United States Patent 10,314,828: Scope, Claims, Expiration and Rifaximin Patent Landscape

U.S. Patent No. 10,314,828 protects a specific rifaximin treatment regimen for maintaining remission of hepatic encephalopathy. The independent claim requires daily administration of approximately 1,000 to 1,200 mg of rifaximin for at least 12 months in a patient with a MELD score from 1 to 24. The commercially relevant embodiment is 550 mg twice daily, or 1,100 mg per day.

The patent is a method-of-use patent, not a composition-of-matter patent. Its enforceability depends on proving the prescribed dose, treatment duration, patient population, and remission-maintenance objective. It does not broadly cover every use of rifaximin, every hepatic encephalopathy regimen, or short-term treatment.

What does U.S. Patent 10,314,828 protect?

U.S. Patent 10,314,828 protects a long-term rifaximin regimen for maintaining remission of hepatic encephalopathy in patients stratified by MELD score.

Field	Patent 10,314,828
Patent number	U.S. 10,314,828
Title	Methods of maintaining remission of hepatic encephalopathy
Patent type	Method of treatment
Active ingredient	Rifaximin
Commercial product	Xifaxan 550 mg tablets
Patent holder/assignee	Salix Pharmaceuticals, Ltd.
Grant date	June 11, 2019
Core indication	Maintenance of remission of hepatic encephalopathy
Core dosage	About 1,000-1,200 mg rifaximin daily
Preferred dosage	1,100 mg daily
Commercial dosing embodiment	550 mg twice daily
Treatment duration	At least 12 months
Patient population	MELD score 1-24
Key formulation	Oral rifaximin
Combination therapy	Rifaximin with lactulose
Patent territory	United States

The patent claims a treatment method defined by several cumulative limitations. A potentially infringing regimen must satisfy the limitations of claim 1 unless a dependent claim is separately asserted.

What are the claims of Patent 10,314,828?

Independent claim 1

Claim 1 requires all of the following:

A human subject in need of treatment.
Hepatic encephalopathy.
Maintenance of remission of HE.
Daily rifaximin dosing of about 1,000 to about 1,200 mg.
Treatment for 12 months or longer.
A MELD score between about 1 and 24.

The claim does not expressly require oral tablets, 550 mg tablets, twice-daily dosing, lactulose, or a particular rifaximin polymorph. Those elements appear in dependent claims or in the commercial product context.

Dependent claims

Claim	Added limitation	Practical significance
2	MELD score less than or equal to 10	Covers lower-severity liver disease
3	MELD score 11-18	Covers intermediate MELD scores
4	MELD score 19-24	Covers higher MELD scores within the claimed range
5	Remission defined as Conn score 0 or 1	Adds a clinical endpoint
6	Two or more overt HE episodes within six months before treatment	Narrows the high-risk patient population
7	Oral administration	Aligns with Xifaxan tablets
8	1,100 mg rifaximin per day	Captures the labeled 550 mg twice-daily dose
9	550 mg twice daily	Directly tracks the commercial dosing schedule
10	Concurrent administration of lactulose	Covers combination therapy

Claim 9 is dependent on claim 8 despite the text supplied referring to “claims 8.” The substantive limitation is clear: 550 mg twice daily.

How should the claim scope be construed?

The claim is narrower than a general rifaximin-for-HE claim because it combines dose, duration, disease status, and MELD score.

Dose limitation

“Between about 1,000 mg to about 1,200 mg” is centered on the approved 1,100 mg daily regimen. The term “about” may create a factual dispute over permissible variation. Courts generally assess the specification, prosecution history, technical meaning, and whether the accused dose falls within a scientifically meaningful range.

A 550 mg tablet administered twice daily is the clearest literal infringement scenario under claims 8 and 9. A 1,000 mg or 1,200 mg daily regimen may fall within claim 1 even if it does not use the commercial tablet strength.

A materially lower or higher daily dose would face a stronger noninfringement position, although the doctrine of equivalents could become relevant depending on the prosecution history and the function of the dosing range.

Duration limitation

Treatment must continue for 12 months or longer. A prescription or treatment course lasting less than 12 months does not literally satisfy claim 1. A generic label authorizing use without a 12-month minimum could reduce inducement exposure, but actual prescribing, promotional activity, and product use remain relevant.

The duration element is commercially important. A product used for acute HE episodes or short-term stabilization would fall outside the express duration requirement unless another patent claim applies.

MELD limitation

The claimed patient must have a MELD score from approximately 1 to 24. Claims 2 through 4 divide that range into clinically meaningful subgroups:

MELD score of 10 or below;
MELD score from 11 through 18; and
MELD score from 19 through 24.

