Scope of United States Patent 6,258,795 (Acyl Derivatives of Uridine): Claim Breadth, Coverage Boundaries, and US Patent Landscape

United States Patent 6,258,795 claims acyl derivatives of uridine (and, via dependent claims, cytidine-containing combinations and dosage forms), where “acyl” is broadly defined as acyl radicals derived from a large set of fatty acids and other carboxylic acids (including amino acids and dicarboxylic acids), with at least one substituent not being hydrogen. The estate is structurally designed to read on multiple tri-O-acyl uridines (e.g., 2′,3′,5′-tri-O-acetyl/propionyl/butyryl uridine) while also covering “mixed” acyl patterns (different substituents across R1/R2/R3, and in the formula (I) framework where R4 is separately defined).

However, without the full specification, priority data, prosecution history, and the complete claim set beyond claims 1–23 shown, it is not possible to map (i) the exact claim construction boundaries tied to formulas (I)–(III), (ii) whether the patent includes additional independent claims not included in the excerpt, (iii) the actual expiration and exclusivity timing in the US, or (iv) whether the patent was later limited/clarified by office actions, terminal disclaimers, or court construction.

What follows is a claim-scope and “freedom-to-operate style” landscape analysis strictly from the claim language provided.

What patents protect acyl derivatives of uridine like 2′,3′,5′-tri-O-acetyl uridine under US 6,258,795?

Direct answer: US 6,258,795 protects acyl derivatives of uridine where acyl groups are derived from a large menu of carboxylic acids (including many fatty acids and specific non-fatty acids), with the claims requiring that at least one acyl substituent is non-hydrogen (and, in certain compositions, that specific acyl patterns apply). It also protects pharmaceutical compositions using those derivatives, including unit doses and dosage forms and, in one dependent claim set, mixtures with specific acyl derivatives of cytidine.

Claim architecture that drives coverage

The claim set is organized into:

Core chemical product claims for “acyl derivatives of uridine” (independent claims 1 and 2; claim 3 adds amino-acid restriction).
Composition claims (claims 4–5, 8, 10–23), including:
- pharmaceutically acceptable carriers spanning excipients and coatings,
- unit dose ranges expressed as “equivalent of 10–3000 mg of uridine,”
- dosage forms including oral and injectable/suppository routes (claim 8),
- an explicit combination concept with specific cytidine tri-O-acyl derivatives (claims 6–7),
- narrower dependent hooks to specific uridine tri-O-acyls (claim 9).

How broad are the uridine acyl derivative claims (claims 1 and 2) and what limits them?

Direct answer: The scope is broad at the “acyl menu” level but constrained by (i) how the formulas define where and how many acyl substituents exist (R1/R2/R3, and R4 in formula (I)), (ii) the requirement that at least one substituent is non-hydrogen, and (iii) a conditional fatty-acid carbon-number rule when hydrogen appears among R1/R2/R3.

Claim 1 key scope elements

Claim 1 covers “An acyl derivative of uridine having the formula (II)” where:

R1, R2, R3 are each hydrogen or an acyl radical of a defined carboxylic-acid source from four groups:
- (a) unbranched fatty acids with 5–22 carbons,
- (b) amino acids (a specified list),
- (c) dicarboxylic acids with 3–22 carbons,
- (d) specific carboxylic acids list (includes glycolic, pyruvic, lactic, enolpyruvic, lipoic, pantothenic, acetoacetic, p-aminobenzoic, β-hydroxybutyric, orotic acid) and creatine.
The claim requires:
- at least one of R1/R2/R3 is not hydrogen.
- a conditional rule: if any of R1/R2/R3 is hydrogen and the other substituents are acyl radicals of a straight-chain fatty acid, then that straight-chain fatty acid must be 8–22 carbons.

Coverage boundary created by the conditional fatty-acid carbon number rule:

If all R1/R2/R3 are acyl (no hydrogen present), fatty acids can be in the 5–22 band under group (a).
If the molecule is “mixed” (at least one position is hydrogen) and the remaining acyl groups are straight-chain fatty acids, then those fatty acids must be 8–22 (not 5–7).

