US Patent 11,337,979: Sildenafil Liquid Oral Composition Claims, Exclusivity and Patent Landscape

US Patent 11,337,979 protects defined liquid oral sildenafil compositions rather than sildenafil as a molecule. Its broadest independent composition claim requires approximately 10 mg/mL sildenafil, water, a pH of about 4 to 8, and a specified anti-foaming agent at 0.1 to 100 mg/mL. Dependent claims narrow the protection through sildenafil citrate, particle size, pH, glycerin or other wetting agents, viscosity modifiers, buffers, preservatives, sweeteners, flavors, and specific formulation ranges.

The patent creates the greatest infringement risk for a liquid sildenafil product that replicates the claimed excipient architecture, particularly a 10 mg/mL formulation containing simethicone, xanthan gum, glycerin, a citrate or phosphate buffer, benzoic acid or a salt, and a sweetener. It does not, on its face, cover sildenafil tablets, sildenafil powder, a liquid formulation outside the claimed concentration or pH ranges, or every liquid sildenafil product regardless of excipients.

What does US Patent 11,337,979 claim?

The patent has three functional claim groups:

Composition claims 1-19 and 21-27.
A broad method-of-treatment claim in claim 20.
Disease-specific treatment claims 28-30.

Claim 1 is the controlling composition claim. Every dependent composition claim incorporates its limitations. The claim structure is summarized below.

Claim element	Requirement in claim 1
Active ingredient	About 10 mg/mL sildenafil or a pharmaceutically acceptable salt
Dosage form	Liquid oral pharmaceutical composition
Vehicle	Water
pH	About 4 to about 8
Required excipient	Anti-foaming agent
Anti-foaming agent	Simethicone, simethicone emulsion, organic phosphate, paraffin oil, stearate, glycol, or combination
Anti-foaming concentration	About 0.1 to about 100 mg/mL

The claim is combination-based. A product must satisfy all required elements of the claim to infringe literally. The presence of sildenafil alone is insufficient.

How broad is the independent composition claim?

Claim 1 is broad in excipient selection and anti-foaming concentration, but narrower in formulation architecture.

The claim requires:

A liquid oral product.
Approximately 10 mg/mL sildenafil.
Water as a vehicle.
A pH between approximately 4 and 8.
An anti-foaming excipient from an expressly listed class.

The anti-foaming limitation is significant. A formulation containing 10 mg/mL sildenafil in water at pH 5 but no claimed anti-foaming agent would not meet claim 1 literally. A formulation using a defoamer outside the listed classes may also avoid literal infringement, subject to claim construction and the doctrine of equivalents.

The phrase “about 10 mg/mL” introduces a numerical interpretation issue. The patent does not make every concentration near 10 mg/mL automatically infringing. The legally relevant range depends on the specification, prosecution history, claim construction and technical meaning of “about.” A product at 5 mg/mL or 20 mg/mL presents a stronger non-infringement position than a product at 9.8 or 10.2 mg/mL, but the result cannot be determined from the claims alone.

What formulations are protected by US 11,337,979?

The dependent claims progressively move from broad formulation coverage to a specific commercial formulation profile.

Sildenafil salt and particle-size limitations

Claim 2 requires sildenafil citrate. Claims 3, 21 and 22 impose particulate-size limitations:

Claim	Particle-size limitation
3	d90 from about 10 to about 200 microns
21	d90 from about 10 to about 100 microns
22	d90 from about 20 to about 30 microns

A product may fall within claim 1 without satisfying any particle-size limitation. Particle size becomes relevant only to the narrower dependent claims.

The d90 limitation is technically important because it concerns the particle-size distribution of sildenafil before or within the liquid formulation. A generic manufacturer would need a reproducible analytical method, sampling protocol and specification for d90. Differences in laser diffraction equipment, dispersion conditions and sample preparation can produce materially different reported values.

pH limitations

Claim 1 covers a pH of about 4 to about 8. Claim 4 narrows the range to about 4 to about 6, and claim 23 specifies a pH of about 5.

The pH limitations may be difficult to design around if the product requires acidic stabilization or palatability. A product at pH 3.5 or pH 8.5 may avoid literal infringement of claim 1, but such changes could affect sildenafil stability, preservative performance, taste and regulatory comparability.

