Details for Patent: 5,464,826

US Patent 5,464,826: Scope, Claims, and Patent Landscape

US Patent 5,464,826 claims a method-of-treatment for susceptible neoplasms in mammals using a specific nucleoside analog scaffold defined by a structural formula and enumerated substituent constraints. The independent claim is broad on the use context (treating susceptible neoplasms in mammals) and narrow on chemistry (the compound must match the formula definition and the allowed substituent set for the base and alkyl/halo pattern). Dependent claims lock in particular named compounds and specify neoplasm classes.

What is claimed in US 5,464,826?

Is this a composition claim or a method claim?

It is a method claim. The preamble and body of Claim 1 require:

• “A method of treating susceptible neoplasms in mammals”
• by “administering to a mammal in need of such treatment a therapeutically effective amount of a compound” matching the formula
• including “pharmaceutically-acceptable salts”

So the exclusivity hook is tied to therapeutic use via administration of the claimed compounds, not to ownership of the compounds as standalone products.

What is the core chemical scope in Claim 1?

Claim 1 requires a compound of the formula (as depicted in the patent) with these definitional elements:

• R1: hydrogen
• R3: hydrogen
• X: C-R4
• R2: “a base defined by one of the formulae” in the patent (substructure shown as multiple allowed base alternatives)
• R4: hydrogen, or C1-C4 alkyl, or bromo, fluoro, chloro, or iodo
• The compound includes “pharmaceutically-acceptable salts thereof”

The functional impact is straightforward:

• The sugar/side-chain positions tied to R1 and R3 are fixed to hydrogen.
• The “base” portion is restricted to the base formula set provided in the patent.
• The substituent at R4 is limited to small alkyl or specific halogens (Br, F, Cl, I) or hydrogen.
• The claim is not written to require a specific salt form; it covers any pharmaceutically acceptable salt.

How do dependent claims narrow the scope?

Dependent claims enumerate specific compounds as examples of the Claim 1 scaffold:

Claim 2

• 1-(4-amino-2-oxo-1H-pyrimidin-1-yl)-2-desoxy-2,2-difluororibose
• or pharmaceutically acceptable salt

Claim 3

• 1-(4-amino-2-oxo-1H-pyrimidin-1-yl)-2-desoxy-2,2-difluoroxylose
• or salt

Claim 4

• 1-(2,4-dioxo-1H,3H-pyrimidin-1-yl)-2-desoxy-2,2-difluororibose
• or salt

Claim 5

• 1-(4-amino-5-methyl-2-oxo-1H-pyrimidin-1-yl)-2-desoxy-2,2-difluororibose
• or salt

Claim 6

• The susceptible neoplasm is selected from:
  • leukemias, sarcomas, carcinomas, and myelomas

Claim 7

• Requires the compound of Claim 2 (the 4-amino-2-oxo pyrimidinyl difluororibose form) for the method of Claim 6

Net effect:

• Claims 2-5 define concrete claim targets that fall inside Claim 1’s formula boundary.
• Claims 6-7 restrict the disease subset and combine with the compound of Claim 2 for the narrowest method species.

Claim-by-claim scope map

Claim 1 (independent): what it covers

Claim 1 covers any method of treating susceptible neoplasms in mammals by administering a therapeutically effective amount of a compound that matches the formula constraints:

Fixed substitution set

• R1 = H
• R3 = H

Variable substitution set

• R2 is a base restricted to the “base defined by one of the formulae” (the patent’s allowed base variants)
• X = C-R4 (so the structural linkage to the variable R4 is defined)
• R4 can be:
  • H
  • C1-C4 alkyl
  • Br, F, Cl, I

Therapeutic framing

• “susceptible neoplasms” (broad phenotype term used for cancer-treatment methods)
• administration to “mammal in need”
• “therapeutically effective amount”
• includes pharmaceutically acceptable salts

Practical scope implication

• The claim is broad on indication framing (susceptible neoplasms).
• The claim is narrow on chemistry (exact scaffold features plus defined base set and limited R4 substituents).

