United States Patent 6,013,657 (US6013657): Scope, Claim Construction, and Patent Landscape

US 6,013,657 claims a chemically stable mupirocin composition in specific lipophilic carriers (castor oil, oleyl alcohol, or mixtures), with optional inclusion of a pharmaceutically acceptable base and defined classes of surfactant additives. The claim set is primarily directed to formulation scope (carrier selection, optional base type, optional surfactant chemistry), with limited claim coverage around dosing form as “drop formulation.”

What is the core inventive scope?

The patent’s claim scope centers on four linked formulation knobs:

Active: mupirocin at a “therapeutically effective amount,” including a numeric embodiment in claim 12 (1-5%).
Carrier system: one of:
- oleyl alcohol
- castor oil
- mixture of castor oil and oleyl alcohol
Optional formulation matrix/base: a “pharmaceutically acceptable base,” further exemplified as a “hard fat ointment base” with defined hard fat range (10-90%).
Optional surfactant/additive chemistry:
- hydrophobic and/or hydrophilic surfactants
- hydrophobic surfactant specifically: propylene glycol stearate
- hydrophilic surfactant specifically: sucrose ester, including sucrose stearate/palmitate/oleate/myristate

The scope is formulation-defined, not mechanism-of-action-defined. It does not claim new mupirocin molecules or new therapeutic indications in the text provided; it claims stable formulations.

How are the independent and dependent claims layered?

Claim 1 (independent): chemically stable mupirocin composition in defined carriers

Claim 1 defines the broadest composition set:

Composition: “chemically stable”
Drug: mupirocin at therapeutically effective amount
Carrier: selected from oleyl alcohol, castor oil, or mixture thereof
Optional: pharmaceutically acceptable base

Claim 1 is the backbone. If a competitor uses a different carrier, or if it avoids “carrier selected from” the specified list, it falls outside claim 1 even if it uses the same active and still reports stability.

Claims 2 and 3: expand to optional additives and surfactant classes

Claim 2: adds optional other pharmaceutically acceptable additives.
Claim 3: limits that class to hydrophobic and/or hydrophilic surfactants (when surfactant additives are used).

This creates a conditional expansion. Claim 2 is additive without chemistry restriction; claim 3 is additive with chemistry constraint to surfactant functionality.

Claims 4-6: specify particular surfactant exemplars and a sucrose ester sub-family

Claim 4: hydrophobic surfactant = propylene glycol stearate
Claim 5: hydrophilic surfactant = a sucrose ester
Claim 6: the sucrose ester is selected from:
- sucrose stearate
- sucrose palmitate
- sucrose oleate
- sucrose myristate

This is narrower than claim 3 because it anchors hydrophobic/hydrophilic selection to named chemical entities and a defined sucrose ester sub-family.

Claims 7-9: quantify carrier proportions and capture mixtures

Claim 7: castor oil content 1 to 99%
Claim 8: oleyl alcohol content 1 to 99%
Claim 9: explicitly claims “mixture of castor oil and oleyl alcohol”

Claims 7 and 8 effectively cover almost any blend within those bounds, and they support breadth arguments for mixed-carrier products.

Claims 10-11: constrain optional base to hard-fat ointment base

Claim 10: base = “hard fat ointment base”
Claim 11: hard fat concentration 10% to 90%

These depend on claim 1 and only apply if a base is present and fits the hard-fat ointment base definition.

Claim 12: a dosage-form-specific “drop formulation” embodiment

“A drop formulation according to claim 1”
Mupirocin 1-5% dissolved in castor oil

This claim narrows further by requiring:

a “drop formulation”
dissolution in castor oil specifically (not oleyl alcohol or mixture as written)

Claim 12 is a strong handle for ophthalmic/otic drop-like products formulated with mupirocin in castor oil at 1-5%.

What is the practical claim coverage versus design-around levers?

