U.S. Patent 11,850,228: Scope, Claim Analysis, Expiration Risk and Solriamfetol Patent Landscape

U.S. Patent No. 11,850,228 protects renal-function-based dosing of solriamfetol, marketed as Sunosi, for excessive daytime sleepiness. Its core limitation is a patient-specific dosing algorithm tied to eGFR, dose escalation, maximum daily dose, and exclusion of unstable cardiovascular disease. The patent is narrower than a basic composition-of-matter patent but can create meaningful method-of-use and prescribing-infringement risk for generic solriamfetol products.

The strongest claims are claims 1 and 12. Claim 1 covers moderate and severe renal impairment. Claim 12 covers patients with no, mild, moderate, or severe renal impairment and establishes separate dosing pathways for eGFR categories. Claims 2-4 and 13-15 narrow the indication to narcolepsy, obstructive sleep apnea, and shift work disorder. Claims 24 and 25 add depression-related excessive daytime sleepiness.

What drug does U.S. Patent 11,850,228 protect?

U.S. Patent 11,850,228 covers dosing methods for the active pharmaceutical ingredient identified in the claims as [R]-2-amino-3-phenylpropylcarbamate, or APC. APC corresponds to the active moiety in solriamfetol hydrochloride, marketed by Jazz Pharmaceuticals as Sunosi.

Item	Patent relevance
Active ingredient	Solriamfetol, administered as solriamfetol hydrochloride
Product	Sunosi tablets
Drug class	Dopamine and norepinephrine reuptake inhibitor
Approved uses	Excessive daytime sleepiness associated with narcolepsy or obstructive sleep apnea
Dosage forms in claims	APC-HCl equivalents of approximately 44.7 mg, 89.3 mg and 178.5 mg
Core technical issue	Dose adjustment based on renal function
Primary protected population	Patients with eGFR from approximately 15 to at least 90 mL/min/1.73 m²
Regulatory pathway	New drug application, not a biologic

The FDA-approved label recommends lower starting and maximum doses for patients with moderate or severe renal impairment. It also states that solriamfetol is not recommended for patients with end-stage renal disease [2].

What are the independent claims of U.S. Patent 11,850,228?

The patent has two principal independent method claims.

Claim 1: Moderate and severe renal impairment

Claim 1 requires all of the following:

Treatment of excessive daytime sleepiness.
A subject with moderate or severe renal impairment.
Selection of a subject without unstable cardiovascular disease.
Determination of eGFR.
For eGFR of approximately 30-59:
- 37.5 mg APC daily from day one through day n1;
- 75 mg APC daily beginning on day n1+1;
- n1 equal to at least five;
- no daily dose above 75 mg APC.
For eGFR of approximately 15-29:
- 37.5 mg APC daily;
- no daily dose above 37.5 mg APC.

The claim therefore covers a titration protocol, not merely the administration of solriamfetol to a patient with renal impairment.

Claim 12: All major renal-function categories

Claim 12 is broader in patient coverage. It addresses patients with no, mild, moderate, or severe renal impairment and divides them into three eGFR groups:

eGFR range	Initial dose	Escalation	Maximum dose
15-29	37.5 mg APC	No escalation stated	37.5 mg APC
30-59	37.5 mg APC	75 mg after the initial period	75 mg APC
60-89 or at least 90	37.5 mg APC	75 mg after at least three days, then 150 mg after at least three additional days	150 mg APC

The claim uses "about" before the eGFR ranges. That language may provide some tolerance around the numerical boundaries, but it does not eliminate the importance of eGFR testing or create an unrestricted dosing claim.

What formulations and doses are protected?

Claims 5-6 and 16-18 translate APC free-base equivalents into APC hydrochloride amounts:

APC equivalent	APC-HCl amount in claims	Commercial significance
37.5 mg APC	About 44.7 mg APC-HCl	Corresponds to a half-strength starting dose
75 mg APC	About 89.3 mg APC-HCl	Corresponds to the intermediate dose
150 mg APC	About 178.5 mg APC-HCl	Corresponds to the highest claimed dose

The claims are drafted around active-moiety equivalents rather than only a particular tablet strength. A generic product using a different tablet size, score configuration, excipient system, or packaging format could still fall within the claims if it delivers the specified solriamfetol hydrochloride equivalent.

