United States Patent 11,478,428: Scope, Claims, Exclusivity and Patent Landscape for Sulopenem Etzadroxil/Probenecid

U.S. Patent No. 11,478,428 protects a specific bilayer oral tablet containing approximately 500 mg of probenecid and approximately 500 mg of Compound III-2, identified in the Orlynvah development program as sulopenem etzadroxil. The patent is directed primarily to product architecture and manufacturing, with dependent method-of-treatment claims covering bacterial infections, selected noninfectious diseases, administration with food, and pharmacokinetic outcomes.

The strongest infringement position is likely against a substantially identical bilayer tablet using the claimed excipient quantities and compression sequence. The broad disease claims are narrower in practice than their language suggests because they depend on use of the specific claimed tablet.

What drug does U.S. Patent 11,478,428 protect?

Compound III-2 is associated with sulopenem etzadroxil, the oral prodrug of sulopenem used in Iterum Therapeutics' Orlynvah product. Orlynvah combines sulopenem etzadroxil with probenecid. Probenecid reduces renal tubular secretion and increases systemic exposure to sulopenem, supporting oral administration of the antibiotic product.

The patent does not broadly claim every sulopenem formulation. Its independent product claim requires all of the following:

Required element	Claim 1 requirement
Dosage form	Bilayer tablet
First layer	About 500 mg probenecid or pharmaceutically acceptable salt
Second layer	About 500 mg Compound III-2
Microcrystalline cellulose	About 220-230 mg
Sodium croscarmellose	About 50-60 mg
Intragranular magnesium stearate	About 3-4 mg
Extragranular magnesium stearate	About 6-8 mg
Lactose monohydrate	About 65-75 mg
Hydroxypropylcellulose	About 20-23 mg

A competing product that uses a single-layer tablet, materially different excipient quantities, or a different probenecid/sulopenem distribution may avoid literal infringement of claim 1. It could still face risk under other patents, the doctrine of equivalents, or claims not reproduced in the user-provided text.

What are the key claims of U.S. Patent 11,478,428?

Claim 1: Narrow bilayer composition

Claim 1 is the central composition claim. It requires a first layer containing probenecid and a second layer containing Compound III-2 plus specified excipients.

The claim is narrower than a conventional active-ingredient claim in three respects:

It requires a bilayer tablet.
It assigns probenecid to the first layer and Compound III-2 to the second layer.
It specifies quantitative windows for each major excipient and distinguishes intragranular from extragranular magnesium stearate.

The quantitative limitations are commercially important. A generic manufacturer could seek design-around protection by changing the tablet architecture or shifting excipients outside the claimed ranges. The practical strength of the claim will depend on how the ranges are construed, whether "about" permits modest variation, and whether the accused product uses the same manufacturing classification for magnesium stearate.

Claim 2: Sequential compression process

Claim 2 requires:

compression of a probenecid-containing first granular material;
formation of a pre-compressed first layer;
addition of a second granular material containing Compound III-2; and
final compression using a second force.

This is a process claim dependent on claim 1. It does not merely require production of a bilayer tablet. It requires a staged compression sequence and two compression forces.

The claim creates a manufacturing-disclosure issue. A finished tablet may reveal its composition and layer structure, but it may not reveal whether the manufacturer used the claimed compression sequence. Discovery, batch records, equipment parameters, technical literature, or process inspections would normally be needed to establish infringement.

Claims 3-8: Treatment and administration

Claim 3 covers administering the claimed bilayer tablet to treat or prevent a disease. Claim 4 limits the subject to a human.

Claim 5 lists bacterial populations, including:

Escherichia coli;
Klebsiella species;
Proteus species;
Enterobacter species;
Citrobacter species;
Haemophilus species;
Staphylococcus species;
Streptococcus species;
Bacteroides species;
Clostridium species; and
other organisms associated with urinary, respiratory, intra-abdominal, bone, joint, skin and gastrointestinal infections.

