United States Patent 4,939,130 (Drug) Scope, Claims, and U.S. Patent Landscape
What does US 4,939,130 claim, in scope terms?
US 4,939,130 is a U.S. patent whose claim set centers on a narrow compound class defined as heteroarylalkanediphosphonic acids bearing an imidazole substituent and a 1-hydroxy on the alkanediphosphonic backbone. The claims then extend into drug product (pharmaceutical composition) and use (method of treating impaired calcium metabolism).
Core claim architecture
The independent claim is Claim 1, defining a structural formula with substituent variables:
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Claim 1 (compound class):
A heteroarylalkanediphosphonic acid of the formula (formula shown in the patent) where:
- R1 denotes an 1-imidazolyl or 2-(1-methyl)imidazolyl radical
- R2 represents hydroxy, or a salt thereof
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Claims 2 and 3 (specific embodiments):
- Claim 2: 2-(imidazol-1-yl)-1-hydroxy-ethane-1,1-diphosphonic acid (or salt)
- Claim 3: 2-(1-methylimidazol-2-yl)-1-hydroxyethane-1,1-diphosphonic acid (or salt)
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Claims 4 and 5 (pharmaceutical and method use):
- Claim 4: pharmaceutical composition for diseases associated with impaired calcium metabolism containing a therapeutically effective amount of Claim 1 compound (free form or salt) with conventional carriers
- Claim 5: method of treating diseases associated with impaired calcium metabolism by administering a therapeutically effective amount of Claim 1 compound (free form or salt) to a warm-blooded animal
Claim scope boundaries (practical)
1) Target pharmacophore is fixed
The claims require a diphosphonic acid on an ethane-like backbone with a hydroxy substitution at carbon-1 (“1-hydroxy-ethane-1,1-diphosphonic acid” in the enumerated examples).
2) Heteroaryl scope is limited to imidazole variants
The only allowed heteroaryl substitution patterns in Claim 1 are:
- imidazole N-substituted at the “1-imidazolyl” position, and
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N-methylated imidazole defined as “2-(1-methyl)imidazolyl”.
There is no express inclusion of other heterocycles, other imidazole substitution positions beyond the stated “1” or the “2-(1-methyl)” definition, or other functional groups replacing hydroxy.
3) R2 is restricted to hydroxy (or salts)
Claim 1 limits R2 to hydroxy; the only formal expansion is “or a salt thereof.” This means the chemical scope is not broadly open-ended to other alcohols, halogens, carboxylates, or ether equivalents unless they still satisfy the literal “hydroxy” requirement or are treated as salts.
4) Claims 4 and 5 tie use to impaired calcium metabolism
The medical use language is not a single disease indication; it is a functional disease category: “diseases associated with impaired calcium metabolism.” That typically captures conditions where calcium homeostasis is disrupted (for example, bone resorption disorders), but the claim language stays broad to a category rather than a named disease.
How broad are Claims 1-3 as chemical coverage?
What exactly is claimed in Claim 1?
Claim 1 covers any heteroarylalkanediphosphonic acid matching the formula with:
- R1 = 1-imidazolyl OR 2-(1-methyl)imidazolyl
- R2 = hydroxy
- plus the qualifier “or a salt thereof”
This is a classic structure-and-substituent claim that can capture multiple stereochemical or salt forms, while remaining structurally anchored.
Enumerated “anchor compounds” in Claims 2 and 3
Claims 2 and 3 lock down two specific species:
| Claim |
Compound name (as stated) |
Key structural requirements captured |
| 2 |
2-(imidazol-1-yl)-1-hydroxy-ethane-1,1-diphosphonic acid |
imidazole N at 1; 1-hydroxy-ethane-1,1-diphosphonic acid core |
| 3 |
2-(1-methylimidazol-2-yl)-1-hydroxyethane-1,1-diphosphonic acid |
N-methylated imidazole at specified position; 1-hydroxy-ethane-1,1-diphosphonic acid core |
“Salt thereof” in scope
The phrase “or a salt thereof” expands coverage beyond the free acid to pharmaceutically acceptable salts, and at least in principle to any salt form that falls within the patent’s definition and supporting disclosure. The use claims (4 and 5) expressly allow free form or salt.
What do Claims 4 and 5 add beyond the compound claims?
Claim 4: pharmaceutical composition
Claim 4 adds a formulation claim that is largely functional:
- “a pharmaceutical composition”
- “for the treatment or prophylaxis of diseases associated with impaired calcium metabolism”
- contains “a therapeutically effective amount” of Claim 1 compound (free or pharmaceutically acceptable salt)
- with “conventional pharmaceutical carriers”
Scope characteristics:
- It is not limited to a specific dosage form (tablet, capsule, solution, etc.) in the claim excerpt you provided. It can cover multiple conventional carrier systems.
- It is limited by the drug substance: the active ingredient must be within Claim 1’s compound definition.
Claim 5: method of treatment
Claim 5 adds a medical method claim:
- “administering a therapeutically effective amount” of Claim 1 compound (free or pharmaceutically acceptable salt)
- “to a warm-blooded animal”
- for “diseases associated with impaired calcium metabolism”
Scope characteristics:
- Broad patient class: “warm-blooded animal” captures humans and veterinary use.
- Functional indication: still the same disease category (impaired calcium metabolism), not a named disease.
How does the claim language impact infringement risk (U.S. enforcement posture)?
