US Patent 6,010,718: Scope, Claim Analysis, Expiration, and Clarithromycin Extended-Release Patent Landscape

US Patent 6,010,718 covers oral extended-release pharmaceutical compositions containing an erythromycin derivative and a pharmaceutically acceptable polymer. The commercial relevance is concentrated in extended-release clarithromycin, including the formulation associated with Biaxin XL. The patent issued January 4, 2000 and reached the end of its standard 20-year patent term in 2017, based on its 1997 US filing and 1996 priority date. It is therefore expired and does not currently block generic manufacture or sale in the United States.

The patent’s strongest technical concept is the combination of a hydrophilic polymer matrix and a defined pharmacokinetic profile: lower peak concentrations and reduced plasma fluctuation while preserving exposure, minimum concentrations, and substantially equivalent bioavailability relative to an immediate-release formulation.

What does US Patent 6,010,718 cover?

The patent covers extended-release compositions and treatment methods for erythromycin derivatives, with the principal commercial embodiment being clarithromycin formulated with hydroxypropylmethyl cellulose, or HPMC.

Its claim architecture has four layers:

Broad composition claims based on extended-release pharmacokinetics.
Polymer-class claims directed to hydrophilic, water-soluble polymers.
Narrow formulation claims directed to HPMC concentration and viscosity.
A clarithromycin-specific composition claim.

The patent does not claim clarithromycin as a molecule. It claims a dosage-form technology for controlling release of an erythromycin derivative in the gastrointestinal tract.

Key patent data

Field	Data
Patent	US 6,010,718
Title	Extended release pharmaceutical compositions
Patent type	US utility patent
Filing date	1997
Earliest priority	1996
Issue date	January 4, 2000
Likely standard expiration	2017
Principal commercial product	Extended-release clarithromycin
Relevant formulation technology	Hydrophilic polymer matrix
Key polymer	Hydroxypropylmethyl cellulose
Key viscosity range	About 50 to about 200 cps
Narrowest disclosed viscosity	About 100 cps
Key polymer loading	About 10% to about 30% in the narrower claims
Key active loading	About 50% clarithromycin in the narrowest claim
Current US status	Expired

The expiration analysis assumes the patent’s ordinary 20-year term from the earliest effective US nonprovisional filing and no material patent-term adjustment or extension. Patent-term calculations should be confirmed against the USPTO Patent Center record and any terminal disclaimer history.

How broad are the independent claims?

Claims 1, 4, 5, and 6 are independent claims. They protect different legal theories and have materially different vulnerability profiles.

Claim 1: composition with reduced fluctuation

Claim 1 requires:

An erythromycin derivative.
About 5% to about 50% by weight of a pharmaceutically acceptable polymer.
Oral extended release in the gastrointestinal environment.
A statistically significantly lower mean fluctuation index than an immediate-release composition.
Bioavailability substantially equivalent to the immediate-release comparator.

The claim is broad in its ingredient selection. “Erythromycin derivative” can encompass several derivatives, while “pharmaceutically acceptable polymer” is not limited to HPMC. The claim becomes narrower through its pharmacokinetic limitations.

The fluctuation-index limitation is important. A composition that releases drug more slowly is not necessarily within claim 1 unless the accused product produces the required statistically significant reduction in mean fluctuation index against the specified immediate-release comparator.

Potential claim-construction issues include:

The identity of the immediate-release comparator.
The meaning of “statistically significantly lower.”
The study design, sample size, and statistical test required.
The meaning of “substantially equivalent” bioavailability.
Whether the polymer percentage is calculated against total composition weight.

These limitations can make infringement dependent on clinical or pharmacokinetic testing rather than ingredient comparison alone.

Claim 4: lower peak concentration with preserved exposure

Claim 4 requires:

An erythromycin derivative.
About 5% to about 50% polymer.
Lower maximum plasma concentration than an immediate-release composition.
Substantially equivalent area under the curve.
Substantially equivalent minimum plasma concentration.

Compared with claim 1, claim 4 replaces the fluctuation-index requirement with a Cmax limitation and expressly requires comparable AUC and Cmin. The claim targets a product profile in which the extended-release formulation smooths exposure without materially reducing total systemic exposure or trough concentration.

A generic product could avoid infringement if it has the required polymer composition but does not meet the claimed comparative PK relationships. Conversely, a product with similar PK behavior could face risk even if its manufacturing process and excipient supplier differ.

Claim 5: method of treatment

Claim 5 covers administering an extended-release composition containing:

An erythromycin derivative.
A pharmaceutically acceptable polymer.
An amount effective to treat bacterial infection in a mammal.
AUC substantially equivalent to the immediate-release formulation.