Claim 6 recites specific infectious diseases, including uncomplicated and complicated urinary tract infections, complicated intra-abdominal infection, pneumonia, otitis media, sinusitis, gonococcal urethritis, pelvic inflammatory disease, prostatitis, bone infection, joint infection, diabetic foot infection and infectious diarrhea.

Claim 7 adds neurodegenerative disease, amyotrophic lateral sclerosis, Parkinson's disease, Alzheimer's disease, Huntington's disease, cancer and inflammatory bowel disease. These indications are substantially broader than the FDA-approved indication for Orlynvah and may reflect research-use or mechanistic coverage rather than current commercial labeling.

Claim 8 requires administration with food. That limitation corresponds to the product's food-effect instructions and could strengthen an infringement theory where a generic label instructs administration with food.

Claims 9-10: Pharmacokinetic limitations

Claim 9 requires administration resulting in higher beta-lactam AUC than a comparable composition. Claim 10 requires a substantially similar Cmax compared with a comparable composition.

These claims seek to protect a pharmacokinetic profile rather than only a formulation. They may be difficult to enforce against a generic without comparative pharmacokinetic data. The terms "comparable subject," "comparable composition" and "substantially the same" may create claim-construction and proof issues.

How strong is the patent estate for Orlynvah?

U.S. Patent 11,478,428 is a formulation and manufacturing patent, not a broad composition-of-matter patent for sulopenem itself. Its commercial value therefore depends on whether the approved Orlynvah tablet matches the claimed formulation and whether alternative formulations can achieve acceptable exposure without using the claimed architecture.

Risk factor	Assessment
Exact approved-product read-on	Potentially strong if the marketed tablet matches the claimed quantities
Design-around difficulty	Moderate; bilayer and excipient changes may be possible
Manufacturing-process enforcement	Moderate to difficult without process evidence
Method-of-use breadth	Broad in wording but limited by the claimed tablet
PK claim enforceability	Fact-intensive and potentially difficult
Chemical composition protection	Not established by the supplied claims
Biosimilar relevance	None; this is a small-molecule antibiotic
Generic litigation exposure	Significant after ANDA filings, subject to listed patents and exclusivity

The patent is most valuable as part of a layered estate that may include active-ingredient, prodrug, salt, formulation, process and method-of-use patents. Patent 11,478,428 alone does not establish protection through the end of the product's commercial life.

When does U.S. Patent 11,478,428 expire?

The patent issued on October 25, 2022. Its effective expiration is governed by the earliest applicable nonprovisional priority date, terminal disclaimers, patent-term adjustment and any patent-term extension. The patent's nominal term is expected to extend into the late 2030s based on its modern filing history.

A precise expiration date should be taken from the USPTO Patent Center record and any applicable terminal-disclaimer or patent-term-adjustment data. The issue date alone cannot establish the expiration date.

For commercial planning, the more immediate barriers are likely to be:

FDA regulatory exclusivity for Orlynvah;
other listed patents covering sulopenem etzadroxil or the combination;
formulation and manufacturing patents;
and the timing of any Paragraph IV ANDA challenge.

What is the FDA regulatory status of Orlynvah?

The FDA approved Orlynvah, an oral combination of sulopenem etzadroxil and probenecid, in September 2024 for adult women with uncomplicated urinary tract infections caused by designated susceptible microorganisms when alternative oral antibacterial treatments are limited or unavailable.[1]

The approval is narrower than the full indication language in claims 5-7 of U.S. Patent 11,478,428. The patent's references to pneumonia, intra-abdominal infection, neurodegenerative disease, cancer and inflammatory bowel disease do not establish FDA approval for those uses.

The marketed product uses a fixed-dose combination in a bilayer tablet. The approved dosing regimen is taken with food, consistent with claim 8 and the product labeling.[1]

FDA exclusivity and Orange Book implications

As a newly approved oral antibacterial product, Orlynvah may receive regulatory exclusivity independent of patent protection. The applicable period depends on FDA classification of sulopenem etzadroxil and the combination product, including whether the approval qualifies for new chemical entity, new product or other exclusivity.

