United States Patent 5,968,976 (US5968976): Scope, Claims, and Landscape for Lanthanum Carbonate in Hyperphosphataemia
US5968976 claims lanthanum carbonate hydrate compositions and treatment methods for hyperphosphataemia, with a crystallisation-state-defined active (La2(CO3)3·xH2O where 3 ≤ x ≤ 6) and a matched dose and oral delivery scope. The patent also claims a defined wet-chemistry process that generates lanthanum carbonate octahydrate as an intermediate and then dries to a hydrate state in the claimed range.
What exactly is claimed (core claim set)?
Independent claim coverage
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Composition (active hydrate state + oral-ready formulation):
“A pharmaceutical composition for the treatment of hyperphosphataemia comprising lanthanum carbonate of the formula La2(CO3)3·xH2O where x has a value from 3 to 6, in admixture with a pharmaceutically acceptable diluent or carrier in a form for administration to the gastrointestinal tract.”
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Process (route to hydrate state via octahydrate intermediate):
Steps (i) to (iii) specify: La2O3 + HCl → LaCl3; then LaCl3 solution + alkali metal carbonate → wet cake of lanthanum carbonate octahydrate; then drying to yield lanthanum carbonate with 3 to 6 waters of crystallisation.
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Method of treatment (systemic medical use tied to hydrate state):
Administer lanthanum carbonate of La2(CO3)3·xH2O (3 ≤ x ≤ 6) effective to treat hyperphosphataemia.
10 narrows administration to oral route (“The method of any of claims 7-9 wherein said administering is by an oral route.”)
Claim 1-3: hydrate state narrowing
- 3.5 ≤ x ≤ 5
- 3.8 ≤ x ≤ 4.5
This creates a nested spectrum of crystalline/hydration states:
- Broad: 3 to 6
- Medium: 3.5 to 5
- Narrow: 3.8 to 4.5
Claim 4: dose range
- Unit dosage form to provide 0.1 to 20 g/day of lanthanum carbonate.
Claim 6: specific base
- alkali metal carbonate is sodium carbonate.
Claim 8-9: method hydrate narrowing
- 3.5 ≤ x ≤ 5
- 3.8 ≤ x ≤ 4.5
Claim 10: oral
- administration by oral route.
How broad is the composition scope in practice?
Active definition: the key limiting element
The active must be lanthanum carbonate hydrate with a specific hydration parameter x in 3 to 6. The patent does not confine:
- particle size,
- morphology,
- tablet or powder type,
- binder or excipient selection beyond “pharmaceutically acceptable diluent or carrier,”
- specific patient subgroup beyond “a subject” with hyperphosphataemia.
That said, the enforceability boundary turns on whether a competitor’s product:
- contains lanthanum carbonate hydrate where the hydrate state falls within 3 ≤ x ≤ 6 (and, for narrower claims, 3.8 ≤ x ≤ 4.5, etc.), and
- provides the active in a formulation for gastrointestinal administration (which most oral phosphate binders do).
Carrier and formulation language is permissive
The phrase “in admixture with a pharmaceutically acceptable diluent or carrier in a form for administration to the gastrointestinal tract” supports many conventional oral formats:
- tablets,
- powders,
- granules,
- capsules with direct GI delivery.
This claim structure tends to make the hydrate parameter the dominant differentiation lever for validity and infringement analysis.
What is the method-of-treatment scope, and how is it constrained?
Medical use tied to hydrate state
Claim 7 is not merely “lanthanum carbonate for hyperphosphataemia.” It ties the efficacy claim to the hydrated lanthanum carbonate of formula La2(CO3)3·xH2O with 3 ≤ x ≤ 6. Claims 8 and 9 further narrow x.
Route constraint
Claim 10 limits the method to oral administration. If a competitor develops:
- enteric, GI-local delivery,
- or a non-oral route,
then claim 10 may not read, although broader claims (7-9 without the oral limitation) still exist.
Dose is not explicitly in the method claims
The dose range appears in claim 4 (composition in unit dosage form). The method claims (7-10) describe “administering an amount … effective to treat.” That means a competitor can argue dose mapping only affects specific composition claims unless their dosage form is designed to hit claim 4 and their clinical regimen matches it.
What is the process claim scope (and what does it actually lock down)?
Claim 5 covers a manufacturing sequence that makes a specific intermediate state:
- (i) produce LaCl3 from La2O3 + HCl
- (ii) react LaCl3 with alkali metal carbonate to make a “wet cake of lanthanum carbonate octahydrate”
- (iii) dry the wet cake to obtain lanthanum carbonate with 3 to 6 waters of crystallisation
Key enforceability points
- Octahydrate intermediate: The process claim explicitly requires formation of “lanthanum carbonate octahydrate” as a wet cake.
- Drying outcome: The drying step must produce a hydrate with 3 to 6 molecules of water.
If a competitor’s process:
- makes a different hydrate intermediate (not octahydrate), or
- bypasses the wet cake step and crystallises from another solvent system, or
- dries to a hydrate state outside 3 to 6,
then claim 5 is harder to map.
Specifics with sodium carbonate
Claim 6 adds an additional constraint: alkali metal carbonate is sodium carbonate. This is a narrower process variant.
Claim set mapping to product and process design choices
If you commercialize an oral lanthanum carbonate drug
Your product most directly implicates claim 1 (and via it claim 2-3 and claim 4).