Claim 2 key scope elements

Claim 2 covers “acyl derivative of uridine having formula (I)” with:

R1/R2/R3 are hydrogen or acyl radicals from a similar broad menu, but now:
- fatty acids are “fatty acid of 2–22 carbon atoms” (wider lower bound than claim 1),
- carboxylic acid menu is similar (glycolic, pyruvic, lactic, enolpyruvic, amino acid, lipoic, pantothenic, succinic, fumaric, adipic, acetoacetic, p-aminobenzoic, β-hydroxybutyric, orotic, creatine).
R4 is separately an acyl radical from another menu (carboxylic acids including fatty acids 2–22 and many non-fatty acids; notably amino acids are included for R4 as well).
The claim requires:
- at least one of the R substituents (R1/R2/R3/R4 as used in the claim language) is not hydrogen.

Practical effect: claim 2 is structured to capture additional substitution patterns compared with claim 1 (given the presence of R4), while still keeping the acyl menu broad.

Claim 3 narrows the amino-acid list for a subset

Claim 3 depends from claim 2 and restricts:

amino acid selection to a list that includes many standard L-amino acids, plus phenylalanine and methionine/tryptophan, etc.
This limits variants where the amino-acid acyl group is outside that enumerated set.

Does US 6,258,795 protect specific tri-O-acyl uridines (and which ones)?

Direct answer: Yes. Claim 9 explicitly lists tri-O-acyl uridines:

2′,3′,5′-tri-O-acetyl uridine
2′,3′,5′-tri-O-propionyl uridine
2′,3′,5′-tri-O-butyryl uridine

This is a direct, high-value hook for products that use small aliphatic acyl groups to prodrug uridine.

How claims 1 and 2 also capture these compounds implicitly

Even without relying on claim 9, these compounds likely fall within:

the “glycolic/pyruvic/lactic/enolpyruvic” style menu is not needed for acetyl/propionyl/butyryl,
fatty-acid acyl radicals are covered if they fit “unbranched fatty acids” (claim 1) or “fatty acid of 2 to 22 carbon atoms” (claim 2).
Acetyl (C2), propionyl (C3), and butyryl (C4) map more cleanly to claim 2’s 2–22 band than claim 1’s 5–22 band. That means claim 2 is the stronger implicit fit for the smallest acyls, while claim 9 gives explicit coverage.

What compositions and dosage forms are covered by US 6,258,795?

Direct answer: The patent covers pharmaceutical compositions containing the claimed acyl derivatives with extensive carrier definitions and multiple dosage forms, plus explicit unit dose ranges and an explicit combination composition with specific cytidine tri-O-acyl derivatives.

Core composition claims

Claim 4: composition comprising the acyl derivative of claim 1 + pharmaceutically acceptable carrier.
Claim 5: unit dose where the acyl derivative amount equals 10–3000 mg of uridine.

Oral and non-oral dosage form coverage

Claim 8: composition in forms including:
- liquid,
- suspension,
- tablet,
- dragee,
- injectable solution,
- suppository.
Claim 10: pharmaceutical composition (uridine acyl derivative of formula (I) or salt) with carrier, in oral suspension/tablet/dragee/capsule form.

Vehicle and excipient scope (carrier-specific dependent claims)

Claims 12–23 expand carriers into:

fillers (sugar: lactose/sucrose/mannitol/sorbitol; cellulose preparations; calcium phosphate),
binders (starches, gelatin, methyl cellulose, HPMC, CMC-Na, PVP),
disintegrants or related matrix agents (carboxymethylstarch, cross-linked PVP, agar, alginic acid salts),
flow regulators/lubricants (silica, talc, stearic acid and magnesium/calcium stearate; plus PEG),
coatings (sugar solutions with gum arabic/talc/PVP/PEG/TiO2; lacquer solutions; cellulose preparations like acetylcellulose phthalate or HPMCP),
gelatin base,
bases like triglycerides/paraffin hydrocarbons/PEG/higher alkanols,
lipophilic solvents/vehicles (fatty oils, fatty acid esters),
aqueous injection suspension components (Na CMC, sorbitol, dextran).

This excipient coverage reduces design-around space for formulation teams, because it is hard to avoid infringement while still using common solid oral formulation components.

What cytidine combination does US 6,258,795 claim, and why it matters for generic and licensing strategy?

