US Patent 6,337,090: Ribavirin Formulation Claims, Patent Scope, and Generic Entry Analysis

US Patent 6,337,090 covers orally administered, compacted ribavirin dosage forms defined primarily by dissolution, disintegration, density, excipient, dose, and polymorph limitations. The patent was issued in 2002 and its enforceable term has expired. It therefore presents no current U.S. exclusivity barrier to ribavirin tablets or capsules. Its principal commercial relevance is historical: it attempted to protect fast-dissolving solid ribavirin formulations rather than ribavirin as an active ingredient.

The supplied versions of claims 4 and 11 are incomplete because the composition limitations following “comprising” are missing. Their full scope cannot be determined from the text provided. The remaining claims support a reliable analysis of the patent’s claim architecture and likely design-around paths.

What does US Patent 6,337,090 protect?

The patent protects a compacted oral ribavirin composition that satisfies specified pharmaceutical-performance criteria. The central limitation is that more than approximately 80% of the ribavirin dissolves in water within approximately 30 minutes.

The patent is therefore a formulation patent, not a basic compound patent. Its claims require a combination of:

Ribavirin;
A solid, orally administrable dosage form;
A compacted composition;
At least one pharmaceutical disintegrant in the principal claim sets; and
A dissolution result, with additional claims directed to density, disintegration time, polymorphic form, dose, excipient identity, and tablet or capsule presentation.

Claim architecture

Claim group	Main subject matter	Principal limitation
Claim 1	Broad compacted ribavirin dosage form	Disintegrant and more than 80% dissolution in about 30 minutes
Claim 2	Defined excipient formulation	Listed filler, disintegrant, and lubricant classes
Claim 3	Dosage amount	About 200 mg to about 400 mg ribavirin
Claim 4	Independent formulation claim	Incomplete in the supplied text
Claims 5-6	Disintegrant and polymorph limitations	Croscarmellose sodium, PVP, mixtures, or substantially nonpolymorphic ribavirin
Claims 7 and 9	Density limitations	At least about 0.6 g/mL, or about 0.75-0.85 g/mL
Claim 8	Disintegration limitation	Less than about 10 minutes
Claims 10, 20-25	Tablet format	Dependent tablet claims
Claims 11-18	Additional independent and dependent claims	Claims 11 and 12-18 focus on dissolution, density, polymorph, and disintegration
Claims 19 and 25	Combined performance limitations	Less than 10-minute disintegration and more than 80% dissolution in about 30 minutes
Claims 26-34	Capsule format	Dependent capsule claims
Claim 27	PVP addition	Polyvinylpyrrolidone

Which claims are the broadest in US Patent 6,337,090?

Claim 1 appears to be the broadest complete claim in the supplied text. It requires only:

An orally administrable solid dosage form;
A compacted ribavirin composition;
Ribavirin;
A pharmaceutically acceptable disintegrant; and
More than about 80% dissolution in water within about 30 minutes.

Claim 19 is also important because it independently combines a short disintegration time with the dissolution requirement:

Disintegration in less than about 10 minutes; and
More than about 80% ribavirin dissolution in about 30 minutes.

Claim 2 is narrower than claim 1 because it requires a filler, disintegrant, and lubricant selected from specified Markush groups. Claims 3, 5-10 and 18-34 narrow the claims through dosage, excipient, density, dosage-form, dissolution, disintegration, or solid-state limitations.

Claim 1 compared with claim 2

Claim 1 is potentially broader because it does not identify a specific filler or lubricant. A formulation could fall within claim 1 without containing any of the fillers or lubricants listed in claim 2, provided it contains a pharmaceutically acceptable disintegrant and meets the dissolution limitation.

Claim 2 is easier to test compositionally because it identifies closed lists of excipient classes. It is narrower but may be more predictable in litigation if the formulation uses conventional excipients such as lactose, microcrystalline cellulose, croscarmellose sodium, sodium starch glycolate, and magnesium stearate.

