Details for Patent: RE41920

United States RE41920: Scope, Claim Structure, and US Patent Landscape for Pain Treatment Methods

What does US RE41920 claim in plain scope terms?

US RE41920 is a reissue-style patent directed to methods for treating pain by administering compounds defined by “Formula I” (or specific exemplified embodiments and salts) to a mammal (with human-directed dependent claims). The claims are method-of-treatment claims, not composition claims, and they hinge on the structure parameters R1, R2, R3 plus optionally stereochemical definition and salt formation.

Core independent claim 1: Formula I pain-treatment method

Claim 1 recites a method for treating pain by administering a therapeutically effective amount of a compound:

• Compound of Formula I
• to a mammal in need of treatment
• where:
  • R1 is:
  • straight or branched alkyl of 1 to 6 carbons, or
  • phenyl, or
  • cycloalkyl of 3 to 6 carbons
  • R2 is hydrogen or methyl
  • R3 is hydrogen, methyl, or carboxyl

Key scope levers in claim 1

• Pain is not limited to a single etiology in claim 1.
• Target class is broad: “to a mammal.”
• Chemical coverage is controlled by R1/R2/R3 definitions; the claim is broad within those enumerated substituent constraints.
• Stereochemistry: claim 1 includes “diastereomer, or enantiomer thereof,” which is typically read as permitting any stereoisomer unless narrowed elsewhere.

Claim 2: Tightened substituent and stereo language (still method claims)

Claim 2 is a dependent method claim that narrows the administered compound to a specific subclass:

• Administer a compound of Formula I where:
  • R3 and R2 are hydrogen
  • R1 is —(CH2)0-2—iC4H9 isobutyl
• The compound is administered “as an (R), (S), or (R,S) isomer.”

Practical effect

• Claim 2 collapses the Formula I breadth into a specific side-chain architecture (isobutyl via the —(CH2)0-2— spacer motif) and removes variability at R2 and R3 (both fixed at hydrogen).

Claim 3: Specific named acids (multiple stereochemical possibilities)

Claim 3 narrows to named compounds that align with the compound class used throughout the claim set:

• (S)-3-(aminomethyl)-5-methylhexanoic acid
• and 3-aminomethyl-5-methylhexanoic acid (no explicit stereopreference on the second citation)

This claim consolidates the landscape into a known acid scaffold plus specific stereochemical embodiments.

Claims 4–15: Pain subtype limitations (highly enumerated)

Claims 4 through 15 are dependent method claims that limit the pain type to enumerated categories:

• Inflammatory pain (claim 4)
• Neuropathic pain (claim 5)
• Cancer pain (claim 6)
• Postoperative pain (claim 7)
• Phantom limit limb pain (claim 8; likely “phantom limb pain” as a transcription artifact)
• Burn pain (claim 9; user text shows “bum burn pain”)
• Gout pain (claim 10)
• Osteoarthritic pain (claim 11)
• Trigeminal neuralgia pain (claim 12)
• Acute herpetic and postherpetic pain (claim 13)
• Causalgia pain (claim 14)
• Idiopathic pain (claim 15)

Practical effect

• These claims create multiple data-anchored infringement hooks: a defendant using the same compound but targeting one named pain etiology can land squarely inside a subtype claim.

Claims 16–18: Human-focused independent narrowing to (S)-3-(aminomethyl)-5-methylhexanoic acid and salts

Claim 16 is a method claim directed to:

• administering (S)-3-(aminomethyl)-5-methylhexanoic acid or a pharmaceutically acceptable salt
• to a human

Claims 17–18

• Claim 17 specifies administering (S)-3-(aminomethyl)-5-methylhexanoic acid
• Claim 18 specifies administering a pharmaceutically acceptable salt of that same compound

Practical effect

• Claims 16–18 increase enforceability against human dosing by removing mammal breadth.

Claims 19–25: Chronic and specific pain subcategories

Claims 19–25 refine the human method to additional pain selections:

• Chronic pain (claim 19)
• Selected pain list (claim 20): inflammatory, neuropathic, cancer, postoperative, idiopathic
• Neuropathic pain (claim 21)
• Diabetic neuropathic pain (claim 22)
• Acute herpetic pain (claim 23)
• Postherpetic pain (claim 24)
• Fibromyalgia pain (claim 25)

Practical effect

• These claims map to patient cohorts and clinical trial endpoints that are often used for pain drug development.