Coverage targets (what competitors would likely need to avoid)

A product is high risk if it meets these elements concurrently:

Mupirocin + carrier from {oleyl alcohol, castor oil, castor oil/oleyl alcohol mixtures}
“Chemically stable” formulation characterization (wording in the claim)
If surfactants are used, and particularly if:
- hydrophobic surfactant is propylene glycol stearate, and/or
- hydrophilic surfactant is a sucrose ester from the named group
If an ointment base is used, and it is a hard fat ointment base with hard fat at 10-90%
If marketed as drops, and it is a drop formulation with 1-5% mupirocin dissolved in castor oil

Most direct design-around levers (structurally)

To avoid claim 1 and its descendants, a design-around typically must break at least one of these required anchors:

Carrier substitution: use a carrier system not listed in claim 1.
Surfactant substitution: if surfactants are used, avoid:
- propylene glycol stearate (for the hydrophobic surfactant slot), and
- sucrose esters from the specified list for the hydrophilic slot.
Base type and concentration: if an ointment base is used, avoid a “hard fat ointment base” or avoid a hard fat fraction of 10-90%.
Drop form constraint: avoid a “drop formulation” and/or avoid “mupirocin dissolved in castor oil” at 1-5%.

Claim-by-claim scope map (as provided)

Claim	Required elements	Carrier / additive constraints that narrow risk
1	Chemically stable composition; therapeutically effective mupirocin; carrier is oleyl alcohol or castor oil or mixture; base optional	Carrier is the core limiter
2	Claim 1 + other pharmaceutically acceptable additives (optional)	No chemistry restriction
3	Claim 2 + additives are hydrophobic and/or hydrophilic surfactants	Limits additive class to surfactants
4	Claim 3 + hydrophobic surfactant = propylene glycol stearate	Exact named hydrophobic surfactant
5	Claim 3 + hydrophilic surfactant = sucrose ester	Exact hydrophilic class
6	Claim 5 + sucrose ester is one of sucrose stearate/palmitate/oleate/myristate	Exact named sucrose ester options
7	Claim 1 + castor oil content 1-99%	Quantified castor oil content
8	Claim 1 + oleyl alcohol content 1-99%	Quantified oleyl alcohol content
9	Claim 1 + mixture of castor oil and oleyl alcohol	Confirms mixed-carrier coverage
10	Claim 1 + base = hard fat ointment base	Base category is constrained
11	Claim 10 + hard fat concentration 10-90%	Numeric concentration for hard fat
12	Claim 1 + drop formulation + 1-5% mupirocin dissolved in castor oil	Dosage form + dissolution carrier + numeric API range

How strong is the claim breadth for market surveillance and freedom-to-operate?

Breadth in carrier selection

Claim 1’s carrier selection is a compact but powerful list. It covers:

pure oleyl alcohol
pure castor oil
any mixture between them, because claims 7-9 support “almost any proportion” framing (1-99%) for each component.

This means a large fraction of “lipid-based ointment” or “oil-based topical formulations” could map into the claim set if they are built around those excipients and present as chemically stable.

Breadth in optional base

“Pharmaceutically acceptable base” in claim 1 is open-ended. Claim 10 narrows to a hard fat ointment base, but claim 1 does not require that narrower base type.

So the broad risk path remains claim 1 even if a competitor uses a non-hard-fat base, as long as the carrier still matches the specified oils/alcohol.

Breadth in surfactant scope

Surfactants are only optional. Claim 3 narrows by surfactant class, but claim 1 does not require any surfactant at all. That makes surfactant changes less effective for avoiding claim 1, unless they also change carrier or otherwise break another required element.

Strength of the drop-embodiment claim

Claim 12 is narrower but provides clear coverage for topical or mucosal “drop” presentations where:

mupirocin is 1-5%
dissolved in castor oil

If the product line includes any drop format, claim 12 becomes a key target for competitive formulation teams.

What does this imply for competitor formulation strategy?

High-level decision rule: if a competitor wants to stay in the vicinity of mupirocin topical stability using lipids, claim 1 will likely be the controlling constraint. The formulation team will typically need to shift away from the carrier anchors.

Common ways to reduce risk (conceptually aligned to claim structure):

use different solvents/oils than castor oil and oleyl alcohol (carrier substitution)
avoid formulations that can be characterized as “drop formulations” with mupirocin 1-5% dissolved in castor oil
if using surfactants, avoid the named sucrose ester family and propylene glycol stearate, but do not treat surfactant-only changes as sufficient to avoid claim 1

Patent landscape signals (based on claim structure)

Because only claim text is provided (no bibliographic metadata, family members, prosecution history, cited references, or jurisdictional equivalents), the landscape can be characterized only at the level of what this patent is likely trying to own, and where later patents typically crowd.