What technical features drive infringement risk?

The material infringement variables are not simply the presence of ribavirin. They are the interaction between composition and measured performance.

Dissolution limitation

The principal performance requirement is:

More than about 80% by weight of ribavirin dissolves in water in about 30 minutes.

Claims 12 and 18 raise the threshold:

More than about 90% dissolves in about 15 minutes.

A product may avoid a claim if it does not satisfy the applicable dissolution result. That determination depends on the test method, medium, apparatus, agitation, temperature, sampling, assay method, and treatment of undissolved material. “Water” is materially different from a conventional buffered dissolution medium. The exact construction of “about 30 minutes” and “more than about 80%” would be central to any enforcement analysis.

Disintegration limitation

Claims 8, 16, and 19 require disintegration in less than about 10 minutes. A product that dissolves rapidly but does not meet the disintegration requirement could avoid claims containing that limitation. Conversely, rapid disintegration does not by itself establish the required dissolution result.

Tap-density limitation

Claims 7, 9, 13, and 14 require:

At least about 0.6 g/mL; or
Approximately 0.75-0.85 g/mL.

Tap density is a process-sensitive parameter. Measurement conditions, tapping apparatus, number of taps, sample mass, particle segregation, and powder conditioning can affect the result. Density limitations may therefore be useful for distinguishing products, but they can create factual disputes over test reproducibility.

Polymorph limitation

Claims 6 and 15 require ribavirin to be “substantially free” of polymorphic forms. That language raises two issues:

The scope of “substantially free”; and
The analytical method used to detect polymorphs.

X-ray diffraction, thermal analysis, infrared spectroscopy, and other methods may produce different detection thresholds. A generic manufacturer could reduce risk by documenting the solid-state form and maintaining batch-level characterization.

How strong is the patent estate for ribavirin tablets and capsules?

The estate is narrow in technology but no longer commercially blocking because the patent has expired.

Strengths

The claims use multiple measurable formulation characteristics.
Claim 1 does not require the specific filler and lubricant lists found in claim 2.
Claims cover both tablets and capsules.
Claims address both ordinary dissolution and faster dissolution.
The claim set includes density, disintegration, dosage, excipient, and polymorph fallback positions.

Weaknesses

The claims do not cover ribavirin alone.
They require a compacted solid dosage form.
They depend heavily on dissolution and, in some claims, disintegration results.
Several terms are approximate, including “about,” “effective amount,” “substantially free,” and “antivirally effective amount.”
Claim 2 is limited by enumerated excipient lists.
The supplied versions of claims 4 and 11 are incomplete.
The patent term has ended, eliminating current enforcement value in the United States.

The formulation limitations may have provided meaningful design-around opportunities even during the patent term. A manufacturer could have pursued a noncompacted dosage form, a liquid formulation, a formulation with slower dissolution, or a composition outside the listed excipient combinations, subject to the scope of the complete issued claims and any applicable doctrine of equivalents.

When did US Patent 6,337,090 lose exclusivity?

US Patent 6,337,090 was issued on January 8, 2002. Its term was governed by the modern 20-year patent-term framework applicable to the relevant nonprovisional filing and priority chain, subject to any patent-term adjustment or extension shown in the official record.[1][2]

The patent expired no later than the end of the ordinary patent term associated with its filing and priority dates. It was expired by the time generic ribavirin products were broadly marketed and does not provide current U.S. exclusivity.

Event	Date or status
Patent issuance	January 8, 2002
Patent type	Utility formulation patent
Subject matter	Compacted oral ribavirin dosage forms
Ordinary term framework	20 years from the applicable nonprovisional filing date, subject to statutory adjustment
Current status	Expired
Current blocking effect	None in the United States

Patent expiration does not erase historical infringement exposure for conduct occurring before expiration. It does eliminate prospective injunctive and exclusionary rights after expiration.

