Patent 9,301,932 (US) Nitisinone Oral Suspension: Claim Scope, Patent Estate Boundaries, and Freedom-to-Operate Implications
US 9,301,932 is directed to an oral liquid (suspension) formulation of nitisinone (micronized) at 1–10 mg/mL in a citric acid buffer with pH 2.5–3.5, with dependent claims narrowing to specific excipient systems (HPMC suspending agent, glycerol sweetener, paraben or sodium benzoate preservatives, polysorbate 80 surfactant) and specific buffered recipes, plus method-of-use claims for treating multiple medical conditions including HT-1 (pediatric included).
The practical scope is concentrated on: (1) the combination of nitisinone suspension particle state + citric acid/citrate buffer pH window, and (2) a defined excipitor functional package. The method claims broaden disease coverage but still require administration of the claimed formulation.
What does US Patent 9,301,932 claim for nitisinone oral liquid formulations (scope of independent claim 1)?
Core claim 1 elements (all required):
- Liquid pharmaceutical formulation suitable for oral administration
- Contains a suspension of micronized nitisinone at 1–10 mg/mL
- Contains citric acid buffer
- pH 2.5–3.5 for the liquid formulation
Claim 1 scope in plain patent terms
- Ingredient scope
- Nitisinone: constrained by micronized state and concentration window.
- Buffer: constrained to citric acid buffer (citric acid/citrate system, not a generic “acidic buffer” concept).
- Physicochemical scope
- pH: constrained to 2.5 to 3.5.
- Formulation scope
- Suspension: implies dispersed solid API (not a solution, not a gel).
- Oral suitability
- Administration route is baked into the formulation definition, but the claim does not specify dosage volume or viscosity limits.
What is excluded by claim 1 (high-impact design-around boundaries)
- Different buffer chemistry (e.g., phosphate, acetate, lactate buffers) falls outside the “citric acid buffer” limitation.
- pH outside 2.5–3.5 falls outside claim 1.
- Non-micronized API or a formulation where nitisinone is not “micronized” is outside claim 1.
- Nitisinone concentration outside 1–10 mg/mL is outside claim 1.
How do dependent claims narrow the formula and tighten infringement risk? (claims 2–15)
Claim 1 is broadest; dependent claims supply alternative embodiments that increase literal infringement likelihood if a competitor lands on the same excipient/pH recipe.
Concentration narrowing (claim 2)
- Claim 2 locks nitisinone at 4 mg/mL.
Excipient package functionalization (claims 3–12)
- Claim 3: adds “one or more pharmaceutically acceptable constituents” selected from:
- suspending agents, sweeteners, preservatives, surfactants, flavoring agents.
- Claim 4: suspending agent is hydroxypropyl methylcellulose (HPMC).
- Claim 5: HPMC is 1–20 mg/mL.
- Claim 6: sweetener is glycerol.
- Claim 7: glycerol 100–500 mg/mL.
- Claim 8–10 preservatives:
- Claim 8: methyl paraben and/or propyl paraben
- Claim 9: methyl paraben 1–2 mg/mL and propyl paraben 0.1–0.2 mg/mL
- Claim 10: sodium benzoate 0.2–5 mg/mL
- Claim 11–12 surfactant:
- Claim 11: polysorbate 80
- Claim 12: polysorbate 80 0.1–20 mg/mL
Specific formulation exemplars (claims 13–14)
These are infringement hotspots because they are concrete recipes.
Are there “numerical window” claims that create easier literal infringement targets? (claims 20–25)
Yes. These are tightening limitations that can be triggered by product formulation selection.
- Claim 20: formulation pH = 3.0
- Claim 21: HPMC 5 mg/mL (explicit)
- Claim 22: glycerol 500 mg/mL
- Claim 23: methyl paraben 1.4 mg/mL and propyl paraben 0.14 mg/mL
- Claim 24: sodium benzoate 1 mg/mL
- Claim 25: polysorbate 80 0.10–0.15 mg/mL
Implication
- If a competitor’s oral suspension matches these values and still uses citric acid buffer with pH 2.5–3.5 (and micronized nitisinone), the product sits close to strict literal claim coverage.