Orange Book listing must be evaluated separately from patent validity. A patent can be valid without being listed, and listing does not establish validity or enforceability. A listed patent may nevertheless require an ANDA applicant to certify under Paragraph I, II, III or IV.

What Paragraph IV challenges and generic entry risks exist?

A generic applicant seeking approval of a substantially identical sulopenem etzadroxil/probenecid product could file an ANDA with certifications addressing listed patents. A Paragraph IV certification would assert that a listed patent is invalid, unenforceable or not infringed.

Potential generic strategies include:

challenging the validity of the bilayer formulation claims;
designing around the claimed excipient ranges;
using a different layer assignment;
changing the compression process;
disputing whether the generic label induces the claimed methods of treatment;
arguing that PK claims are indefinite or not met; and
relying on a noninfringing labeling carve-out where legally available.

A Paragraph IV notice concerning a listed patent can trigger a 45-day period for the patent holder to file suit and may create a 30-month stay of FDA approval under the Hatch-Waxman framework.[2] The stay does not automatically extend to every patent in the estate, and it does not prevent an applicant from continuing development or, in some circumstances, launching at risk.

No biosimilar pathway applies. Orlynvah is a small-molecule drug, so competition would arise through ANDAs or, depending on the product and regulatory strategy, a 505(b)(2) application.

What patent litigation affects sulopenem etzadroxil?

The supplied claims do not establish that U.S. Patent 11,478,428 has been litigated. Patent litigation status must be checked against federal district court dockets, the Patent Trial and Appeal Board and FDA Orange Book certifications.

The principal litigation questions would be:

whether the approved Orlynvah tablet falls within every limitation of claim 1;
whether the generic uses the claimed two-stage compression process;
whether "about" ranges are definite and properly construed;
whether the disease and PK claims satisfy written-description and enablement requirements;
whether any terminal disclaimer affects patent life;
and whether the patent is listed for the approved product.

A post-grant review or inter partes review could target obviousness, anticipation, indefiniteness or lack of written description. Formulation patents often face obviousness challenges based on known excipients, standard bilayer-tablet techniques and routine optimization. The patent holder's strongest response would be evidence that the specific layer architecture and excipient balance produced an unexpected pharmacokinetic or manufacturing result.

What licensing deals support the sulopenem program?

Iterum obtained rights to develop sulopenem from Pfizer. Iterum's corporate filings describe sulopenem as an asset acquired from Pfizer and developed for oral and intravenous use.[3] The licensing history is commercially relevant because it indicates that product rights, patent ownership and royalty obligations may be distributed between Iterum and the original developer.

The relevant diligence points include:

ownership of U.S. formulation patents;
royalty or milestone obligations to Pfizer;
rights to improvements developed after the original license;
territorial rights outside the United States;
and rights to intravenous sulopenem or other prodrug forms.

How does U.S. Patent 11,478,428 compare with competing anti-infective products?

Product or class	Regulatory route	Relationship to Orlynvah	Patent risk
Orlynvah	NDA	Reference product	Protected by product, formulation and process estate
Oral beta-lactam generics	ANDA	Potential substitutes for selected infections	Lower cost, but not necessarily therapeutically interchangeable
Fluoroquinolones	ANDA/NDA	Alternative oral antibiotics	Safety restrictions and resistance limit substitution
Nitrofurantoin	ANDA	UTI alternative	Narrower infection utility
Fosfomycin	ANDA	UTI alternative	Different dosing and resistance profile
Other oral penems	NDA or development-stage	Direct class competition	Product-specific patent and regulatory risk
Intravenous carbapenems	ANDA/NDA	Route-of-administration substitutes	Higher administration burden

Orlynvah's commercial differentiation is the oral delivery of sulopenem exposure supported by probenecid. That positioning depends on the approved indication, antimicrobial stewardship policies, susceptibility data and the availability of other oral options.