This is a method-of-use claim rather than a pure composition claim. It requires an administration step and treatment of bacterial infection. It also lacks the express 5% to 50% polymer range found in several composition claims.

Before expiration, claim 5 could have supported a method-of-use infringement theory against commercial administration or instructions for treating bacterial infection. The claim would have been less useful against a product sold without a bacterial-infection indication unless induced infringement could be established through labeling, promotional activity, or other evidence.

Claim 6: improved taste

Claim 6 covers an extended-release composition containing an erythromycin derivative and a pharmaceutically acceptable polymer, where the product has an improved taste profile compared with the immediate-release formulation.

This claim has no express polymer percentage, specific polymer, PK requirement, or clarithromycin limitation. Its breadth is offset by the potentially difficult evidentiary question of what constitutes an “improved taste profile.”

Taste comparison could require:

A defined immediate-release comparator.
A reproducible sensory-testing protocol.
Evidence that the improvement results from the claimed extended-release composition.
Proof that the improvement is more than an unsubstantiated formulation preference.

The claim could have been commercially relevant for pediatric or swallowability-sensitive products, but its current enforceability ended with patent expiration.

What formulations are protected by the dependent claims?

The dependent claims progressively identify a preferred hydrophilic polymer matrix, particularly low-viscosity HPMC.

Claim	Limitation
2	Hydrophilic, water-soluble polymer
3	Polymer selected from specified polymer classes and mixtures
7	HPMC
8	HPMC viscosity of about 50 to about 200 cps
9	HPMC viscosity of about 100 cps
10	Polymer concentration of about 5% to about 45%
11	Erythromycin derivative concentration of about 45% to about 60%
12	About 50% erythromycin derivative
13	Polymer concentration of about 10% to about 30%
14	About 10% to about 30% HPMC at about 100 cps
15	Clarithromycin
16	About 50% clarithromycin

Claim 3 polymer scope

Claim 3 identifies:

Polyvinylpyrrolidone.
Hydroxypropyl cellulose.
Hydroxypropylmethyl cellulose.
Methyl cellulose.
Vinyl acetate/crotonic acid copolymers.
Methacrylic acid copolymers.
Maleic anhydride/methyl vinyl ether copolymers.
Derivatives and mixtures.

The claim language appears to use “polyvinylpyrrolidine,” while the conventional excipient name is polyvinylpyrrolidone. That discrepancy could have created a claim-construction or prosecution-history issue, depending on the issued patent text, specification, prosecution record, and whether the term was treated as an obvious typographical error.

Claims 7 through 9: HPMC viscosity

Claims 7 through 9 narrow the polymer to HPMC and then to a low-viscosity range. The 100-cps limitation in claim 9 is particularly specific. A formulation using HPMC outside the 50-to-200-cps range would not literally satisfy claim 8 or claim 9, although the doctrine of equivalents could have been relevant before expiration.

Viscosity must be measured under a defined testing method. HPMC grades are commonly identified by nominal viscosity, but temperature, concentration, shear, and measurement protocol can affect the result. An infringement analysis would need to compare the accused excipient’s technical specification and actual measured viscosity with the patent’s intended measurement conditions.

Claims 10 through 16: composition windows

The narrowest commercial-style formulation is claim 16:

Clarithromycin.
About 50% by weight.
With the limitations inherited through claims 15, 14, 13, 10, and 2.

That claim effectively targets a clarithromycin matrix tablet containing approximately 10% to 30% HPMC with a viscosity of approximately 100 cps and approximately 50% clarithromycin.

The ranges overlap in ways that require careful claim interpretation. For example, claim 10 allows 5% to 45% polymer, while claim 13 narrows that range to 10% to 30%. Claim 11 allows 45% to 60% erythromycin derivative, and claim 12 narrows it to about 50%.

How does the patent protect extended-release pharmacokinetics?

The patent uses comparative pharmacokinetic performance as a central claim boundary.

PK parameter	Claimed relationship
Mean fluctuation index	Statistically significantly lower than immediate release, claim 1
Cmax	Lower than immediate release, claim 4
AUC	Substantially equivalent to immediate release, claims 1, 4, and 5
Cmin	Substantially equivalent to immediate release, claim 4
Bioavailability	Substantially equivalent to immediate release, claim 1

This structure distinguishes the invention from a simple sustained-release product that reduces exposure. The claimed product must maintain overall exposure while modifying the shape of the concentration-time curve.