The claims do not appear limited to a particular excipient, coating, release profile, polymorph, manufacturing process, or tablet geometry. Their principal limitations are therapeutic and dosing-related.

How does the patent define the dosing schedule?

The dosing schedule is a central infringement limitation.

For moderate renal impairment, the patient must receive 37.5 mg APC for at least five days under the literal language of claim 1 before increasing to 75 mg. Claim 12 uses inconsistent variable references, discussed below, but appears intended to require the same initial titration concept.

For patients with eGFR of at least 60, claim 12 requires:

37.5 mg APC initially;
escalation to 75 mg after at least three days; and
escalation to 150 mg after at least three additional days.

Claims 7-8 and 19-20 add timing limitations. The doses must be administered:

upon awakening; or
more than nine hours before bedtime.

A prescribing protocol that starts at 75 mg without the claimed lower-dose period may avoid literal infringement of the escalation limitations, depending on the applicable claim construction and the actual instructions for use. A protocol that uses the same sequence, however, presents greater exposure.

What are the renal impairment limitations?

The patent divides renal function into clinically meaningful dosing groups.

Severe renal impairment

For eGFR of approximately 15-29, the claimed ceiling is 37.5 mg APC per day. The patient cannot receive a higher daily dose under claims 1 or 12.

Moderate renal impairment

For eGFR of approximately 30-59, the patient begins at 37.5 mg APC and may increase to 75 mg after the specified initial period. The claim prohibits a daily dose above 75 mg APC.

Mild or no renal impairment

For eGFR of approximately 60-89 or at least 90, claim 12 covers escalation to 150 mg APC. This category is commercially important because it captures the conventional Sunosi titration pathway for patients without the renal restrictions applicable to lower eGFR groups [2].

The claims require determining eGFR. Claim 10 and claim 22 specify use of the Modification in Diet in Renal Disease equation. Claims do not expressly require a particular laboratory vendor, blood test platform, serum creatinine assay, or electronic medical-record system.

What diseases and conditions are covered?

The dependent claims identify five sources of excessive daytime sleepiness:

Condition	Claim coverage
Narcolepsy	Claims 2 and 13
Obstructive sleep apnea	Claims 3 and 14
Shift work disorder	Claims 4 and 15
Depression	Claims 24 and 25
Unspecified excessive daytime sleepiness	Claims 1 and 12

The FDA-approved indications for Sunosi are excessive daytime sleepiness associated with narcolepsy or obstructive sleep apnea. Shift work disorder and depression-related sleepiness are included in the patent claims but are not identified as approved Sunosi indications in the FDA labeling cited here [2].

That distinction affects product labeling and inducement analysis. A generic applicant that omits unapproved uses from its label may reduce, but not necessarily eliminate, the risk that its product is used according to the patented regimen. Narcolepsy and obstructive sleep apnea remain the commercially dominant claim categories because they correspond to approved use.

What claim-construction issues affect patent strength?

Several drafting issues are material.

Undefined variable in claim 11

Claim 11 recites that "m is an integer equal to or greater than 7," but claim 1 uses n1 rather than m. As supplied, claim 11 contains an apparent antecedent or typographical problem. Its enforceability would depend on the issued patent text, prosecution history, and whether a court treats the defect as correctable or as an indefiniteness problem.

Variable inconsistency in claim 12

Claim 12 states that the first dose is provided from day one to day m, then defines n1 as an integer equal to or greater than five and n2 as n1+1. This appears inconsistent. The claim may have intended to use n1 rather than m. The error creates potential vulnerability under 35 U.S.C. §112(b), although courts can sometimes resolve obvious drafting errors from the intrinsic record.

"About" language

The eGFR thresholds are approximate. A patient with an eGFR near 30, 60, or 90 could create a boundary dispute. The relevant question would be whether the measured value falls within the claim's construction of "about" and whether the treating party used that value to select the dose.