What disease-treatment method claims are included in US 9,301,932 and what do they require to infringe? (claims 16–18, 19)
Method claim structure
- Claim 16: administering an “effective amount” of the formulation according to claim 1, where the medical condition is selected from:
- tyrosinaemia
- Parkinson’s disease
- depression
- restless leg syndrome
- alkaptonuria
- Claim 17: condition is hereditary tyrosinaemia type 1 (HT-1)
- Claim 18: condition is HT-1 in a pediatric patient
- Claim 19: claim 14 plus flavoring agent (formulation claim dependency, tied back into method if asserted with those dependencies)
Key legal/technical dependency
- Infringement of the method claims requires:
- Administering an effective amount; and
- The administered product must fall within the formulation of claim 1 (or the narrower formulation dependencies, depending on which method claim theory is used).
What method claims broaden and what they do not
- They broaden by adding disease areas, including off-class neuropsychiatric labels (depression, restless leg syndrome) and alkaptonuria.
- They do not broaden beyond the claimed formulation limitation. A clinician using a different nitisinone formulation (non-citric-buffered or different pH window or non-micronized suspension) is positioned to avoid method claim literal coverage.
What patents protect nitisinone oral suspensions with acidic citric buffers in the US—what is the likely landscape around 9,301,932?
With only claim text provided, a complete portfolio map cannot be reconstructed accurately, so the analysis here focuses on structural claim boundaries that typically correspond to how adjacent patent families are drafted around drug-product manufacturing, stability, buffers, and pediatric oral dosing.
Commonly adjacent US patent clusters in nitisinone oral liquid space
- API form and particle engineering
- Micronized/state-of-API patents or specifications controlling particle size distribution.
- Solution/suspension stability and pH windows
- Claims on buffering agents and pH ranges to control degradation or solubility.
- Excipitor system patents
- HPMC suspending systems; glycerol or other polyols as osmolytes.
- Preservative systems (parabens vs benzoate).
- Surfactant selection (polysorbate 80) and concentration windows.
- Recipe-specific exemplars
- Concrete compositions like the claim 13 and 14 embodiments.
- Method-of-use
- Labeling and off-label therapeutic methods that still require administration of the claimed formulation.
How 9,301,932’s claim drafting signals what likely sits next door
- The claim is unusually explicit about:
- citric acid monohydrate + trisodium citrate dehydrate pair,
- exact excipient amounts in dependent claims,
- and specific pH = 3.0.
- That pattern typically indicates the inventors were capturing a specific development formulation rather than only generic concept protection. Adjacent patents are therefore often:
- different pH windows (e.g., 3.6–4.5),
- alternative buffering systems with similar acid strength,
- alternative suspending polymers (e.g., PVP, xanthan gum, CMC) or alternative surfactants (e.g., poloxamers),
- or alternative preservative chemistries.
Operational takeaway
- For FTO or design-around: the biggest lever is changing at least one of the following:
- citric acid buffer requirement,
- pH window,
- micronized nitisinone state,
- or the specific recipe-dependent excipient concentrations (if the market product uses an identical or near-identical formulation).
How many infringement “paths” does US 9,301,932 create for a competitor product? (claim coverage map)
A competitor can infringe via:
- Claim 1 path
- Micronized nitisinone suspension 1–10 mg/mL + citric acid buffer pH 2.5–3.5.
- Claim 2 path
- Same as claim 1, but nitisinone fixed at 4 mg/mL.
- Claim 3–12 path
- Same as claim 1, plus HPMC + glycerol + selected preservative system + polysorbate 80 at specified ranges.
- Claim 13 path
- Exact “recipe” embodiment: paraben preservatives at the specified mg/mL values.
- Claim 14 path
- Exact “recipe” embodiment: sodium benzoate at 1.0 mg/mL plus specified polysorbate 80.
- Claim 16–18 path (method claims)
- Administration of the claim 1 formulation to covered diseases, including HT-1 pediatric.
Practical result
- If the market product matches the same API concentration and buffer/excipient system, the infringement case is not limited to one claim theory. Multiple dependent claims can be asserted in parallel.
When does US 9,301,932 lose exclusivity (expiration framework and litigation-driven timing)?
A precise expiration date requires the patent’s filing date, priority claims, maintenance status, and any terminal disclaimers. Those facts are not provided in the prompt. The analysis therefore cannot produce a specific calendar date.
What can be stated from the claim set alone:
- Exclusivity/expiration timing controls whether generic or biosimilar entry is legally feasible, but entry risk for formulations hinges on:
- whether an ANDA-type pathway exists (small molecule) and whether a Paragraph IV notice is filed against this US patent,
- whether there are triggering Orange Book listings tied to the specific dosage form.
No specific exclusivity timeline can be asserted here without the patent’s bibliographic data and FDA listing linkage.
What Orange Book status matters for US 9,301,932 and how would it affect generic entry risk?