The phrase “substantially equivalent” is not identical to the FDA’s formal bioequivalence standard under 21 C.F.R. § 320. It is a patent claim term interpreted in context, although FDA bioequivalence studies could provide relevant evidence. A product can be FDA-bioequivalent yet still raise a separate patent issue if the patent’s claimed PK relationship is broader or differently defined than the regulatory endpoint.

What was the FDA and Orange Book status?

The commercial reference product associated with this patent was Biaxin XL, an extended-release clarithromycin product marketed by Abbott Laboratories. Clarithromycin is a macrolide antibacterial and a semisynthetic erythromycin derivative.

FDA regulatory relevance included:

Immediate-release clarithromycin products marketed as Biaxin.
Extended-release clarithromycin tablets marketed as Biaxin XL.
ANDA-based generic competition after applicable regulatory exclusivity and patent barriers ended.
Orange Book patent listing analysis for the extended-release product.

The Orange Book separates regulatory exclusivity from patent protection. A listed patent can delay approval of an ANDA through a Paragraph IV dispute, but an expired patent no longer provides a live statutory bar to approval or commercial launch. Current Orange Book status should be read together with Drugs@FDA product history and the patent’s USPTO term record. FDA, Approved Drug Products with Therapeutic Equivalence Evaluations, is the controlling public source for listed patents and exclusivity data (FDA, 2024a, 2024b).

When did US Patent 6,010,718 lose exclusivity?

US Patent 6,010,718 lost ordinary patent exclusivity in 2017. The likely expiration date was May 22, 2017, based on the 1996 priority date and the 20-year US patent term framework.

The exclusivity timeline was approximately:

Event	Timing
Earliest priority filing	1996
US application filing	1997
Patent issued	January 4, 2000
Biaxin XL commercial period	Early 2000s onward
Standard patent expiration	2017
Post-expiration status	Generic competition legally permitted, subject to other live rights

Regulatory exclusivity may have expired earlier than the patent. Pediatric exclusivity, if granted for a relevant product, would have added six months to applicable FDA exclusivity or patent-related periods, but it would not ordinarily extend the patent beyond its statutory term unless the extension attached to an eligible patent under the Hatch-Waxman framework.

Which companies challenged the patent?

The best-known litigation involving this patent was Abbott Laboratories’ dispute with Andrx Pharmaceuticals concerning generic extended-release clarithromycin. The Federal Circuit addressed the patent in Abbott Laboratories v. Andrx Pharmaceuticals, Inc., 452 F.3d 1331 (Fed. Cir. 2006).

The litigation illustrates the commercial risk profile of this patent:

Generic applicants had to evaluate both formulation composition and comparative PK.
Abbott relied on the patent to protect the extended-release clarithromycin product.
The dispute involved claim interpretation and infringement issues relevant to an ANDA product.
The patent was commercially significant during the period before its 2017 expiration.

A Paragraph IV certification against a listed patent could trigger a 30-month stay under 21 U.S.C. § 355(j)(5)(B)(iii), subject to the statutory conditions and litigation timing. Once the patent expired, that patent no longer supported a 30-month stay or a continuing injunction against launch.

No current Paragraph IV threat based solely on US 6,010,718 is viable because the patent is expired. Later patents, formulation patents, process patents, or patents covering a different clarithromycin dosage form would require separate analysis.

What other patents formed the clarithromycin extended-release landscape?

The relevant landscape included several categories of rights rather than a single patent.

Core formulation patents

US 6,010,718 is the principal patent identified with the extended-release erythromycin-derivative formulation concept. Related Abbott patent families may have addressed:

Specific clarithromycin extended-release compositions.
Tablet manufacturing and matrix formation.
Release-control excipients.
Dosing regimens.
Packaging or product-specific features.

A related patent should not be assumed to share the same expiration date. Continuations, divisionals, terminal disclaimers, and later-filed improvements can have different terms.

Method-of-use patents

Method claims could cover treatment of bacterial infections using extended-release clarithromycin. Such claims are narrower than composition claims because they require a treatment method and a relevant therapeutic use.

Manufacturing and process barriers

A generic manufacturer could design around the listed polymer by using:

A different hydrophilic polymer.
A multilayer tablet.
A coating-controlled system.
A different viscosity grade.
A different active-to-polymer ratio.
A nonmatrix release-control technology.

Those approaches would not automatically avoid infringement. The analysis would require mapping each product element to the issued claims and testing whether the resulting PK profile falls within claims 1 or 4.

Geographic coverage

US 6,010,718 provides protection only in the United States. Foreign counterparts may have existed in Europe, Canada, Japan, and other markets, but each jurisdiction required separate validity, prosecution, and expiration analysis. Foreign patent rights would not create a US launch barrier after the US patent expired.

