Executive summary US Patent 4,423,050 claims a method of treating viral infections in warm-blooded or cold-blooded animals by administering 9-(1,3-dihydroxy-2-propoxymethyl)guanine or pharmaceutically acceptable salts or compositions containing it. The claim scope is broad on (i) viral indication class (no virus-specific limitation), (ii) patient species (warm-blooded and cold-blooded covered), and (iii) administration by an “effective amount” without dose, regimen, or formulation constraints in the independent claim. The estate’s enforceability risk hinges on whether accused products can be characterized as delivering the claimed active (or a salt/composition containing it) and whether prior art or later-recognized overlaps exist for the same compound’s antiviral use.

US Patent 4,423,050 scope and claims: what is protected for 9-(1,3-dihydroxy-2-propoxymethyl)guanine antiviral treatment?

US 4,423,050 is a method-of-treatment patent. Its core protective boundary is the therapeutic use of 9-(1,3-dihydroxy-2-propoxymethyl)guanine (and salts/compositions containing it) to treat viral infections in animals.

What does claim 1 actually cover?

Claim 1 recites a method comprising:

Treating a viral infection
In a warm-blooded or cold-blooded animal
By administering an effective amount of:
- 9-(1,3-dihydroxy-2-propoxymethyl)guanine, or
- a pharmaceutically acceptable salt thereof, or
- a composition containing same as an active ingredient.

Implications for claim scope

Indication breadth: “viral infections” is not limited to a specific virus, family, or organ system.
Species breadth: warm-blooded and cold-blooded coverage is explicit.
Therapeutic framing: a treatment method ties the active compound to an antiviral therapeutic effect, not prophylaxis.
Dosage/regimen ambiguity: “effective amount” is functional and can be satisfied by many dosing schedules, depending on proof.
Composition breadth: coverage extends to formulations, as long as the formulation contains the claimed active or its salt.

What do claims 2 and 3 add?

Claim 2 narrows to warm-blooded animals.
Claim 3 narrows to cold-blooded animals.

Practically, claims 2 and 3 are dependent wrappers around claim 1 that confirm the method’s reach across the two broad animal categories. They do not add technical constraints (no dosage or administration route limitations appear in the text provided).

What patents protect antiviral treatment methods using 9-(1,3-dihydroxy-2-propoxymethyl)guanine in the US?

Key protected subject matter

Based on the provided claim language, US 4,423,050 protects:

Method of treatment
- Administration of the compound for treating viral infections.
Use of the specific active
- 9-(1,3-dihydroxy-2-propoxymethyl)guanine.
Salt and composition variants
- “pharmaceutically acceptable salt” and “composition containing same.”

What is not protected by this claim text

The claim language provided does not add explicit protection around:

A specific route of administration (oral, IV, topical, etc.)
A specific viral target (e.g., herpesvirus vs influenza)
A specific dose, interval, or regimen
A specific animal model or species
A specific manufacturing method
A specific formulation type (tablet, capsule, suspension, etc.), although the phrase “composition containing same” does create formulation coverage.

This matters in freedom-to-operate evaluations: competitors can still face risk if they use the claimed active for any “viral infection” treatment context, but their defenses often turn on whether the accused activity is properly characterized as treating viral infections with this specific compound.

How strong is the patent estate for US 4,423,050 given “viral infections” breadth and “effective amount” language?

Strength drivers

No virus limitation: “viral infections” is broad and reduces the need for virus-specific proof in enforcement narratives.
Explicit animal coverage: warm-blooded and cold-blooded coverage prevents easy “species carve-out” arguments.
Active ingredient capture: salts and compositions containing the active extend coverage beyond pure API use.

Enforcement friction points

Even with breadth, method patents face common proof hurdles:

Infringement requires method performance
- The accused party must perform the claimed method elements: treating a viral infection by administering an effective amount of the claimed active.
“Effective amount” is fact-intensive
- Demonstrating that a given dosing supports a therapeutic antiviral effect is evidentiary. If an accused regimen is sub-therapeutic or framed as supportive care, infringement arguments can weaken.
Characterization of “viral infection”
- If the claimed activity is for non-viral indications, or the “viral” element is disputed, the claim can narrow in practice even if broad in text.

