United States Patent 11,759,468: Scope, Claim Coverage, and Sildenafil Liquid Oral Formulation Landscape
Executive summary
US Patent 11,759,468 is a US composition-of-matter and use patent centered on a liquid oral sildenafil (or pharmaceutically acceptable salt) formulation in water-based vehicle with tight pH 4 to 8, specific excipient system (notably glycerin as wetting agent in 100–1000 mg/mL and an anti-foaming agent such as simethicone/simethicone emulsion and/or oil/phosphate/stearate/glycol classes), plus optional claim branches covering suspension particle size (d90 ranges), buffering systems, viscosity-modifying hydrocolloids, preservatives, stability/impurity limits, and pharmacokinetic performance targets. The claims also contain method-of-treatment coverage for a broad set of sildenafil-labeled indications (notably hypertension/pulmonary arterial hypertension and erectile dysfunction) and combination indication sets.
Because the independent claim anchors on a combination of parameters (drug form factor + aqueous vehicle + pH window + glycerin wetting range + anti-foaming agent presence), the enforceable scope is strongest against generic or licensed “sildenafil liquid” products that intentionally replicate that excipient architecture and pH/composition ranges, not against all sildenafil liquids in general.
What does US Patent 11,759,468 claim for liquid oral sildenafil in water at pH 4 to 8?
Core scope (Claim 1): A liquid oral pharmaceutical composition comprising:
- Sildenafil or a pharmaceutically acceptable salt
- Pharmaceutically acceptable excipients
- Vehicle comprising water
- pH about 4 to about 8
- Excipients include:
- Wetting agent comprising glycerin
- Anti-foaming agent
- Glycerin amount: about 100 mg/mL to about 1000 mg/mL
This is the principal infringement axis: a challenger must read on the entire claim (or on a dependent claim’s tighter parameters). The structure is not “sildenafil in a liquid”; it is sildenafil in a liquid with a very specific excipient identity and glycerin concentration band, plus an aqueous pH window, plus anti-foaming agent.
Immediate boundary conditions implied by Claim 1
- Delivery system: liquid oral (includes solutions or suspensions depending on dependent branches).
- Vehicle: water-based.
- pH: broad enough (4–8) to capture many oral aqueous formulations, but still a defined band.
- Glycerin: the wetting agent is not optional; it is required, and its concentration is bounded 100–1000 mg/mL.
- Anti-foaming agent: required as a component of excipients (identified more specifically in dependent claims).
Which excipient and concentration ranges are locked down by the patent claims?
How tightly is glycerin specified as the wetting agent?
- Claim 1: glycerin 100–1000 mg/mL
- Claim 12: glycerin 200–1000 mg/mL
- Claim 13: glycerin 200–800 mg/mL
- Claim 14: glycerin 200–600 mg/mL
Enforcement implication: If a generic uses glycerin outside 100–1000 mg/mL, or uses a different wetting system without glycerin, it avoids these dependent branches and may still avoid Claim 1 if glycerin is absent or out of range.
Which anti-foaming agent classes are named?
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Claim 15: anti-foaming agent comprises one or more of:
- simethicone
- simethicone emulsion
- organic phosphate
- paraffin oil
- stearate
- glycol
- combinations
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Claim 16: that anti-foaming agent system in an amount 0.1 mg/mL to 100 mg/mL
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Claim 17: anti-foaming agent system in an amount about 0.5 mg/mL
Enforcement implication: A product using different anti-foaming chemistries (not in the recited list or not in the recited “comprises” structure) likely avoids dependent claim reads. Products using simethicone or analogous phosphate/oil/stearate/glycol families remain exposed.
How is buffering specified?
- Claim 7 adds “buffering agent”
- Claim 8 enumerates many buffering acids/bases and salts (e.g., citric acid/citrate, sodium phosphate, tromethamine/trolamine, succinic acid, etc.)
Enforcement implication: Buffering is optional in Claim 1, but if present it must fall within (or at least be encompassed by) the recited list to trigger Claim 8.
What particle size limits apply if the formulation is a suspension?
- Claim 9: liquid composition is a suspension
- Claim 10: d90 10–100 microns
- Claim 11: d90 20–30 microns
Enforcement implication: A liquid that is a true suspension may fall into these particle-size dependent claim ranges. A solution (no dispersed particles) would avoid suspension branches.
