Executive summary: US Patent 5,705,517 is an expansive, structure-based claimset covering a broad class of biphenyl/benzene substituted benzimidazole carboxylates with tightly defined linker, heteroatom, and anionic functionalities (notably tetrazolyl, plus sulfo/phosphono/amido variants) and extensive permissible substituents on both aromatic and ester/oxycarbonyloxy groups. Independent claim 1 reads on multiple specific prodrug-like “carboxylate/oxymethyl” exemplars in dependent claims 17–26 and covers both formulation (claim 27) and therapeutic use (claim 28) for angiotensin II antagonism. As a result, the practical freedom-to-operate around this patent turns less on whether a candidate has the “same API core” and more on whether it falls inside the claim’s permitted permutations for ring A substitution, R1 and R2 substituents, X/Y linker definition, and the ester/oxycarbonyl substitution patterns.
Important: A complete, accurate “US patent landscape” (expiration dates, Orange Book status, assignment/chain-of-title, prosecution history, co-owned continuation families, and whether competing products are positioned around this specific claim scope) requires bibliographic and regulatory data that are not provided. Per constraints, the analysis below is limited to claim scope, enforceable subject matter categories, and what the claims practically capture. No external patent/register facts are asserted.
US 5,705,517 scope: what compounds are claimed under claim 1?
Bottom line: Claim 1 covers a pharmaceutically acceptable salt of a compound of the form:
- A core containing a benzene ring (“ring A”) and a second aromatic fragment consistent with biphenyl substitution (made explicit in dependent examples),
- A benzimidazole carboxylate motif with an –COOCH(R7)OCOR8 type group (prodrug/ester-like functionality),
- A defined anionic/acidic substituent at R2 (commonly tetrazolyl),
- A defined linker region via X and Y,
- A nitrogen-containing substituent region with R1 and X/Y combination that can form piperidino or morpholino rings.
What is the “scaffold” implied by the claim language?
Claim 1 is drafted to cover a family with:
- Ring A: benzene ring optionally substituted, and specifically permitting substitution patterns including “when two substituents are present at the 4 and 5 or 5 and 6 positions … they may be taken together” to form an extended benzene ring (a drafting device to permit fused/condensed aromatic mapping in the Markush set).
- A constrained aromatic carboxylate/ester system: “with a substituent selected from … --COOCH(R7)OCOR8” and extensive permissible R7/R8 definitions.
- A second key pharmacophore: R2 is an anionic group set: carboxyl, tetrazolyl, phosphono, sulfo, trifluoromethanesulfonic amido, cyano, or alkoxycarbonyl (some protected), with a broad protection/derivatization allowance.
- A nitrogen linker definition: X and Y restrict the heteroatom connectivity; the combined R1 and R4 can cyclize to piperidino or morpholino.
Key claim variables and what they practically do
Ring A substitution: which substituents are allowed?
Ring A may carry one or two substituents “at various positions,” and each permitted substituent is selected from:
- Halogen; nitro; cyano; amino; N-alkylamino; N,N-dialkylamino
- Phenylamino, naphthylamino, benzylamino, naphthylmethylamino
- Morpholino, piperidino, piperazino, N-phenylpiperazino
- A flexible group: –W–R13 where W can be bond, O, S, or an additional atom arrangement (as shown by a ring depiction in the claim)
- A second flexible group: –(CH2)p–CO–D with p = 0 or 1 and D selected from a large set including hydrogen, hydroxyl, amino, N-alkylamino/dialkylamino, various alkoxys (C1–6), alkylthio, dioxolenyl, and 5-methyl-2-oxo-1,3-dioxolen-4-yl (a carbonate-like motif)
- A third flexible group: –OCH(R9)OCOR10 with R9 and R10 enumerated broadly over alkyl/cycloalkyl/aryl/alkenyl/alkoxy/phenoxy variants and substituted aryl/alkoxy variants
- Tetrazolyl (optionally protected with alkyl/alkanoyl/benzoyl)
- Trifluoromethanesulfonic amido; phosphono; sulfo
Enforcement consequence: ring A substituent permissiveness plus “two substituents taken together” is designed to make claim 1 very hard to avoid via minor aryl substitution changes.
R1: how broad is the substituent on the ring nitrogen system?
R1 includes:
- Hydrogen
- Alkyl/alkenyl/alkynyl/cycloalkyl (C1–8 or C3–6) with optional hydroxyl/amino/halogen/alkoxy
- Phenyl optionally substituted
- Phenyl-alkyl optionally substituted
R1 is also linked to Y/R4 for cyclization to piperidino/morpholino (see below).
Enforcement consequence: R1 changes are generally still within the claim unless they step outside the enumerated carbon count and substitution lists.
