US Patent 6,384,013: Scope, Claim Strength, and Landscape for Echinocandin B Amino Acylated Derivatives
What does US 6,384,013 claim cover?
US 6,384,013 claims acylated derivatives of Echinocandin B formed by acylating the amino nucleus of Echinocandin B with an active ester of a carboxylic acid. The claimed chemical space is defined by the acyl group(s) introduced through that amino-acylation step.
Based on the claim language you provided, the claim set centers on:
- Core scaffold: Echinocandin B (amino nucleus acylated)
- Coupling chemistry: acylation using an active ester of a defined carboxylic acid
- Acyl group definition: R is restricted to specific alkoxy/ether or tert-alkoxy acyl substituents (the claim text defines R in multiple places)
Claim-by-claim scope (as provided)
| Claim |
What it covers |
Key limitations present in the claim |
| 1 |
“A compound having the following formula” (formula not shown in your excerpt) |
Formula scope controls; R or substituent definition is not visible from your excerpt for claim 1 |
| 2 |
A compound represented by a formula where R is one of five substituent options, made by acylating an amino nucleus of Echinocandin B with an active ester of a defined carboxylic acid |
Requires (i) Echinocandin B amino acylation, (ii) active ester, (iii) R restricted to the listed options |
| 3 |
Claim 2 compound where R = —O(CH2)4CH3 |
R narrowed to one value |
| 4 |
Claim 2 compound where the active ester is specifically a 2,4,5-trichlorophenyl ester |
Active ester identity narrowed (specific leaving group) |
| 5 |
A second compound “represented by the formula” with R restricted to the same five options |
Formula scope differs from claim 2 but shares the R set |
| 6 |
A third formula claim “represented by the formula” (formula not shown in your excerpt) |
Formula scope controls; formula details not visible in your excerpt |
| 7 |
A pharmaceutically acceptable salt of a compound according to claim 6 |
Salt coverage depends on the base compound of claim 6 |
The R substituent set (core constraint)
Across claim 2 and claim 5, the substituent R is restricted to exactly five options (as shown in your excerpt):
- —O(CH2)3CH3
- —O(CH2)4CH3
- —O(CH2)5CH3
- —O(CH2)2O(CH2)3CH3
- —O(CH2)2OC(CH3)3
This is the dominant scope gate. Even if a compound is otherwise an Echinocandin B derivative, it falls outside the explicit R-defined embodiments if the introduced acyl group does not match these R definitions.
How is the claimed chemistry constrained?
The claims are not limited to “products” defined only by structure in the abstract; they also include a preparation requirement in claim 2 (“prepared by acylating … with an active ester …”). In practice, for infringement purposes, “prepared by” language often functions as a structural/product limitation depending on how the claims are construed, but it still signals that the claimed compounds arise from a specific transformation:
- Starting material: Echinocandin B
- Reactive site: “amino nucleus” of Echinocandin B
- Acylating agent: an active ester of a carboxylic acid with R defined as above
Active ester specificity
Claim 2 requires an “active ester,” and claim 4 tightens to a concrete active ester class:
- 2,4,5-trichlorophenyl ester (claim 4)
That active ester constraint affects both:
- literal scope (claim 4)
- fallback coverage (if other active esters are used, claim 4 is not met, but claim 2 may be if the active ester qualifies generally)
What is the practical breadth of the product claims?
Within the disclosed claim language, US 6,384,013 is broad at the “class of derivatives” level but narrow at the “substitution pattern” level.
Breadth drivers
- The invention covers multiple R substituents (5 enumerated options).
- It covers pharmaceutically acceptable salts for the compound of claim 6 (claim 7).
- It includes at least two distinct formula claims (claims 2 and 5, plus claims 1 and 6 not fully visible in your excerpt).
Breadth limiters
- R is exhaustively enumerated in the excerpt. No generic “alkoxyalkyl” latitude appears beyond those five.
- The compounds must be derivatives from acylation of Echinocandin B’s amino nucleus with the specified acid/active ester scheme.
- The active ester is generic in claim 2 but becomes specific in claim 4.
Where does this fit in the echinocandin patent landscape?
Echinocandins (including caspofungin, micafungin, and related lipopeptide/peptidomimetic derivatives) have dense IP landscapes built around:
- core scaffold variants,
- prodrug and salt forms,
- formulation and dosing inventions,
- and synthetic routes to those variants.
US 6,384,013 is positioned as a derivative-claim patent focusing on chemical modification of Echinocandin B via amino acylation, with a tight R substituent selection and explicit active ester chemistry.
Key landscape implication
This patent most likely targets competitors making:
- Echinocandin B amino-acylated derivatives using carboxylic acid esters where the acyl group corresponds to the specified R set.
If a competitor’s derivative changes either:
- the identity of the introduced acyl group’s R substituent, or
- the reactive site chemistry (no amino acylation of Echinocandin B), or
- the base scaffold away from Echinocandin B,
then literal claim coverage likely collapses.
What does the claim set imply about enforceability and design-around?
Design-around levers visible from the claims
The R set creates straightforward design paths:
- use acyl substituents with different alkyl/ether lengths or branching not matching the five enumerated R options,
- introduce different linkers (if not conforming to the listed ether/alkyl patterns),
- use a different active ester leaving group while still using the acylation strategy (this mainly affects claim 4, less so claim 2).
Salt coverage scope
Claim 7 extends coverage to “pharmaceutically acceptable salts” of claim 6’s base compound. This is a common extension that can capture:
- different counterions for the same base structure, and
- commercial product forms.
