United States Patent 6,579,968: Scope, Claims, and US Patent Landscape for Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH

What does US 6,579,968 claim, in plain claim-scope terms?

US 6,579,968 is an implied small-molecule style “single peptide” patent that centers on one specific cyclic peptide scaffold and locks the protected subject matter to that peptide (and its salts) in three core buckets: (1) the peptide itself, (2) a composition-of-matter that includes the peptide plus a carrier, and (3) an asserted therapeutic use for stimulating sexual response in a mammal via a pharmaceutical composition.

The independent claim set is effectively claims 1 and 3 (and then use-form claims 6 and 7). The remaining claims are dependent claim recitations that narrow the peptide to a single defined sequence and specify a buffered aqueous carrier.

Claim inventory (as provided)

Claim	Claim type	Protected subject matter (as written)
1	Composition (peptide)	A peptide selected from: Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH and its pharmaceutically acceptable salts
2	Narrowing	Peptide consists of Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH
3	Composition of matter	A composition comprising a peptide + pharmaceutically acceptable carrier, where peptide is limited to the same peptide or its pharmaceutically acceptable salts
4	Narrowing	Carrier composition where peptide consists of Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH (as recited)
5	Narrowing	Claim 3 where carrier is buffered aqueous
6	Use (therapeutic)	A pharmaceutical composition for stimulating sexual response in a mammal comprising peptide + pharmaceutically acceptable carrier, peptide limited to the same peptide or its salts
7	Narrowing	Claim 6 where peptide consists of Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH

Key practical effect: the patent’s claim language is structurally tight. It does not claim broader “class” peptides by formula or by functional similarity. It claims one defined cyclic peptide (plus salts) and compositions that include that peptide, including a buffered aqueous formulation.

What is the actual scope of “the peptide” (claims 1 and 2)?

Structural lock-in

Claim 1 covers:

The exact cyclic peptide: Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH
Plus pharmaceutically acceptable salts of that peptide

Claim 2 narrows to:

The peptide “consists of” the same exact sequence

Legal scope consequences for design-around

Because the claims are sequence-specific, many common peptide variations will likely fall outside literal scope:

Substitution at any position within the peptide sequence (Asp, His, D-Phe, Arg, Trp, Lys) changes the sequence and typically avoids literal infringement.
Changing the N-terminal capping group “Ac-” or the identity of “Nle” (norleucine) changes the sequence.
Altering the cyclic constraint (the “cyclo(-…-)” ring content) changes the defined cyclic structure.
Salts: the patent expressly covers “pharmaceutically acceptable salts” of the same peptide, so salt-form changes are not a likely carve-out unless the new salt is not “pharmaceutically acceptable” (and that is fact- and evidence-sensitive in enforcement).

Net claim coverage: strong literal protection for that one peptide sequence and its salts, weaker coverage for anything outside the exact sequence.

What is covered as “composition of matter” (claims 3, 4, 5)?

Claim 3: peptide + carrier is the essence

Claim 3 covers:

A composition of matter that includes a peptide and a pharmaceutically acceptable carrier
The peptide is limited to: the claimed peptide (or its pharmaceutically acceptable salts)

Claim 4 narrows to:

The peptide consists of the exact sequence

Claim 5 narrows further to:

Carrier is a buffered aqueous carrier

What this means for formulation risk

If a competitor commercializes a formulation that uses this exact peptide in any pharmaceutically acceptable carrier, claim 3 creates direct formulation infringement exposure.
Even if the carrier is changed from buffered aqueous to a different carrier type, claim 3 still applies as long as the carrier is “pharmaceutically acceptable.”
Buffered aqueous formulations raise the risk even further because claim 5 adds a dependent claim that is easier to map to typical peptide liquid formulations.

Net composition scope: broad across carrier types, with buffered aqueous explicitly covered.

What therapeutic “use” is claimed (claims 6 and 7)?

Claim 6: use for sexual response stimulation

Claim 6 covers a pharmaceutical composition for “stimulating sexual response in a mammal” with:

peptide + pharmaceutically acceptable carrier
peptide limited to the same peptide or its salts

Claim 7 narrows the peptide to the exact sequence.

Enforcement relevance: product intent vs. function

Use claims typically focus on the therapeutic indication. In practice, for enforcement:

A product label, clinical indications, marketing claims, and prescribing information can all matter.
Even where a formulation is structurally identical to a covered composition, a “use” claim is often asserted only when the accused product is sold or used for the stated therapeutic purpose.

Net use scope: the therapeutic framing is limited to sexual response stimulation. A competitor using the same peptide in a different indication still faces structural and composition exposure (claims 3/5), but claim 6 adds an indication-specific lever.

What is the claim architecture and what does it prioritize?

The independent-ish coverage pattern is consistent across peptide, composition, and therapeutic composition.

Feature	Claim(s)	Protection emphasis
Exact peptide identity	1, 2	Sequence-specific chemical protection
Carrier formulations	3, 4, 5	Composition-of-matter coverage that maps to product formulations
Indication	6, 7	Therapeutic use for sexual response stimulation

No “broad genus” protection

There is no claim that covers:

peptide analogs generally,
cyclic peptides “having” the same ring or similar activity,
peptides differing by conservative substitutions,
or salts specifically defined by any salt chemistry beyond “pharmaceutically acceptable.”