What generic launch scenarios should investors model?

Scenario 1: No early challenge

If no ANDA applicant files a Paragraph IV certification, entry may be delayed until regulatory exclusivity and relevant patents expire or become irrelevant.

Scenario 2: Formulation design-around

A challenger could develop a different tablet structure or excipient profile. This approach may reduce claim 1 risk but could require new bioequivalence work and may not avoid other patents.

Scenario 3: Paragraph IV litigation

A patent challenge could produce a 30-month stay, settlement, licensed entry or accelerated litigation. The outcome would depend on claim construction and the scope of the listed patent estate.

Scenario 4: At-risk launch

An applicant could launch after regulatory approval while litigation remains unresolved. Exposure would include damages, injunctive relief and potential willfulness allegations.

Scenario 5: 505(b)(2) competition

A modified formulation or different dosing regimen could seek approval through a 505(b)(2) pathway. This route may create a separate patent-certification and labeling dispute rather than a conventional ANDA case.

Key Takeaways

U.S. Patent 11,478,428 is centered on a bilayer tablet containing approximately 500 mg each of probenecid and sulopenem etzadroxil.
Its most commercially important limitations are the two-layer structure, the specific excipient ranges and the staged compression process.
The treatment claims are broad in disease language but remain dependent on the claimed tablet.
Claims 9 and 10 add AUC and Cmax limitations that may be difficult to prove without comparative pharmacokinetic data.
Orlynvah was FDA-approved in September 2024 for selected uncomplicated urinary tract infections in adult women with limited oral treatment options.
This is a small-molecule product. Biosimilar analysis does not apply.
Generic competition would likely proceed through ANDAs, Paragraph IV certifications, design-around formulations or a 505(b)(2) strategy.
Patent 11,478,428 should be analyzed together with the full Orange Book listing, related sulopenem patents, FDA exclusivity and any terminal-disclaimer or patent-term-adjustment records.

FAQs

Is U.S. Patent 11,478,428 a composition-of-matter patent?

No. The supplied claims primarily protect a specific bilayer formulation, its manufacturing sequence and methods of using that formulation.

Does the patent cover all probenecid and sulopenem tablets?

No. The independent claim requires a bilayer tablet, specified active-ingredient amounts and defined excipient ranges. Other tablet designs may fall outside claim 1.

Can a generic use the same active ingredients with different excipients?

Potentially. A different excipient profile could avoid literal infringement of claim 1, but the product could remain exposed to other formulation, active-ingredient, process or method-of-use patents.

Does FDA approval for Orlynvah validate the patent claims?

No. FDA approval and patent validity are separate legal determinations. Regulatory approval does not establish that the claims are valid or enforceable.

Is probenecid itself protected by this patent?

The patent does not broadly protect probenecid as a molecule. It claims probenecid as one component of the specified bilayer tablet and related treatment methods.

References

U.S. Food and Drug Administration. (2024). Orlynvah prescribing information. FDA.
U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, Pub. L. No. 98-417, 98 Stat. 1585.
Iterum Therapeutics plc. (2023). Annual report on Form 10-K. U.S. Securities and Exchange Commission.
United States Patent and Trademark Office. (2022). U.S. Patent No. 11,478,428. USPTO.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Iterum Therap	ORLYNVAH	probenecid; sulopenem etzadroxil	TABLET;ORAL	213972-001	Oct 25, 2024		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y			USE IN TREATING UNCOMPLICATED URINARY TRACT INFECTIONS CAUSED BY ESCHERICHIA COLI, KLEBSIELLA PNEUMONIAE, OR PROTEUS MIRABILIS	⤷ 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
Argentina	117510	⤷ Start Trial
Australia	2019429755	⤷ Start Trial
Brazil	112021015744	⤷ Start Trial
Canada	3129337	⤷ Start Trial
China	112739330	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,478,428

Which drugs does patent 11,478,428 protect, and when does it expire?

Summary for Patent: 11,478,428