Details for Patent: 5,492,897

United States Patent 5,492,897: Scope, Claims, and Patent Landscape for T-Cell Lymphoblastic Leukemia

US Patent 5,492,897 claims a treatment method for T-cell lymphoblastic leukemia using 9-β-D-arabinofuranosyl-2-amino-6-methoxy-9H-purine (and pharmaceutically acceptable salts), with dependent claims limited by route of administration (injection) and claim scope expanding from the compound alone to the compound plus salts.

What exactly is claimed?

1) What is the independent claim scope (Claims 1 and 2)?

Both independent claims are method-of-treatment claims tied to a single therapeutic regimen concept: administering an “effective” amount of a specific compound to a mammal with T-cell lymphoblastic leukemia.

Claim 1 (compound-specific)

• A method of treating T-cell lymphoblastic leukemia in a mammal having the disease
• Comprises administering an “effective” treatment amount of:
  • 9-β-D-arabinofuranosyl-2-amino-6-methoxy-9H-purine

Claim 2 (compound + salts)

• Same disease and method structure as Claim 1
• Comprises administering an “effective” leukemia treatment amount of:
  • 9-β-D-arabinofuranosyl-2-amino-6-methoxy-9H-purine
  • or a pharmaceutically acceptable salt thereof

Practical scope read-through

• The claim does not require a specific dosing schedule, dose size, or duration in the text provided.
• “Effective amount” is functional language that typically covers a range of dose levels and treatment schedules that produce therapeutic effect.
• Claim 2 broadens Claim 1 to cover salt forms, which can matter in formulation infringement analysis.

2) How do the dependent claims narrow the claim scope (Claims 3 and 4)?

Claim 3

• Depends from Claim 1
• Adds: compound is administered by injection

Claim 4

• Depends from Claim 2
• Adds: compound or salt is administered by injection

Practical scope read-through

• These claims carve out method infringement that occurs through injectable administration.
• If a competitor uses oral, topical, or other routes, it would avoid the injection-limited dependent claims, though the independent claims could still be asserted depending on how broadly “administering” is construed and how the specification defines administration.

How strong is the claim structure for enforcement?

Are these claims broad or narrow in practice?

Broad elements

• Disease target is specific: T-cell lymphoblastic leukemia
• Chemical identity is specific: the compound is named directly
• Route restriction appears only in dependent claims

Narrowing elements

• The method must be directed to the specified disease context
• The active ingredient is limited to the named compound or salts
• If a drug candidate is structurally different, uses an analog, or is a prodrug not captured as a salt of the named compound, it is outside the literal claim scope based on the claim language given.

What are the key infringement touchpoints?

1. Medical indication match: treatment must be for T-cell lymphoblastic leukemia
2. Active ingredient match: the administered therapeutic agent must be 9-β-D-arabinofuranosyl-2-amino-6-methoxy-9H-purine (or salt in Claim 2/4)
3. Route match (for dependent claims): injection for Claims 3 and 4

Claim construction risk points

Does “pharmaceutically acceptable salt” expand the claim meaning?

Yes. Claim 2 and Claim 4 expand coverage from the free base/named compound to salt forms. In infringement practice, “pharmaceutically acceptable” typically allows conventional salts (acid addition salts, base salts) that meet formulation acceptability criteria in the patent record or in the art.

The competitive implication: a competitor can reduce risk only if it avoids administering a salt that is considered pharmaceutically acceptable of the named compound, or by using a different chemical entity not covered by the salt language.

Does “effective amount” create enforceability ambiguity?

It increases factual disputes in litigation because it is not pegged to a numeric range, but it also avoids the rigidity that can defeat claims when dosing differs. Enforcement typically turns on whether the administered regimen is recognized as producing therapeutic effect in T-cell lymphoblastic leukemia.

Patent landscape mapping around US 5,492,897

What does this patent type protect?

US 5,492,897 protects therapeutic methods using a named nucleoside-like purine compound for a specified leukemia type. It does not protect the compound generically through a “composition” claim on the information provided. The claims provided are strictly method claims.

