Scope, Claims, and US Patent Landscape for US 11,464,778 (Sildenafil liquid oral composition with glycerin wetting agent)
What is the invention actually claiming?
US 11,464,778 is centered on a liquid oral pharmaceutical composition of sildenafil (or a pharmaceutically acceptable salt) in which glycerin is used as a “wetting agent” at a tightly defined concentration and the product pH is controlled. The claims then expand into: (i) allowable liquid dosage presentation formats, (ii) optional excipient packages, (iii) particle size metrics for suspensions, (iv) stability and impurity thresholds, and (v) pharmacokinetic (PK) performance ranges relative to a “marketed or known formulation” at the same dose. It also claims methods of treating a large set of conditions, with dependent claims narrowing to specific indications.
Core claim architecture (independent and highest-value dependencies)
Independent claim (claim 1):
- Liquid oral pharmaceutical composition comprising:
- Sildenafil or a pharmaceutically acceptable salt
- Wetting agent: glycerin at about 200 to about 400 mg/mL
- pH: about 4 to about 8
Dependent claim layers:
- Claim 2: broad excipient universe (solvents, solubilizers, surfactants, buffering agents, preservatives, mucoadhesives, viscosity modifiers, etc.).
- Claims 3-5: liquid form taxonomy (dispersion/suspension/solution/emulsion/syrup/elixir/drop/concentrate; with explicit “solution” and “suspension” dependents).
- Claims 6 and 24-25: suspension particle size via d90 ranges:
- Claim 6: 10 to 200 microns
- Claim 24: 10 to 100 microns
- Claim 25: 20 to 30 microns
- Claim 17: stability and impurity control:
- Stable up to 6 months at 25°C/60% RH
- Individual impurity < 0.2%
- Total impurities < 1.0%
- Claim 18: PK improvement windows (Cmax and AUC and/or Tmax), measured in plasma vs a “marketed or known formulation” at the same dose.
- Claims 19-22: method-of-treatment over a long condition list; then specific indication narrowings (pulmonary arterial hypertension; erectile dysfunction).
- Claims 23, 26, 27-40: further compositions and performance-linked subranges (sildenafil citrate at 10 mg/mL, pH setpoint about 5, viscosity modifiers in mg/mL, anti-foaming ranges, antioxidant/preservative/surfactant/buffer agent lists and concentration windows, etc.).
What exactly are the enforceable boundaries of claim 1?
Claim 1 is the central infringement hook. It requires the simultaneous presence of three elements:
1) Liquid oral format
2) Sildenafil (or salt)
3) Glycerin as wetting agent at 200-400 mg/mL
4) pH 4-8
Key quantitative limits in claim 1
- Glycerin concentration: 200 to 400 mg/mL
- pH: 4 to 8
Practical claim scope implications
- Any competitor product that is a liquid oral sildenafil formulation with glycerin intentionally functioning as a wetting agent falls inside the claim field, if it meets the exact concentration and pH ranges.
- The phrase “wetting agent comprising glycerin” is critical: formulations using glycerin as a mere viscosity component or bulking agent may argue glycerin is not acting as a wetting agent, but the claim requires glycerin “comprising” as wetting agent, which typically gives the patentee latitude in formulation characterization (wetting is often a functional role in wet-milling, dispersion stability, and solid wetting).
How do the dependent claims materially narrow or expand scope?
How broad is the excipient package (claim 2)?
Claim 2 allows essentially standard oral liquid excipient categories and does not carve out exclusions. The list includes:
- Vehicle/solvent/co-solvent
- Solubilizer and solubility enhancers
- Viscosity modifiers and penetration enhancers
- Tonicity agents and mucoadhesives
- Bulking/auxiliary suspending agents
- Chelating agents, anti-foaming/anti-caking
- Stabilizing agents, antioxidants
- pH modifying/adjusting
- Surfactants
- Preservatives
- Sweeteners, flavoring, coloring
- “Any combination thereof”
Landscape impact: this makes claim 1 the primary novelty gate. If glycerin concentration and pH are met, most excipient choices do not prevent infringement.
What forms are protected (claims 3-5)?
Claim 3 enumerates liquid presentation forms:
- dispersion, suspension, solution, emulsion, spray, syrup, elixir, drop, concentrate
Claims 4 and 5 carve out:
- Claim 4: solution
- Claim 5: suspension
Landscape impact: the patent protects both true solutions and suspensions/dispersion systems, as long as claim 1’s glycerin and pH constraints hold.
Suspension particle size is claimable (claims 6, 24, 25)
- Claim 6: d90 10 to 200 μm
- Claim 24: d90 10 to 100 μm
- Claim 25: d90 20 to 30 μm
Landscape impact: even if a competitor stays within claim 1 glycerin/pH, particle size targets may determine whether they land inside the stronger suspension-specific dependents. Still, for many infringement scenarios, claim 1 may be enough; particle-size dependents strengthen position where the formulation is clearly a suspension.
What do stability and impurity claims add (claim 17)?
Claim 17 adds a performance-style limitation:
- stable up to 6 months at 25°C/60% RH
- any individual impurity < 0.2%
- total impurities < 1.0%
Landscape impact: this is a credibility and evidentiary support claim. For infringement, these are often used to argue formulation quality; for design-around, competitors may target less strict stability/impurity profiles, but regulatory constraints typically push suppliers to good impurity control anyway.
What are the PK improvement thresholds (claim 18)?
