US Patent 10,703,763: Rifaximin Delta and Epsilon Scope, Claims, and Patent Landscape
US Patent No. 10,703,763 is directed to methods of treating gastrointestinal bacterial activity with two specified solid-state forms of rifaximin: rifaximin delta and rifaximin epsilon. The patent does not claim rifaximin generally. Its central limitation is the powder X-ray diffraction profile of the administered rifaximin form.
The highest-risk products are oral rifaximin products containing delta or epsilon material, including tablets, capsules, pellets, powders, and other listed oral dosage forms. Conventional rifaximin products containing another polymorph, including rifaximin alpha, do not fall within the claims solely because they contain the same active ingredient.
What does US Patent 10,703,763 protect?
The patent protects treatment methods requiring all of the following elements:
- A subject with bacterial activity in the gastrointestinal tract.
- Administration of a pharmaceutical composition.
- A therapeutically effective amount of rifaximin delta or rifaximin epsilon.
- The claimed powder X-ray diffraction peaks for that solid form.
- For the principal oral claims, an administration route and, for rifaximin delta and epsilon, specified excipient limitations.
The patent contains two independent oral-treatment claims and two independent topical-treatment claims:
| Claim |
Solid form |
Administration |
Composition limitation |
Key technical limitation |
| 1 |
Rifaximin delta |
Oral |
Requires a listed pharmaceutically acceptable excipient |
Delta XRPD pattern |
| 3 |
Rifaximin delta |
Topical |
No express excipient requirement |
Delta XRPD pattern |
| 6 |
Rifaximin epsilon |
Oral |
Requires a listed pharmaceutically acceptable excipient |
Epsilon XRPD pattern |
| 8 |
Rifaximin epsilon |
“Topical” by oral route |
No express excipient requirement |
Epsilon XRPD pattern |
Claims 2, 4, 5, 7 and 9 depend on those independent claims and narrow them by dosage form or water content.
How do the rifaximin delta claims differ from the rifaximin epsilon claims?
The delta and epsilon claim sets are distinguished by separate XRPD fingerprints.
Rifaximin delta
Claim 1 requires peaks at approximately:
5.7°, 6.7°, 7.1°, 8.0°, 8.7°, 10.4°, 10.8°, 11.3°, 12.1°, 17.0°, 17.3°, 17.5°, 18.5°, 18.8°, 19.1°, 21.0° and 21.5° 2θ.
Claim 5 adds a water-content limitation of 3.0% to 4.5%.
Rifaximin epsilon
Claim 6 requires peaks at approximately:
7.0°, 7.3°, 8.2°, 8.7°, 10.3°, 11.1°, 11.7°, 12.4°, 14.5°, 16.3°, 17.2°, 18.0° and 19.4° 2θ.
The epsilon claims do not include the delta water-content limitation.
The two patterns overlap at certain approximate regions, particularly around 8.7°, but the full pattern requirement is different. A product analysis therefore must compare the complete XRPD profile rather than one or two individual peaks.
What are the key claim limitations for infringement analysis?
The XRPD profile is the core limitation
The claims require that the administered rifaxin material “has” the specified XRPD peaks, each within approximately ±0.2° 2θ. A composition containing rifaximin is not enough. The accused material must correspond to the claimed crystalline form.
Relevant analytical questions include:
- Whether the material is crystalline or amorphous.
- Whether all claimed peaks are present.
- Whether the peaks fall within the stated angular tolerances.
- Whether polymorph conversion occurs during manufacturing, storage or formulation.
- Whether the tested batch is representative of the administered product.
- Whether excipients interfere with peak detection.
- Whether the alleged delta or epsilon form is present as a major phase, minor phase or mixture.
The claims do not state minimum peak intensities, relative intensity ratios, crystallinity thresholds or phase-purity percentages. That omission may create disputes over mixed solid forms and weak or partially obscured peaks.
The method-of-treatment requirement matters
These are method claims, not claims to rifaximin compounds in the abstract. Liability generally depends on use of the claimed product in the claimed treatment context. A manufacturer’s sale of rifaximin delta or epsilon may create different issues from direct treatment by a patient, physician or healthcare provider.