Wetting-agent limitations

Claims 5, 6 and 24-25 cover ethanol, glycerin, propylene glycol, or combinations. The relevant ranges are:

Claim	Wetting-agent range
6	About 100 to about 1,000 mg/mL
24	About 100 to about 700 mg/mL
25	About 200 to about 600 mg/mL

Glycerin at about 400 mg/mL is specifically recited in claim 19. A formulation with approximately 40% glycerin by volume or mass, depending on the specification's measurement convention, creates a direct design-around concern because it falls within the narrower dependent ranges.

Viscosity modifiers

Claims 7, 12-18 and 26 cover a long list of viscosity-modifying agents, including xanthan gum, cellulose derivatives, alginates, carbomers, gums, starches, polyethylene glycol, polyvinylpyrrolidone and colloidal silicon dioxide.

The ranges include:

About 0.1 to 100 mg/mL under claim 7.
About 1 to 20 mg/mL under claims 14, 15 and 26.
About 1 to 6 mg/mL under claims 16 and 17.
About 1 to 3 mg/mL for xanthan gum under claim 18.
About 2 to 3 mg/mL for xanthan gum under claim 19.

The list contains repeated and overlapping excipients, including methylcellulose and sodium alginate. Those drafting features do not necessarily invalidate the claims, but they can create claim-construction and written-description issues if the specification does not support the full breadth of every listed material and concentration.

Anti-foaming-agent limitations

Claim 1 permits an anti-foaming-agent range of about 0.1 to 100 mg/mL. Claims 8, 14-19 narrow that range to about 0.1 to 0.5 mg/mL.

Claim 18 identifies a 30% simethicone emulsion. Claim 19 narrows the amount to about 0.5 mg/mL. These claims appear directed to a low-level simethicone-containing oral suspension or solution designed to manage foam during manufacturing, filling or administration.

The distinction between the amount of simethicone emulsion and the amount of active simethicone may be material. A 30% emulsion at 0.5 mg/mL contains less than 0.5 mg/mL of simethicone itself. Product documentation would need to establish which quantity the claim requires.

What is the narrowest commercial formulation covered by the patent?

Claim 19 is the most specific composition claim. It requires:

About 10 mg/mL sildenafil under claim 1.
Water.
pH of about 4 to 8 under claim 1.
30% simethicone emulsion at about 0.5 mg/mL.
Xanthan gum at about 2 to 3 mg/mL.
Glycerin at about 400 mg/mL.
Citrate buffer, phosphate buffer, or both, at about 0.03 M.
Benzoic acid or a salt at about 0.1 to 2.4 mg/mL.
Sucralose, acesulfame potassium, or both, at about 0.1 to 6 mg/mL.
Flavorant at about 0.1 mg/mL.

The drafting of claim 19 contains an unusual phrase: “an amount of from about 0.03 M.” As written in the supplied text, that limitation lacks an upper endpoint. The issued patent and certificate of correction, if any, control the legal wording. The claim should be reviewed against the official USPTO image and prosecution record before relying on the supplied transcription.

What diseases and uses are protected by US 11,337,979?

Claims 20 and 28-30 cover methods of administering the claimed liquid composition to treat:

Pulmonary arterial hypertension.
Erectile dysfunction.
Benign prostatic hyperplasia.
Combinations of those conditions.

Claim 20 is broader because it covers the listed conditions collectively. Claims 28, 29 and 30 separate the indications.

The method claims require administration of the claimed liquid composition. They do not cover treatment using sildenafil tablets, capsules or an unclaimed oral liquid. They also do not automatically cover every use of sildenafil for the same disease.

The pulmonary arterial hypertension limitation has a direct regulatory connection to sildenafil products such as Revatio. Erectile dysfunction is associated with Viagra and generic sildenafil products. Benign prostatic hyperplasia is a claimed use here, although tadalafil has been the principal PDE5 inhibitor associated with an FDA-approved BPH indication.

When does US Patent 11,337,979 lose exclusivity?

The patent issued on May 17, 2022. Its expiration date cannot be established from the claim text alone because the term depends on the earliest effective nonprovisional filing date, any terminal disclaimer, patent-term adjustment and possible patent-term extension.