Claim 18 requires one or more PK criteria achieved vs a “marketed or known formulation” at the same dose:
- Cmax: at least 50% to 1900% greater
- AUC: at least 25% to 1200% greater
- Tmax: less than about 6 to 8 hours
- any combination of (a), (b), and (c)
Landscape impact: this is high leverage for litigation and settlements because it frames superiority in measurable exposure. It can also complicate validity challenges: if the patent’s application provides comparative PK data tying glycerin/pH/suspension parameters to exposure gains, claim 18 is difficult to dismiss as arbitrary.
What methods are covered (claims 19-22)?
Claim 19 is a method-of-treatment claim with a long condition list that includes, among others:
- pulmonary hypertension (pulmonary, arterial)
- hypertension
- erectile dysfunction
- several cardiovascular, oncologic, neurologic, inflammatory/autoimmune, fibrotic, and infectious categories
- plus rare/adjacent conditions such as priapism, Raynaud’s phenomenon, lymphatic malformations, nontuberculous mycobacterial infection, idiopathic pulmonary fibrosis
Claim 20 narrows to:
- hypertension, pulmonary hypertension, arterial hypertension, pulmonary arterial hypertension, erectile dysfunction, and combinations
Claim 21 narrows to:
- pulmonary arterial hypertension
Claim 22 narrows to:
Landscape impact: for sildenafil, the most commercially relevant indications are typically erectile dysfunction and pulmonary arterial hypertension. The claims support both, and claim 21 and 22 create clean “indication-specific” pathways for enforcement.
What are the “product variants” explicitly called out?
- Claim 11: comprising sildenafil
- Claim 12: comprising sildenafil citrate
- Claim 23: sildenafil citrate at 10 mg/mL
- Claim 26: pH about 5
- Claim 13: pH 4 to 6
- Claim 17: stability/impurity
- Claims 14-16: buffering agents and glycerin:buffer ratio
- buffering agents include citric acid monohydrate and tri-sodium citrate dihydrate (and combinations)
- ratio glycerin to buffering agent about 40:60
- Claims 27-30: viscosity modifying agents (water-soluble hydrocolloids) in 1 to 20 mg/mL
- Claims 31-32: anti-foaming agents (simethicone family, organic phosphate, paraffin oil, stearate, glycol) in 0.1 to 100 mg/mL
- Claims 33-34: antioxidants, and concentration range up to 100 mg/mL
- Claims 35-36: preservatives list and concentration range 0.1 to 100 mg/mL (claim 36 is the quantified dependent)
- Claims 37-38: surfactants list and concentration range 0.1 to 100 mg/mL (claim 38 quantified dependent)
- Claims 39-40: buffering agent list and buffering concentration 0.01 M to 0.1 M
Patent landscape and scope positioning in the US (what this means for competitors)
Without the document’s full bibliographic record (filing/priority dates, assignee, specification disclosure, and prosecution history) and without querying the US patent register for related family members, a complete “landscape” cannot be produced from the claim text alone. What can be asserted strictly from the claim set is the following competitive positioning:
Where this patent is likely strongest
1) Liquid oral sildenafil where glycerin is used at 200-400 mg/mL with pH 4-8
2) Suspension formulations with d90 20-30 μm (claims 25 and likely claim 6/24)
3) Comparative PK advantage formulations that meet the Cmax/AUC/Tmax improvement windows versus a benchmark product at same dose
4) Buffered systems using citrate and meeting glycerin:buffer ~40:60 (claim 16), with pH often around 5-6 (claims 13 and 26)
Where design-around pressure is predictable
- Adjust glycerin concentration below ~200 mg/mL or above ~400 mg/mL (would miss claim 1’s wetting-agent requirement).
- Move pH outside 4-8 (would miss claim 1).
- Use glycerin but avoid asserting it as the “wetting agent” (this is often not feasible to guarantee if glycerin is functionally controlling wetting of particles or interface).
- If relying on suspension particle-size dependents, adjust particle sizing outside 10-200 μm or especially 20-30 μm, to avoid the tighter dependents (claims 6/24/25).
Key Takeaways
- US 11,464,778 is a glycerin wetting-agent and pH-controlled liquid oral sildenafil patent, with claim 1 requiring glycerin 200-400 mg/mL and pH 4-8.
- The excipient sections are broad, leaving the enforceable boundary anchored mainly on glycerin concentration and pH, then strengthened by suspension particle d90 ranges, stability/impurity thresholds, and PK superiority windows.
- Method claims cover major commercial sildenafil spaces, especially erectile dysfunction and pulmonary arterial hypertension.
FAQs
1) Does claim 1 cover both solutions and suspensions?
Yes. Claim 1 covers a liquid oral composition generally, and claims 4 and 5 explicitly depend on whether the liquid is a solution or suspension.
2) What is the single most important numerical limit?
The glycerin wetting agent concentration: 200 to 400 mg/mL in claim 1, coupled with pH 4 to 8.
3) Are there multiple glycerin-based dependents?
Yes. The claim set includes specific embodiments, including glycerin comprising about 400 mg/mL (claim 7) and a citrate-buffer ratio glycerin:buffer about 40:60 (claim 16).
4) Do the PK claims require all Cmax, AUC, and Tmax?
No. Claim 18 allows any combination of the listed Cmax, AUC, and Tmax criteria.
5) How does particle size matter if the product is a suspension?
It matters most for the suspension-specific dependents:
- d90 10-200 μm (claim 6)
- 10-100 μm (claim 24)
- 20-30 μm (claim 25)
References
[1] US Patent 11,464,778, claims 1-40 (text provided by user).