The claims target treatment of “bacterial activity in the gastrointestinal tract.” They do not identify a single disease such as hepatic encephalopathy, irritable bowel syndrome with diarrhea or travelers’ diarrhea. The wording is broader than an indication-limited claim, but the accused use still must correspond to gastrointestinal bacterial treatment.
The oral claims require an excipient from a defined group
Claims 1 and 6 require a pharmaceutically acceptable excipient selected from:
- Diluting agents
- Binding agents
- Lubricating agents
- Disintegrating agents
- Colouring agents
- Flavouring agents
- Sweetening agents
The language appears to require at least one excipient from the group. It does not require a particular excipient, concentration, ratio or release profile.
This limitation is significant for tablets, capsules, pellets and powders. A pure rifaximin delta or epsilon active ingredient administered without one of the listed excipients would present a non-infringement argument under the literal language of claims 1 and 6, although other claims or infringement doctrines could become relevant.
What formulations are protected by the patent?
Oral dosage forms
Claims 2 and 7 identify the following formulations:
- Coated tablets
- Uncoated tablets
- Hard gelatin capsules
- Soft gelatin capsules
- Sugar-coated pills
- Lozenges
- Wafer sheets
- Pellets
- Powder in sealed packets
The claims do not require a specific dose, tablet strength, coating material, dissolution profile, enteric-release mechanism or manufacturing process.
An oral product containing the claimed solid form in a different dosage form may still fall within claim 1 or claim 6 because those independent claims are not limited to the forms enumerated in claims 2 and 7. The dependent claims provide narrower, expressly listed embodiments rather than necessarily defining the full oral-product universe.
Topical and oral-topical formulations
Claims 4 and 9 identify:
- Ointments
- Pomades
- Creams
- Gels
- Lotions
Claim 3 describes topical administration of rifaximin delta. Claim 8 uses the phrase “topically administering ... by oral route” for rifaximin epsilon. That wording is internally unusual because topical administration ordinarily refers to application to a surface, while oral route refers to administration through the mouth and gastrointestinal tract.
The construction of claim 8 could become material in litigation. A court may consider the specification, prosecution history and claim context to determine whether the language covers oral gastrointestinal administration, topical oral-cavity administration, or a broader formulation concept. The supplied claim text alone does not resolve that construction issue.
How strong are the patent’s claims?
The patent has a narrow but technically identifiable scope.
| Strength factor |
Assessment |
Commercial effect |
| Solid-state specificity |
Strong |
Requires analytical comparison against delta or epsilon XRPD patterns |
| Disease scope |
Broadly worded |
Captures multiple gastrointestinal bacterial-treatment uses |
| Dosage limitations |
Limited |
Does not require a specific dose or dosing schedule |
| Oral formulation scope |
Broad in independent claims |
Covers multiple conventional dosage forms |
| Excipient limitation |
Moderate constraint |
May create design-around opportunities |
| Process limitations |
Absent from supplied claims |
Manufacturing route alone is not the claim focus |
| Water content |
Narrow dependent limitation |
Relevant mainly to delta products |
| XRPD intensity requirements |
Not stated |
Potential dispute for mixtures or low-level phases |
| Route terminology |
Unusual for claims 3 and 8 |
Construction and enablement issues may arise |
The strongest practical feature is the combination of a broad gastrointestinal treatment purpose with a narrow, testable solid-state fingerprint. The principal vulnerability is that the claims do not specify intensity ratios, phase purity or a manufacturing process. A competitor may attempt to formulate rifaximin in a different polymorph, amorphous state or solid-state mixture while avoiding the claimed pattern.
How does US Patent 10,703,763 compare with rifaximin alpha patents?
Rifaximin patent protection has historically included several layers:
| Patent layer |
Typical subject matter |
Relationship to Patent 10,703,763 |
| Compound and early-use patents |
Rifaximin and antimicrobial use |
Earlier-generation protection |
| Product and formulation patents |
Tablets, oral dosage forms and compositions |
May overlap commercially but use different claim elements |
| Rifaximin alpha patents |
Specific alpha crystalline form |
Directed to a different polymorph |
| Delta and epsilon patents |
XRPD-defined solid forms |
Directly represented by Patent 10,703,763 |
| Method-of-use patents |
Hepatic encephalopathy, IBS-D and other indications |
May create separate use restrictions |
| Manufacturing patents |
Crystallization, purification and solid-form preparation |
Can block production even where a treatment claim is avoided |
Patent 10,703,763 should therefore be analyzed as part of a layered rifaximin estate. Avoiding this patent does not necessarily eliminate exposure to earlier composition claims, formulation claims, later indication claims or manufacturing patents.