"Equivalent to" language

The dose limitations are expressed as APC equivalents. This can reach products labeled by APC-HCl weight even where the salt mass differs from the free-base mass. A generic manufacturer cannot necessarily avoid the claims by changing only the salt-weight presentation.

What FDA and Orange Book status applies to Sunosi?

Sunosi was approved by the FDA in March 2019 under NDA 211230 for excessive daytime sleepiness associated with narcolepsy or obstructive sleep apnea [2, 3].

The Orange Book is the principal FDA source for approved drug products, therapeutic equivalence evaluations, and listed patents. U.S. Patent 11,850,228 should be assessed together with all current Sunosi Orange Book listings, including any continuation, method-of-use, formulation, or other patents listed for the NDA [3].

A patent listing does not establish validity or infringement. It can, however, affect abbreviated new drug application timing and Paragraph IV litigation under the Hatch-Waxman framework.

When does U.S. Patent 11,850,228 lose exclusivity?

The patent issued on December 26, 2023. Its enforceable term is governed by the earliest effective nonprovisional filing date, any patent-term adjustment, and any applicable patent-term extension. The issuance date is not the expiration date.

Because the claims concern solriamfetol dosing and appear to belong to a continuation-style patent family, the expiration analysis must account for terminal disclaimers and the earliest effective priority date. The relevant commercial question is not the patent's issuance date but whether the patent remains listed and enforceable when a generic applicant files or receives approval.

The FDA Orange Book and the USPTO patent record should be read together. Orange Book listing information determines regulatory relevance, while the USPTO front page and patent-term records control the statutory term [1, 3].

Which companies are challenging the Sunosi patent estate?

Publicly actionable challenge analysis should distinguish among:

Paragraph IV certifications filed against Orange Book-listed patents.
Declaratory-judgment actions.
Inter partes review petitions.
ANDA litigation under 21 U.S.C. §355(j).
Commercial generic development without a publicly disclosed challenge.

The supplied claim set does not establish that a specific company has filed a Paragraph IV certification or that litigation has been instituted against U.S. Patent 11,850,228. The patent number alone is not evidence of a filed challenge, settlement, license, or authorized generic agreement.

For diligence, the relevant sources are FDA paragraph-IV notice records, federal district-court dockets, PTAB proceedings, SEC filings by Jazz Pharmaceuticals, and current Orange Book entries. No biosimilar pathway applies because solriamfetol is a small-molecule drug, not a biologic.

How strong is the patent estate for generic solriamfetol?

The patent's strength is mixed.

Factor	Assessment
Technical specificity	High; claims define eGFR bands, titration periods and dose ceilings
Product coverage	Moderate; claims reach solriamfetol dosing but are not composition claims
Label dependence	High; infringement risk increases if the generic label instructs the claimed regimen
Design-around potential	Moderate; alternative titration instructions may avoid literal limitations
Clinical-practice relevance	High; the regimen tracks renal dosing concepts in FDA labeling
Formulation barrier	Low based on the supplied claims; no excipient or manufacturing limitation is apparent
Biosimilar barrier	Not applicable
Litigation exposure	Dependent on Orange Book listing, claim validity and generic labeling

The patent does not appear to block every solriamfetol product. It targets a particular method of administering the product to patients after eGFR assessment. A generic developer could evaluate a label that omits certain dosing instructions, but that strategy must be tested against FDA labeling requirements, induced-infringement theories and the full patent family.

What generic launch scenarios exist?

Scenario 1: Full label carve-out

A generic applicant removes protected renal dosing or unapproved-use language where legally permissible. This may reduce inducement exposure but can conflict with FDA requirements if the omitted information is necessary for safe use.

Scenario 2: Paragraph III certification

The applicant accepts the listed patent and delays approval until expiration. This produces the lowest litigation risk but postpones market entry.

Scenario 3: Paragraph IV challenge

The applicant asserts invalidity, unenforceability or non-infringement. Potential defenses include indefiniteness arising from variable inconsistencies, lack of written description, obviousness over renal-dose studies and solriamfetol labeling, and non-infringement based on an alternative titration schedule.

Scenario 4: Non-infringing label strategy

The applicant markets a product with dosing instructions that do not reproduce the claimed sequence. This approach carries regulatory and induced-infringement risk because the relevant analysis extends beyond the literal text of the label.