How is the claim hierarchy structured for infringement and design-around?

The claim set is structured in tiers:

1. Chemical breadth tier (Claim 1)
   • broad Formula I substituent scope (R1/R2/R3 enumerated)
   • broad beneficiary class (mammal)
2. Structural narrowing tier (Claim 2)
   • fixes R2=H, R3=H
   • restricts R1 to a specific isobutyl-related arrangement
   • allows stereoisomer variation
3. Specific scaffold tier (Claim 3)
   • narrows further to named aminomethyl-methylhexanoic acids, including (S)
4. Pain-etiology tier (Claims 4–15)
   • multiple dependent “pain category” claims
5. Human dosing + stereochemical tier (Claims 16–18)
   • (S)-3-(aminomethyl)-5-methylhexanoic acid and salts
   • explicit human target
6. Specific clinical subtype tier (Claims 19–25)
   • chronic and selected named pain conditions

Design-around pressure points

• Stereochemistry: Claims 16–18 are limited to (S) (unless a court reads broader coverage from the earlier claims still in the patent family). If a product uses a different stereoisomer exclusively, it may reduce direct coverage under the human-(S) claims but not necessarily under the Formula I claims if those are still asserted against isomeric forms permitted by claim 1/2.
• R2/R3 identity: Claim 2 requires R2=H and R3=H.
• Salt form: multiple claims explicitly include “pharmaceutically acceptable salt,” expanding formulation coverage.
• Pain category: even with the same compound, claims 4–15 and 19–25 require specific pain types.

What is the practical scope of “pain” coverage across the claim set?

Across the claims provided, pain is covered through:

• General pain treatment method (claim 1)
• Specific etiology-labeled pain subsets (claims 4–15)
• Chronic and select subsets (claims 19–25)
• Overlap exists: neuropathic pain appears in multiple claims, diabetic neuropathic pain and fibromyalgia appear as higher-specificity dependent claims.

Enumerated pain types in the provided claim text

From the claims you supplied, the explicit pain types are:

• inflammatory pain
• neuropathic pain
• cancer pain
• postoperative pain
• phantom limb pain (text shows “phantom limit limb pain”)
• burn pain (text shows “bum burn pain”)
• gout pain
• osteoarthritic pain
• trigeminal neuralgia pain
• acute herpetic pain and postherpetic pain (claim 13)
• causalgia pain
• idiopathic pain
• chronic pain
• diabetic neuropathic pain
• fibromyalgia pain

Commercial implication A compound captured by claims 1–3 but used clinically for one of these labeled indications has a direct infringement pathway via dependent claims.

What compounds does RE41920 cover, based on the claim text provided?

The compounds described fall into two layers:

1) “Formula I” with defined substituent ranges (Claim 1)

• R1: alkyl C1–C6, phenyl, or cycloalkyl C3–C6
• R2: H or methyl
• R3: H, methyl, or carboxyl
• stereochemistry: any diastereomer/enantiomer included (claim 1)

2) Narrowed embodiment: isobutyl-linked motif with R2=H, R3=H (Claim 2)

• R1 = —(CH2)0-2—iC4H9 isobutyl
• R2 = H
• R3 = H
• stereochemistry: (R), (S), or (R,S) allowed (claim 2)

3) Named acid embodiments (Claims 3, 16–18)

• (S)-3-(aminomethyl)-5-methylhexanoic acid
• 3-aminomethyl-5-methylhexanoic acid
• pharmaceutically acceptable salts of (S)-3-(aminomethyl)-5-methylhexanoic acid

Where does RE41920 sit in the US patent landscape for this scaffold and indication space?