When does US 4,423,050 lose exclusivity for viral infection treatment claims?

This question is outcome-determinative and depends on legal status, filing date, grant date, and any term adjustments or patent term adjustments. The provided information contains only the claim text, not the application filing date, priority date, or any PTA/TSA. Without that data, a correct exclusivity timeline cannot be produced.

What is the Orange Book status of US 4,423,050 and does it cover an FDA-approved drug?

Method patents of this type can be listed in the FDA publication ecosystem only if they relate to FDA-approved drugs and are submitted for listing. Orange Book status cannot be determined from the claim text alone because it requires:

The relevant FDA NDA/ANDA/BLA(s)
Patent listing entries and expiration dates
Whether the patent was submitted and qualifies for listing

No FDA listing identifiers are provided, so Orange Book status cannot be stated accurately.

Can a generic or biosimilar enter before the claims of US 4,423,050 expire?

This depends on whether:

The active ingredient is approved in an FDA product and whether the patent is listed for that product
Entry occurs via ANDA (small molecules) where method patents may be triggered through carve-out Paragraph IV theories
In practice, whether the generic’s label includes the patented method of treatment and whether that causes statutory infringement under 35 USC 271(e)(2)

US 4,423,050 is a small-molecule method-of-use type claim (based on chemical specificity), not a biologic claim. Biosimilar entry is not the appropriate pathway, unless the compound were provided in a biologic format, which is not implied by the claim text.

A definitive “generic entry risk” assessment cannot be produced without knowing the FDA product, the listing and Orange Book status, and any Paragraph IV/BTD litigation.

What patent litigation affects US 4,423,050 and what settlement terms typically matter?

Litigation status cannot be determined from the claim text alone. Enforcement often turns on:

Claim construction
Evidence of “effective amount” and antiviral effect in the accused regimen
Whether the accused product contains the active or a salt/composition that falls within “composition containing same”
Whether defenses apply under invalidity theories (anticipation/obviousness) or non-infringement

No case captions, docket numbers, or settlement terms are provided, so litigation impact cannot be stated.

How do claims of US 4,423,050 compare with neighboring method-of-use patents for antiviral nucleosides?

Claim-design pattern

The structure matches a common early antiviral patent template:

Define a specific antiviral nucleoside-like compound
Tie use to “viral infection”
Cover broad species categories
Use functional dosing language (“effective amount”)
Include “salt” and “composition” variants

Practical compare-and-contrast

Where neighboring patents diverge, it is usually on:

Virus limitation (e.g., specific virus or disease)
Route (e.g., oral only)
Species (e.g., mammals only)
Regimen (e.g., daily dosing or specific duration)
Formulation limitations (e.g., sustained release)

Here, the provided claims appear comparatively broad because they lack those additional constraints.

Which companies could face risk if they market formulations containing 9-(1,3-dihydroxy-2-propoxymethyl)guanine for treating viral infections?

Company risk mapping requires:

Identification of commercial products containing this active ingredient (or salts)
Their labeled indication(s)
Their prescribing instructions and intended use
Their distribution to warm-blooded or cold-blooded animals and whether they target “viral infections”

No company identifiers or product records are provided. A defensible list cannot be produced.

What formulations are protected by US 4,423,050: salts, compositions, and delivery systems?

Composition coverage: what is inside the claim boundary

The text expressly includes:

“a pharmaceutically acceptable salt thereof”
“a composition containing same as an active ingredient”

This creates coverage for:

Salt forms that are “pharmaceutically acceptable”
Formulations where the claimed active is present as an active ingredient

What is not explicitly constrained

The provided claims do not restrict:

Dosage form (solid, liquid, injectable, etc.)
Excipient selection
Controlled release technologies
Administration route

So, formulation design changes alone do not avoid risk if the accused product still contains the active and is administered as treatment for viral infections in animals.

Method-of-use versus product claims: how does US 4,423,050 differ from composition-of-matter protection?

US 4,423,050 is method-of-treatment. It protects performance of the antiviral treatment method.
If there were separate composition-of-matter patents on the compound itself (synthesis, polymorphs, crystal forms, salts with specific properties), those could block manufacture or sale of the active regardless of labeled indication.
With only the method claim as provided, a party could potentially design around by avoiding administration for “viral infection treatment” contexts, though evidentiary and labeling realities often negate easy workarounds.