Claim 2-5 (compound species): what is explicitly included

These four compound definitions are “locked-in” species that a defendant could not argue are outside Claim 1 if they fall within the formula. Their value is that they:

• provide explicit wording that may track preferred embodiments
• create clearer infringement targets for enforcement or freedom-to-operate (FTO) mapping

Included named species (as written):

• 4-amino-2-oxo pyrimidinyl difluororibose (Claim 2)
• 4-amino-2-oxo pyrimidinyl difluoroxylose (Claim 3)
• 2,4-dioxo pyrimidinyl difluororibose (Claim 4)
• 4-amino-5-methyl-2-oxo pyrimidinyl difluororibose (Claim 5)

Claim 6-7 (disease refinement): what disease subsets are explicitly required

Claim 6 turns the broad “susceptible neoplasms” term into an enumerated set:

• leukemias
• sarcomas
• carcinomas
• myelomas

Claim 7 then combines:

• disease subset from Claim 6
• with compound identity from Claim 2

So Claim 7 is the tightest map: it is a specific compound used to treat specific cancer classes.

How broad is the legal coverage: formula constraints vs therapeutic claims

Key breadth drivers

1. Method claim format
   The claim covers “treating” by administration. This can reach clinical/label-style uses and investigator dosing regimens if they match the compound and amount framing.

2. Broad disease term in Claim 1
   “Susceptible neoplasms” is not confined to a single tumor type. Even though dependent Claim 6 enumerates classes, Claim 1 is not limited to those classes.

3. R4 substituent permissiveness within limits
   R4 includes H, C1-C4 alkyl, and four halogens. That allows multiple analogs around a fixed scaffold.

Key narrowing drivers

1. Fixed R1 and R3
   By requiring R1 = H and R3 = H, the claim excludes analogs that alter those positions.

2. Base restricted to the patent’s defined base formula set
   The claim is not open-ended for base chemistry. It only permits bases within the “formulae” shown in the patent (multiple allowed variants, but still restricted).

3. X is defined as C-R4
   This fixes the linkage pattern at that point. Structural isosteres that change linkage connectivity could fall outside even if they retain similar pharmacology.

4. Therapeutically effective amount As a practical matter, infringement theory often requires linkage to actual dosing, not just potential use. Still, the claim wording is typical for method patents.

Patent landscape: where enforcement risk typically concentrates

Because the request is specifically “scope and claims and patent landscape,” the landscape must be anchored in what US 5,464,826 is: a method-of-treatment patent with explicit nucleoside-analog species and limited substituent variation. Without additional docket data (application family, priority, assignee, related patents, prosecution history, or cited references), only a structural landscape can be stated reliably from the claim set alone: which types of adjacent patents most commonly exist around this kind of scaffold and claim format.

1) Closest “same family” risk: related method patents on the same scaffold

For nucleoside analog oncology programs, families commonly branch into:

• additional method claims using the same scaffold with alternate disease subsets or dosing regimens
• method claims with alternate routes of administration or combination therapy language
• additional species claims around closely related sugar/base modifications

US 5,464,826 itself already shows that pattern: Claim 1 broad scaffold and Claim 2-5 enumerated species and Claim 6-7 disease refinement.

2) Closest chemistry risk: composition patents on the same scaffold

Even though US 5,464,826 is a method claim, composition patents usually exist in parallel:

• patents claiming the compound(s) by structure (free base and salt)
• patents claiming crystalline forms or prodrugs if developed later (not evidenced in the claims provided, so not asserted here)

If a compound is used that falls within the scaffold, composition coverage can independently create enforcement risk even if the method claim is avoided. Here, US 5,464,826 covers “pharmaceutically-acceptable salts,” so even salt-only product variants can matter for method infringement.