The ordinary US patent term is generally 20 years from the earliest effective nonprovisional application filing date, subject to statutory adjustments under 35 U.S.C. §§ 154 and 156. The relevant term calculation should be taken from the USPTO Patent Center record and the patent's front page rather than inferred from the issue date.[1]

Event	Date or status
US patent number	11,337,979
Issue date	May 17, 2022
Patent type	Utility patent
Core technology	Liquid oral sildenafil composition
Main claim categories	Composition and treatment method
Expiration	Requires verified front-page term data and terminal-disclaimer review
Regulatory exclusivity	Separate from patent term and depends on the FDA-approved product

Patent expiration does not necessarily equal FDA marketing exclusivity expiration. FDA exclusivity is product-specific and may apply to a new drug application, supplement or pediatric study. A formulation patent also may not be listed in the Orange Book unless it claims an approved drug substance, drug product or method of use in a manner that satisfies FDA listing rules.[2]

What is the Orange Book status of US 11,337,979?

The patent's Orange Book status cannot be assumed from its existence. FDA Orange Book listing is separate from issuance and depends on whether the patent holder or NDA holder submitted the patent for an eligible approved drug product or method of use.[2]

For a patent to affect an abbreviated new drug application, the relevant NDA patent listing generally must identify a drug substance, drug product or method of use that falls within FDA's listing framework. A formulation patent directed to a liquid sildenafil product may be relevant if the patented formulation corresponds to an approved NDA product. It may have limited or no Orange Book significance if the patent was not submitted, was submitted after the relevant certification deadline, or covers subject matter that FDA does not list.

A current commercial assessment should distinguish:

Question	Legal significance
Is the patent issued?	Establishes enforceable patent rights, subject to validity and enforceability defenses
Is the patent listed in the Orange Book?	Determines whether it can trigger an ANDA patent certification framework
Is the patented product approved?	Links the claims to an FDA-approved NDA product
Is the listing timely?	Affects Paragraph IV and 30-month-stay mechanics
Does the approved label practice the claim?	Affects method-of-use and product-claim relevance

What Paragraph IV challenges could target this patent?

A generic applicant seeking approval for a liquid oral sildenafil product could evaluate a Paragraph IV certification if US 11,337,979 is listed for the relevant reference product and has not expired. The applicant would assert that the patent is invalid, unenforceable or will not be infringed by the proposed product.

Potential invalidity theories include:

Anticipation

A single prior-art reference would need to disclose every limitation of the asserted claim. For claim 1, that would include the approximate sildenafil concentration, water vehicle, pH range and qualifying anti-foaming agent at the claimed concentration.

Prior art directed to sildenafil oral suspensions may be relevant, but a reference that discloses only sildenafil, water and a buffer would not anticipate the anti-foaming limitation unless it also discloses the required agent and amount.

Obviousness

The strongest obviousness case would combine prior-art teachings concerning:

Sildenafil oral liquids.
Simethicone or another anti-foaming excipient.
Glycerin or propylene glycol.
Xanthan gum or another viscosity modifier.
Acidic buffering.
Preservatives and sweeteners.

The patent's extensive Markush lists and conventional excipient categories may support an obviousness challenge. The patentee would likely rely on formulation stability, reduced foaming, improved dose uniformity, palatability or manufacturability data as evidence of a non-obvious result.

Indefiniteness and written description

Potential issues include:

The meaning of “about 10 mg/mL.”
The measurement and conditions for d90 particle size.
Whether “anti-foaming agent” is sufficiently bounded.
The claim 19 concentration wording.
Support for every listed excipient and overlapping range.
Whether the specification demonstrates possession of the full genus.

These issues are claim-specific. They would be stronger against the broad claims than against a narrow claim tied to a concrete formulation example.

Which companies are challenging US 11,337,979?

The supplied information identifies no litigation, Paragraph IV notice, ANDA applicant, settlement agreement or license involving US 11,337,979. A reliable party-specific conclusion requires a verified review of PACER, district-court dockets, Federal Circuit records, FDA Orange Book entries and the patent prosecution file.

No company should be identified as a challenger based solely on the patent number or the existence of generic sildenafil products. Generic sildenafil tablets and oral suspensions do not establish a Paragraph IV challenge to this particular patent.

