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Patent landscape, scope, and claims: |
Scope and Claims Breakdown for US Patent 5,246,925: Method of Treating Hyperparathyroidism Using 19-Nor Vitamin D Compounds
US 5,246,925 claims a treatment method for hyperparathyroidism (and, via the claim language, treatment of renal osteodystrophy) by suppressing parathyroid activity with specific 19-nor vitamin D side-chain analogs at defined daily dose ranges, with broad compound Markush scope and multiple administration routes.
What does US Patent 5,246,925 claim for treating hyperparathyroidism?
Core claimed invention: a method for treating hyperparathyroidism by suppressing parathyroid activity through administration of at least one compound defined by a structural formula (vitamin D analog family), administered by oral, topical, or parenteral routes at about 1 µg to about 500 µg per day, sufficient to suppress parathyroid activity, and thereby treating renal osteodystrophy (as written in the preamble/statement of purpose).
Claim 1 is the independent, structure-and-dosing method claim
Claim 1 ties together four elements that define claim scope:
- Patient condition
- “a patient having such a disorder” (hyperparathyroidism per claim preamble)
- Mechanism/outcome requirement
- “suppressing parathyroid activity”
- Compound scope
- administration of “at least one compound having the formula ##STR9##”
- with Markush definitions for substituents at multiple positions and an explicit allowance that positions 20, 22, or 23 in the side chain may be replaced by O, S, or N
- plus a special conditional rule: “when n is 1 then R2 and R3 must both be methyl”
- Route and dose
- administered “by oral, topical or parenteral means”
- dose “from about 1 μg to about 500 μg per day”
Legal consequence for scope: Because the compound is defined structurally (and through extensive Markush parameterization), the claim is not limited to one named drug; it covers a class of 19-nor vitamin D analogs and related stereochemical/heteroatom variations that fall within the formula constraints.
Dependent claims narrow administration formulation
- Claim 2: compound administered together with a pharmaceutically acceptable excipient.
- Claim 3: compound in a solid or liquid vehicle ingestible by and non-toxic to the patient.
Claims 4–9 provide explicit exemplars inside claim 1
Claim 1’s structure scope is further “anchored” by specific compound selections:
- Claim 4: 1α,25-dihydroxy-19-nor-vitamin D3
- Claim 5: 1α-hydroxy-19-nor-vitamin D3
- Claim 6: 1α,25-dihydroxy-19-nor-vitamin D2
- Claim 7: 1α-hydroxy-19-nor-vitamin D2
- Claim 8: 1α-hydroxy-19-nor-24 epi-vitamin D2
- Claim 9: 1α,25-dihydroxy-19-nor-24 epi-vitamin D2
Practical effect: Even if a competitor argued the broad formula is ambiguous, claims 4–9 create coverage for specific named analogs that fall squarely within the family.
How broad is the compound Markush scope in US 5,246,925?
Best read: Claim 1 is designed to capture multiple generations of vitamin D analogs by specifying variable substituents and allowing heteroatom replacements in the side chain.
Markush architecture in the claim
Claim 1 defines:
- A general “formula ##STR9##” with variables X1, X2, R, R1–R7, n, m
- A secondary “side chain” group defined by formula ##STR10## in which:
- R1 ∈ {hydrogen, hydroxy, O-acyl}
- R2, R3 ∈ {alkyl, hydroxyalkyl, fluoroalkyl} or together represent —(CH2)m— where m ∈ [2..5]
- R4, R5 ∈ {hydrogen, hydroxy, fluorine, O-acyl, alkyl, hydroxyalkyl, fluoroalkyl} or R4+R5 taken together represent “double-bonded oxygen”
- R6, R7 ∈ {hydrogen, hydroxy, O-acyl, fluorine, alkyl} or together form carbon-carbon double bond
- “carbon at any one of positions 20, 22, or 23 … replaced by O, S, or N”
- n ∈ [1..5]
- conditional restriction when n = 1: R2 and R3 must both be methyl
What this captures (functionally)
This is not limited to a single chemical scaffold. It covers:
- 19-nor vitamin D core analogs (by virtue of “19-nor” being consistent with the claim’s exemplars and the side-chain flexibility)
- D2 vs D3 analog variants
- hydroxy vs dihydroxy (1α-hydroxy vs 1α,25-dihydroxy)
- 24-epi variants
- halogenated and fluoroalkyl variants
- various esterified (O-acyl) forms
- side-chain saturation or specific unsaturation/double bonds
- heteroatom replacements at key side-chain positions (O/S/N replacements), which increases the chance of catching metabolites, prodrug-like ester forms (depending on interpretation of O-acyl), and structural analogs that retain the biological activity profile.
Scope risk for defendants: If a competitor’s compound falls within these variable constraints, it is within claim 1 even if not listed in claims 4–9.
When does US 5,246,925 expire, and what does exclusivity usually look like?
No timeline analysis can be produced from the claim text alone. Expiration depends on:
- filing and priority dates
- whether a patent term adjustment or PTA applies
- whether maintenance fees were paid
- whether the patent was terminally disclaimed
- whether there are related continuation patents
- the Orange Book/NDA/ANDA status of any covered products
Under the operating constraints, producing an expiration date or exclusivity window without those dates would be inaccurate.
What is the likely regulatory target: NDA/ANDA/Biologics context?
The claims are method-of-treatment using small-molecule analogs administered by oral/topical/parenteral routes. This aligns with typical drug (NDA) formulations and generic or 505(b)(2) pathways for small molecules, but the claim itself does not specify:
- FDA approval status
- a particular trade name
- a specific dosage form (capsule, injection, ointment, solution, etc.)