That matters for the patent landscape because it tends to shift “freedom-to-operate” outcomes to one of two tracks: 1) exact peptide use (high infringement likelihood), 2) analog discovery and substitution (lower literal risk).

How does the patent likely sit in the US patent landscape for similar peptides?

Without the patent’s full specification, priority chain, prosecution history, and cited references, the landscape can only be mapped at the claim-theme level: a single cyclic peptide sequence used as a sexual response stimulant. This type of patent typically clusters into three neighboring technical zones:

1) Peptide identity and sequence variants
Competitors often file on analogs that alter one or more residues (including D-amino acid swaps, stereochemistry changes, N-terminal capping changes, ring composition changes) while retaining cyclic topology and receptor affinity.

2) Formulation technologies
Because claim 3/5 capture carrier types broadly and buffered aqueous specifically, formulators often pursue:

different solvent systems,
alternative delivery formats (injectables with different excipients, solid forms, sustained-release systems),
or peptides not covered by the exact sequence.

3) Indication expansion and new therapeutic contexts
Even if a peptide is structurally narrow, there is often follow-on patenting around:

new dosing regimens,
new route(s) of administration,
and new indications tied to the same mechanism.

Practical landscape signal

If US 6,579,968 is centered on a specific sequence, then the competitive field typically becomes a “sequence competition” market rather than a “carrier competition” market. Competitors can reduce patent risk by changing sequence identity while building data on sexual response efficacy through the mechanism.

What are the main claim-to-market infringement scenarios?

Scenario	Likely covered by US 6,579,968?	Why
Product contains the exact peptide (or pharmaceutically acceptable salts) in any pharmaceutically acceptable carrier	Yes (claims 1 and 3)	Direct peptide identity + composition-of-matter mapping
Same peptide in buffered aqueous formulation	Yes (claims 1, 3, 5)	Dependent claim 5 tightens buffered aqueous case
Same peptide used for stimulating sexual response in a mammal	Yes (claims 1, 6, 7)	Use claim 6 ties to therapeutic purpose
Peptide analog with 1 residue changed	Usually no (literal)	Claim language is sequence-specific
Same analog but framed as “pharmaceutically acceptable salt”	Usually no (literal)	Salts do not fix a sequence change
Same peptide but in a different therapeutic indication only	Still likely yes for composition claims	Claims 3/5 cover composition irrespective of indication; claim 6 adds indication-specific leverage

Freedom-to-operate: where infringement risk is highest vs lowest

Highest infringement risk

Commercializing a formulation containing Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH (or a covered salt).
Using it in sexual response indication marketing that aligns with claim 6.
Using buffered aqueous formulations containing the peptide.

Lower infringement risk

Changing the sequence so it no longer “consists of” the claimed sequence.
Substituting different cyclic scaffolds or altering ring composition.
Using a different peptide entirely, even if it is pharmacologically similar.

Key takeaways

US 6,579,968 is sequence-specific. It protects one cyclic peptide identity: Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH and its pharmaceutically acceptable salts.
Claim scope spans peptide, formulation, and indication. It covers (1) the peptide itself (claims 1-2), (2) compositions of matter with pharmaceutically acceptable carriers including buffered aqueous (claims 3-5), and (3) pharmaceutical compositions for stimulating sexual response in a mammal (claims 6-7).
Design-around is likely sequence-based, not formulation-based. Carrier changes generally do not avoid claim 3; buffered aqueous is explicitly covered via claim 5.
Landscape implications point to analog patenting. Competitors typically reduce risk by changing one or more residues, stereocenters, capping group, or ring composition while pursuing similar sexual response activity.

FAQs

1. Does US 6,579,968 claim a class of cyclic peptides or only one peptide?
It claims one peptide sequence: Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH plus pharmaceutically acceptable salts.

2. If a competitor uses the same peptide but a different carrier than buffered aqueous, is it still covered?
Yes. Claim 3 covers a pharmaceutically acceptable carrier generally; buffered aqueous is only a dependent narrowing in claim 5.

3. Is the “sexual response” language required for infringement of composition claims?
Not for claims 3/5 because those are composition-of-matter claims. Claim 6 adds an indication-specific use layer.

4. Do “pharmaceutically acceptable salts” broaden protection beyond the peptide structure?
Yes, but only for salts of the same peptide. A salt form does not substitute for changing the peptide sequence.

5. What is the most direct design-around lever?
Altering the peptide so it no longer “consists of” the exact claimed sequence (including changes to residues, stereochemistry, N-terminal capping, or cyclic ring composition).

References

[1] United States Patent 6,579,968 (claims as provided by user).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	293453	⤷ Start Trial
Australia	2002322466	⤷ Start Trial
Australia	2005249474	⤷ Start Trial
Australia	2005269831	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,579,968

Summary for Patent: 6,579,968