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Patent landscape, scope, and claims: |
United States RE47739 Patent Landscape: Scope, Claim Coverage, and Design-Around Risk for Formula I–II Compounds
RE47739 is an issued US reissue patent directed to a broad class of heteroaromatic compounds defined by a Formula I scaffold (and dependent Formula II embodiments), plus salts and pharmaceutical compositions. The independent claim coverage is driven by a wide substitution-variable schema (X1/X2/X3, R1–R5/R6, T, Q, W, ring-containing substituents), while dependent claims materially narrow to specific substituent sets and then to a long list of named examples, including salts, compositions, and two tight “anchor” species: 6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one (claim 11/8) and a closely related ethyl ester/ketone form (claim 10).
The practical consequence for business, licensing, or litigation strategy is that RE47739 functions as a genus-to-species estate: it can be asserted broadly against many analogs built on the same core “pyrido[2,3-d]pyrimidin-7-one” motif and substitution pattern classes, while also reaching specific commercial candidates named in the claim list.
What is the scope of United States patent RE47739 and what does claim 1 cover?
Short answer: Claim 1 covers compounds of Formula I (and pharmaceutically acceptable salts) containing a defined core heterocycle and a highly permissive substitution framework across X1/X2/X3 (site substituents), R1 (alkyl at a defined position), T (linking heteroatom), Q (heteroatom-containing ring/heterocycle substituent class), W (counterion), and R2/R4/R5/R6/R3 groups, subject to the constraint that at least one of X1, X2, X3 is hydrogen.
Formula I claim architecture that sets the infringement boundary
Claim 1 is structurally “gated” by three major claim levers:
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Core scaffold is fixed by the claimed Formula I structure
The claim language is written to require the Formula I heteroaromatic framework (including pyrido[2,3-d]pyrimidin-7-one-type connectivity as reflected in the enumerated examples). The broad variable lists do not eliminate the need to fit the core skeleton.
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Substitution at three defined positions X1/X2/X3 has a hydrogen-at-least-one constraint
X1/X2/X3 are each independently hydrogen or a large menu of substituents (halogen; alkyl/haloalkyl; alkoxy/alkoxyalkyl; CN; NO2; OR5; NR5R6; carbonyl substituents and sulfonamide/sulfone/phosphonate variants). The claim requires:
- At least one of X1, X2, X3 must be hydrogen.
That is the principal “workable” design-around handle in the X-position schema.
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Large freedom on “side” fragments via T, Q, R2/R4, and R5/R6
- n = 0–2 governs sulfinyl/sulfone-like substituent variants via S(O)nR5.
- R4 can include the ability to form an aromatic ring with one of X1/X2/X3 (explicitly: “R4 and one of X1, X2 and X3 may form an aromatic ring…”).
- Q includes O/S/NR7/N(O)R7/NR7R8W/CO2 and larger ring systems including “carbocyclic group containing 3–7 ring members” with detailed substitution limitations (non-adjacent ring oxygens if two+ present, and up to three substituents chosen from a constrained list).
- R5/R6 are independently drawn from very broad substituent sets; when both are on the same nitrogen, they form a heterocycle ring with restrictions on heteroatom counts and adjacency rules.
X1/X2/X3 substituent menu: what analogs fit?
X1/X2/X3 independently allow the following classes (non-exhaustive but representative of breadth):
- Halogen
- Alkyl (C1–C6), haloalkyl (C1–C6), alkoxy (C1–C8), alkoxyalkyl (C1–C8)
- CN, NO2
- OR5, NR5R6
- CO2R5 / COR5
- Sulfur-oxide substituents: S(O)nR5, SO2NR5R6, NR5SO2R6
- Phosphonate-like: P(O)(OR5)(OR6)
This is a typical “functional genus” substitution list. The hydrogen-at-least-one constraint is the main limitation.
Counterion W: narrow for salts, but relevant for formulation licensing
W is limited to: chloride, bromide, trifluoroacetate, and triethylammonium.
If a competitor uses other salts (e.g., sulfate or mesylate), that may affect literal salt coverage but not necessarily free-base compound coverage.
T and Q: how do they expand protected space?
- T can be O, S, NR7, N(O)R7, NR7R8W, or CR7R8.
- Q supports heteroatom/linker or ring system substituents, including carbocyclic rings and heteroaryl-like constructs.
Together they make claim 1 cover a wide range of linker chemistry and ring substitutions that still remain within Formula I.
Enforced “at least one carbon in carbocycle” and ring-oxygen adjacency rule
Q’s carbocyclic option is limited by:
- at least one carbon in the ring
- if two or more ring oxygens, oxygens are not adjacent
These conditions matter in design-around where cyclic ethers or di-oxygen motifs are used.