Direct answer: Claim 6 claims a composition mixture of:

at least one uridine acyl derivative of claim 1, and
at least one cytidine acyl derivative selected from:
- 2′,3′,5′-tri-O-acetyl cytidine
- 2′,3′,5′-tri-O-propionyl cytidine
- 2′,3′,5′-tri-O-butyryl cytidine with pharmaceutically acceptable carrier.

Claim 7 unit dose constraint: equivalent amounts:

10–3000 mg of uridine and
10–3000 mg of cytidine.

Strategic implication

This creates an enforceable claim boundary for combo products targeting pathways where both nucleosides are co-formulated, even if a competitor chooses not to market the “uridine-only” product.

What does US 6,258,795 not cover based on the claim text provided?

Direct answer: Based on the excerpt, coverage is limited to:

“uridine acyl derivatives” within the defined formula frameworks and acyl menu, and
compositions containing those derivatives with the explicitly covered carrier and dosage form elements (and cytidine combination in the specified manner).

The excerpt does not show:

coverage for other nucleoside cores beyond uridine/cytidine,
claims for specific therapeutic indications or methods of treatment,
claims for specific manufacturing processes (e.g., esterification methods),
biologics-like coverage (not relevant here),
combination partners beyond the cytidine tri-O-acyl derivatives listed.

That matters for pipeline competitors planning:

non-cytidine combinations,
different nucleoside cores,
or alternative prodrug architectures not captured by R definitions.

Where are the “design-around” pressure points in the claims?

Direct answer: The claim language creates three main design-around levers: (i) whether the molecule matches the formula substitution logic (R1/R2/R3/R4), (ii) whether the acyl group is within the defined acyl menu and carbon-number constraints, and (iii) whether the final product is used in a claimed dosage form and with typical carriers.

1) Substitution logic (R1/R2/R3/R4)

Even with the broad acyl menu, infringement depends on matching the claimed formulas (I) or (II) and the substituent definitions. If a candidate has:

different substitution count/position relative to the formula constructs, or
a substituent that is neither “hydrogen” nor an “acyl radical of” the listed carboxylic acids,
it can fall outside.

2) Acyl menu and carbon-number gates

Claim 1: fatty acids are C5–C22 if unbranched fatty acids under group (a).
Claim 1 conditional: if any R1/R2/R3 is hydrogen and the remaining acyls are straight-chain fatty acids, those straight-chain fatty acids must be C8–C22.
Claim 2: fatty acids are C2–C22 for the relevant lists.

So candidates using very short acyl groups (C2–C4) are more likely to map to claim 2’s coverage than claim 1’s core fatty-acid band, unless claim 9’s explicit tri-O examples are also implicated.

3) Combination claim (cytidine)

Avoiding claims 6–7 is possible if no cytidine tri-O-acyl derivative from the listed set is included, or if the dosing equivalent structure differs from claim 7’s unit dose constraints.

How does this patent likely position against FDA “Orange Book” challenges, Paragraph IV, and generic entry risk?

Direct answer: Based on the claim text, the highest generic-entry risk is for:

uridine prodrug products that use small acyl groups to form tri-O-acyl uridine derivatives that fall within claims 1/2/9, and
formulation attempts that use standard carriers and dosage forms recited in claims 8 and 10–23.

Paragraph IV strategy for an ANDA-based generic route typically hinges on whether the FDA-listed reference product uses a covered active (uridine acyl derivative). The excerpt does not identify the listed drug name(s) or FDA Orange Book records. Without that linkage, the compliance exposure cannot be mapped to a specific NDA/BLA.

Strength of the patent estate for the relevant chemical space (based on claim drafting)

Direct answer: The claims show “breadth-first” drafting: broad acyl definitions and wide excipient and dosage-form coverage. The explicit listing of common tri-O-acyl uridine embodiments (claim 9) and tri-O-acyl cytidine embodiments (claims 6–7) provides enforceable anchors that reduce the impact of narrow chemical arguments.

Claim-strength indicators from the language provided

Broad claim 1/2 chemical menus covering many carbonyl sources.
Explicit “at least one not hydrogen” requirement prevents trivial hydrogen-only exclusion.
Conditional carbon-number limitation in claim 1 blocks some low-carbon straight-chain fatty variants when partial deacylation exists.
Large dependent tree on carriers and dosage forms that can be difficult for generic or formulation competitors to avoid.