What viscosity modifiers are covered?
- Claim 18: viscosity modifying agent comprising water-soluble hydrocolloids
- Claim 19: amount 1–20 mg/mL
- Claim 20 and Claim 21: enumerates many hydrocolloids (acacia/gum arabic, agar, alginic acid, carbomer, croscarmellose sodium-like materials, PVP, veegum, xanthan, carageenan, guar gum, HPMC/hypromellose, sodium alginate, microcrystalline cellulose, colloidal silica, etc.)
Enforcement implication: If a generic uses the same class of viscosity modifiers, the relevant dependent claims are at risk, but the claims are still gated by other Claim 1 requirements (pH and glycerin/anti-foaming system).
What preservatives are included?
- Claim 22: preservatives selected from a long list including ethanol, phenoxyethanol, potassium benzoate, benzyl alcohol, parabens, benzalkonium chloride, and similar preservatives
- Claim 23: an amount 0.1 mg/mL to 100 mg/mL
Enforcement implication: Preservative inclusion is not required unless targeting dependent claims; however, many liquid pediatric/adult products include preservatives.
What pH and formulation stability limitations matter for infringement?
pH tightening sub-claims
- Claim 5: pH about 4 to about 6
- Claim 6: pH about 5
These do not remove coverage from Claim 1, but create narrower dependent claim targets.
Six-month stability and impurity limits
- Claim 25: stable for up to 6 months at 25°C and 60% RH
- Characterized by:
- any individual impurity < 0.2%
- total impurities < 1.0%
Enforcement implication: This can strengthen litigation leverage on manufacturing evidence if a product is challenged on stability/quality criteria, but stability-based limitations can be harder for a challenger to “read on” without testing and batch records.
“Ready to use”
- Claim 24: composition is a ready to use composition.
Are there pharmacokinetic (PK) performance claims that broaden or constrain the scope?
Claim 26 adds PK windows/targets:
- Cmax at least about 50% to about 1900% greater than marketed/known formulation Cmax at same dose
- AUC at least about 25% to about 1200% greater than marketed/known formulation AUC
- Tmax less than about 6 to 8 hours
- Or any combination of (a), (b), (c)
Enforcement implication: This is a high-information dependent claim potentially requiring comparative PK evidence, dosing conditions, and reference formulation definition (“marketed or known formulation administered at the same dose”). It can deter “design-around” that focuses only on excipients and pH without matching performance, but it also can become evidence-intensive.
Does the patent cover method-of-use for hypertension, pulmonary arterial hypertension, and erectile dysfunction?
Yes. The patent includes treatment method claims.
Which conditions are explicitly listed?
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Claim 27: administering to treat a broad set including:
- hypertension
- pulmonary hypertension
- arterial hypertension
- pulmonary arterial hypertension
- erectile dysfunction
- multiple additional conditions spanning oncology and vascular/inflammatory indications (e.g., solid tumor, heart failure, atherosclerosis, Parkinson’s disease, pre-eclampsia, prostate/pancreatic cancer, hepatic encephalopathy, pulmonary fibrosis, idiopathic pulmonary fibrosis, Raynaud’s phenomenon, BPH, Waldenstrom’s macroglobulinemia, etc.)
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Claim 28: narrowed combination: hypertension + pulmonary hypertension/arterial forms + erectile dysfunction
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Claim 29: pulmonary arterial hypertension
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Claim 30: erectile dysfunction
Enforcement implication
- If the formulation is used for these indications, the method claims add another litigation layer beyond composition constraints.
- For generic liquids with the same formulation scope, method-of-use claims typically matter for labeling and carve-outs. A generic can attempt to avoid method infringement by labeling strategy, but composition infringement may still exist.
How strong is the US patent estate likely to be around this glycerin/sildefan liquid formulation concept?
The provided claim text suggests a patent built to cover:
- form factor (liquid oral)
- aqueous pH range
- high concentration glycerin wetting agent
- required anti-foaming agent
- optional but meaningful dependent layers (suspension particle size, hydrocolloids, preservatives, stability, PK boost)
Practical strength drivers for enforcement
- Multi-parameter gatekeeping: Claim 1 is specific; it reduces risk of being read on by any arbitrary sildenafil liquid.