This analysis is structural; it does not identify other patents because only one patent’s claim text is provided.

How many patents cover 9-(1,3-dihydroxy-2-propoxymethyl)guanine antiviral use in the US?

A count requires a full patentability and landscape search (US patents and publications, priority chain mapping, INPADOC family, and legal status). The input provides only one patent’s claims, not the broader portfolio.

Key Takeaways

US 4,423,050 protects a broad antiviral method: administering 9-(1,3-dihydroxy-2-propoxymethyl)guanine (or salts/compositions) in a warm-blooded or cold-blooded animal with a viral infection.
Claims 2 and 3 are species-category refinements without adding formulation, route, virus, or regimen constraints (based on the provided claim text).
The enforceability core turns on whether an accused activity performs the method: viral infection treatment plus administration of an effective amount of the specific active (or a qualifying salt/composition).
A concrete timeline for exclusivity loss, Orange Book status, litigation status, and generic entry risk cannot be concluded from claim text alone.

FAQs

1) Does US 4,423,050 require proof of a specific virus type?
No virus species is specified in claim 1 as provided; the method requires treatment of “viral infections.”

2) Can a competitor argue design-around by changing the formulation but keeping the same active?
The claim includes “composition containing same,” so formulation changes do not avoid coverage if the active is the same and used for the claimed antiviral treatment.

3) Does the patent cover both warm-blooded and cold-blooded animals?
Yes. Claim 1 covers both categories, and claims 2 and 3 separately specify each.

4) Is labeling wording required to prove infringement of a method-of-use claim?
Method-of-use infringement typically relies on evidence of actual method performance and intended/induced use; however, the claim text alone does not define proof standards.

5) Is this patent relevant to ANDA Paragraph IV strategies?
Only if a relevant FDA-approved product and listed patent ecosystem connects the method claim to the ANDA product; that link is not provided here.

References

None provided in the input beyond the claim text of US 4,423,050.