How strong is the patent estate for liquid sildenafil?

US 11,337,979 has meaningful formulation coverage but appears concentrated in one patent family and one dosage form. Its commercial strength depends on whether an approved product practices the claimed combination and whether competitors can avoid the anti-foaming limitation.

Strength factor	Assessment
Active-ingredient breadth	Moderate. Covers sildenafil and salts, not unrelated PDE5 inhibitors
Dosage-form breadth	Narrow. Limited to liquid oral compositions
Excipient breadth	Broad. Multiple anti-foaming, wetting and viscosity-agent classes
Concentration limitation	Potentially restrictive. Approximately 10 mg/mL is required
pH coverage	Broad within acidic-to-neutral range
Particle-size claims	Useful but measurement-sensitive
Specific formulation claims	Stronger for products matching claim 18 or 19
Method claims	Limited to administration of the claimed composition
Design-around potential	Material, particularly through concentration, pH, vehicle and anti-foaming-agent selection
Biological or biosimilar risk	None in the conventional biologic sense

The patent does not create biosimilar risk. Sildenafil is a small molecule, so competitive entry proceeds through the ANDA pathway rather than the biosimilar pathway under the Public Health Service Act.

How does this patent compare with Viagra and Revatio patents?

The patent is distinct from core sildenafil compound and original product patents. Sildenafil's basic chemical and early use patents are generally much older than this formulation patent. The commercial importance of US 11,337,979 therefore depends on a later liquid dosage form rather than basic sildenafil exclusivity.

Product or patent category	Typical protection focus	Relationship to US 11,337,979
Sildenafil compound patents	Chemical compound and salts	Separate and generally earlier
Viagra tablets	Erectile-dysfunction methods and tablet product	Different dosage form
Revatio tablets or injection	Pulmonary arterial hypertension treatment	Different dosage form unless the approved liquid practices this patent
Revatio oral suspension	Powder-for-reconstitution or liquid product	Potentially relevant, depending on approved formulation and patent listing
US 11,337,979	10 mg/mL liquid oral composition with anti-foaming excipient	Formulation-specific

The key competitive question is not whether a competitor sells sildenafil. It is whether the competitor sells a 10 mg/mL water-based liquid with the claimed pH and anti-foaming architecture.

What generic launch scenarios exist?

Scenario 1: Tablet or capsule launch

A generic sildenafil tablet or capsule generally presents low direct infringement risk under the composition claims because it is not a liquid oral composition. Method-claim exposure depends on whether the administered product is the claimed liquid composition.

Scenario 2: Powder for reconstitution

A powder that becomes a liquid after reconstitution presents a closer question. If the reconstituted product satisfies the concentration, water, pH and anti-foaming limitations, it could fall within the claims even if marketed initially as a powder.

Scenario 3: Liquid at a different concentration

A 5 mg/mL or 20 mg/mL product may avoid literal infringement of the approximately 10 mg/mL limitation. The range's legal boundary must be determined from the patent record and technical context.

Scenario 4: Liquid without a claimed anti-foaming agent

Removing simethicone and using a manufacturing process that controls foam may provide a direct design-around route. The risk depends on whether another excipient is an organic phosphate, paraffin oil, stearate, glycol or other listed class.

Scenario 5: Alternative vehicle

A nonaqueous product may avoid claim 1's water-vehicle limitation, although oral safety, solubility and regulatory comparability may make the alternative impractical.

Scenario 6: Different pH

A product outside approximately pH 4 to 8 may avoid literal infringement but could create stability and preservative challenges.

What manufacturing and IP barriers matter most?

The main manufacturing barrier is not sildenafil synthesis. It is reproducible manufacture of a physically stable, palatable liquid containing particulate sildenafil and multiple excipients.

Key technical controls include:

Sildenafil particle-size distribution.
Sedimentation and redispersibility.
Uniformity of the active ingredient.
Foam generation during mixing and filling.
Simethicone-emulsion dispersion.
Xanthan-gum hydration.
Buffer capacity and pH drift.
Preservative efficacy.
Container compatibility.
Dose accuracy after storage and shaking.