Key Takeaways

US 6,258,795 claims broad classes of acylated uridine derivatives, with acyl groups selected from a wide set of fatty acids and specified carboxylic acids/amino acids; at least one acyl substituent must be non-hydrogen.
The core breadth is concentrated in claims 1 and 2; claim 9 explicitly covers 2′,3′,5′-tri-O-acetyl/propionyl/butyryl uridine.
The composition claims extend infringement risk into formulation choices: tablets, dragees, capsules, suspensions, injectables, and suppositories, using common excipients and coatings.
Claim 6–7 creates enforceable protection for uridine-acyl + cytidine tri-O-acyl combinations (acetyl/propionyl/butyryl cytidine) with unit-dose equivalents capped within 10–3000 mg ranges.

FAQs

Do claims 1 and 2 cover mixed acyl patterns where only some uridine hydroxyls are acylated?
Yes, the presence of hydrogen as a permitted R1/R2/R3 state and the conditional carbon-number rule in claim 1 indicates mixed substitution is within scope if the formula and restrictions are met.
Is 2′,3′,5′-tri-O-acetyl uridine covered even if acetyl is treated as a C2 acyl?
Claim 9 explicitly includes it, and claim 2’s fatty-acid definition includes 2–22 carbon atoms, aligning with small acyls.
Can a competitor avoid the patent by changing excipients only?
Carrier changes may avoid some dependent claim elements, but independent composition coverage (claim 4 and claim 10’s active+carrier structure) still captures compositions if the active derivative matches the chemical claims.
Does the patent protect uridine acyl derivatives formulated only as oral tablets/capsules?
Yes. Claim 8 covers many oral and non-oral forms; claim 10 specifically covers oral suspension/tablet/dragee/capsule.
What is the main risk area for combo products that include cytidine?
Claim 6–7 covers specific cytidine tri-O-acyl derivatives (acetyl/propionyl/butyryl) in a mixture with at least one claim 1 uridine acyl derivative, with unit-dose equivalent constraints.

References

US Patent 6,258,795 (claims provided in prompt).

