the biosimilar pathway under the Public Health Service Act.

Did the patent create Paragraph IV risk?

During the patent term, an ANDA applicant seeking approval before January 2017 could have filed a Paragraph IV certification asserting that the patent was invalid, unenforceable, or not infringed. A Paragraph IV certification can trigger patent litigation under Hatch-Waxman procedures if the NDA holder brings suit within the statutory period. [4]

The patent’s narrow formulation scope created two principal Paragraph IV strategies:

Argue that the proposed product did not contain one or more required ingredients or concentrations.
Challenge validity based on anticipation, obviousness, written description, enablement, or indefiniteness.

Because the patent has expired, a current applicant no longer needs to overcome the patent through a Paragraph IV certification to obtain launch rights. Any remaining regulatory requirements are separate from the expired patent.

No current generic launch is blocked by US 6,025,389. Historical litigation or settlement rights cannot extend the expired patent term.

What generic launch scenarios exist?

Launch after patent expiration

The principal current scenario is a conventional generic launch after satisfaction of FDA requirements. A manufacturer can pursue a formulation that is pharmaceutically equivalent to the reference product or a product that relies on a different formulation pathway where permitted by FDA requirements.

Formulation design-around

A manufacturer may avoid the expired patent’s historical claim scope by using:

A different oil phase;
A different emulsifier;
Alternative fatty alcohol concentrations;
A different preservative system;
No xanthan gum or a substitute rheology modifier;
A different calcium mupirocin concentration; or
A different solid-state or hydration form, where pharmaceutically and regulatorily acceptable.

The expiration of the patent eliminates infringement risk under these claims, but formulation changes can still affect equivalence, stability, delivery, preservative effectiveness, and clinical performance.

Authorized or licensed launch

A commercial party could also launch through a license, acquisition, supply agreement, or authorized-generic arrangement. The patent record does not establish a continuing license requirement after expiration. Any historical relationship between the originator and a generic manufacturer would need to be evaluated from transaction and regulatory records rather than inferred from the patent.

What formulation and manufacturing barriers remain?

Patent expiration does not eliminate technical barriers. The formulation contains a high mineral-oil fraction, water, fatty alcohols, a nonionic surfactant, xanthan gum, and preservatives. A developer would need to control:

Emulsion stability;
Uniform calcium mupirocin distribution;
Phase separation;
Preservative effectiveness;
Microbial limits;
Viscosity and spreadability;
Tube or container compatibility;
Chemical stability;
Particle-size distribution; and
Batch-to-batch content uniformity.

The patent claims do not expressly cover a manufacturing method. A process patent or trade-secret manufacturing process could create a separate barrier, but US 6,025,389 itself does not provide such protection.

What geographic protection does the patent provide?

US 6,025,389 provided rights only in the United States. It could support exclusion of unauthorized making, using, selling, offering for sale, or importing of the claimed invention in the United States during its enforceable term.

The U.S. expiration date does not determine the status of corresponding foreign applications or patents. Foreign rights require separate family-level review, including national filing dates, patent-term adjustments, supplementary protection certificates, national litigation, and local regulatory exclusivity.

How does this patent compare with broader mupirocin patents?

Protection category	US 6,025,389
Mupirocin molecule generally	Not claimed
Mupirocin calcium generally	Not claimed broadly
Specific topical cream formulation	Claimed
Calcium mupirocin dihydrate formulation	Claimed in dependent claim 3
General bacterial-infection treatment with mupirocin	Not claimed broadly
Treatment with the specified formulation	Claimed
Manufacturing process	Not expressly claimed
Packaging or delivery device	Not claimed
Current enforceability	Expired

The patent should therefore be classified as a formulation and formulation-use patent, not as a foundational active-ingredient patent.

What is the current commercial risk?

The current patent risk from US 6,025,389 is zero as an exclusionary patent risk because the patent has expired. The commercial issues are now regulatory and technical:

Whether an FDA-approved reference product supports the intended ANDA route;
Whether the proposed product meets topical bioequivalence requirements;
Whether the formulation can be manufactured consistently;
Whether other unexpired patents cover the proposed product or process;
Whether trademarks, trade dress, or labeling rights create separate restrictions; and
Whether the originator retains meaningful market share or distribution advantages.

Revenue exposure from this patent is therefore historical. During the patent term, the patent could have supported premium pricing for Bactroban Cream and delayed formulation-specific generic competition. After expiration, it no longer supports exclusivity or royalty claims by itself.

Key Takeaways

US 6,025,389 covers a specific calcium mupirocin topical formulation.
Claim 1 requires all listed ingredients in approximately the stated percentages.
Claims 2 and 4 cover treatment methods only when the claimed formulation is applied.
Claim 3 narrows the formulation to calcium mupirocin dihydrate.
The patent’s standard term expired in January 2017.
It is not a current barrier to generic calcium mupirocin cream entry.
The patent does not broadly claim mupirocin, calcium mupirocin, all mupirocin creams, or a manufacturing process.
Current development risk is centered on FDA requirements, formulation performance, other patent families, manufacturing controls, and market access.
Biosimilar analysis is inapplicable because mupirocin is a small-molecule antibacterial drug.

FAQs About US 6,025,389 and Calcium Mupirocin

Is US 6,025,389 still enforceable?

No. Its standard U.S. patent term expired in January 2017.

Does the patent cover all mupirocin cream products?

No. It covers a specific composition containing the listed ingredients and approximate concentrations.

Can a generic company use calcium mupirocin dihydrate today?

Yes, subject to FDA approval requirements and any other unexpired patents or regulatory restrictions. US 6,025,389 itself no longer blocks use.

Was Bactroban Cream protected by a biosimilar exclusivity period?

No. Bactroban Cream contains the small-molecule drug mupirocin calcium and is regulated through the small-molecule drug framework, not the biosimilar pathway.

Does patent expiration guarantee immediate generic approval?

No. Expiration removes the patent exclusion, but FDA approval, product quality, equivalence, manufacturing, labeling, and any other unexpired rights still apply.

References

U.S. Patent and Trademark Office. (2000). U.S. Patent No. 6,025,389, Mupirocin compositions.
U.S. Food and Drug Administration. (n.d.). Bactroban Cream prescribing information.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations (Orange Book).
U.S. Food and Drug Administration. (2017). ANDA submissions: Content and format of an ANDA.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	9321876	Oct 22, 1993
United Kingdom	9322288	Oct 29, 1993

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
African Regional IP Organization (ARIPO)	608	⤷ Start Trial
African Regional IP Organization (ARIPO)	9600798	⤷ Start Trial
Austria	202467	⤷ Start Trial
Australia	692486	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,025,389

Summary for Patent: 6,025,389