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Patent landscape, scope, and claims: |
US Patent 7,390,791 (Scope & Claim Construction) for Diastereomerically Enriched Heterocycle Compounds With Hydrolyzable Oxyesters and Amino-Acid Residues
US Patent 7,390,791 is a compound-and-composition patent centered on diastereomerically enriched chemical entities defined by heterocyclic base scaffolds plus amino-acid-derived groups at a phosphorus center, with an explicit constraint on the weight fraction of a specific undesired diastereomer (claims 1–10). It also claims topical gel compositions (claims 11–13).
The claim set is structured to (1) capture broad families of analogs by variable-group definitions and (2) fence in potency-relevant stereochemical control via “less than X% by weight” limitations for defined diastereomers.
What do the claims of US 7,390,791 actually cover at a chemical-structure level?
What is the core structural concept in claim 1
Claim 1 covers “a diastereomerically enriched compound having the structure (3)” with a stereochemical purity threshold, plus a set of substituent definitions:
Key enforced elements
- Diastereomeric enrichment limitation: “contains less than 40% by weight of the diastereomer (4).”
- R1: an oxyester hydrolyzable in vivo or hydroxyl.
- B: heterocyclic base.
- R2: hydroxyl OR an amino-acid residue attached to the phosphorus atom through an amino group; amino-acid carboxyl substituents can be optionally esterified, but not simultaneously with hydroxyl at both R1 and R2 (see below).
- E: a defined linker motif selected from multiple substituted ethyl/propyl variants and cyclic/functionalized linkers (examples include —(CH2)2—, —CH(CH3)CH2—, —CH(CH2F)CH2—, —CH(CH2OH)CH2—, allyl-containing, alkynyl-containing, azido-containing, and branched ether/alkyl ether variants).
- Double bond optionality: broken line represents optional double bond within the drawn structure family.
- R4 and R5: each independently H, hydroxy, halo, amino, or a 1–5 carbon substituted group chosen from acyloxy, alkyoxy, alkylthio, alkylamino, dialkylamino.
- R6 and R6’: independently H or C1–C6 alkyl/hydroxyalkyl or C2–C7 alkanoyl.
- R7: either H or C1–C6 alkyl, or taken together to form —O— or —CH2—.
- R8: H or C1–C6 alkyl/hydroxyalkyl/haloalkyl.
- R9: H, hydroxymethyl, or acyloxymethyl.
- Allowed end states: salts, free base, and solvates.
Critical “either/or” constraint
- “but not both of R1 and R2 are hydroxyl” means if R2 is hydroxyl, R1 cannot be hydroxyl; if R1 is hydroxyl, R2 must not be hydroxyl (it must be amino-acid residue when R2 is not hydroxyl).
What claim 2–3 do
- Claim 2 tightens the stereochemical threshold to <20 wt% of diastereomer (4).
- Claim 3 tightens further to <5 wt% of diastereomer (4).
These are classic “purity fall-back” claims. They also function as a risk lever for generics or entrants who may start with racemates and rely on enrichment that might not meet the particular wt% impurity limit.
How broad are claim 1’s substituent definitions (and what does that mean for design-around)?
Freedom points
Claim 1 is broad in multiple dimensions because it defines substituents by:
- heterocyclic base (B) without enumerating a single ring system in the text you provided,
- a multi-option E linker set with functionalized substituents,
- broad “selected from” lists for R4/R5,
- broad ranges for R6/R6’, R7, and R8/R9.
This breadth increases the probability that analogs with the same stereochemical motif and the same phosphorus-amino-acid logic fall within the claim even if the periphery is modified.
Two major narrowing points
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Stereochemical purity as a quantitative wt% limit
The claim is not only structural; it is also manufacturing- and analytical-method dependent because the accused product must be tested against the defined diastereomer quantity.
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R1/R2 hydroxyl mutual exclusion
This “not both hydroxyl” condition forces at least one side of the molecule to be functionalized as oxyester (for R1) or amino-acid residue (for R2), or R1 hydroxyl with R2 not hydroxyl.
Design-around implication
A competitor can attempt to evade by:
- changing the stereochemical composition so it does not meet “less than X%” impurity limits (but that may be incompatible with therapeutic performance and may still be reachable via other dependent purity claims if the competitor achieves high enrichment anyway),
- altering the scaffold to remove the amino-acid residue attachment through the amino group to the P atom,
- changing the “E” linker class to an excluded motif (if their linker lies outside the enumerated set),
- shifting substituents in a way that falls outside the enumerated options for R4/R5, R6/R6’, R7, R8, or R9.
Which claim set covers “diastereomerically enriched” structures with amino-acid side chains and different R groups (claims 4–6)?
Claim 4 scope
Claim 4 covers a diastereomerically enriched compound with structure (5a) and enforces a stereochemical threshold for diastereomer (5b):
Key enforced elements
- Diastereomer impurity limit: “contains less than 40% by weight of diastereomer (5b).”
- R5: methyl or hydrogen.
- R6: either:
- H/alkyl/alkenyl/alkynyl/aryl/arylalkyl, OR
- same with up to 1–3 substituents from a long list (alkylamino classes, hydroxy/oxo/halo/amino, alkylthio, alkoxy and alkoxyalkyl, aryloxy and aryloxyalkyl, aryloxyalkoxy type, haloalkyl, nitro/nitroalkyl, azido/azidoalkyl, alkylacyl, carboxyl, alkylacylamino).
- R7: side chain of a naturally occurring or pharmaceutically acceptable amino acid; if the side chain includes carboxyl, that carboxyl can be optionally esterified.
- R11: amino/alkylamino/oxo/dialkylamino.
- R12: amino or H.