Patients with a MELD score above 24 are outside the literal scope of claim 1. Patients without a documented MELD score could create proof problems in an infringement case, although clinical records, prescribing criteria, and trial enrollment data may provide evidence.

Remission limitation

Claim 1 requires maintaining remission of HE. Claim 5 defines remission as a Conn score of 0 or 1. The Conn scoring system evaluates the severity of hepatic encephalopathy. A product label or clinical protocol that describes prevention of recurrent HE may implicate the claim even if it does not use the exact phrase “maintaining remission.”

Prior HE episodes

Claim 6 requires at least two overt HE episodes during the six months preceding rifaximin treatment. This limitation is narrower than claim 1. A patient with only one prior episode may satisfy claim 1 but not claim 6.

Lactulose combination

Claim 10 covers rifaximin administered together with lactulose. Lactulose is commonly used as background therapy in HE. The claim may be relevant where a generic applicant markets rifaximin with instructions that encourage concurrent lactulose administration.

What is the commercial embodiment protected by the patent?

The most important embodiment is:

Xifaxan 550 mg tablet;
oral administration;
550 mg twice daily;
1,100 mg total daily dose;
continued for at least 12 months;
in a patient with MELD score 1-24;
to maintain remission of HE;
often with lactulose.

This regimen corresponds closely to the FDA-approved Xifaxan HE indication, which is reduction in the risk of overt HE recurrence in adults [1]. The pivotal clinical evidence supporting the HE indication evaluated recurrent HE prevention over an extended treatment period, with many patients receiving concomitant lactulose [2].

The patent does not require a specific brand, manufacturer, tablet color, excipient profile, or packaging configuration. A generic rifaximin tablet with the same active ingredient and dosing regimen could practice the claimed method even if the tablet formulation differs, provided the method limitations are met.

When does Patent 10,314,828 expire?

The patent claims priority to a 2013 filing date and was granted on June 11, 2019. The ordinary 20-year patent term is expected to extend into 2033, subject to any patent-term adjustment, terminal disclaimer, or other USPTO term calculation.

Milestone	Date
Earliest reported priority	May 31, 2013
U.S. grant	June 11, 2019
Expected ordinary term endpoint	Approximately May 31, 2033
Relevant post-grant issue	Patent-term adjustment and Orange Book listing data

The controlling expiration date should be taken from the USPTO patent-term calculation and the FDA Orange Book listing rather than calculated solely from the grant date. Patent expiration is distinct from FDA regulatory exclusivity. A patent may remain enforceable after regulatory exclusivity ends, and a patent expiration date may differ from the end of any pediatric or other FDA exclusivity period [3][4].

What is the Orange Book status of Patent 10,314,828?

Patent 10,314,828 has been associated with Xifaxan 550 mg tablets and the hepatic encephalopathy indication in the Orange Book patent-listing framework. An Orange Book listing gives an NDA holder a mechanism to identify patents that it believes claim the approved drug or an approved method of use.

For an ANDA applicant, the relevant certification options include:

Paragraph I: no patent information is listed;
Paragraph II: the listed patent has expired;
Paragraph III: approval is requested after patent expiration;
Paragraph IV: the patent is invalid, unenforceable, or will not be infringed.

A Paragraph IV certification can trigger patent litigation under the Hatch-Waxman Act if the NDA holder sues within the statutory period. The litigation risk turns on the exact claims certified, the proposed generic label, and whether the generic applicant seeks approval for the HE indication.

Are there Paragraph IV challenges to the Xifaxan HE patent estate?

The Xifaxan franchise has faced ANDA challenges involving rifaximin patents covering HE treatment and related indications. Norwich Pharmaceuticals and other generic applicants have pursued challenges to Salix’s Xifaxan patent estate, including patents directed to hepatic encephalopathy treatment and dosing.

The litigation has focused heavily on:

obviousness of rifaximin treatment regimens;
whether clinical evidence supports the claimed patient population;
the scope of the approved label;
patent validity in light of earlier rifaximin studies;
whether an ANDA label induces infringement; and
whether patents listed for Xifaxan block approval or commercial launch.

A Paragraph IV challenge to one Xifaxan patent does not automatically eliminate all patent risk. The estate contains patents with different claim categories and expiration dates. A generic applicant can prevail against one patent and remain blocked by another.

The central strategic issue for Patent 10,314,828 is whether the claimed MELD-based population and long-term dosing regimen would have been obvious from earlier evidence concerning recurrent HE and the known 550 mg twice-daily dose. The patent holder can respond that the specific MELD stratification, extended treatment period, and maintenance-of-remission endpoint were not disclosed or predictably established in the prior art.

Which companies are challenging Xifaxan exclusivity?