This matters because method patents often face different design-around strategies than compound patents:

• Switching to a different active ingredient
• Targeting a different disease indication
• Using a non-injection route (to evade injection-dependent dependent claims)
• Using non-salt forms (to evade salt-including dependent claims)

How does this sit relative to the broader chemotherapy and nucleoside-purine space?

The compound name is consistent with a purine nucleoside analog structure (arabinofuranosyl + amino-methoxy purine). In the T-ALL treatment landscape, the standard-of-care typically relies on combination regimens built from agents such as antimetabolites, corticosteroids, and chemotherapy backbones. US 5,492,897’s method claims target one specific agent.

For competitors, landscape risk increases where:

• Their investigational regimen includes the same compound as an administered agent (or its pharmaceutically acceptable salt)
• Their trial or label indicates the same disease and mammal treatment context
• Their administration is by injection, aligning with Claims 3 and 4

Where do investors typically look to assess blocking power?

Blocking power for a method patent is driven by:

• Whether the compound is already used in the clinic for T-ALL and whether it is administered by injection
• Whether other parties hold earlier or later compound or formulation patents that expand/contract freedom-to-operate
• Whether later patents claim additional uses, combinations, or modified routes that can support design-around

However, the specific “blocking” outcome depends on the underlying patent family, earlier priority dates, expiration status, and whether there are separate composition-of-matter or formulation patents not shown in the claims provided.

Scope comparison by claim layer

What is the effective coverage envelope?

Below is a direct mapping of each claim to its minimum infringement prerequisites.

Net effect

• Independent claims (1 and 2) are broader than dependent claims (3 and 4) because they do not require injection.
• Salt language only exists in Claims 2 and 4.

Landscape implications for competitors and challengers

How can a competitor design around these claims?

Based on claim language provided, design-around options fall into three buckets:

1. Change the active ingredient

   • Using a different compound, analog, or prodrug not captured as the named compound or a salt thereof avoids the core limitation.

2. Change the route for dependent claims

   • If a product uses a non-injection route, Claims 3 and 4 are harder to assert.
   • Independent claims still cover “administering” without a route limitation in the text provided.

3. Change the disease context

   • If use is for a different leukemia subtype or not for T-cell lymphoblastic leukemia, the disease-specific limitation is not met.

What likely sustains enforcement leverage?

Even without numeric dosing in the claim text, enforcement leverage can persist where:

• Clinical protocols administer the same compound to T-ALL patients
• Administration is injection-based (aligning with dependent claims)
• The formulation uses a salt that is considered pharmaceutically acceptable

Key takeaways

• US 5,492,897 claims method-of-treatment for T-cell lymphoblastic leukemia using 9-β-D-arabinofuranosyl-2-amino-6-methoxy-9H-purine.
• Claim 2 expands Claim 1 by covering pharmaceutically acceptable salts of the named compound.
• Claims 3 and 4 add an injection route limitation, narrowing enforcement to injectable administration.
• The patent’s practical protection is strongest when an accused regimen uses the same compound (or its acceptable salt) and treats T-ALL via injection (for dependent claims).

FAQs

1) Does US 5,492,897 claim the compound’s manufacture or composition?

The provided claims are method-of-treatment claims, not composition-of-matter claims.

2) What is the difference between Claim 1 and Claim 2?

Claim 2 includes pharmaceutically acceptable salts of 9-β-D-arabinofuranosyl-2-amino-6-methoxy-9H-purine.

3) Do Claims 3 and 4 require injection?

Yes. Claims 3 and 4 add that the compound (or salt) is administered by injection.

4) Can non-injection administration avoid infringement?

It can avoid the injection-limited dependent claims (3 and 4), but the independent claims (1 and 2) do not impose a route limitation in the provided text.

5) What is the disease scope?

The claims are limited to treating T-cell lymphoblastic leukemia in a mammal.

References

[1] US Patent No. 5,492,897. (Claims provided in prompt text.)