3) Design-around risk: analogs changing only R4

Claim 1 permits R4 = H, C1-C4 alkyl, or halogens (Br/F/Cl/I). That means:

• analogs that vary R4 within that set remain high risk
• analogs that change R4 beyond that set (e.g., larger alkyl, CF3, cyano, hydroxyl, amino, ether substituents) may fall outside Claim 1, but only if the structural definition does not capture them through the base/structural constraints elsewhere

4) Design-around risk: sugar changes at positions constrained by R1 and R3

The fixed “R1 = H” and “R3 = H” indicate excluded modifications at those defined positions. For ribose/xylose analog series, the claim already captures “2-desoxy-2,2-difluoro” variants (as named in Claims 2-5). Analog strategies that alter those fixed positions may reduce risk relative to modifications at R4, but they must still match the base set and the “X = C-R4” linkage.

5) Enforcement posture: company actions most likely to rely on Claims 1 and 6-7

In practice, method patents like this are commonly enforced by:

• focusing on specific named compounds (Claims 2-5) because they are clear infringement targets
• focusing on specified oncology indications (Claims 6-7) when trial or label data align

So the enforcement priority set is:

1. Claim 7 (tightest: specified compound plus specified cancer classes)
2. Claims 2-5 (species)
3. Claim 6 (disease classes)
4. Claim 1 (scaffold breadth)

Infringement claim parsing: what a competitor must avoid to exit coverage

Based on the claim language alone, a “safe” design-around has to address at least one of the following in a way that removes the product from the formula:

Chemical off-ramps

• Change R1 away from H
• Change R3 away from H
• Modify the base so it is no longer “a base defined by one of the formulae” in the patent
• Change the linkage so X is no longer C-R4
• Use an R4 substituent that is not among:
  • H
  • C1-C4 alkyl
  • Br/F/Cl/I

Therapeutic framing off-ramps

• Treating a cancer type not encompassed by the “susceptible neoplasms” term may be difficult because Claim 1 is broad.
• Avoiding Claim 6 disease classes (leukemias, sarcomas, carcinomas, myelomas) helps only for the dependent claim; it does not avoid Claim 1 unless the disease is outside “susceptible neoplasms” as construed in practice.

Key Takeaways

• US 5,464,826 is a method-of-treatment patent covering administration of a specific nucleoside-analog scaffold to treat susceptible neoplasms in mammals.
• Claim 1 provides the broad chemical boundary: R1 = H, R3 = H, X = C-R4, with R4 allowed as H, C1-C4 alkyl, or Br/F/Cl/I, and R2 restricted to bases defined in the patent.
• Claims 2-5 enumerate four concrete compound species within the scaffold, anchoring enforcement and FTO risk.
• Claims 6-7 narrow disease scope to leukemias, sarcomas, carcinomas, and myelomas, with Claim 7 tying a specific compound to those cancer classes.
• For competitor design-around, the highest-leverage escape routes are changing the fixed-position hydrogen requirements (R1, R3), breaking the X = C-R4 linkage definition, or moving R4 beyond the enumerated set.

FAQs

1) Does US 5,464,826 cover manufacturing or selling the compounds?

No. It claims a method of treating via administering a therapeutically effective amount of a compound matching the formula.

2) Are the listed compounds in Claims 2-5 guaranteed to fall under Claim 1?

Yes by claim construction: Claims 2-5 recite compounds as particular embodiments of the Claim 1 formula, and they are written as dependent claims.

3) Can a competitor avoid infringement by treating a cancer outside leukemias, sarcomas, carcinomas, and myelomas?

That only addresses Claim 6. Claim 1 still covers “susceptible neoplasms,” which is broader than the enumerated set in Claim 6.

4) If a compound changes only R4 within H, C1-C4 alkyl, or halogens, is risk still high?

Yes. Claim 1 explicitly permits those R4 substituents, so analogs that stay within that set remain inside the formula boundary.

5) What is the tightest claim in the set?

Claim 7, because it combines the specific compound of Claim 2 with the specific cancer classes of Claim 6.

References

[1] United States Patent 5,464,826 (claims as provided).