What is the likely Orange Book relevance?
FDA Orange Book listing depends on the relationship between the patent claims and an approved drug product. Method-of-treatment patents may be listed if they claim an approved use. A polymorph patent may be relevant to listing if the approved product contains the claimed form and the patent meets FDA listing requirements.
For rifaximin, the relevant regulatory product is Xifaxan, marketed by Salix Pharmaceuticals, a division of Bausch Health, for FDA-approved gastrointestinal indications including travelers’ diarrhea, reduction in risk of overt hepatic encephalopathy recurrence and irritable bowel syndrome with diarrhea.[2]
The supplied claim text does not establish:
- Whether Patent 10,703,763 is listed in the current Orange Book.
- Which approved product or indication is associated with the patent.
- Whether the patent was listed as a drug-substance, drug-product or method-of-use patent.
- Whether the listing has been delisted, challenged or retained.
- Whether an approved product contains rifaximin delta or epsilon rather than another form.
Those issues must be determined from the applicable Orange Book edition, FDA listing records and the patent’s regulatory correspondence.
What Paragraph IV risks exist for generic rifaximin?
A generic applicant could challenge Patent 10,703,763 through several theories:
Non-infringement
The applicant could certify that its product does not contain rifaximin delta or epsilon as defined by the claimed XRPD pattern. This position would require supporting solid-state data.
Other non-infringement positions could focus on:
- Absence of a listed excipient in an oral product.
- A dosage form outside the dependent claims.
- Absence of a gastrointestinal bacterial-treatment indication.
- Failure of the product to meet the full peak list.
- Use of a different polymorph or amorphous material.
Invalidity
Potential validity arguments may concern:
- Anticipation by prior-art rifaximin solid forms.
- Obviousness based on known polymorph screening.
- Lack of written description for the full range of XRPD variation.
- Enablement of the full claim scope.
- Indefiniteness of “about,” “therapeutically effective amount” or “bacterial activity.”
- Ambiguity in claim 8’s “topical” and “oral route” language.
The absence of peak intensities and phase-purity thresholds could be relevant to definiteness and written-description arguments, although the ultimate result would depend on the specification, prosecution history and technical record.
Invalidity based on prior disclosure
The most important prior-art question is whether delta or epsilon forms, or XRPD patterns materially equivalent to them, were publicly disclosed before the relevant priority date. Patent-family publications, conference materials, regulatory submissions and earlier polymorph-screening work may be relevant.
Which companies are likely to be exposed?
The principal exposure is for companies developing or manufacturing rifaximin products that reproduce the claimed delta or epsilon solid forms. The risk is higher for:
- Generic applicants using the same solid form as the reference product.
- Contract manufacturers receiving a specified delta or epsilon starting material.
- API suppliers selling characterized delta or epsilon rifaximin.
- Licensees commercializing an oral gastrointestinal rifaximin product.
- Product developers relying on the same XRPD data in regulatory filings.
The risk is lower for products using rifaximin alpha, a demonstrably different crystalline form, an amorphous form or a formulation in which the claimed phase is absent. That conclusion must be tested batch by batch because solid-state conversion can occur during milling, granulation, drying, compression and storage.
What manufacturing and IP barriers does the patent create?
The patent creates an analytical barrier rather than a direct process barrier. It does not, based on the supplied claims, require a particular crystallization solvent, temperature, drying cycle or seed crystal.
The practical barriers are:
- Polymorph control during API production.
- Prevention of delta-to-epsilon or epsilon-to-other-form conversion.
- Batch-release XRPD testing.
- Validation of water content for delta material.
- Stability testing under humidity and temperature stress.
- Assessment of excipient effects on solid-state behavior.
- Separation of claimed forms from unclaimed polymorphs.
- Consistency between development batches and commercial batches.