How does this patent compare with composition and formulation patents?

U.S. Patent 11,850,228 is a method-of-use patent. It differs from:

composition-of-matter patents covering solriamfetol or its chemical structure;
formulation patents covering tablets, excipients, release characteristics or stability;
manufacturing patents covering synthesis, purification or crystallization;
polymorph or salt patents covering a particular solid form.

A generic manufacturer that avoids a formulation patent may still face this method patent. Conversely, a challenge to U.S. Patent 11,850,228 would not necessarily invalidate separate composition, formulation or process patents.

The principal manufacturing barrier is therefore distinct from the principal clinical-use barrier. The supplied claims do not independently protect API synthesis or tablet manufacturing.

Key Takeaways

U.S. Patent 11,850,228 covers renal-function-based solriamfetol dosing for excessive daytime sleepiness.
Claims 1 and 12 are the central claims.
Severe renal impairment is limited to 37.5 mg APC daily.
Moderate renal impairment permits escalation from 37.5 mg to 75 mg APC, subject to an initial titration period.
Patients with eGFR of at least 60 may escalate to 150 mg APC under claim 12.
The claims also require eGFR determination and exclude subjects with unstable cardiovascular disease.
APC-HCl amounts of approximately 44.7 mg, 89.3 mg and 178.5 mg correspond to 37.5 mg, 75 mg and 150 mg APC equivalents.
The patent is a method-of-use patent, not a composition, formulation or manufacturing patent.
Claims 11 and 12 contain apparent variable inconsistencies that may create indefiniteness and claim-construction issues.
Orange Book status, terminal disclaimers, patent-term adjustment and the full Sunosi patent family are necessary to determine the practical generic entry date.
No biosimilar pathway applies to solriamfetol.

FAQs About U.S. Patent 11,850,228

Does the patent cover all Sunosi prescriptions?

No. It covers specified dosing methods tied to eGFR, escalation timing, maximum dose and other patient-selection limitations.

Can a generic avoid the patent by using a different tablet strength?

Not necessarily. The claims use APC-equivalent dosing. Changing tablet strength alone may not avoid infringement.

Does the patent cover solriamfetol for depression?

Claims 24 and 25 expressly recite depression-related excessive daytime sleepiness. That claimed use is distinct from the FDA-approved Sunosi indications.

Is eGFR testing required under the patent?

Yes. Claims 1 and 12 require determining eGFR, and claims 10 and 22 specify the Modification in Diet in Renal Disease equation.

Does the patent block solriamfetol use in end-stage renal disease?

The claims supplied cover eGFR beginning at approximately 15 mL/min/1.73 m². The FDA label states that Sunosi is not recommended for end-stage renal disease [2].

References

United States Patent and Trademark Office. (2023). U.S. Patent No. 11,850,228: Methods of treating excessive daytime sleepiness. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2024). Sunosi (solriamfetol) prescribing information. Jazz Pharmaceuticals, Inc.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. U.S. Department of Health and Human Services.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Axsome Malta	SUNOSI	solriamfetol hydrochloride	TABLET;ORAL	211230-001	Jun 17, 2019	AB	RX	Yes	No	11,850,228	⤷ Start Trial				TREATMENT OF EXCESSIVE DAYTIME SLEEPINESS BY ADMINISTERING SOLRIAMFETOL TO A SUBJECT HAVING NO, MILD, MODERATE, OR SEVERE RENAL IMPAIRMENT	⤷ Start Trial
Axsome Malta	SUNOSI	solriamfetol hydrochloride	TABLET;ORAL	211230-002	Jun 17, 2019	AB	RX	Yes	Yes	11,850,228	⤷ Start Trial				TREATMENT OF EXCESSIVE DAYTIME SLEEPINESS BY ADMINISTERING SOLRIAMFETOL TO A SUBJECT HAVING NO, MILD, MODERATE, OR SEVERE RENAL IMPAIRMENT	⤷ 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

Details for Patent: 11,850,228

Which drugs does patent 11,850,228 protect, and when does it expire?

Summary for Patent: 11,850,228