Title:	9-(1,3-Dihydroxy-2-propoxymethyl)guanine as antiviral agent
Abstract:	The compound 9-(1,3-dihydroxy-2-propoxymethyl)guanine and the pharmaceutically acceptable salts thereof are useful as antiviral agents.
Inventor(s):	Julien P. H. Verheyden, John C. Martin
Assignee:	Syntex USA LLC
Application Number:	US06/380,969
Patent Claim Types: see list of patent claims	Use; Composition; Compound;
Patent landscape, scope, and claims:	Executive summary US Patent 4,423,050 claims a method of treating viral infections in warm-blooded or cold-blooded animals by administering 9-(1,3-dihydroxy-2-propoxymethyl)guanine or pharmaceutically acceptable salts or compositions containing it. The claim scope is broad on (i) viral indication class (no virus-specific limitation), (ii) patient species (warm-blooded and cold-blooded covered), and (iii) administration by an “effective amount” without dose, regimen, or formulation constraints in the independent claim. The estate’s enforceability risk hinges on whether accused products can be characterized as delivering the claimed active (or a salt/composition containing it) and whether prior art or later-recognized overlaps exist for the same compound’s antiviral use. US Patent 4,423,050 scope and claims: what is protected for 9-(1,3-dihydroxy-2-propoxymethyl)guanine antiviral treatment? US 4,423,050 is a method-of-treatment patent. Its core protective boundary is the therapeutic use of 9-(1,3-dihydroxy-2-propoxymethyl)guanine (and salts/compositions containing it) to treat viral infections in animals. What does claim 1 actually cover? Claim 1 recites a method comprising: Treating a viral infection In a warm-blooded or cold-blooded animal By administering an effective amount of: 9-(1,3-dihydroxy-2-propoxymethyl)guanine, or a pharmaceutically acceptable salt thereof, or a composition containing same as an active ingredient. Implications for claim scope Indication breadth: “viral infections” is not limited to a specific virus, family, or organ system. Species breadth: warm-blooded and cold-blooded coverage is explicit. Therapeutic framing: a treatment method ties the active compound to an antiviral therapeutic effect, not prophylaxis. Dosage/regimen ambiguity: “effective amount” is functional and can be satisfied by many dosing schedules, depending on proof. Composition breadth: coverage extends to formulations, as long as the formulation contains the claimed active or its salt. What do claims 2 and 3 add? Claim 2 narrows to warm-blooded animals. Claim 3 narrows to cold-blooded animals. Practically, claims 2 and 3 are dependent wrappers around claim 1 that confirm the method’s reach across the two broad animal categories. They do not add technical constraints (no dosage or administration route limitations appear in the text provided). What patents protect antiviral treatment methods using 9-(1,3-dihydroxy-2-propoxymethyl)guanine in the US? Key protected subject matter Based on the provided claim language, US 4,423,050 protects: Method of treatment Administration of the compound for treating viral infections. Use of the specific active 9-(1,3-dihydroxy-2-propoxymethyl)guanine. Salt and composition variants “pharmaceutically acceptable salt” and “composition containing same.” What is not protected by this claim text The claim language provided does not add explicit protection around: A specific route of administration (oral, IV, topical, etc.) A specific viral target (e.g., herpesvirus vs influenza) A specific dose, interval, or regimen A specific animal model or species A specific manufacturing method A specific formulation type (tablet, capsule, suspension, etc.), although the phrase “composition containing same” does create formulation coverage. This matters in freedom-to-operate evaluations: competitors can still face risk if they use the claimed active for any “viral infection” treatment context, but their defenses often turn on whether the accused activity is properly characterized as treating viral infections with this specific compound. How strong is the patent estate for US 4,423,050 given “viral infections” breadth and “effective amount” language? Strength drivers No virus limitation: “viral infections” is broad and reduces the need for virus-specific proof in enforcement narratives. Explicit animal coverage: warm-blooded and cold-blooded coverage prevents easy “species carve-out” arguments. Active ingredient capture: salts and compositions containing the active extend coverage beyond pure API use. Enforcement friction points Even with breadth, method patents face common proof hurdles: Infringement requires method performance The accused party must perform the claimed method elements: treating a viral infection by administering an effective amount of the claimed active. “Effective amount” is fact-intensive Demonstrating that a given dosing supports a therapeutic antiviral effect is evidentiary. If an accused regimen is sub-therapeutic or framed as supportive care, infringement arguments can weaken. Characterization of “viral infection” If the claimed activity is for non-viral indications, or the “viral” element is disputed, the claim can narrow in practice even if broad in text. When does US 4,423,050 lose exclusivity for viral infection treatment claims? This question is outcome-determinative and depends on legal status, filing date, grant date, and any term adjustments or patent term adjustments. The provided information contains only the claim text, not the application filing date, priority date, or any PTA/TSA. Without that data, a correct exclusivity timeline cannot be produced. What is the Orange Book status of US 4,423,050 and does it cover an FDA-approved drug? Method patents of this type can be listed in the FDA publication ecosystem only if they relate to FDA-approved drugs and are submitted for listing. Orange Book status cannot be determined from the claim text alone because it requires: The relevant FDA NDA/ANDA/BLA(s) Patent listing entries and expiration dates Whether the patent was submitted and qualifies for listing No FDA listing identifiers are provided, so Orange Book status cannot be stated accurately. Can a generic or biosimilar enter before the claims of US 4,423,050 expire? This depends on whether: The active ingredient is approved in an FDA product and whether the patent is listed for that product Entry occurs via ANDA (small molecules) where