What is the Orange Book status of US Patent 6,337,090?

US Patent 6,337,090 is not a current Orange Book barrier for generic ribavirin approval. The FDA Orange Book lists patents and exclusivity associated with approved drug products, but an expired formulation patent cannot support a current period of Orange Book-based approval delay.[3]

Ribavirin has been approved in multiple dosage forms and products, including capsule and tablet products used in antiviral regimens. FDA product records and labeling identify ribavirin products, dosage strengths, and approved indications, but current approval status must be assessed product by product because branded products, abbreviated new drug applications, and discontinued products can have different records.[4][5]

The practical consequence is straightforward: an ANDA applicant does not face a current 30-month stay or launch prohibition based solely on US Patent 6,337,090.

Are there Paragraph IV challenges to US Patent 6,337,090?

A current Paragraph IV challenge to this patent would have no commercial purpose because the patent is expired. Paragraph IV certifications are relevant to unexpired patents listed for an approved reference product. They do not create a meaningful launch delay for an expired patent.

Historical ANDA litigation may have involved ribavirin products, but the supplied information does not establish a particular defendant, docket, settlement, judgment, or Paragraph IV notice tied to this patent. No current Paragraph IV risk attributable to US Patent 6,337,090 remains.

What generic launch risks exist for ribavirin products?

The principal current risks are regulatory, commercial, and manufacturing risks rather than patent risks.

Regulatory risks

A generic applicant must establish pharmaceutical equivalence and bioequivalence or satisfy the applicable FDA approval pathway. Dissolution testing remains relevant to product quality and, depending on the application, may be part of comparative performance evaluation. The applicant must also address stability, impurities, content uniformity, manufacturing controls, and labeling.

Manufacturing risks

Ribavirin is a high-dose active ingredient in many oral products. The formulation must control:

Powder flow;
Blend uniformity;
Tablet weight and hardness;
Disintegration;
Dissolution;
Solid-state characteristics;
Moisture sensitivity; and
Content uniformity across commercial-scale batches.

These issues may make the formulation technically challenging even though the patent no longer blocks entry.

Commercial risks

Ribavirin demand has declined from its historical role in hepatitis C treatment because direct-acting antiviral therapies displaced many interferon-ribavirin regimens. Current demand is concentrated in narrower indications and combination therapies. The expired patent therefore has little direct revenue-protection value for a branded manufacturer.

How does US Patent 6,337,090 compare with other ribavirin intellectual property?

Ribavirin intellectual property falls into several distinct categories:

IP category	Typical subject matter	Relevance today
Compound patents	Ribavirin and related chemical inventions	Historical; generally expired
Formulation patents	Tablets, capsules, dissolution, density, excipients	US 6,337,090 is in this category; expired
Method-of-use patents	Treatment of viral infections	Product- and indication-specific; must be checked separately
Combination-therapy patents	Ribavirin with interferon or other antivirals	Mostly historical for older regimens
Manufacturing patents	Crystallization, polymorph control, purification, tableting	May create process know-how barriers, but not based on US 6,337,090
Regulatory exclusivity	New-drug, orphan, pediatric, or other FDA exclusivity	Separate from patent rights and product-specific

US Patent 6,337,090 does not claim a biologic, biosimilar, injectable product, or manufacturing process. Biosimilar risk is therefore irrelevant to this patent. The relevant competitors are generic manufacturers and authorized or formerly branded ribavirin suppliers.

What patent litigation affects US Patent 6,337,090?

The patent’s expiration removes the principal basis for prospective U.S. patent litigation. Any historical case would require separate review of the complaint, asserted claims, prosecution history, claim construction, settlement terms, and final judgment.

The available claim text alone does not establish:

A particular Paragraph IV notice;
A district-court infringement action;
A Federal Circuit appeal;
A covenant not to sue;
A settlement restricting generic launch;
A royalty-bearing license; or
A surviving field-of-use restriction.

