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Patent landscape, scope, and claims: |
United States Patent 3,985,758: Scope, Claim Coverage, and US Patent Landscape for 1,4-Dihydropyridine Carboxylic Acid Derivatives
US Patent 3,985,758 claims a broad genus of substituted 1,4-dihydropyridine (DHP) compounds defined by a structural formula and narrowed by specific substituent variables, with dependent claims enumerating particular nitro-aryl and esterified dicarboxylic acid embodiments. The patent’s enforceable scope is driven by (i) the broad Markush-style variable ranges in independent claim 1 and (ii) the detailed stereochemical/ester-form recitations in dependent claims 2 through 9, which map to specific substitution patterns on the DHP ring (notably a 2,6-dimethyl pattern and a 4-(3’-nitrophenyl) substituent) and to specific ester groups at the 3-β and 5-positions.
What is the claim scope of US Patent 3,985,758 (1,4-dihydropyridine compound formula) and what do the Markush variables cover?
Short answer: Claim 1 covers a genus of 1,4-dihydropyridine compounds with fixed ring substitution at 2,6 positions (via R1/R2 = methyl) and fixed dicarboxylic acid architecture (carboxylic acid positions esterified or otherwise substituted per R5), while allowing variation in ring substitution at the 4-position aryl/benzyl-like group (R3 plus R4 variants), and variation in ester/alkyl substituents through A and the moieties defined by R5 and R6 (nitro or trifluoromethyl).
Claim 1 structure: what is fixed vs variable
Independent claim 1 is written as:
- Core scaffold: “A compound of the formula” (formula omitted in the prompt but defined by the claim variables)
- Fixed variables:
- R1 and R2 each = methyl (locks the 2,6-dimethyl motif)
- R6 = nitro or trifluoromethyl (locks the ring’s electron-withdrawing group option at the defined position in the formula)
- Variable variables:
- R = hydrogen or lower alkyl (substitution at the position labeled R)
- R3 = phenyl, benzyl, halobenzyl, lower alkoxy-benzyl
- R4 = hydrogen, methyl or ethyl
- A = lower alkylene (defines the linker between functional groups as drawn)
- R5 =
- methyl, or
- lower alkoxy, or
- lower alkoxy substituted with lower alkoxy, or
- an additional substituent defined by “##EQU1##” (a further structural option in the claim)
How this translates into practical design space
From a freedom-to-operate perspective, claim 1 is best read as a substituted DHP genus where:
- The 2,6-dimethyl DHP is non-negotiable because R1 and R2 are each constrained to methyl.
- The 4-position aryl/benzyl substituent family is broad (phenyl and multiple benzyl derivatives), and it can include halogenated benzyl and lower alkoxy-benzyl.
- The allowed R4 (H, Me, Et) changes the substitution pattern on the aryl/benzyl group (as defined in the formula), widening coverage beyond “only nitro phenyl” to other substituted benzyl/phenyl analogs within those bounds.
- R6 provides an explicit electronics fork: nitro or CF3.
- R5 expands the protected region around the ester/carboxyl substitution pattern by including multiple lower-alkyl and lower-alkoxy types and at least one additional defined structural alternative.
Claim breadth vs enforceability reality
Even with a broad genus, litigation risk often turns on claim construction:
- Markush selection: Because claim 1 uses nested alternatives (for R3, R4, R5, R6), the prosecution and file history (not provided here) usually affect whether a narrowing interpretation is applied.
- “Lower” qualifiers: “Lower alkyl / lower alkoxy / lower alkylene” generally mean short-chain groups, often C1-C4, but exact scope depends on construction.
- The “##EQU1##” branch in R5: This is a major driver of scope. If it covers a specific esterification/derivatization motif, it can make the claim read on specific prodrug-like or solubilizing derivatives.
Which specific compounds are explicitly covered by dependent claims 2–9 (nitrophenyl, 2,6-dimethyl, ester variants)?
Short answer: Dependent claims 2–9 enumerate specific 2,6-dimethyl DHP-3,5-dicarboxylic acid derivatives with a 4-(3’-nitrophenyl) group and nitro substitution, and they specify multiple ester variants at the 3-β side-chain and at the 5-position.
Claim 2: a narrower subgenus with fixed substituents
Claim 2 narrows claim 1 to:
- R = hydrogen
- R1/R2 = methyl
- R3 = benzyl
- R4 = methyl or ethyl
- R5 = lower alkoxy
- R6 = nitro
This subgenus keeps the nitro option and converts the 4-position substituent family to benzyl with limited substitution (R4).
Claim 3: specific embodiment with ethyl ester vs methyl ester
Claim 3 recites:
- 2,6-dimethyl-4-(3’-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid
- 3-β-(N-benzyl-N-methylamino ethyl ester)
- 5-methyl ester
Claim 4: 5-ethyl ester analog
Claim 4 differs by:
- 3-β-(N-benzyl-N-methylamino) ethyl ester
- 5-ethyl ester
Claim 5: 5-isopropyl ester analog
Claim 5 differs by:
- 5-isopropyl ester
- same 3-β-(N-benzyl-N-methylamino ethyl ester) motif
Claim 6: N-ethylamino analog, 5-isopropyl ester
Claim 6 recites:
- 3-β-(N-benzyl-N-ethylamino) ethyl ester
- 5-isopropyl ester
Claim 7: propyl ester extension at 3-β position, 5-isopropyl ester
Claim 7 recites:
- 3-β-(N-benzyl-N-methylamino) propyl ester
- 5-isopropyl ester
Claim 8: p-methoxybenzyl, 5-ethyl ester
Claim 8 recites:
- 3-β-(N-p-methoxybenzyl-N-methylamino) ethyl ester
- 5-ethyl ester
Claim 9: p-chlorobenzyl, 5-ethyl ester
Claim 9 recites:
- 3-β-(N-p-chlorobenzyl-N-methylamino) ethyl ester
- 5-ethyl ester
What the dependent claim set reveals about the inventor’s focus
Across claims 3–9, the protected chemistry concentrates on:
- A single aryl core: 4-(3’-nitrophenyl)
- A 2,6-dimethyl DHP ring
- A 3,5-dicarboxylic acid framework
- A consistent 3-β aminoalkyl ester motif with benzyl substitution on the nitrogen
- Variation in:
- ester alcohol identity at 5 (Me vs Et vs iPr)
- N-substitution (methyl vs ethyl on the amino nitrogen)
- benzyl ring electronics (unsubstituted benzyl vs p-MeO vs p-Cl)
- chain length at 3-β ester (ethyl vs propyl)
How would an accused product infringe claim 1 vs dependents 2–9 (practical infringement map)?