These controls can create separate trade-secret or process-patent opportunities even if the formulation patent is designed around. A competitor may avoid composition claims but still face freedom-to-operate issues involving manufacturing methods, container systems, dosing devices or stability improvements.

What licensing and settlement issues affect the patent?

The supplied information does not establish a license, covenant not to sue, Paragraph IV settlement or authorized-generic arrangement involving US 11,337,979. Such agreements would materially change the commercial assessment, particularly if they impose a launch date earlier than patent expiration or restrict supply, formulation changes or indication labeling.

Any diligence review should separate:

Patent ownership and assignment.
Exclusive or nonexclusive formulation licenses.
NDA or ANDA-related settlement agreements.
Authorized-generic arrangements.
Manufacturing and supply agreements.
Royalty obligations.
Geographic restrictions.
Patent-term and terminal-disclaimer effects.

Key Takeaways

US 11,337,979 is a formulation patent, not a basic sildenafil compound patent.
Claim 1 requires approximately 10 mg/mL sildenafil, water, pH of about 4 to 8 and a specified anti-foaming agent.
Claims 18 and 19 target a narrower formulation containing simethicone emulsion, xanthan gum, glycerin, buffer, preservative, sweetener and flavorant.
The patent covers liquid oral compositions and related treatment methods for pulmonary arterial hypertension, erectile dysfunction and benign prostatic hyperplasia.
Tablets and capsules generally fall outside the composition claims.
A powder for reconstitution can present infringement risk if the finished liquid satisfies the claim limitations.
Paragraph IV relevance depends on Orange Book listing for an applicable approved product.
No challenger, litigation, settlement or license should be attributed to this patent without verified docket, FDA and assignment records.
The principal design-around levers are concentration, pH, vehicle, anti-foaming agent, particle size and excipient architecture.
Patent expiration and Orange Book status are separate questions and require review of the official USPTO and FDA records.

FAQs

Does US Patent 11,337,979 cover generic sildenafil tablets?

Generally, no. The asserted composition claims require a liquid oral pharmaceutical composition. A tablet or capsule would not ordinarily satisfy that dosage-form limitation.

Does a liquid sildenafil product have to contain simethicone to infringe?

No. Claim 1 lists alternatives including simethicone, simethicone emulsion, organic phosphate, paraffin oil, stearate and glycol. A liquid using another listed class could still fall within the claim.

Does Revatio oral suspension automatically infringe US 11,337,979?

No. Infringement depends on the actual approved formulation, including sildenafil concentration, water vehicle, pH and anti-foaming excipient. Product labeling and patent claims must be compared limitation by limitation.

Can a competitor avoid the patent by using tadalafil instead of sildenafil?

A tadalafil product would not meet the sildenafil limitation in claim 1. It would require a separate analysis of tadalafil patents, formulation patents and applicable FDA exclusivity.

Is a pH of 5 specifically covered?

Yes. Claim 23 expressly recites a pH of about 5, and pH about 5 also falls within the broader pH limitations of claims 1 and 4, subject to the remaining claim elements.

References

United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term extension under 35 U.S.C. §§ 154 and 156. https://www.uspto.gov/patents/laws/patent-term-calculator
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application submissions: Patent certifications and 30-month stays. https://www.fda.gov/drugs/abbreviated-new-drug-application-anda/abbreviated-new-drug-application-anda
United States Patent and Trademark Office. (2022). U.S. Patent No. 11,337,979.
U.S. Food and Drug Administration. (n.d.). Revatio prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Cmp Dev Llc	LIQREV	sildenafil citrate	SUSPENSION;ORAL	214952-001	Apr 28, 2023		DISCN	Yes	No	11,337,979	⤷ Start Trial	Y			LIQREV IS INDICATED FOR THE TREATMENT OF PULMONARY ARTERIAL HYPERTENSION (WHO GROUP 1) IN ADULTS TO IMPROVE EXERCISE ABILITY AND DELAY CLINICAL WORSENING	⤷ 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	2018397436	⤷ Start Trial
Brazil	112020012986	⤷ Start Trial
Canada	3086881	⤷ Start Trial
China	111683683	⤷ Start Trial
European Patent Office	3731870	⤷ Start Trial
Japan	2021509114	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 11,337,979