Landscape segmentation by formulation element

Carrier-centered reformulations
- Patents in this segment usually compete by switching excipient oils/alcohols to claim different stability systems.
- US 6,013,657 is directly anchored to castor oil and oleyl alcohol carriers; that creates a measurable “avoid list” for later entrants.
Surfactant and solubilizer refinement
- The explicit inclusion of propylene glycol stearate and sucrose esters signals that stability and compatibility are expected to benefit from these specific stabilizer systems.
- Later patents often try to claim alternative surfactants to escape the dependent claim coverage.
Dosage-form embodiments
- Claim 12’s “drop formulation” shows the patent set tries to cover a specific market presentation.
- Later entrants can attempt to avoid “drop” characterization by repositioning presentation, though claim interpretation can still turn on functional/physicochemical reality.

Landscape competition pattern to expect

Given this claim style, the competitive set most likely includes:

formulation patents for mupirocin stability using other excipient systems
ophthalmic or nasal/aural drop formulation patents using alternative solubilizers and vehicles
ointment base patents that avoid “hard fat ointment base” or change hard fat fraction, if they still want to use hard fats

Where are the main claim vulnerabilities for enforcement and validity analysis?

From the claim wording alone:

“Chemically stable composition” is a functional property
- Stability is a claim limitation. The claim scope depends on whether the formulation is chemically stable versus the baseline.
- Enforcement often turns on stability testing methodology and thresholds. A competitor can try to challenge stability evidence.
Carrier list is the primary gate
- If a product uses alternative carriers, claim 1 does not attach.
- That makes carrier selection the most visible vulnerability for both enforcement and invalidity arguments.
Dependent claims restrict to named surfactants
- Claims 4-6 require specific surfactants. If competitors use different solubilizers (even if surfactants are hydrophilic/hydrophobic), these dependent claims do not map.

Key takeaways

US 6,013,657 owns mupirocin chemical-stability formulation space built on carriers selected from castor oil, oleyl alcohol, or their mixtures. Carrier selection is the central enforceable hook.
Surfactants are optional but, when used, the patent specifies propylene glycol stearate (hydrophobic) and sucrose esters (hydrophilic) including sucrose stearate/palmitate/oleate/myristate.
If a hard fat ointment base is used, it is constrained to 10-90% hard fat in the dependent claim set.
The drop-formulation embodiment is explicit: 1-5% mupirocin dissolved in castor oil. This is a high-signal coverage claim for drop products.
For design-around, the most direct lever is carrier substitution, not surfactant tweaking. Surfactant substitution mainly affects dependent claim coverage (claims 3-6), while claim 1 remains carrier-driven.

FAQs

1. Does claim 1 require a specific dosage form (ointment, cream, drops)?
No. Claim 1 is a composition claim. The “drop formulation” requirement appears only in claim 12.

2. If a product uses mupirocin at 1-5% in castor oil but does not market it as drops, is claim 12 still in play?
Claim 12 requires “drop formulation.” Whether a product is considered a drop formulation can depend on product characteristics and presentation, but the claim text itself narrows to that dosage form category.

3. Can a formulation avoid dependent claims 4-6 by using different surfactants while still using castor oil or oleyl alcohol carriers?
Yes for those dependent claims only. Claim 1 still applies if the carrier is within {oleyl alcohol, castor oil, mixture} and the composition is chemically stable with therapeutically effective mupirocin.

4. Are castor oil and oleyl alcohol covered only in pure form or also in mixtures?
Both. Claim 1 covers either single-carrier options and “mixture thereof,” and claims 7-9 quantify carrier proportions and explicitly claim mixed systems.

5. What excipient restriction does claim 10 impose on optional bases?
It restricts the optional base (when used in the dependent path) to a “hard fat ointment base,” with hard fat concentration constrained to 10-90% in claim 11.

References

[1] United States Patent 6,013,657. “Chemically stable mupirocin compositions.” Claims as provided in the prompt.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Israel	123143	Feb 02, 1998

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	2259764	⤷ Start Trial
Germany	69900561	⤷ Start Trial
European Patent Office	0933081	⤷ Start Trial
Spain	2165723	⤷ Start Trial
Israel	123143	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,013,657

Summary for Patent: 6,013,657