A manufacturer may avoid the patent’s literal solid-form limitations while facing separate manufacturing or formulation patents. Freedom-to-operate analysis must therefore examine API, formulation, process, indication and regulatory patents together.
What generic launch scenarios exist?
| Scenario |
Patent 10,703,763 risk |
Commercial implication |
| Generic uses rifaximin alpha |
Lower direct risk from this patent |
Earlier patents and Orange Book listings remain relevant |
| Generic uses amorphous rifaximin |
Lower direct XRPD risk |
Stability and bioequivalence issues may increase |
| Generic uses delta |
High risk |
Likely requires a non-infringement or validity position |
| Generic uses epsilon |
High risk |
Same issue under claims 6-9 |
| Product contains a mixed phase |
Fact-dependent |
Peak intensity and phase-purity evidence become central |
| Product omits listed excipients |
May avoid oral claim limitation |
Other composition or formulation patents may apply |
| Product pursues a different indication |
May reduce method-of-use exposure |
Product and polymorph claims may remain relevant |
| Authorized or licensed launch |
Contract and royalty exposure |
May avoid litigation but not necessarily all patent costs |
What is the litigation and settlement significance?
The supplied information does not identify litigation, a Paragraph IV notice, a settlement, a consent judgment or a license associated specifically with Patent 10,703,763. The patent number alone does not establish that a generic challenge has occurred or that a settlement limits launch timing.
For transaction and litigation diligence, the relevant records are:
- ANDA litigation complaints and docket entries.
- Paragraph IV notices.
- FDA Orange Book patent-listing records.
- Patent assignments and ownership changes.
- Maintenance-fee status.
- Terminal disclaimers.
- Patent-term-adjustment calculations.
- License and settlement agreements.
- Any covenant not to sue or authorized-generic arrangement.
Key Takeaways
- US Patent 10,703,763 is centered on rifaximin delta and rifaximin epsilon solid forms defined by XRPD peak patterns.
- It does not claim rifaximin generically.
- The principal commercial risk concerns oral gastrointestinal products containing either claimed form.
- Claims 1 and 6 require a listed pharmaceutical excipient; claims 3 and 8 do not state the same excipient requirement.
- Claim 5 adds a 3.0% to 4.5% water-content limitation for rifaximin delta.
- The patent does not specify peak intensities or phase-purity thresholds, creating potential analytical and claim-construction disputes.
- Rifaximin alpha, amorphous rifaximin and other solid forms may provide design-around routes, subject to separate patents.
- The unusual wording of claim 8 creates a potential construction issue concerning “topical” administration by the oral route.
- Orange Book listing, patent-term status, Paragraph IV activity and settlement history require review of the current FDA, USPTO and federal court records.
- A complete freedom-to-operate opinion must evaluate this patent with earlier rifaximin composition, polymorph, formulation, use and manufacturing patents.
Frequently Asked Questions
Does Patent 10,703,763 cover Xifaxan automatically?
No. Coverage depends on whether the marketed product contains rifaximin delta or epsilon matching the claimed XRPD pattern and whether the use satisfies the applicable method claim.
Can rifaximin alpha avoid this patent?
Potentially. The claims supplied are directed to delta and epsilon, not alpha. A separate analysis of alpha patents and the product’s actual solid-state composition remains necessary.
Is a different rifaximin dosage enough to avoid the patent?
Not necessarily. The independent claims do not specify a particular dose. Changing tablet strength or dosing frequency may not avoid a claim if the same solid form and treatment elements remain present.
Does a formulation with only a small amount of delta infringe?
The claim text does not establish a minimum amount or phase-purity threshold. The issue would depend on whether the administered composition can properly be characterized as having the claimed XRPD pattern and on the governing claim construction.
Does the patent block non-gastrointestinal rifaximin products?
The supplied claims require treatment of bacterial activity in the gastrointestinal tract. A use outside that context may not satisfy these claims, although other rifaximin patents could apply.
References
- United States Patent and Trademark Office. (2020). U.S. Patent No. 10,703,763, Rifaximin polymorphs and uses thereof.
- U.S. Food and Drug Administration. (2024). Xifaxan (rifaximin) prescribing information.
- U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
- United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure.