How do dependent claims narrow RE47739 from Formula I to Formula II?
Short answer: Claim 2 depends on claim 1 and locks in a specific Formula II substitution pattern: X1/X2/X3 are all hydrogen, R1 = methyl, R2 = acetyl, R3 = cyclopentyl, and R4 = NR5R6, with defined heterocycle composition for the NR5R6 substituents.
Claim 2: what is fixed
Claim 2 sets:
- X1, X2, X3 = hydrogen (removes the “at least one hydrogen” issue because all are H)
- R1 = methyl
- R2 = acetyl
- R3 = cyclopentyl
- R4 = NR5R6
- R5 and R6 together with the attached nitrogen form a heterocyclic ring (3–8 members)
with up to four heteroatoms selected from O, S, S(O), S(O)2, N.
Constraints:
- at least one carbon in the heterocycle
- if two+ oxygens, oxygens are not adjacent
- heterocycle can be unsubstituted or substituted with one to three groups from hydroxyl/C1–C4 alkyl/amino.
Claims 3–5: narrowing on R3/R1/R2
- Claim 3: R3 is cyclopentyl.
- Claim 4: R1 is methyl.
- Claim 5: R2 is (CO)CH3 (acetyl).
These align with the fixed parameters in claim 2 and likely reflect the “commercial candidate” set.
Which specific compounds are explicitly named in RE47739 claims 6–12?
Short answer: Claims 6 and 7 enumerate many specific members of the protected chemical class (including salts). Claims 8 and 11 crystallize one key species as a salt and as an independent compound claim, and claims 9/12 protect a pharmaceutical composition containing the key species.
Claim 6: large named list (species coverage)
Claim 6 lists dozens of compounds built on the Formula I/II core with variations such as:
- substitutions including 6-acetyl, 8-cyclopentyl
- core nitro/halo/ethenyl-like variants (e.g., 6-bromo, 1-ethoxy-vinyl)
- varied amine/heterocycle substituents at the pyridinyl anilide position (piperazine, morpholine, pyrrolidine, diazepane, azepane, azetidine, thiomorpholine-like groups, and others)
- carbonyl/protection variants (carbamic acid tert-butyl ester motifs; sulfonamide/sulfonyl motifs)
- additional ring fusion variants (naphthyridinyl-amino example is included)
This list is a strong indication that the reissue patent is intended to capture a catalog of fallback structures from the original disclosure.
Claim 7: smaller enumerated subset
Claim 7 lists five specific structures (plus “pharmaceutically acceptable salts thereof”), including:
- 6-Bromo-8-cyclopentyl-5-methyl-2-(5-piperizin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one
- 6-Bromo-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one
- 2-[5-(4-tert-Butoxycarbonyl-piperazin-1-yl)-pyridin-2-ylamino]-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidine-6-carboxylic acid ethyl ester
- 6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one
- 6-Bromo-8-cyclopentyl-5-methyl-2-(pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one
Claim 8 and 11: anchor compound
Two claims single out the same principal molecule:
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Claim 8: “A pharmaceutically acceptable salt of
6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one.”
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Claim 11: “6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one or a pharmaceutically acceptable salt thereof.”
This is the narrowest literal capture point in the set.
Claims 9 and 12: composition coverage
- Claim 9: pharmaceutical composition comprising a therapeutically effective amount of a compound according to claim 1 (and claim 2) plus carrier/diluent/excipient.
- Claim 12: composition comprising a therapeutically effective amount of
6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one (or salt) plus carrier/diluent/excipient.
For licensing or enforcement, claim 12 is the most direct composition claim tied to a single species.
Claim 10: two-compound composition gate
- Claim 10: compound according to claim 6 selected from two named species:
- the ethyl ester variant (tert-butoxycarbonyl-piperazine-containing precursor class)
- the acetyl/piperazinyl species: 6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one
What does RE47739’s claim breadth imply for design-around strategies?
Short answer: The strongest literal vulnerability is the substitution “genus” in claim 1, moderated mainly by (i) the X1/X2/X3 at-least-one-hydrogen constraint and (ii) the specific core scaffold required by Formula I, plus the limited salt anions W.
Likely “safe” or “risky” change vectors
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Altering the X positions to eliminate hydrogen at all three sites
Because claim 1 requires at least one of X1/X2/X3 is hydrogen, a competitor analog designed with substituents at all three may avoid claim 1.
Risk remains because claim 2 sets X1/X2/X3 = hydrogen, so any compound without all-H would not read on claim 2. That can reduce dependent claim coverage but does not remove risk from claim 1 if at least one X is still hydrogen.