Title:	Acylated uridine and cytidine and uses thereof
Abstract:	The invention relates to compositions comprising acyl derivatives of cytidine and uridine. The invention also relates to methods of treating hepatopathies, diabetes, heart disease, cerebrovascular disorders, Parkinson's disease, infant respiratory distress syndrome and for enhancement of phospholipid biosynthesis comprising administering the acyl derivatives of the invention to an animal.
Inventor(s):	Reid Warren von Borstel, Michael Kevin Bamat
Assignee:	BTG International Inc
Application Number:	US08/466,145
Patent Claim Types: see list of patent claims	Composition; Formulation; Compound; Dosage form;
Patent landscape, scope, and claims:	Scope of United States Patent 6,258,795 (Acyl Derivatives of Uridine): Claim Breadth, Coverage Boundaries, and US Patent Landscape United States Patent 6,258,795 claims acyl derivatives of uridine (and, via dependent claims, cytidine-containing combinations and dosage forms), where “acyl” is broadly defined as acyl radicals derived from a large set of fatty acids and other carboxylic acids (including amino acids and dicarboxylic acids), with at least one substituent not being hydrogen. The estate is structurally designed to read on multiple tri-O-acyl uridines (e.g., 2′,3′,5′-tri-O-acetyl/propionyl/butyryl uridine) while also covering “mixed” acyl patterns (different substituents across R1/R2/R3, and in the formula (I) framework where R4 is separately defined). However, without the full specification, priority data, prosecution history, and the complete claim set beyond claims 1–23 shown, it is not possible to map (i) the exact claim construction boundaries tied to formulas (I)–(III), (ii) whether the patent includes additional independent claims not included in the excerpt, (iii) the actual expiration and exclusivity timing in the US, or (iv) whether the patent was later limited/clarified by office actions, terminal disclaimers, or court construction. What follows is a claim-scope and “freedom-to-operate style” landscape analysis strictly from the claim language provided. What patents protect acyl derivatives of uridine like 2′,3′,5′-tri-O-acetyl uridine under US 6,258,795? Direct answer: US 6,258,795 protects acyl derivatives of uridine where acyl groups are derived from a large menu of carboxylic acids (including many fatty acids and specific non-fatty acids), with the claims requiring that at least one acyl substituent is non-hydrogen (and, in certain compositions, that specific acyl patterns apply). It also protects pharmaceutical compositions using those derivatives, including unit doses and dosage forms and, in one dependent claim set, mixtures with specific acyl derivatives of cytidine. Claim architecture that drives coverage The claim set is organized into: Core chemical product claims for “acyl derivatives of uridine” (independent claims 1 and 2; claim 3 adds amino-acid restriction). Composition claims (claims 4–5, 8, 10–23), including: pharmaceutically acceptable carriers spanning excipients and coatings, unit dose ranges expressed as “equivalent of 10–3000 mg of uridine,” dosage forms including oral and injectable/suppository routes (claim 8), an explicit combination concept with specific cytidine tri-O-acyl derivatives (claims 6–7), narrower dependent hooks to specific uridine tri-O-acyls (claim 9). How broad are the uridine acyl derivative claims (claims 1 and 2) and what limits them? Direct answer: The scope is broad at the “acyl menu” level but constrained by (i) how the formulas define where and how many acyl substituents exist (R1/R2/R3, and R4 in formula (I)), (ii) the requirement that at least one substituent is non-hydrogen, and (iii) a conditional fatty-acid carbon-number rule when hydrogen appears among R1/R2/R3. Claim 1 key scope elements Claim 1 covers “An acyl derivative of uridine having the formula (II)” where: R1, R2, R3 are each hydrogen or an acyl radical of a defined carboxylic-acid source from four groups: (a) unbranched fatty acids with 5–22 carbons, (b) amino acids (a specified list), (c) dicarboxylic acids with 3–22 carbons, (d) specific carboxylic acids list (includes glycolic, pyruvic, lactic, enolpyruvic, lipoic, pantothenic, acetoacetic, p-aminobenzoic, β-hydroxybutyric, orotic acid) and creatine. The claim requires: at least one of R1/R2/R3 is not hydrogen. a conditional rule: if any of R1/R2/R3 is hydrogen and the other substituents are acyl radicals of a straight-chain fatty acid, then that straight-chain fatty acid must be 8–22 carbons. Coverage boundary created by the conditional fatty-acid carbon number rule: If all R1/R2/R3 are acyl (no hydrogen present), fatty acids can be in the 5–22 band under group (a). If the molecule is “mixed” (at least one position is hydrogen) and the remaining acyl groups are straight-chain fatty acids, then those fatty acids must be 8–22 (not 5–7). Claim 2 key scope elements Claim 2 covers “acyl derivative of uridine having formula (I)” with: R1/R2/R3 are hydrogen or acyl radicals from a similar broad menu, but now: fatty acids are “fatty acid of 2–22 carbon atoms” (wider lower bound than claim 1), carboxylic acid menu is similar (glycolic, pyruvic, lactic, enolpyruvic, amino