The landscape, based on US reissue practice and claim structure, divides into three enforceable zones that matter for freedom-to-operate (FTO):

1. Method-of-treatment claims for pain using the specific compound class
2. Indication-specific dependent claims that lock in common pain trial endpoints
3. Stereochemistry- and human-use narrowing that can preserve enforceability even if some variants are marketed

Landscape mapping for investors and R&D teams

When assessing competing assets or generic/biosimilar-style entry in method claims, the key questions that determine risk are:

• Is the marketed therapy chemically within Formula I (claim 1), or at least within the narrowed “isobutyl motif” (claim 2)?
• Is dosing human and (S)-3-(aminomethyl)-5-methylhexanoic acid (claims 16–18) in scope?
• Are the approved or marketed indications among the enumerated pain categories (claims 4–15, 19–25)?
• Is the product administered as a salt (claims explicitly include pharmaceutically acceptable salts)?

If the product hits on chemical scope plus any one enumerated indication claim path, RE41920 can become an infringement target even if the exact dosing regimen differs, because these are method claims keyed to administration of a therapeutically effective amount.

How strong is claim coverage against typical development and marketing strategies?

Clinical development patterns that align to these claims

• Pain programs often split by neuropathic, inflammatory, postoperative, and cancer pain endpoints. RE41920 aligns directly to these categories via dependent claims 4–7 and 5.
• Large markets for trigeminal neuralgia, herpetic neuralgia, diabetic neuropathic pain, and fibromyalgia align directly to claims 12, 13/23/24, 22, and 25.

Marketing labeling patterns that can trigger coverage

If a label (or clinical use pathway) matches a named pain category that appears in the dependent claims, the claim set creates multiple infringement “landing zones.” For human products, claims 16–18 plus the more granular claims 19–25 matter most.

What should be treated as “core” claim inventions for litigation strategy?

Based solely on the provided claims, the core inventive thrust is:

• administering a defined aminomethyl-methylhexanoic acid scaffold (as Formula I or specific embodiment) for pain relief, including neuropathic and inflammatory etiologies, in humans.

Litigation typically centers on:

• whether the accused product falls within the Formula I substituent definitions
• whether it is the (S) stereoisomer (for the human-scoped claims)
• whether the accused indication matches one of the enumerated pain categories

Key Takeaways

• US RE41920 is a method-of-treatment patent for pain using Formula I compounds with defined R1/R2/R3 substituent scope, plus explicit coverage for (S)-3-(aminomethyl)-5-methylhexanoic acid and its pharmaceutically acceptable salts in humans.
• The claim set is layered: broad scaffold coverage in claims 1–3, then multiple pain-etiology dependent claims (claims 4–15) and a human-(S) focus with additional pain subtypes (claims 16–25).
• The most leverage for enforceability comes from the combination of:
  (i) defined chemical scope, (ii) explicit inclusion of salt forms, and (iii) enumerated pain indications including neuropathic (including diabetic neuropathic), herpetic, trigeminal neuralgia, and fibromyalgia.

FAQs

1) Is RE41920 limited to a single pain indication?

No. Claim 1 is framed as “treating pain,” and dependent claims enumerate multiple pain categories including inflammatory, neuropathic, cancer, postoperative, osteoarthritis, trigeminal neuralgia, herpetic pain, diabetic neuropathic pain, and fibromyalgia.

2) Does RE41920 require the (S)-enantiomer for all claims?

No. Claims 1–2 include stereochemistry flexibility (claim 1 includes diastereomers/enantiomers; claim 2 permits (R), (S), or (R,S)). The human-focused claims 16–18 specifically recite (S)-3-(aminomethyl)-5-methylhexanoic acid.

3) Do the claims cover salts?

Yes. Claim 1 includes “pharmaceutically acceptable salt,” and claims 16–18 explicitly include pharmaceutically acceptable salts of (S)-3-(aminomethyl)-5-methylhexanoic acid.

4) Can a product avoid infringement by changing pain indication?

If the product stays within the claimed compound scope, choosing an indication outside the enumerated categories in dependent claims reduces direct fit to those dependent claims, but claim 1 still broadly covers “treating pain” by administering a therapeutically effective amount of the Formula I compound to a mammal.

5) What claim features are most likely to be litigated?

Typically the two axes are: (1) whether the accused product falls within Formula I (or the narrowed R2/R3 and R1 isobutyl motif), and (2) whether the accused use aligns with the human-(S) and specific pain subtype dependent claims.

References

[1] United States Patent RE41920 (claims provided in prompt).