The principal competitive threat has come from generic pharmaceutical companies pursuing ANDA approval for rifaximin tablets. Norwich Pharmaceuticals has been the most visible challenger in reported Xifaxan patent litigation.

Company or group	Role in the landscape	Primary pathway
Salix Pharmaceuticals	Xifaxan marketer and patent holder	NDA
Bausch Health	Parent-company commercial exposure through Salix	NDA commercialization
Norwich Pharmaceuticals	Generic challenger	ANDA and Paragraph IV litigation
Other potential ANDA applicants	Future generic competition	ANDA

Generic entry is more difficult for Xifaxan than a simple tablet substitution because the product has multiple indications, a complex patent estate, and potential litigation over the HE label.

How strong is the patent estate for rifaximin and Xifaxan?

The Xifaxan estate has historically included several patent categories:

Patent category	Protection focus	Risk to generic entry
Composition and solid-state patents	Rifaximin form, polymorph, or manufacturing characteristics	Can block product manufacture or sale
HE method patents	Treatment or prevention of recurrent HE	Can block an HE-labeled generic
Dosing patents	Dose, frequency, and treatment duration	Can cover commercial use
Formulation patents	Tablet composition and delivery characteristics	May create product-specific risk
IBS-D method patents	Rifaximin use in diarrhea-predominant IBS	Relevant to a separate indication
Manufacturing patents	Processes for producing rifaximin	Can limit alternative supply routes

Patent 10,314,828 is strongest against a product that carries an HE indication and expressly adopts 550 mg twice-daily dosing for recurrent HE. It is weaker against:

a product limited to a non-HE indication;
a label that omits the HE indication;
a regimen below or above the claimed dose range;
treatment courses expressly limited to less than 12 months; or
a product used outside the claimed MELD population.

Those strategies can be constrained by the FDA’s requirements for labeling, physician prescribing behavior, and the commercial value of the HE market.

What formulation patents protect Xifaxan?

Patent 10,314,828 does not principally protect a tablet formulation. Its claims are directed to a treatment method. The claim language does not require a particular excipient, dissolution profile, coating, particle size, crystal form, or manufacturing process.

Formulation and solid-state patents are analytically separate. They can create infringement exposure even when a generic applicant avoids the method claims. Conversely, designing around a formulation patent does not necessarily avoid infringement of Patent 10,314,828 if the generic product is used under the claimed HE regimen.

For litigation purposes, the relevant questions are:

Is the generic product the same rifaximin active ingredient?
Does the proposed label include HE recurrence reduction?
Does the label recommend 550 mg twice daily?
Does the label encourage treatment for at least 12 months?
Does it identify the same patient population or clinical objective?

Does the patent create biosimilar risk?

No. Rifaximin is a small-molecule drug, not a biologic. A competing product would ordinarily proceed through the ANDA pathway under Section 505(j) of the Federal Food, Drug, and Cosmetic Act, not through the biosimilar pathway under Section 351(k) of the Public Health Service Act.

The relevant competitive risks are generic substitution, Paragraph IV litigation, authorized generic entry, and label carve-outs. Biosimilar interchangeability standards do not apply.

What FDA exclusivity applies to Xifaxan?

Xifaxan was approved for reduction in the risk of overt HE recurrence in adults in 2010. FDA approval of the HE indication created regulatory exclusivity separate from patent protection. The original new chemical entity exclusivity period has expired. Any later indication-specific exclusivity periods also do not replace the patent analysis.

The practical barrier to entry is therefore patent-based rather than current NCE exclusivity-based. An ANDA applicant must address the listed patents and may seek a section viii statement or indication carve-out where legally available [1][3].

What litigation affects Patent 10,314,828?

The material litigation themes are:

Salix enforcement of Xifaxan patents against ANDA applicants;
Paragraph IV allegations that HE patents are invalid or not infringed;
obviousness challenges based on earlier rifaximin clinical data;
disputes over whether a generic label induces use for recurrent HE;
the effect of a skinny label on infringement;
the relationship between patent expiration and FDA approval timing.

Patent 10,314,828 should be evaluated together with the rest of the Orange Book-listed Xifaxan estate. A judgment invalidating or limiting another HE patent does not necessarily determine the validity of the '828 claims. Claim-specific prosecution history, expert evidence, and the proposed generic label remain decisive.

What generic launch scenarios exist?

Scenario 1: Full HE label

A generic applicant seeks approval for rifaximin 550 mg tablets with the HE indication and the same 550 mg twice-daily regimen. This creates the highest direct risk under claims 8 and 9.

Scenario 2: Carved-out HE indication

The applicant removes the HE indication from its label and seeks approval for another rifaximin use, such as IBS-D. This reduces direct label-based infringement exposure but does not eliminate possible induced or contributory infringement theories based on actual use or promotional conduct.