acid, lipoic, pantothenic, succinic, fumaric, adipic, acetoacetic, p-aminobenzoic, β-hydroxybutyric, orotic, creatine). R4 is separately an acyl radical from another menu (carboxylic acids including fatty acids 2–22 and many non-fatty acids; notably amino acids are included for R4 as well). The claim requires: at least one of the R substituents (R1/R2/R3/R4 as used in the claim language) is not hydrogen. Practical effect: claim 2 is structured to capture additional substitution patterns compared with claim 1 (given the presence of R4), while still keeping the acyl menu broad. Claim 3 narrows the amino-acid list for a subset Claim 3 depends from claim 2 and restricts: amino acid selection to a list that includes many standard L-amino acids, plus phenylalanine and methionine/tryptophan, etc. This limits variants where the amino-acid acyl group is outside that enumerated set. Does US 6,258,795 protect specific tri-O-acyl uridines (and which ones)? Direct answer: Yes. Claim 9 explicitly lists tri-O-acyl uridines: 2′,3′,5′-tri-O-acetyl uridine 2′,3′,5′-tri-O-propionyl uridine 2′,3′,5′-tri-O-butyryl uridine This is a direct, high-value hook for products that use small aliphatic acyl groups to prodrug uridine. How claims 1 and 2 also capture these compounds implicitly Even without relying on claim 9, these compounds likely fall within: the “glycolic/pyruvic/lactic/enolpyruvic” style menu is not needed for acetyl/propionyl/butyryl, fatty-acid acyl radicals are covered if they fit “unbranched fatty acids” (claim 1) or “fatty acid of 2 to 22 carbon atoms” (claim 2). Acetyl (C2), propionyl (C3), and butyryl (C4) map more cleanly to claim 2’s 2–22 band than claim 1’s 5–22 band. That means claim 2 is the stronger implicit fit for the smallest acyls, while claim 9 gives explicit coverage. What compositions and dosage forms are covered by US 6,258,795? Direct answer: The patent covers pharmaceutical compositions containing the claimed acyl derivatives with extensive carrier definitions and multiple dosage forms, plus explicit unit dose ranges and an explicit combination composition with specific cytidine tri-O-acyl derivatives. Core composition claims Claim 4: composition comprising the acyl derivative of claim 1 + pharmaceutically acceptable carrier. Claim 5: unit dose where the acyl derivative amount equals 10–3000 mg of uridine. Oral and non-oral dosage form coverage Claim 8: composition in forms including: liquid, suspension, tablet, dragee, injectable solution, suppository. Claim 10: pharmaceutical composition (uridine acyl derivative of formula (I) or salt) with carrier, in oral suspension/tablet/dragee/capsule form. Vehicle and excipient scope (carrier-specific dependent claims) Claims 12–23 expand carriers into: fillers (sugar: lactose/sucrose/mannitol/sorbitol; cellulose preparations; calcium phosphate), binders (starches, gelatin, methyl cellulose, HPMC, CMC-Na, PVP), disintegrants or related matrix agents (carboxymethylstarch, cross-linked PVP, agar, alginic acid salts), flow regulators/lubricants (silica, talc, stearic acid and magnesium/calcium stearate; plus PEG), coatings (sugar solutions with gum arabic/talc/PVP/PEG/TiO2; lacquer solutions; cellulose preparations like acetylcellulose phthalate or HPMCP), gelatin base, bases like triglycerides/paraffin hydrocarbons/PEG/higher alkanols, lipophilic solvents/vehicles (fatty oils, fatty acid esters), aqueous injection suspension components (Na CMC, sorbitol, dextran). This excipient coverage reduces design-around space for formulation teams, because it is hard to avoid infringement while still using common solid oral formulation components. What cytidine combination does US 6,258,795 claim, and why it matters for generic and licensing strategy? Direct answer: Claim 6 claims a composition mixture of: at least one uridine acyl derivative of claim 1, and at least one cytidine acyl derivative selected from: 2′,3′,5′-tri-O-acetyl cytidine 2′,3′,5′-tri-O-propionyl cytidine 2′,3′,5′-tri-O-butyryl cytidine with pharmaceutically acceptable carrier. Claim 7 unit dose constraint: equivalent amounts: 10–3000 mg of uridine and 10–3000 mg of cytidine. Strategic implication This creates an enforceable claim boundary for combo products targeting pathways where both nucleosides are co-formulated, even if a competitor chooses not to market the “uridine-only” product. What does US 6,258,795 not cover based on the claim text provided? Direct answer: Based on the excerpt, coverage is limited to: “uridine acyl derivatives” within the defined formula frameworks and acyl menu, and compositions containing those derivatives with the explicitly covered carrier and dosage form elements (and cytidine combination in the specified manner). The excerpt does not show: coverage for other nucleoside cores beyond uridine/cytidine, claims for specific therapeutic indications or methods of treatment, claims for specific manufacturing processes (e.g., esterification methods), biologics-like coverage (not relevant here), combination partners beyond the cytidine tri-O-acyl derivatives listed. That matters for pipeline competitors planning: non-cytidine combinations, different nucleoside cores, or alternative prodrug architectures not captured by R definitions. Where are the “design-around” pressure points in the claims? Direct answer: The claim language creates three main design-around levers: (i) whether the molecule matches the formula substitution logic (R1/R2/R3/R4), (ii) whether the acyl group is within the defined acyl menu and carbon-number constraints, and (iii) whether the final product is used in a claimed dosage form and with typical carriers. 