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Changing the piperazinyl/heterocycle substitution motif (R5/R6 on R4 nitrogen)
Claim 2 restricts the heterocycle formed by R5 and R6 (3–8 members, limited heteroatom types, oxygen adjacency restriction, and substitution limited to hydroxyl/C1–C4 alkyl/amino).
Compounds using larger heterocycles or different substitution sets may fall outside claim 2 but remain within claim 1, which is more permissive about R5/R6 substituent types.
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Counterion swapping
Because W for claim 1 salts is limited to chloride, bromide, trifluoroacetate, and triethylammonium, other salt forms can avoid literal salt coverage under the claim 1 salt provision. However, claim 11 explicitly covers “a pharmaceutically acceptable salt” without listing W in the claim text excerpt provided, creating potential broader salt coverage at least for that anchor compound.
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Core scaffold disruption
The claim is scaffold-driven. Modifying the core away from Formula I connectivity is the only robust way to avoid the genus. Substitution tweaks alone often remain within the claim’s permissive variable scope.
How many patents likely cover these species, and which ones matter most?
Short answer: RE47739 alone appears to be designed to cover a large genus and a commercially relevant subset by multiple claim tiers (genus claim 1, restricted embodiment claim 2, plus enumerated species claim 6/7, and anchor species claim 8/11 with composition claim 12). Without the prosecution history or the family set (not provided), it is not possible to enumerate additional US members or related jurisdictions from reliable identifiers.
What is the likely enforcement posture for RE47739 in US litigation?
Short answer: The estate’s strongest “assertion routes” are:
- compound infringement on the anchor species (claim 11) and
- composition infringement for that species (claim 12),
while broader claim 1 supports wider analog discovery and early settlement pressure against candidates that retain the Formula I core and at least one hydrogen on X1/X2/X3.
Claim 11 and claim 12: highest leverage
Because claim 11 is a direct “compound or pharmaceutically acceptable salt” claim to the named acetyl/piperazinyl/cyclopentyl/methyl scaffold and claim 12 protects compositions, these are the most litigation-ready hooks.
Claim 6 enumeration: expanded settlement surface
Enumerated lists in claim 6/7 can be used to show specific coverage and reduce arguments about “unintended” scope, because the patentee chose the examples as claim targets.
How does RE47739 relate to FDA Orange Book status and generic entry risks?
Short answer: Orange Book status, FDA approval date, and any listed NDA/BLA-to-patent ties cannot be derived from the claim text alone. Generic entry risk hinges on whether the approved product contains the same active ingredient, the same salt, and whether the generic is designed to read outside claim 1/2/11/12 literal coverage.
Key Takeaways
- RE47739 claim 1 is a wide genus covering Formula I compounds with flexible substituent classes, constrained mainly by X1/X2/X3 hydrogen-at-least-one and the fixed Formula I core scaffold.
- Claim 2 is a much tighter embodiment with X1/X2/X3 all hydrogen, R1=methyl, R2=acetyl, R3=cyclopentyl, and R4=NR5R6 where R5/R6 form a heterocycle constrained by size, heteroatom types, and oxygen adjacency.
- The estate is built to reach a commercial anchor species:
6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one via claim 11 (compound/salt) and claim 12 (composition).
- Design-around is most plausible by disrupting the core Formula I scaffold or by making X1/X2/X3 all non-hydrogen to evade the claim 1 hydrogen requirement; salt anion switching may evade some salt forms but not necessarily all anchor claims.
FAQs
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Can a compound that lacks hydrogen at X1, X2, and X3 avoid RE47739 claim 1?
Yes, the claim 1 constraint requires at least one of X1/X2/X3 to be hydrogen.
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Does RE47739 require a specific counterion for all salts?
Claim 1 limits W to chloride, bromide, trifluoroacetate, and triethylammonium; dependent/anchor claims use broader “pharmaceutically acceptable salt” language in the provided excerpt.
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Are pharmaceutical compositions covered even without a new formulation patent?
Yes. Claim 9 covers compositions with the Formula I/claim 2 compounds, and claim 12 covers compositions with the anchor species.
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Is the anchor compound covered as a standalone chemical even if marketed as a different dosage form?
Yes. Claim 11 covers the compound (or salt), and claim 12 covers compositions, which typically map to formulation and method-of-use licensing leverage.
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Does enumerating specific compounds in claim 6/7 narrow the enforceable scope?
Enumeration can increase enforceability against those exact species while claim 1 still provides broader genus coverage, so it does not eliminate wider reach if the accused product fits Formula I.
References
- Claim text provided in the prompt for US reissue patent RE47739 (claims 1–12).
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