United States Patent 4,413,141: Scope, Claims, and US Patent Landscape
What does US 4,413,141 claim?
US Patent 4,413,141 claims a specific amino acid and two narrower embodiments defined by stereochemistry and salt form.
Claim set (verbatim substance)
Claim 1
- 2-Difluoromethyl-2,5-diaminopentanoic acid, or a pharmaceutically acceptable salt.
Claim 2
- The compound of claim 1, where the compound is the (-)-isomer of 2-difluoromethyl-2,5-diaminopentanoic acid, or a pharmaceutically acceptable salt.
Claim 3
- The compound of claim 1 or 2, where the compound is the monohydrochloride salt.
Scope implications
- The patent has a single core chemical identity (2-difluoromethyl-2,5-diaminopentanoic acid), plus (i) stereochemical limitation to the (-)-isomer and (ii) salt limitation to monohydrochloride.
- Claim 1 is broad as it covers:
- the racemate (if applicable),
- any enantiomeric form other than the (-)-isomer is not excluded by claim language,
- and all pharmaceutically acceptable salts (a large salt universe unless constrained by prosecution history or specification).
- Claims 2 and 3 are narrow and directly cap coverage:
- claim 2 restricts to the (-)-isomer,
- claim 3 restricts to monohydrochloride.
How broad is “pharmaceutically acceptable salt” in claim 1?
Claim 1 includes “pharmaceutically acceptable salt thereof,” which typically expands coverage beyond the free base to salts formed with common pharmaceutically acceptable acids.
Practical claim coverage boundaries
| Element |
Covered by |
Effect on scope |
| Free base form |
Claim 1 |
Included if the compound is not defined as only a salt |
| Any salt form |
Claim 1 |
Included if “pharmaceutically acceptable” is met |
| Specific salt (monohydrochloride) |
Claim 3 |
Guaranteed coverage for that salt even if others are litigated as not “acceptable” |
| (-)-isomer |
Claim 2 |
Covered only by claim 2 and claim 3 when tied to monohydrochloride |
What the claim language does not do
- It does not limit the salt counterion beyond “pharmaceutically acceptable.”
- It does not limit the stereochemistry in claim 1 (stereochemistry is only explicitly limited in claim 2).
- It does not specify particle form, polymorph, hydrate state beyond monohydrochloride in claim 3, or crystalline form. Those limitations would need to appear in the specification and be tied to the claims, but the claim set provided contains none.
What is the effective coverage perimeter for competitors?
Coverage depends on whether a competitor makes, uses, sells, or imports:
1) the exact chemical (2-difluoromethyl-2,5-diaminopentanoic acid) or
2) a pharmaceutically acceptable salt of that chemical or
3) the (-)-isomer or
4) the monohydrochloride salt.
Design-around logic
A competitor can only avoid literal infringement if the product falls outside claim 1’s chemical identity or salt definition, or if it targets a different compound not encompassed by the exact structure.
Literal non-infringement pathways
- Use a different core scaffold (different substitution pattern or different chain substitution).
- Use a different ring/chain length that changes the compound away from “2,5-diaminopentanoic acid” base framework.
- Use salts that fail the “pharmaceutically acceptable” characterization, which is often difficult to enforce without a strong evidentiary record.
Stereochemical non-infringement
- Claim 2 is limited to the (-)-isomer, so a competitor using a pure (+)-enantiomer is not eliminated by claim 2.
- But claim 1 still covers the compound generally, so stereochemical changes do not automatically remove infringement risk if the product is still the same chemical compound definition.
How do claims map to typical chemical patent infringement scenarios?
For a chemical composition patent with direct product claims, infringement usually concentrates on product identity.
Claim-by-claim mapping
| Competitor product |
Claim 1 |
Claim 2 |
Claim 3 |
| Free base of 2-difluoromethyl-2,5-diaminopentanoic acid |
Yes |
If (-) isomer only |
If monohydrochloride (no) |
| Racemate or mixture containing the compound |
Yes |
Only if (-) isomer is the product |
Only if monohydrochloride |
| Pure (+)-isomer free base |
Yes (claim 1 still covers the compound) |
No |
No |
| (-)-isomer free base |
Yes |
Yes |
No |
| Any pharmaceutically acceptable salt |
Yes |
Yes if (-)-isomer salt |
Only if monohydrochloride |
| Monohydrochloride salt |
Yes |
Yes (if tied to (-) form) |
Yes |
This is why claim 1 drives most enforcement leverage.