1) Substitution logic (R1/R2/R3/R4) Even with the broad acyl menu, infringement depends on matching the claimed formulas (I) or (II) and the substituent definitions. If a candidate has: different substitution count/position relative to the formula constructs, or a substituent that is neither “hydrogen” nor an “acyl radical of” the listed carboxylic acids, it can fall outside. 2) Acyl menu and carbon-number gates Claim 1: fatty acids are C5–C22 if unbranched fatty acids under group (a). Claim 1 conditional: if any R1/R2/R3 is hydrogen and the remaining acyls are straight-chain fatty acids, those straight-chain fatty acids must be C8–C22. Claim 2: fatty acids are C2–C22 for the relevant lists. So candidates using very short acyl groups (C2–C4) are more likely to map to claim 2’s coverage than claim 1’s core fatty-acid band, unless claim 9’s explicit tri-O examples are also implicated. 3) Combination claim (cytidine) Avoiding claims 6–7 is possible if no cytidine tri-O-acyl derivative from the listed set is included, or if the dosing equivalent structure differs from claim 7’s unit dose constraints. How does this patent likely position against FDA “Orange Book” challenges, Paragraph IV, and generic entry risk? Direct answer: Based on the claim text, the highest generic-entry risk is for: uridine prodrug products that use small acyl groups to form tri-O-acyl uridine derivatives that fall within claims 1/2/9, and formulation attempts that use standard carriers and dosage forms recited in claims 8 and 10–23. Paragraph IV strategy for an ANDA-based generic route typically hinges on whether the FDA-listed reference product uses a covered active (uridine acyl derivative). The excerpt does not identify the listed drug name(s) or FDA Orange Book records. Without that linkage, the compliance exposure cannot be mapped to a specific NDA/BLA. Strength of the patent estate for the relevant chemical space (based on claim drafting) Direct answer: The claims show “breadth-first” drafting: broad acyl definitions and wide excipient and dosage-form coverage. The explicit listing of common tri-O-acyl uridine embodiments (claim 9) and tri-O-acyl cytidine embodiments (claims 6–7) provides enforceable anchors that reduce the impact of narrow chemical arguments. Claim-strength indicators from the language provided Broad claim 1/2 chemical menus covering many carbonyl sources. Explicit “at least one not hydrogen” requirement prevents trivial hydrogen-only exclusion. Conditional carbon-number limitation in claim 1 blocks some low-carbon straight-chain fatty variants when partial deacylation exists. Large dependent tree on carriers and dosage forms that can be difficult for generic or formulation competitors to avoid. Key Takeaways US 6,258,795 claims broad classes of acylated uridine derivatives, with acyl groups selected from a wide set of fatty acids and specified carboxylic acids/amino acids; at least one acyl substituent must be non-hydrogen. The core breadth is concentrated in claims 1 and 2; claim 9 explicitly covers 2′,3′,5′-tri-O-acetyl/propionyl/butyryl uridine. The composition claims extend infringement risk into formulation choices: tablets, dragees, capsules, suspensions, injectables, and suppositories, using common excipients and coatings. Claim 6–7 creates enforceable protection for uridine-acyl + cytidine tri-O-acyl combinations (acetyl/propionyl/butyryl cytidine) with unit-dose equivalents capped within 10–3000 mg ranges. FAQs Do claims 1 and 2 cover mixed acyl patterns where only some uridine hydroxyls are acylated? Yes, the presence of hydrogen as a permitted R1/R2/R3 state and the conditional carbon-number rule in claim 1 indicates mixed substitution is within scope if the formula and restrictions are met. Is 2′,3′,5′-tri-O-acetyl uridine covered even if acetyl is treated as a C2 acyl? Claim 9 explicitly includes it, and claim 2’s fatty-acid definition includes 2–22 carbon atoms, aligning with small acyls. Can a competitor avoid the patent by changing excipients only? Carrier changes may avoid some dependent claim elements, but independent composition coverage (claim 4 and claim 10’s active+carrier structure) still captures compositions if the active derivative matches the chemical claims. Does the patent protect uridine acyl derivatives formulated only as oral tablets/capsules? Yes. Claim 8 covers many oral and non-oral forms; claim 10 specifically covers oral suspension/tablet/dragee/capsule. What is the main risk area for combo products that include cytidine? Claim 6–7 covers specific cytidine tri-O-acyl derivatives (acetyl/propionyl/butyryl) in a mixture with at least one claim 1 uridine acyl derivative, with unit-dose equivalent constraints. References US Patent 6,258,795 (claims provided in prompt). More… ↓ ⤷ Start Trial

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Details for Patent: 6,258,795

Summary for Patent: 6,258,795