- Most likely infringement hinge: whether your finished drug’s lanthanum carbonate hydrate parameter x is within the patented window.
- Secondary hinge: whether your formulation is “for administration to the gastrointestinal tract” (oral usually satisfies).
If you commercialize alternative hydration-state materials
- A form where the hydrate state cannot be shown to fall within 3 ≤ x ≤ 6 can be positioned as outside the independent composition and method claims.
- A form engineered to be outside 3.5 to 5 and 3.8 to 4.5 further reduces overlap with dependent claims.
If you use alternative manufacturing
- A process not generating an octahydrate wet cake is more likely to avoid claim 5.
- Even with octahydrate present, drying must land in the 3 to 6 hydrate parameter window.
Where the patent sits in the broader hyperphosphataemia binder landscape
This patent sits in the core “lanthanum carbonate as an oral phosphate binder” space for hyperphosphataemia, where competitive differentiation often focuses on:
- chemical form (hydrate state),
- dose form factors,
- manufacturing route,
- physicochemical properties that relate to binding performance and tolerability.
US5968976 is anchored to a chemical definition (hydrate state) and an oral GI dosing context, not to a novel dosage architecture or a specific regimen.
Patent landscape implications for freedom-to-operate (FTO)
Most likely claim coverage vectors for competitors
- Finished product overlap:
Any oral lanthanum carbonate drug where the active hydrate state can be measured as x between 3 and 6 risks coverage of claim 1.
- Dose overlap:
A product designed so that unit dosage forms supply 0.1 to 20 g/day of lanthanum carbonate risks claim 4, assuming dose is expressed through unit dose design.
- Process overlap:
Any manufacturer using a process consistent with steps (i)-(iii) including octahydrate wet cake and drying to 3 to 6 waters risks claim 5. Using sodium carbonate risks claim 6.
Most common design-around strategies implied by the claim language
- Switch hydrate state: engineer a non-overlapping hydrate parameter outside the x windows (3 to 6).
- Alter process chemistry: avoid forming an “octahydrate wet cake.”
- Change route: if relevant to enforcement, avoid “oral route” where narrower method claims matter.
Key claim interpretation points that control mapping
How to interpret x
The patent uses x as the number of water molecules of crystallisation in La2(CO3)3·xH2O. FTO mapping therefore requires hydrate characterization of the shipped active (or its state after formulation, depending on evidence rules).
“Unit dosage form” and “0.1 to 20 g/day”
Claim 4 is a composition claim in unit dosage form tied to daily delivery. This typically aligns with standard dosing ranges for phosphate binders in CKD-related hyperphosphataemia, but infringement depends on whether the unit dosage and dosing instructions meet the claimed daily exposure.
“Form for administration to the gastrointestinal tract”
This is broad. It reads on oral dosage forms and likely on any GI-intended non-oral route unless competitors interpret it narrowly to GI exposure via swallowing or digestion.
What does the claims structure suggest about the patent’s likely strength?
US5968976’s claim structure emphasizes:
- Specific chemical definition (hydrate range) for composition and method.
- Manufacturing specificity (octahydrate wet cake and drying outcome) for the process claim.
- Route (oral) as a dependent narrowing for the method.
This makes the patent less about excipient invention and more about anchoring a specific active form and specific manufacturing path.
Key Takeaways
- US5968976 claims lanthanum carbonate hydrate with 3 ≤ x ≤ 6 for hyperphosphataemia, in GI-administerable formulations (claim 1) and for oral treatment (claim 10).
- The patent narrows hydrate state to 3.5 ≤ x ≤ 5 and 3.8 ≤ x ≤ 4.5 (claims 2-3, and 8-9).
- It sets a daily dose coverage of 0.1 to 20 g/day in unit dosage form (claim 4).
- The process claim (claim 5) is defined by La2O3 → LaCl3, then reaction with alkali metal carbonate to form a wet cake of lanthanum carbonate octahydrate, followed by drying to 3 to 6 waters of crystallisation. Claim 6 specifies sodium carbonate.
- In a landscape view, infringement risk concentrates on (1) hydrate state in the marketed active, and (2) process steps that produce octahydrate wet cake and dry into the claimed x range.
FAQs
1. What is the main novelty axis in US5968976?
The patent ties hyperphosphataemia treatment and phosphate binding activity to lanthanum carbonate hydrate defined by La2(CO3)3·xH2O where x is 3 to 6, with narrower x ranges in dependent claims.
2. Does US5968976 cover all lanthanum carbonate regardless of hydration state?
No. Coverage is constrained by the hydrate parameter x. Dependent claims narrow x further (up to 3.8 to 4.5).
3. Is oral administration required?
For the method-of-treatment dependent claim 10, yes. Independent method claim 7 is not explicitly limited to oral, but it is limited to administration of the claimed hydrate form effective for treatment.
4. What does claim 5 require in the manufacturing process?
A sequence that produces lanthanum chloride, reacts it with alkali metal carbonate to form a wet cake of lanthanum carbonate octahydrate, then dries to yield x between 3 and 6.
5. How does the dose claim function in infringement analysis?
Claim 4 is a composition claim in unit dosage form providing 0.1 to 20 g/day. It is the clearest place where marketed dosing design and labeling can map to the patent’s numeric range.
References
[1] United States Patent US5968976. “Pharmaceutical compositions and methods for treating hyperphosphataemia using lanthanum carbonate hydrates.” Claims as provided in the user prompt.