- Allowed end states: salts, tautomers, free base, solvates.
Claims 5–6 tighten diastereomer content:
- Claim 5: <20 wt% (5b)
- Claim 6: <5 wt% (5b)
Landscape interpretation
This claim set resembles a second scaffold variant, likely a different arrangement of the phosphorus-bound region or surrounding substituent pattern compared with claim 1. It also keeps the same stereochemical “purity ladder” structure.
What additional structure families are covered in claims 7–10?
Claim 7
- Claims a diastereomerically enriched compound of structure (6) and its salts, tautomers, free base and solvates.
The text you provided does not include the full substituent definition for structure (6), but the claim language indicates the same stereochemical-enrichment concept applies.
Claims 8–10
- Claim 8: diastereomerically enriched compound of structure (7) with “contains less than 40%” of diastereomer (7a).
- Claim 9: <20 wt% of (7a).
- Claim 10: <5 wt% of (7a).
Practical consequence
Even without substituent specifics for (6) and (7) in the excerpt, the dependent ladder establishes that the patent’s novelty and commercial value are tied to being able to manufacture a stereoisomerically enriched product with quantitatively limited presence of a specific diastereomer.
What do claims 11–13 cover on formulation and topical administration?
Claim 11
- “A composition comprising a compound of any of claims 1–8 or 2–10 and a pharmaceutically effective excipient.”
This is a broad formulation claim. It captures any conventional excipient system unless later limited by dependent claims.
Claim 12
- Excipients are limited to a gel.
Claim 13
- Gel is “suitable for topical administration.”
Formulation claim strength
The formulation language is not limited by:
- specific polymer type,
- rheology,
- active concentration,
- penetration enhancers,
- preservatives,
- manufacturing method.
As written, it is a high-level composition claim that can be attacked for breadth depending on the specification, but it still creates a direct licensing point for any topical gel using a claimed stereochemically enriched compound.
How does the stereochemical impurity “wt%” requirement affect enforcement and validity?
Enforcement hinges on analytical disclosure
Because the claims are defined by “less than X% by weight” of a specified diastereomer, infringement analysis depends on:
- which analytical method is used to quantify the diastereomer,
- whether the method measures wt% in the claimed sense (the claims do not define the method, but enforceability will still track whatever quantitation approach is accepted in the record).
This structure is favorable to patentees when the manufacturing process is known to reliably hit low diastereomer impurity targets.
Purity ladder creates multiple potential infringement bands
A single product manufacturing route might:
- fall below 40% (claim 1, 4, 8),
- fall below 20% (claims 2, 5, 9),
- fall below 5% (claims 3, 6, 10).
That increases settlement leverage, because the accused party can find it difficult to argue they are outside the claim without also losing therapeutic positioning if the achieved purity still falls within a ladder rung.
What patent landscape issues matter for US 7,390,791 without adding speculative unrelated patents?
What can be stated from the claim text alone
US 7,390,791’s landscape value is driven by three claim pillars:
- Chemical structure families (3), (5a), (6), (7)
- Quantitative diastereomer impurity ceilings for defined diastereomers (4), (5b), (7a)
- Topical gel compositions built on those compounds
That means the most relevant “landscape competitors” are patents or applications that:
- claim close analogs with the same stereochemical enrichment concept,
- claim the same or overlapping structures but without the exact diastereomer impurity limits,
- claim topical gels using overlapping active ingredients.
Where overlap typically occurs
- Across generations of the same chemistry: later patents often broaden substituents while keeping stereochemical constraints.
- Across formulation patents: gel and topical delivery are commonly claimed in separate IP estates.
- Across stereochemistry process patents: even when the end product claims are broad, competitors can be deterred by process constraints tied to stereochemical enrichment (though such process claims are not shown in your excerpt).
Key takeaways
- US 7,390,791 is a stereochemistry-driven compound patent with quantitative diastereomer impurity limits at 40%, 20%, and 5 wt% tiers.
- Claim 1 is the broadest textually specified scaffold in your excerpt and includes broad structural variability around heterocyclic base (B), linker E, and multiple substituent groups (R4-R6’, R7-R9), subject to the “not both R1 and R2 are hydroxyl” constraint and the diastereomer wt% cap.
- Claims 4–6 define an additional structural family (5a) with its own diastereomer (5b) ladder and a broad R6 substituent menu plus amino-acid side-chain logic at R7.
- Claims 7–10 add further scaffold coverage (6 and 7) using the same impurity-ladder enforcement structure.
- Claims 11–13 expand into a composition claim for topical gel formulations containing compounds from claims 1–8 / 2–10, without specifying gel components or concentration ranges.
FAQs
1. What is the main legal “handle” in US 7,390,791: structure or purity?
Both. The claims require a defined chemical structure family and impose quantitative “less than X wt%” limits for a specified diastereomer.
2. Do claims 2–3 (and 5–6, 9–10) create multiple independent infringement thresholds?
Yes. Each tier can be infringed if the accused product meets the corresponding diastereomer impurity ceiling.
3. Is the topical gel claim limited to particular gel excipients?
No. Claim 12 limits the excipient to a gel, but it does not specify a polymer, penetrant, or concentration range.
4. Can R1 and R2 both be hydroxyl groups under claim 1?
No. Claim 1 expressly states “but not both of R1 and R2 are hydroxyl.”
5. Does the patent cover salts and solvates as well as free base forms?
Yes. Claims 1–10 include “their salts, free base, and solvates,” and claim 11 adds formulation coverage for those compounds in a gel excipient.
References
No references can be generated from the information provided, because no bibliographic record, assignees, filing/publication data, prosecution history, specification details, or citation list were included in the prompt.
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