What does the patent landscape look like in the US?
A complete US landscape requires bibliographic and legal-status data: application numbers, assignee, filing date, expiration, continuation family members, related claims in other patents, and whether there are later patents on polymorphs, stereoisomers, salts, formulations, or methods of use.
That data is not provided in the prompt. Under the constraints, the landscape section below is restricted to what can be grounded directly in the claim text supplied: a chemical product claim family with three claim tiers (general compound, (-)-isomer, monohydrochloride).
Landscape categories that typically cluster around this claim structure
Even without external bibliographic detail, this claim style implies three common US landscape “lanes”:
-
Pre-grant synthesis and compound patents
- Broad chemical product claims to the parent scaffold.
- Enantiomer-specific claims (claim 2) are common when racemates were first filed, then enantiomer enrichment followed.
-
Salt and solid-state follow-on patents
- Claim 3 shows at least one protected salt form, which often spawns additional US filings on:
- hydrates,
- polymorphs,
- alternate counterions,
- or improved stability/solubility.
-
Method-of-use or therapeutic class patents
- Product claims like these often coexist with separate method patents for the therapeutic indication, dosing, or mechanism.
What can be asserted from claim text only
- The protected subject matter is composition-defined (chemical identity and salt/stereochemistry).
- There are no method claims shown in the provided excerpt.
- There are no formulation claims shown (no excipients, capsules, particle size).
- There are no additional substituent variants shown (scope is locked to the specific difluoromethyl-diaminopentanoic acid structure).
What is the risk profile for a generic or follow-on entrant?
If an entrant’s API matches the compound identity, risk is high because:
- claim 1 is not restricted to enantiomer,
- claim 1 includes “pharmaceutically acceptable salts,” and
- claim 3 locks in monohydrochloride coverage.
API-level infringement risk
- High if the API is 2-difluoromethyl-2,5-diaminopentanoic acid in free base form or any acceptable salt.
- High even if the API is the (-)-isomer specifically and marketed as monohydrochloride.
Formulation-level risk
- If the entrant uses the same API but different salts and the formulation is compliant with the definition of “pharmaceutically acceptable salt,” claim 1 remains a direct product barrier.
Key takeaways
- US 4,413,141 is a tight composition patent on 2-difluoromethyl-2,5-diaminopentanoic acid, with claim scope expanded only by “pharmaceutically acceptable salts.”
- Claim 1 is the enforcement anchor (compound identity + any pharmaceutically acceptable salt).
- Claim 2 narrows to the (-)-isomer; it does not eliminate coverage under claim 1 for other stereochemical forms because claim 1 still covers the defined compound generally.
- Claim 3 narrows to monohydrochloride, creating a separate, highly specific product pocket.
- The provided claim text supports a landscape expectation of clustered follow-on patents in salt/solid-state and potentially enantiomer-specific and method-of-use domains, but those cannot be enumerated without bibliographic and legal-status data.
FAQs
1) Does claim 1 require the (-)-isomer?
No. Claim 2 adds the (-)-isomer limitation, but claim 1 covers the compound generally and includes pharmaceutically acceptable salts.
2) Can a competitor avoid infringement by using a different enantiomer?
Using a different enantiomer avoids claim 2 coverage, but not claim 1 coverage if the product still meets the compound definition in claim 1.
3) Does claim 1 cover salts beyond monohydrochloride?
Yes. Claim 1 covers “pharmaceutically acceptable salt” broadly; claim 3 is a specific salt that is also covered.
4) Is there coverage for polymorphs or hydrates in the claims provided?
Not in the claim text supplied. Claims shown are limited to chemical identity, the (-)-isomer, and the monohydrochloride salt.
5) Is this patent limited to a therapeutic method of use?
The claim text provided is composition-only. No method-of-use scope is visible in the supplied claims.
References
[1] US Patent 4,413,141 (claims provided in prompt).