No current license or settlement can be inferred from the patent claims.

What are the principal design-around strategies?

During the patent term, the strongest design-around approaches would have focused on the claim limitations rather than avoiding ribavirin itself:

Use a noncompacted dosage form.
Use a liquid, suspension, or alternative delivery system.
Avoid the claimed dissolution threshold.
Avoid the claimed disintegration threshold where applicable.
Use a formulation outside claim 2’s enumerated excipient groups.
Use a different solid-state form if the polymorph limitation is material.
Use a dosage strength outside the 200-400 mg range for claims dependent on claim 3.
Avoid the claimed tap-density ranges.
Use a formulation that does not contain the claimed disintegrant.
Challenge the meaning or reproducibility of the performance limitations.

Because the patent is expired, these strategies are no longer necessary for prospective U.S. freedom to operate under this patent. They may still matter in historical litigation analysis or in foreign jurisdictions with different patent-family status.

Key Takeaways

US Patent 6,337,090 is a formulation patent covering compacted oral ribavirin tablets and capsules.
Its core limitation is rapid dissolution, principally more than 80% ribavirin dissolution in water within about 30 minutes.
Dependent claims add excipient identity, dose, density, disintegration, polymorph, tablet, and capsule limitations.
Claims 4 and 11 are incomplete in the supplied text, preventing a complete scope analysis for those claims.
The patent is expired and creates no current U.S. patent barrier to generic ribavirin entry.
Current regulatory and commercial risks are more important than patent risk.
The patent does not cover ribavirin as a compound, a biologic, a biosimilar, or a manufacturing process.
No current Paragraph IV stay, settlement restriction, or license obligation can be attributed to this expired patent based on the supplied information.

FAQs About US Patent 6,337,090 and Ribavirin Formulations

Does US Patent 6,337,090 cover generic ribavirin capsules?

It historically covered certain compacted ribavirin capsule formulations if they met the applicable composition and performance limitations. It does not create a current U.S. exclusion right because the patent has expired.

Can a generic ribavirin tablet infringe claim 1 without using the listed fillers in claim 2?

Yes, potentially. Claim 1 does not require the specific filler list in claim 2. A product could implicate claim 1 if it contains ribavirin and a pharmaceutically acceptable disintegrant in a compacted dosage form that meets the dissolution limitation.

Is ribavirin polymorph control still relevant after patent expiration?

Yes, but primarily for product quality, stability, manufacturability, and regulatory control. The expired polymorph claims no longer provide a current U.S. exclusion right.

Does rapid dissolution alone establish infringement of US Patent 6,337,090?

No. The relevant claim must be considered as a whole. Depending on the claim, infringement may also require a compacted composition, a disintegrant, specified excipients, a density threshold, a disintegration time, or a dosage-form limitation.

Does the patent affect ribavirin combination therapies today?

Not as an active U.S. patent right. Separate patents, regulatory exclusivities, labeling restrictions, or method-of-use rights would have to be analyzed independently for any particular combination therapy.

References

U.S. Patent No. 6,337,090, “Ribavirin formulations” (issued Jan. 8, 2002). United States Patent and Trademark Office.
United States Code, 35 U.S.C. § 154. Patent term.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book.
U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs.
U.S. Food and Drug Administration. (n.d.). Ribavirin product labeling and prescribing information.

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Hoffmann-la Roche Inc.	PEGASYS COPEGUS COMBINATION PACK	peginterferon alfa-2a and ribavirin		125083	June 4, 2004	⤷ Start Trial	2020-11-13
Schering Corporation A Subsidiary Of Merck & Co., Inc.	PEGINTRON/ REBETOL COMBO PACK	peginterferon alfa-2b and ribavirin		125196	June 13, 2008	⤷ Start Trial	2020-11-13
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Patent: 6,337,090

Summary for Patent: 6,337,090