But salt protection does not typically prevent competitors from targeting a non-salt-free base compound, unless the base structure is itself captured by other claims.
How strong is claim 4 within the set?
Claim 4 is a narrow dependent claim:
- active ester must be 2,4,5-trichlorophenyl ester.
This narrowness means:
- It provides a specific evidentiary hook if a competitor’s manufacturing process or example uses that exact active ester.
- It is not a broad independent enforcement target because most manufacturing processes can swap active ester leaving groups while keeping product structure constant.
What does the presence of multiple formula claims suggest?
The excerpt indicates claims 1, 2, 5, and 6 all claim “a compound represented by the formula” with varying claim numbers. That pattern typically indicates:
- multiple structural embodiments (e.g., different stereochemical representations, different linkage sites, or different tautomer/charged state representations), or
- multiple derivative families under a single invention theme.
Without the actual formula drawings or textual definition beyond the R set, the exact differences between the formula embodiments cannot be fully mapped from your excerpt. Still, the consistent R restriction across claim 2 and claim 5 indicates the same acyl substituent motif is core to at least part of the claimed invention.
How to read the patent as a claim chart (product-only view)
For the portion of the claim set where the excerpt is explicit, infringement analysis can be structured as:
| Claim element |
Requirement in the excerpt |
How it narrows scope |
| Base scaffold |
Echinocandin B amino acylation |
Excludes non-Echinocandin-B derivatives |
| Transformation |
acylation of the amino nucleus |
Excludes different functionalization routes |
| Acyl donor |
active ester of a carboxylic acid |
Requires the acyl group be introduced via the specified acid/active ester |
| R substituent |
one of the 5 enumerated R structures |
Captures only specific ether/alkyl patterns |
| Dependent narrowing |
claim 3: R = —O(CH2)4CH3 |
Single acyl substituent embodiment |
| Dependent narrowing |
claim 4: active ester is 2,4,5-trichlorophenyl ester |
Only those using that leaving group |
| Salt coverage |
claim 7: salt of claim 6 base compound |
Captures pharmaceutically acceptable counterions |
What is the likely status of this IP in the broader market?
US utility patents like 6,384,013 typically expire on a term schedule tied to filing date and any adjustments. If the patent is still in force, enforcement would likely focus on:
- manufacturing disclosures (active ester selection, acylation method),
- product structure matching the R set,
- and salt/counterion variants.
If it is not in force, the claim language remains relevant for:
- freedom-to-operate screening,
- invalidity or design-around strategies,
- and licensing posture for follow-on patents.
Where are the biggest gaps in coverage based on the excerpt?
From the claims you provided, the biggest coverage gaps are structural specificity-related:
- Claims 1 and 6 are not fully visible in your excerpt (their formulas are not shown).
- Claim 2 and 5 share the R set and thus are more analyzable, but formula-level details (other substituents, regiochemistry, and the exact attachment point) are not fully reconstructible from the excerpt.
As a result, the excerpt supports high-confidence mapping of the acyl R set and the amino-acylation constraint, while leaving formula-level embodiment differences less precisely defined.
Business implications: what would a competitor need to change to avoid capture?
Given the explicit R enumeration and the Echinocandin B amino acylation requirement, a competitor typically needs to diverge in at least one of these axes:
- R divergence: choose an acyl substituent not within the five enumerated R structures.
- Chemistry divergence: avoid acylating the “amino nucleus” of Echinocandin B as required (replace the functionalization approach).
- Salt divergence: sell as a non-salt form does not avoid claims that cover the free base, but can matter for claim 7-specific coverage depending on claim construction.
In parallel, a competitor using the same R set but a different active ester leaving group likely remains in the claim 2 scope unless claim 4 is enforced separately.
Key Takeaways
- US 6,384,013 claims Echinocandin B amino-acylated derivatives where the introduced acyl group is defined by an enumerated R set of 5 ether/alkyl substituents: —O(CH2)3CH3, —O(CH2)4CH3, —O(CH2)5CH3, —O(CH2)2O(CH2)3CH3, and —O(CH2)2OC(CH3)3.
- Claim 2 requires preparation by acylating the amino nucleus of Echinocandin B using an active ester of a carboxylic acid bearing that R.
- Claim 3 narrows to R = —O(CH2)4CH3; claim 4 narrows active ester specifically to 2,4,5-trichlorophenyl ester.
- Claim 7 extends coverage to pharmaceutically acceptable salts of the claim 6 base compound.
- The most direct design-around lever is changing the acyl R substituent so it does not match the enumerated set, followed by shifting away from the claimed amino-acylation of Echinocandin B.
FAQs
-
What is the single most important scope limiter in US 6,384,013?
The acyl substituent R is limited to the five enumerated structures listed in claims 2 and 5.
-
Does the patent cover all echinocandins?
No. The claims focus on derivatives made by acylating Echinocandin B’s amino nucleus.
-
Is claim 4 broader or narrower than claim 2?
Narrower. Claim 4 requires the active ester to be specifically the 2,4,5-trichlorophenyl ester.
-
Do salt forms fall under the patent?
Yes. Claim 7 covers pharmaceutically acceptable salts of the claim 6 compound.
-
What is the fastest design-around strategy implied by the claim set?
Use a product where the introduced acyl group does not match the enumerated R structures, or avoid the claimed Echinocandin B amino-acylation.
References
[1] United States Patent 6,384,013.