Short answer: A product matching the 2,6-dimethyl DHP core and satisfying the R3/R4/R6 and R5 option set could fall under claim 1 even if it does not match the exact enumerated ester embodiments in claims 3–9. If a product is one of the enumerated specific compounds, dependent claims provide a narrower but clearer infringement pathway.
Infringement tiers
- Exact dependent match (claims 3–9):
- If a product’s structure matches one of the recited ester and N-benzyl substitution variants, infringement is straightforward on the claim face.
- Subgenus within dependent constraints:
- If a product shares the same DHP core and broad constraints but swaps ester identities within the “lower alkyl / lower alkoxy” ranges of claim 1 or swaps within Markush alternatives, claim 1 is the likely target.
- Partial overlap (claim 1 only):
- If the product matches the 2,6-dimethyl DHP and nitro/CF3 element but uses a non-covered benzyl/phenyl variant, it may avoid claim 1 depending on how strictly “phenyl/benzyl/halobenzyl/lower alkoxy-benzyl” is construed.
Key “design-around” levers suggested by claim language
- Change the 2,6 substitution: if R1 or R2 cannot be methyl, claim 1 is blocked.
- Change R6 to something other than nitro or CF3.
- Move away from the allowed R3 family (phenyl/benzyl/halobenzyl/lower alkoxy-benzyl).
- Use R5 substitution patterns that do not fall within the enumerated “methyl / lower alkoxy / lower alkoxy substituted with lower alkoxy / ##EQU1##” alternatives.
What US patent landscape surrounds US 3,985,758 (how many related claims and likely continuation families)?
Insufficient information to produce a complete and accurate landscape. The prompt provides claim text but does not include:
- patent title/assignee,
- publication/application numbers,
- filing dates,
- inventor names,
- related continuations or foreign counterparts,
- or any citation data.
Because a patent landscape requires identifying related US filings and cited references (and tying them to scope and expiration), generating a complete, accurate “near-neighbor” map is not possible from the provided content alone.
When does US 3,985,758 expire, and when does exclusivity end (US filing and term rules)?
Insufficient information to produce a complete and accurate expiration timeline. Expiration and any terminal disclaimer effects depend on:
- the application filing date,
- whether this is a patent issued from an application with a particular term calculation basis,
- whether there are PTA/adjustment impacts,
- and any disclaimers.
No filing date or term data is provided, so an accurate exclusivity timeline cannot be produced.
What Orange Book status applies to US 3,985,758 and what generics/biosimilars are at risk?
No determinate answer can be produced from the provided inputs. Orange Book status depends on identifying the drug product associated with the patent (which requires the patent-to-product listing linkage). The prompt does not provide the marketed drug name, NDA/ANDA/BLA number, or Orange Book listing.
How strong is the claim estate for 3,985,758 (claim count, breadth, and likely litigability)?
Short answer: Strength based on the provided claim set appears concentrated in:
- a broad independent Markush genus (claim 1),
- and multiple dependent claims that pin down specific ester/N-benzyl substitution embodiments (claims 3–9), which can support multiple infringement theories against closely related analogs.
But a litigability assessment (validity strength, prior-art exposure, and claim construction vulnerability) requires:
- prosecution history,
- cited references,
- and full claim set (including any additional independent claims beyond claim 1 and dependents shown).
Those inputs are not provided.
Key Takeaways
- Claim 1 protects a genus of substituted 1,4-dihydropyridine compounds with fixed 2,6-dimethyl (R1/R2 = methyl) and nitro or CF3 (R6), while varying aryl/benzyl substitution (R3/R4) and ester/alkoxy derivatization (R5) within defined “lower” and structural options.
- Claims 2–9 provide explicit coverage for a set of 2,6-dimethyl-4-(3’-nitrophenyl) DHP-3,5-dicarboxylic acid derivatives with nitro and specific 3-β aminoalkyl ester and 5-ester variants, including N-benzyl (and p-substituted benzyl) and Me/Et/iPr ester choices.
- Product risk mapping: An accused compound that matches the 2,6-dimethyl DHP core and nitro/CF3 placement is a more likely claim 1 hit; a compound that matches one of the enumerated claims 3–9 is a clearer dependent-claim target.
FAQs
- Which structural elements in US 3,985,758 are non-negotiable for claim 1 coverage?
- How do claims 3–9 narrow the protected scope compared with claim 1’s Markush genus?
- What ester modifications (5-position Me/Et/iPr and 3-β ethyl vs propyl) are explicitly covered?
- Does US 3,985,758 cover both nitro and trifluoromethyl analogs, and where does that appear in the claim language?
- What substitution changes are the most direct claim 1 design-arounds based on R3/R6/R1/R2 constraints?
References
- US Patent 3,985,758. Claims provided in the prompt.
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