No “Orange Book status” mapping is possible from the information provided in the prompt.
What formulations and route-of-administration coverage exists in US 5,246,925?
Routes explicitly covered in claim 1
This is unusually broad for a method-of-use claim. It means infringement theory would not be constrained to oral dosing alone if other routes use a compound that meets the structural definitions.
Dose range explicitly covered
- “about 1 µg to about 500 µg per day”
A competitor operating outside this range may argue non-infringement, though enforcement often turns on interpretation of “about” and clinical dosing practices.
Formulation enabling claims 2 and 3
- Claim 2: excipient combination
- Claim 3: solid or liquid vehicle ingestible and non-toxic
These dependent claims support a theory that infringement includes administration in standard pharmaceutical dosage forms, not just in bulk drug form.
What method outcomes are required to infringe?
Claim 1 requires:
- “suppressing parathyroid activity”
- “thereby treating renal osteodystrophy” (as written)
Claim-construction implication: A method that uses a covered compound at a covered dose range in the context of hyperparathyroidism would likely satisfy the “suppressing” element if the compound is used for its intended pharmacodynamic effect. Litigation practice would focus on:
- whether the patient population matches the claimed disorder
- whether the administered compound meets the formula limitations
- whether dosing aligns with 1–500 µg/day
No additional limitations (for example, baseline PTH thresholds, CKD stage, calcium/phosphate parameters, or duration) are stated in the provided claims.
How does this claim set compare to later vitamin D analog patent families?
A complete comparative landscape requires cited documents and prosecution history for US 5,246,925, along with later successor patents. The prompt provides only claim text and no list of related patents, assignees, or cited art. Under the operating constraints, a comparative landscape cannot be reliably produced without risking factual errors.
Which companies are covered, and what Paragraph IV or biosimilar challenges exist?
The provided information contains no:
- Orange Book listing(s)
- FDA application numbers
- patent link codes
- litigation docket information
- assignees or owners of US 5,246,925
- known settlements or Paragraph IV filings
No company-by-company litigation and challenge analysis can be generated from the prompt alone.
US 5,246,925 claim chart style summary (scope map)
| Claim |
Type |
Key limitations |
What this covers |
| 1 |
Independent method |
Treat hyperparathyroidism by suppressing parathyroid activity using compounds of formula (Markush substitutions); administered oral/topical/parenteral; 1–500 µg/day; includes renal osteodystrophy language; n = 1 forces R2 and R3 both methyl |
Broad class of 19-nor vitamin D analogs with variable side-chain substituents/heteroatom replacements, plus broad dosing and routes |
| 2 |
Dependent |
Add pharmaceutically acceptable excipient |
Standard drug formulation |
| 3 |
Dependent |
Solid/liquid ingestible non-toxic vehicle |
Standard dosage forms |
| 4 |
Dependent |
1α,25-dihydroxy-19-nor-vitamin D3 |
Specific exemplar inside claim 1 |
| 5 |
Dependent |
1α-hydroxy-19-nor-vitamin D3 |
Specific exemplar inside claim 1 |
| 6 |
Dependent |
1α,25-dihydroxy-19-nor-vitamin D2 |
Specific exemplar inside claim 1 |
| 7 |
Dependent |
1α-hydroxy-19-nor-vitamin D2 |
Specific exemplar inside claim 1 |
| 8 |
Dependent |
1α-hydroxy-19-nor-24 epi-vitamin D2 |
Specific exemplar inside claim 1 |
| 9 |
Dependent |
1α,25-dihydroxy-19-nor-24 epi-vitamin D2 |
Specific exemplar inside claim 1 |
Key Takeaways
- US 5,246,925 is a broad method-of-use patent covering treatment of hyperparathyroidism via suppression of parathyroid activity using a Markush-defined family of 19-nor vitamin D analogs.
- Route coverage is broad: oral, topical, and parenteral are all within claim 1.
- Dose coverage is explicit: about 1–500 µg/day.
- The independent claim’s structural language (including optional O/S/N replacements at specific side-chain positions and multiple variable substituent sets) is the main lever for infringement analysis.
- Dependent claims 4–9 list specific analogs (D3/D2 and 24-epi; mono- and di-hydroxy variants), providing concrete footholds inside the broader formula.
FAQs
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Does US 5,246,925 require a specific dose duration or only a daily dose range?
Claim 1 recites a daily dose range (“about 1 µg to about 500 µg per day”) and does not add a duration requirement in the provided text.
-
Are both 1α-hydroxy and 1α,25-dihydroxy 19-nor vitamin D analogs covered?
Yes. They are expressly claimed in dependent claims 4–7 (D3 and D2) with both mono- and di-hydroxy variants.
-
Can topical or parenteral dosing infringe if the compound is within the claimed structure and dose range?
Yes. Claim 1 explicitly includes oral, topical, and parenteral routes.
-
If a competitor modifies the side chain at positions 20, 22, or 23, is it automatically outside the patent?
Not automatically. Claim 1 states that the carbon at those positions may be replaced by O, S, or N, indicating flexibility that may keep modified structures within scope.
-
Do claims 2 and 3 limit infringement to specific dosage forms like tablets or injections?
They do not restrict to a single dosage form. They require use with an excipient (claim 2) and a solid or liquid ingestible, non-toxic vehicle (claim 3), which is compatible with standard pharmaceutical presentations.
References (APA)
- US Patent 5,246,925 (claims text provided in prompt).
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