For US formulation patents, the key question is whether US 9,301,932 is:
- listed in the FDA Orange Book for a specific nitisinone NDA (product, strength, dosage form), and
- listed as covering the drug product (formulation) or a method of use.
That status determines whether a would-be generic filer must address this patent via Paragraph IV certifications and whether the filing triggers litigation-driven stays.
No Orange Book mapping is possible from the provided information because the NDA number, listing type, and dosage form/strength linkage are not provided.
Which design-arounds are most likely to avoid literal infringement of claim 1? (buffer, pH, particle state, concentration)
Because claim 1 has four simultaneous limitations (micronized nitisinone suspension + citric acid buffer + pH 2.5–3.5 + oral liquid), a design-around usually must change at least one of those.
Design-around levers
- Buffer swap
- Replace citric acid buffer with a non-citric buffer system.
- pH shift
- Keep citric acid but move pH outside 2.5–3.5, or use a formulation adjusted after administration.
- Note: “pH of the liquid formulation” is a product property, so the measured pH at release matters.
- API state
- Use nitisinone with a different particle size profile that does not qualify as “micronized.”
- Concentration
- Move outside 1–10 mg/mL, or avoid exactly 4 mg/mL if trying to stay away from dependent claims.
- Switch away from fixed excipient recipes
- If a competitor mirrors the exact exemplar recipes, dependent claims become easier for enforcement. Deviate in excipient selection (e.g., preservative choice, surfactant type) or concentration.
Dependent-claim risk control
- Even if a competitor stays within claim 1, they can reduce exposure to claim 13/14 style enforcement by selecting different preservatives (not methyl/propyl parabens, not sodium benzoate at the claimed concentration), changing HPMC level, or adjusting glycerol and polysorbate 80 concentrations outside the specified ranges.
How strong is the patent estate for an oral nitisinone suspension versus alternative formulation strategies?
Strength cannot be measured without the full prosecution history, spec enablement, and asserted claim scope in prior litigation. Based strictly on the claim architecture:
Areas that increase enforceability
- The claims are numerically constrained to measurable product attributes (pH, mg/mL ranges).
- Dependent claims provide specific embodiments that are easier to compare against real-world formulations.
- The method claims are tied directly to administration of the claimed formulation.
Areas that could be contested (litigation themes)
- “Micronized” can be contested as to particle size definition and measurement methodology.
- “Citric acid buffer” may be litigated if a competing product uses citrate salts with different titration sources or mixed buffer systems.
- “Liquid pharmaceutical formulation suitable for oral administration” may be disputed if the competitor’s formulation is marketed differently or uses different administration formats.
Key Takeaways
- US 9,301,932 claim 1 is a product-by-structure/product-by-parameter claim: it requires micronized nitisinone suspension (1–10 mg/mL) in a citric acid buffer at pH 2.5–3.5.
- The patent adds high-value dependent claims tied to HPMC, glycerol, preservatives (parabens or sodium benzoate), and polysorbate 80, with tight mg/mL windows.
- Claims 13 and 14 contain recipe-level exemplars (exact excipient concentrations) that increase literal infringement risk if a competitor product matches them.
- Method claims cover multiple conditions, including HT-1 and pediatric HT-1, but infringement still depends on administering the claim 1 formulation.
- The most direct design-arounds target at least one claim 1 limiter: citric buffer, pH window, micronized API state, or nitisinone concentration; recipe-dependent dependent claims can be avoided by changing excipient identity and/or concentrations.
FAQs
1) What product attributes most directly determine infringement of US 9,301,932 claim 1?
Micronized nitisinone suspension concentration (1–10 mg/mL), citric acid buffer presence, and pH measurement falling within 2.5–3.5.
2) Does adding HPMC or glycerol alone create infringement?
No. The formulation must also meet the claim 1 core requirements: micronized nitisinone suspension plus citric acid buffer with pH 2.5–3.5.
3) How do claims 13 and 14 change enforcement strategy versus claim 1?
They provide fixed mg/mL formulations. If a marketed product matches those exact amounts (plus the claim 1 core attributes), literal infringement is easier to establish.
4) Can method-of-use infringement be avoided by using a different nitisinone formulation?
Yes. Method claims are limited to administration of the claim 1 formulation (and narrower dependent formulation constraints where applicable).
5) Are pH specifications like “pH of 3.0” required to infringe?
No. pH 3.0 appears in dependent claim 20. Claim 1 covers pH 2.5–3.5, so pH 3.0 is not required unless asserting claim 20 specifically.
References (APA)
- United States Patent 9,301,932.