method patents may be triggered through carve-out Paragraph IV theories In practice, whether the generic’s label includes the patented method of treatment and whether that causes statutory infringement under 35 USC 271(e)(2) US 4,423,050 is a small-molecule method-of-use type claim (based on chemical specificity), not a biologic claim. Biosimilar entry is not the appropriate pathway, unless the compound were provided in a biologic format, which is not implied by the claim text. A definitive “generic entry risk” assessment cannot be produced without knowing the FDA product, the listing and Orange Book status, and any Paragraph IV/BTD litigation. What patent litigation affects US 4,423,050 and what settlement terms typically matter? Litigation status cannot be determined from the claim text alone. Enforcement often turns on: Claim construction Evidence of “effective amount” and antiviral effect in the accused regimen Whether the accused product contains the active or a salt/composition that falls within “composition containing same” Whether defenses apply under invalidity theories (anticipation/obviousness) or non-infringement No case captions, docket numbers, or settlement terms are provided, so litigation impact cannot be stated. How do claims of US 4,423,050 compare with neighboring method-of-use patents for antiviral nucleosides? Claim-design pattern The structure matches a common early antiviral patent template: Define a specific antiviral nucleoside-like compound Tie use to “viral infection” Cover broad species categories Use functional dosing language (“effective amount”) Include “salt” and “composition” variants Practical compare-and-contrast Where neighboring patents diverge, it is usually on: Virus limitation (e.g., specific virus or disease) Route (e.g., oral only) Species (e.g., mammals only) Regimen (e.g., daily dosing or specific duration) Formulation limitations (e.g., sustained release) Here, the provided claims appear comparatively broad because they lack those additional constraints. Which companies could face risk if they market formulations containing 9-(1,3-dihydroxy-2-propoxymethyl)guanine for treating viral infections? Company risk mapping requires: Identification of commercial products containing this active ingredient (or salts) Their labeled indication(s) Their prescribing instructions and intended use Their distribution to warm-blooded or cold-blooded animals and whether they target “viral infections” No company identifiers or product records are provided. A defensible list cannot be produced. What formulations are protected by US 4,423,050: salts, compositions, and delivery systems? Composition coverage: what is inside the claim boundary The text expressly includes: “a pharmaceutically acceptable salt thereof” “a composition containing same as an active ingredient” This creates coverage for: Salt forms that are “pharmaceutically acceptable” Formulations where the claimed active is present as an active ingredient What is not explicitly constrained The provided claims do not restrict: Dosage form (solid, liquid, injectable, etc.) Excipient selection Controlled release technologies Administration route So, formulation design changes alone do not avoid risk if the accused product still contains the active and is administered as treatment for viral infections in animals. Method-of-use versus product claims: how does US 4,423,050 differ from composition-of-matter protection? US 4,423,050 is method-of-treatment. It protects performance of the antiviral treatment method. If there were separate composition-of-matter patents on the compound itself (synthesis, polymorphs, crystal forms, salts with specific properties), those could block manufacture or sale of the active regardless of labeled indication. With only the method claim as provided, a party could potentially design around by avoiding administration for “viral infection treatment” contexts, though evidentiary and labeling realities often negate easy workarounds. This analysis is structural; it does not identify other patents because only one patent’s claim text is provided. How many patents cover 9-(1,3-dihydroxy-2-propoxymethyl)guanine antiviral use in the US? A count requires a full patentability and landscape search (US patents and publications, priority chain mapping, INPADOC family, and legal status). The input provides only one patent’s claims, not the broader portfolio. Key Takeaways US 4,423,050 protects a broad antiviral method: administering 9-(1,3-dihydroxy-2-propoxymethyl)guanine (or salts/compositions) in a warm-blooded or cold-blooded animal with a viral infection. Claims 2 and 3 are species-category refinements without adding formulation, route, virus, or regimen constraints (based on the provided claim text). The enforceability core turns on whether an accused activity performs the method: viral infection treatment plus administration of an effective amount of the specific active (or a qualifying salt/composition). A concrete timeline for exclusivity loss, Orange Book status, litigation status, and generic entry risk cannot be concluded from claim text alone. FAQs 1) Does US 4,423,050 require proof of a specific virus type? No virus species is specified in claim 1 as provided; the method requires treatment of “viral infections.” 2) Can a competitor argue design-around by changing the formulation but keeping the same active? The claim includes “composition containing same,” so formulation changes do not avoid coverage if the active is the same and used for the claimed antiviral treatment. 3) Does the patent cover both warm-blooded and cold-blooded animals? Yes. Claim 1 covers both categories, and claims 2 and 3 separately specify each. 4) Is labeling wording required to prove infringement of a method-of-use claim? Method-of-use infringement typically relies on evidence of actual method performance and intended/induced use; however, the claim text alone does not define proof standards. 5) Is this patent relevant to ANDA Paragraph IV strategies? Only if a relevant FDA-approved product and listed patent ecosystem connects the method claim to the ANDA product; that link is not provided here. References None provided in the input beyond the claim text of US 4,423,050. More… ↓ ⤷ Start Trial

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Details for Patent: 4,423,050

Summary for Patent: 4,423,050