How strong was the patent estate?

The estate was commercially meaningful before expiration but had mixed legal characteristics.

Strengths

It claimed both composition and treatment methods.
It connected formulation structure to measurable PK performance.
The narrower claims identified commercially realistic clarithromycin/HPMC embodiments.
The patent was listed and litigated in the ANDA context.
The claims addressed a practical distinction between immediate release and extended release: lower peaks without materially reduced exposure.

Weaknesses

The independent claims rely on functional and comparative PK limitations.
“Substantially equivalent” and “improved taste profile” can create proof and claim-construction disputes.
The polymer ranges are broad and may overlap known matrix-formulation practice.
The invention’s obviousness exposure would likely focus on combining known clarithromycin formulations with conventional hydrophilic polymers and routine PK optimization.
The claim set does not protect the clarithromycin molecule itself.
Expiration eliminates current enforcement value.

Patent strength is therefore historical rather than current. The patent could have supported meaningful exclusion during the protected period, but it is no longer an enforceable barrier to a properly approved generic product.

What generic launch risks remain after expiration?

The expired patent itself presents no current launch risk. Residual risk could arise from separate rights or regulatory conditions, including:

Later-expiring formulation patents.
Patents covering a particular manufacturing process.
Patents covering a distinct dosage regimen.
Trade secrets involving manufacturing parameters.
Product-specific trademarks and trade dress.
FDA requirements for ANDA approval and therapeutic equivalence.
Drug shortage, supply, or manufacturing compliance issues.

A generic clarithromycin extended-release product would generally face a lower intellectual-property barrier if it avoids all unexpired patents and satisfies FDA requirements. The key technical design-around strategies are changing the polymer system, viscosity grade, release mechanism, or composition ratio while demonstrating acceptable release and bioequivalence.

Key Takeaways

US 6,010,718 covers extended-release erythromycin-derivative compositions, especially clarithromycin matrix formulations using hydrophilic polymers.
The central claims require reduced peak or plasma fluctuation while preserving AUC, Cmin, or overall bioavailability relative to immediate release.
The narrowest commercial embodiment is approximately 50% clarithromycin with 10% to 30% HPMC at approximately 100 cps.
Claims 1, 4, and 5 depend heavily on comparative pharmacokinetic evidence.
Claim 6 addresses improved taste but has potentially difficult proof requirements.
Abbott’s litigation with Andrx demonstrates the patent’s historical Hatch-Waxman significance.
The patent’s standard US term ended in 2017.
US 6,010,718 is expired and cannot independently block a current generic launch.
Current risk must be assessed against later patents, Orange Book listings, FDA approval requirements, and manufacturing-related IP.

FAQs

Is US Patent 6,010,718 still enforceable?

No. The patent reached the end of its ordinary US patent term in 2017 and no longer provides an enforceable patent exclusion right.

Does the patent cover all extended-release clarithromycin tablets?

No. It covers products meeting the issued claim limitations, including polymer content and, for several claims, specified comparative PK performance. A different extended-release technology may fall outside the claims.

Does using HPMC automatically infringe the patent?

No. HPMC is only one claim limitation. Infringement would require satisfaction of all limitations in an applicable claim, including concentration, viscosity, active identity, and applicable PK requirements.

Can a generic launch after expiration without addressing this patent?

Yes, because the patent is expired. The applicant must still address any other unexpired patents, FDA requirements, labeling restrictions, and applicable Orange Book certifications.

What is the most commercially important claim?

Claim 16 is the most commercially specific because it identifies approximately 50% clarithromycin in the narrower HPMC formulation inherited from claims 14 and 15. Claims 1 and 4 are broader and potentially more important for products with comparable extended-release PK performance.

References

Abbott Laboratories. (2000). Extended release pharmaceutical compositions (U.S. Patent No. 6,010,718). U.S. Patent and Trademark Office.
Abbott Laboratories v. Andrx Pharmaceuticals, Inc., 452 F.3d 1331 (Fed. Cir. 2006).
U.S. Food and Drug Administration. (2024a). Approved drug products with therapeutic equivalence evaluations. FDA.
U.S. Food and Drug Administration. (2024b). Drugs@FDA: FDA-approved drugs. FDA.
U.S. Patent and Trademark Office. (2024). Patent term adjustment and patent term extension. USPTO.
21 C.F.R. § 320.1 et seq. (2024).
21 U.S.C. § 355(j) (2024).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	012358	⤷ Start Trial
Argentina	026045	⤷ Start Trial
Austria	253371	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,010,718

Summary for Patent: 6,010,718