R2: what acid/anion groups are covered?
R2 is restricted to:
- Carboxyl
- Tetrazolyl
- Trifluoromethanesulfonic amido
- Phosphono (PO(OH)2)
- Sulfo (SO3H)
- Cyano
- C1–4 alkoxycarbonyl
Each can be protected with:
- C1–4 alkyl optionally substituted with alkoxy or phenyl
- C2–5 alkanoyl
- benzoyl
Enforcement consequence: a competitor that uses a different acidic headgroup might avoid the claim; a competitor that uses a tetrazole or masked tetrazole/carboxyl prodrug is likely still inside.
R7/R8: the –COOCH(R7)OCOR8 group is heavily covered
R7: hydrogen or C1–6 alkyl or cyclopentyl/cyclohexyl/cycloheptyl.
R8: C1–6 alkyl; C2–8 alkenyl; cyclopentyl/cyclohexyl/cycloheptyl; substituted aryl-substituted alkyl variants; substituted alkenyl or alkyl variants; phenyl and substituted aryl; alkoxy and alkenyloxy variants; cycloalkoxy variants; phenoxy/p-nitrophenoxy/naphthoxy.
Enforcement consequence: this is a major reason claim 1 is difficult to design around through “different prodrug ester” selection.
X and Y: what linker architectures are allowed?
- X is either a chemical bond or a divalent chain with straight chain length 1 or 2.
- Y is either:
- --O--; or
- --S(O)m (m = 0,1,2); or
- --N(R4)-- where R4 is H or C1–4 alkyl optionally substituted with hydroxyl or C1–4 alkoxy.
Dependent claims narrow X/Y examples and define them concretely (claim 8 gives a more explicit list).
Enforcement consequence: avoidance by choosing a radically different heteroatom linkage (e.g., carbon-based linker or different oxidation state for sulfur beyond allowed m) can reduce exposure; otherwise the claim targets multiple plausible medchem linker variations.
Combination rule: R1 + R4 cyclize to piperidino/morpholino
Claim 1 states: “whereby R1 and R4 may be taken together with the N atom to form a piperidino or morpholino ring.”
Enforcement consequence: competitors using morpholine/piperidine-containing motifs in the same topological region are structurally aligned with the claim.
Salts
Claim 1 covers “a pharmaceutically acceptable salt.” Dependent claims keep the same compound scope.
Which specific compounds are explicitly captured in dependent claims 17–26?
Bottom line: Dependent claims enumerate particular members that align with a tetrazolyl biphenyl benzimidazole carboxylate where the carboxylate is converted into oxycarbonyloxymethyl or analogous masked ester/prodrug forms at a defined position (the language shows multiple “carbonyloxymethyl” variants and related O-alkyl carbamate variants).
The explicit examples are:
- Claim 17: acetoxymethyl 2-ethoxy-1-(…biphenyl-4-yl)methyl benzimidazole-7-carboxylate
- Claim 18: propionyloxymethyl
- Claim 19: butyryloxymethyl
- Claim 20: isobutyryloxymethyl
- Claim 21: 1-(ethoxycarbonyloxy)ethyl
- Claim 22: 1-(isopropoxycarbonyloxy)ethyl
- Claim 23: cyclohexylcarbonyloxymethyl
- Claim 24: benzoyloxymethyl
- Claim 25: (E)-cinnamoyloxymethyl
- Claim 26: cyclopentylcarbonyloxymethyl
Enforcement consequence: even if a competitor’s exact scaffold argument is contested, these dependent claims function as “anchoring” embodiments that map the generic claim variables to real, synthetically plausible product forms.
What formulations and methods are covered under claims 27–28?
Bottom line: Claim 27 and 28 expand beyond composition-of-matter to include:
- a pharmaceutical composition for antagonizing angiotensin II, and
- a method of antagonizing angiotensin II via administration.
Claim 27: formulation coverage
“A pharmaceutical composition for antagonizing angiotensin II” comprising:
- therapeutically effective amount of claim 1 compound (or salt)
- in admixture with pharmaceutically acceptable carrier/excipient/diluent
Enforcement consequence: generic formulation substitutions typically still fall inside composition claims if they contain the claimed API.
Claim 28: method-of-use coverage
“A method for antagonizing angiotensin II in a mammal” comprising administering:
- therapeutically effective amount of claim 1 compound (or salt)
Enforcement consequence: method-of-use claims can be relevant to “use” triggers in regulatory and litigation contexts, including claims about clinical labeling and therapeutic indications.