Literal claim targeting
Because Claim 1 is a defined structural class with explicit R-group definitions, U.S. enforcement will typically be driven by whether the accused compound:
- has the ethane-1,1-diphosphonic acid core,
- has hydroxy at the 1-position (as required by “R2 represents hydroxy”),
- and has imidazole substitution matching “1-imidazolyl” or “2-(1-methyl)imidazolyl.”
“Design-around” pressure points
The most direct design-around levers, based on the claim language alone, are:
- replacing the hydroxy functionality with another substituent (unless still literally “hydroxy” or treated as salts does not apply to substitution),
- using a different heteroaryl system than imidazole, or a different imidazole substitution pattern not captured by the R1 definitions,
- using a non-matching diphosphonic scaffold that does not satisfy the claimed formula’s “heteroarylalkanediphosphonic acid” structure.
Formulation and use claims move lock-in further
Even if a competitor could potentially avoid Claim 1 by chemical design-around, Claims 4 and 5 only matter if the compound still falls within Claim 1’s structural scope. If Claim 1 is avoided, those dependent claims generally do not apply.
What is the likely U.S. patent landscape around this scaffold?
Without additional document-level bibliographic identifiers (publication number, applicant, assignee, filing dates, or related family member data), the only defensible landscape elements are those that follow directly from the claim content you provided: this patent stakes out imidazole-substituted, hydroxy-ethane-diphosphonic acids for impaired calcium metabolism via compound, composition, and method claims.
Landscape segments to expect around a narrow imidazole-diphosphonate class
1) Competing salts and stereochemical forms
- Because “or a salt thereof” appears in Claim 1, there is typically follow-on patenting and commercial differentiation around pharmaceutically acceptable salts (and sometimes polymorphs) for stability, formulation, and dosing performance.
2) Second-generation analogs varying R1
- Claim 1 restricts R1 to two specific imidazole patterns. Patent activity often clusters around analog series that vary:
- imidazole substitution position,
- N-alkylation state,
- linker length between imidazole and diphosphonate.
- Whether those analogs fall inside or outside this patent depends on whether the variation still satisfies “R1 denotes an 1-imidazolyl or 2-(1-methyl)imidazolyl radical” and the overall formula.
3) Broader diphosphonate families for calcium metabolism disorders
- Impaired calcium metabolism is a broad functional indication category. Landscape activity frequently includes:
- different diphosphonate cores,
- different heteroaryl substitutions,
- different dosing regimens and routes.
- Claims 4 and 5 are tied to the Claim 1 compounds, so broader indication claims do not automatically overlap unless the compound itself is within the Claim 1 scope.
4) Method-of-use patenting and regulatory exclusivity strategies
- U.S. patent practice often yields secondary patents on administration routes, dosing schedules, and treatment regimens. Claim 5 is already broad on “administering a therapeutically effective amount” to warm-blooded animals, which can limit the room for later improvements if they do not add patentable process differences beyond the compound’s therapeutic administration.
What claim scope matters most for freedom-to-operate (FTO)?
FTO hinge: compound identity vs. claim formula match
For a company evaluating whether it can commercialize a candidate drug substance under U.S. law, the primary question is:
- Does the candidate compound satisfy the Claim 1 formula constraints on R1 and R2, including whether “salt thereof” is relevant?
Secondary hinge: product and use alignment
If a candidate compound falls within Claim 1, then:
- A formulation containing it with “conventional pharmaceutical carriers” is a high-risk area under Claim 4.
- A therapeutic regimen for “diseases associated with impaired calcium metabolism” in warm-blooded animals is a high-risk area under Claim 5.
If a candidate compound does not fall within Claim 1, Claims 4 and 5 typically do not provide an independent barrier.
Key Takeaways
- US 4,939,130 covers imidazole-substituted, hydroxy-ethane-1,1-diphosphonic acids via Claim 1, with R1 restricted to 1-imidazolyl or 2-(1-methyl)imidazolyl and R2 restricted to hydroxy (plus “or a salt thereof”).
- Claims 2 and 3 enumerate two specific active agents within the Claim 1 class, locking in 2-(imidazol-1-yl)-1-hydroxy-ethane-1,1-diphosphonic acid and 2-(1-methylimidazol-2-yl)-1-hydroxyethane-1,1-diphosphonic acid (or salts).
- Claims 4 and 5 add patent coverage for formulations and methods of treating impaired calcium metabolism using the same Claim 1 compounds, with standard carrier language for compositions and “warm-blooded animal” language for methods.
- The most direct design-around levers are changing the hydroxy position/functionality or changing the imidazole pattern so the compound no longer fits Claim 1’s stated R-group definitions; otherwise, composition and use claims generally follow.
FAQs
1) Is the patent limited to a single disease indication?
No. The claims use the functional category “diseases associated with impaired calcium metabolism” rather than a named disease.
2) Do the claims cover both free acids and salts?
Yes. Claim 1 includes “or a salt thereof,” and Claims 4 and 5 explicitly cover “free form or…pharmaceutically acceptable salt form.”
3) What heterocycles are covered?
Only imidazole, with R1 limited to “1-imidazolyl” or “2-(1-methyl)imidazolyl.”
4) Does the patent include formulation claims?
Yes. Claim 4 is a pharmaceutical composition claim using conventional pharmaceutical carriers.
5) Does the method claim cover non-human animals?
Yes. Claim 5 covers treatment “to a warm-blooded animal,” which includes humans and veterinary contexts.
References
- United States Patent 4,939,130 (claims as provided by user).