- Broad dependent scaffolding: Buffering agent list and hydrocolloid list are broad, likely capturing many formulation approaches.
- Concentration bands: glycerin and particle size ranges are quantitative; these can be measured.
- Method-of-use breadth: the indication list increases the chance that a marketed use matches the claim set.
Potential vulnerability drivers
- If “glycerin amount” in typical sildenafil liquids is outside 100–1000 mg/mL, generic products could avoid Claim 1.
- If a generic uses glycerin but not as the “wetting agent,” or substitutes another wetting system, it may avoid Claim 1 language.
- If a generic avoids simethicone and uses other anti-foaming systems outside the recited list, it may avoid dependent claims.
What generic entry risks exist if a competitor makes a “sildenafil oral liquid” at pH 4–8?
A competitor is primarily exposed if they:
- Use sildenafil (or salt) in a water vehicle
- Formulate at pH 4–8
- Include glycerin as a wetting agent at 100–1000 mg/mL
- Include an anti-foaming agent that fits the recited categories (including simethicone/simethicone emulsion or other listed types)
Higher risk fact patterns
- Pediatric/adult liquid intended for rapid onset: increased likelihood of PK-targeted formulation choices that could map to Claim 26 performance windows.
- Suspension-based products with controlled d90 distributions (10–100 µm or 20–30 µm).
- Hydrocolloid-based viscosity systems (HPMC/cellulose, carbomer, xanthan, alginate, etc.) at 1–20 mg/mL.
- Preserved, shelf-stable products targeting 6-month storage requirements.
Design-around levers implied by the claim structure
- Shift pH outside 4–8, or set at least one critical component outside the recited ranges.
- Remove glycerin or reduce/raise glycerin concentration outside 100–1000 mg/mL.
- Remove the required anti-foaming class and use a different anti-foaming system not encompassed by Claim 15/16/17.
- Avoid suspension by using a true solution (if feasible) or use particle size outside claimed d90 bands.
- Avoid the specific PK superiority conditions if the formulation strategy is different (evidence required).
What would infringement look like for each claim type?
Composition claims (Claims 1–26)
Infringement analysis typically turns on:
- lab/QA verification of pH
- quantitative assays of glycerin content
- identification of anti-foaming agent and concentration
- classification as solution vs suspension and particle size distribution (d90)
- identification of buffering agents, hydrocolloids, preservatives
- stability/impurity profile and PK comparisons if litigated under dependent claim 25/26
Method claims (Claims 27–30)
Infringement turns on:
- whether the accused product is administered for the listed conditions
- whether labeling/indication matches the method claim (and whether carve-outs exist)
Key Takeaways
- US 11,759,468 is anchored on a water-based liquid oral sildenafil formulation with pH 4–8, glycerin wetting agent at 100–1000 mg/mL, and an anti-foaming agent.
- The most direct infringement path is replicating Claim 1’s composition parameter bundle, not merely using sildenafil in a liquid.
- Dependent claims add layered protection for glycerin tighter sub-ranges, simethicone/oil/phosphate/stearate/glycol anti-foaming systems, suspension d90 bands, hydrocolloid viscosity modifiers (1–20 mg/mL), buffering agent identities, and preservatives.
- The patent’s method-of-use section provides additional leverage for pulmonary arterial hypertension and erectile dysfunction and an expanded set of other conditions.
- Generic risk is highest for competitors whose product development choices lead to the same excipient architecture and quantitative windows, especially where product objectives align with stability and PK performance targets.
FAQs
1) Does the patent cover sildenafil citrate specifically?
Yes. Claim 3 covers sildenafil citrate as a dependent formulation.
2) If an accused product is a suspension, what particle size ranges are covered?
Claims 10–11 require d90 of about 10–100 microns or about 20–30 microns for the specific tighter suspension dependent reads.
3) Is buffering mandatory to infringe?
No. Buffering is required only for dependent Claim 7/8; Claim 1 does not require a buffering agent.
4) What pH ranges are protected beyond the broad 4–8 band?
Claims 5 and 6 narrow to about 4–6 and about 5, respectively.
5) Do the method-of-treatment claims cover erectile dysfunction and pulmonary arterial hypertension?
Yes. Claims 28–30 include erectile dysfunction and pulmonary arterial hypertension explicitly.
References
- Provided patent claims text for United States Patent 11,759,468 (user-provided).