How strong is the patent against design-arounds? (Claim-structure risk analysis)
Bottom line: Claim 1 is drafted as a broad Markush over multiple key moieties and provides multiple pathways to incorporate substitution diversity. That generally increases:
- probability that many plausible analogs remain within the claim,
- leverage against “near-neighbor” generics that keep the same pharmacophore.
Where design-arounds are most feasible
- Headgroup swap: substituting away from R2’s enumerated acidic/anionic options (tetrazolyl/carboxyl/phosphono/sulfo/cyano/alkoxycarbonyl/triflate-amido) is the most direct route to escape.
- Linker topology shift: moving X/Y to architectures not permitted by the claim-defined list (or selecting different heteroatom classes outside O/S/N(R4) definitions) can reduce claim coverage.
- Prodrug/ester architecture shift: replacing the “–COOCH(R7)OCOR8” motif with a qualitatively different functional group (not expressible as that oxycarboxylate framework) is another potential escape route.
Why substitution changes alone may not help
- Ring A substitution includes extensive amines and heterocycles plus flexible –W–R13 and –(CH2)p–CO–D and –OCH(R9)OCOR10 groups.
- R7/R8 accept wide alkyl/alkenyl/cycloalkyl/aryl/alkoxy/aryl-alkoxy variants.
- R1 accepts alkyl/alkenyl/alkynyl/cycloalkyl and phenyl substitutions with multiple allowed substituents.
Net effect: avoidance through “different ester substituent” or “different halogen/alkoxy pattern on ring A” alone is unlikely.
How many separate claim categories does 5,705,517 cover, and what does that mean for licensing?
Bottom line: The patent is not limited to a single API structure; it layers multiple claim categories:
- Composition-of-matter (claim 1): broad Markush of compound + salt.
- Narrower compound subsets (claims 2–16): additional limitations to particular ranges (e.g., R1 C1–5 alkyl or phenyl; R2 tetrazolyl or carboxyl; ring A unsubstituted except for COOCH(R7)OCOR8; explicit X and Y lists).
- Specific embodiments (claims 17–26): enumerated ester/prodrug members.
- Pharmaceutical composition (claim 27).
- Method of use (claim 28).
Licensing impact: this structure supports both (i) licensing an API as such and (ii) licensing downstream product forms, including use and formulation arguments.
Which competitor design profiles are most likely to fall inside claim 1?
Bottom line: The strongest “likely inside” profiles share:
- a tetrazolyl or tetrazolyl-protected equivalent (R2),
- a benzimidazole-7-carboxylate-like region esterified into an oxycarboxylate/prodrug pattern consistent with R7/R8,
- aromatic topology consistent with the biphenyl/benzene ring system,
- X/Y permissive heteroatom connectivity, and
- nitrogen heterocycle presence consistent with R1/R4 cyclization.
Most at-risk: generics or follow-on prodrugs that preserve the same core scaffold but vary ester promoiety length/aryl masking (e.g., acetoxy/propionyloxy/butyryloxy and related carbonyloxymethyl variants already listed).
Key Takeaways
- US 5,705,517 claim 1 is broad: it covers a class of benzimidazole-based angiotensin II antagonists with extensive permissible substitutions on ring A and an unusually wide R7/R8 prodrug ester space.
- The patent has multiple claim layers: compound (1, plus narrower 2–16), specific embodiments (17–26), plus composition (27) and method-of-use (28).
- Design-around is possible but not trivial: headgroup and linker topology changes offer the most credible routes; “minor substitution changes” often remain within the Markush ranges.
- Dependent examples 17–26 are strategically important: they map the claim variables to concrete prodrug/ester variants, which raises the risk for near-neighbor analogs.
FAQs
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Does US 5,705,517 primarily protect the API scaffold or the prodrug ester?
It protects both: claim 1 is scaffold-based while the ester-like “–COOCH(R7)OCOR8” substituent is broadly defined, and dependent claims enumerate multiple ester/prodrug embodiments.
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How can a generic reduce risk under claim 1?
By selecting structures that fall outside the enumerated R2 acidic/anionic set, or that use a linker (X/Y) architecture not expressible under the claim-defined connectivity.
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Are salts within the same scope as the parent compounds?
Yes. Claim 1 covers pharmaceutically acceptable salts, and dependent claims track “compound or salt thereof” language.
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What does claim 28 add beyond the compound itself?
It adds a method-of-use claim for antagonizing angiotensin II via administration of the claimed compound or salt to a mammal.
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Do claim 27 and 28 increase enforcement leverage for generics?
Yes for labeled indication and formulation containing the claimed API: composition-of-matter typically drives infringement analysis, while claims 27–28 can expand enforcement to product formulation and use-based theories.
References (APA)
- United States Patent 5,705,517. (as provided in claim text).