Scenario 3: Post-expiration approval

The applicant files a Paragraph III certification for the relevant patent and receives approval effective after patent expiration. This avoids a validity challenge but delays commercial entry.

Scenario 4: Paragraph IV litigation

The applicant challenges validity or infringement. A successful challenge can accelerate entry. An unsuccessful challenge can result in a statutory stay, judgment-based delay, or settlement restrictions.

Scenario 5: Authorized generic or license

Salix or its commercial partner could resolve the dispute through a license, supply arrangement, or authorized generic launch. The economic outcome would depend on the entry date, royalty rate, volume limits, and restrictions on additional challengers.

How does Patent 10,314,828 compare with competing patent categories?

Issue	Patent 10,314,828	Composition patent	Formulation patent
Protected subject	Patient treatment method	Chemical or solid-state product	Tablet or dosage-form design
Requires clinical use	Yes	No	Usually no
Requires dose	Yes	No	Sometimes
Requires duration	Yes, at least 12 months	No	No
Requires MELD range	Yes	No	No
Design-around potential	Label, patient population, dose, duration	Alternative form may be possible	Alternative formulation may be possible
Main evidence	Clinical use and label	Product identity	Product testing and manufacturing records

Key Takeaways

Patent 10,314,828 is a method-of-use patent covering long-term rifaximin treatment to maintain remission of hepatic encephalopathy.
Claim 1 requires approximately 1,000-1,200 mg daily, treatment for at least 12 months, and a MELD score of 1-24.
Claims 8 and 9 directly capture the commercial 550 mg twice-daily Xifaxan regimen.
Claims 2-4 divide the population by MELD score, while claim 5 uses a Conn score of 0 or 1 to define remission.
Claim 6 narrows the population to patients with at least two overt HE episodes during the prior six months.
Claim 10 covers combination therapy with lactulose.
The patent is expected to extend into approximately 2033 based on its 2013 priority date, subject to the controlling USPTO term calculation.
The patent is a United States method patent and does not itself create foreign protection.
Generic risk is highest for an ANDA carrying the HE indication and recommending 550 mg twice daily for long-term recurrence prevention.
Rifaximin is a small molecule, so generic ANDA litigation, not biosimilar litigation, is the relevant pathway.
The patent must be analyzed with the broader Xifaxan composition, formulation, manufacturing, IBS-D, and HE patent estate.

FAQs About U.S. Patent 10,314,828

Does Patent 10,314,828 cover all rifaximin products?

No. It covers a defined method of using rifaximin in patients with HE, within a specified daily dose range, treatment duration, and MELD-score population.

Can a generic sell rifaximin for IBS-D without practicing this patent?

Potentially. A generic limited to IBS-D may avoid the express HE method claims, but other Xifaxan patents and inducement theories must be evaluated separately.

Does treatment with lactulose avoid infringement?

No. Lactulose is an added limitation in claim 10. Its use does not avoid claims 1 through 9 and may place the regimen within claim 10.

Can a physician infringe the patent by prescribing 550 mg twice daily?

A physician’s prescription may satisfy the claimed method if the patient, duration, dose, and clinical objective meet the claim. Commercial patent disputes typically focus on the conduct of manufacturers and marketers, including induced infringement based on labeling and promotion.

Is Patent 10,314,828 a patent on Xifaxan’s chemical composition?

No. It is directed to a clinical treatment method. Composition, polymorph, formulation, and manufacturing protection must be reviewed in separate patents.

References

U.S. Food and Drug Administration. (2010). Xifaxan (rifaximin) prescribing information. FDA.
Bass, N. M., Mullen, K. D., Sanyal, A., Poordad, F., Neff, G., Le이, J., et al. (2010). Rifaximin treatment in hepatic encephalopathy. New England Journal of Medicine, 362(12), 1071-1081.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
United States Patent and Trademark Office. (2019). U.S. Patent No. 10,314,828: Methods of maintaining remission of hepatic encephalopathy. USPTO.
United States Code. (2024). 35 U.S.C. §§ 154, 271, and 281-285.
United States Code. (2024). 21 U.S.C. § 355(j).

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Salix Pharms	XIFAXAN	rifaximin	TABLET;ORAL	021361-002	Mar 24, 2010	AB	RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				REDUCTION IN RISK OF OVERT HEPATIC ENCEPHALOPATHY (HE) RECURRENCE	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2009298389	⤷ Start Trial
Australia	2010260089	⤷ Start Trial
Australia	2010271070	⤷ Start Trial
Brazil	PI0920465	⤷ Start Trial
Brazil	PI1010028	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 10,314,828