Scope, Claims, and US Patent Landscape for Drug Patent US 5,741,512

US 5,741,512 claims oral cyclosporin A formulations built around a composition design that self-emulsifies in water to form an oil-in-water microemulsion with submicron particle sizes. The claim set is dominated by (i) tight compositional percentage ranges for cyclosporin A, a lower alkanol (1-5 carbons), a lipophilic component, and a surfactant (largely polyoxyethylene-based surfactants), and (ii) a functional microemulsion formation requirement upon dilution with water at specified weight ratios, with particle size limits.

This portfolio is not framed as “formulation with any microemulsion,” but as “formulation that forms a microemulsion with specific particle-size targets under specified dilution conditions,” followed by method claims to reduce bioavailability variability and to administer the composition.

What do the claims actually cover? (Claim architecture and what is essential)

1) Independent claim core: composition + microemulsion function

The central claim (Claim 1) is an oral pharmaceutical composition defined by both composition and in-use behavior:

Cyclosporin A: about 5 to about 25 wt%
Hydrophilic component: about 0.5 to about 90 wt%, defined as a lower alkanol with 1 to 5 carbon atoms
Lipophilic component: about 0.5 to about 90 wt%
Surfactant: about 0.5 to about 90 wt%
Functional limitation (critical): upon dilution with water at 1 part composition : 5 parts water (by weight), the mixture spontaneously forms:
- an oil-in-water microemulsion
- with average particle size < about 1,500 Å

From a scope standpoint, this makes the functional particle-size result a gating limitation. A design-around that forms a microemulsion but with a larger droplet size is outside the literal scope if the measured “average particle size” does not meet the threshold.

2) Particle size dependent claim ladder

Claim 2 and 3 create descending particle size bands:

150 to < 1,100 Å (Claim 2)
< 1,000 Å (Claim 3)

This ladder expands coverage to “better-performing” microemulsions while narrowing the measurement requirement.

3) Dilution condition claim branching

Claim 4 changes dilution from the baseline 1:5 to:

1 part composition : 1 part water (by weight)

This matters for scope because the patent is not only about “self-emulsifying,” it is about self-emulsification under explicit dilution ratios.

4) Ingredient-specification branching

Claims include ingredient “species” claims that lock onto certain families:

Lower alkanol as ethanol: Claim 5
Surfactant family: Claim 6 (“polyoxyethylene fatty acid ester”)
Surfactant genus (multiple families): Claim 33
Polyoxyethylene-sorbitan-fatty acid ester species: Claims 34-36

That structure creates a two-tier claim system: 1) generic composition with functional microemulsion constraints (Claims 1, 12, 14, 45, 59, 73), and
2) narrower dependent claims that cover specific formulation choices (ethanol; polyoxyethylene fatty acid esters; polyoxyethylene-sorbitan esters; specific alkyl sorbitan chain-length + PEG number).

5) Method claims are formulation-linked

Claims 12 through 14 and 59 through 64, 73 through 86 (as provided) are method claims tied to administering a composition meeting the same compositional + microemulsion requirements.

Two method variants appear:

Reducing variability of bioavailability during cyclosporin therapy (Claim 12 and Claim 59)
Oral administration method to a patient in need of cyclosporin therapy (Claim 14 and Claim 73)

These method claims are only as broad as the composition limitations they incorporate.

What are the numeric boundaries that define infringement risk?

A) Composition ranges: the “percent-by-weight envelope”

Across independent composition claims, the same envelope repeats:

Component	Range in principal composition claims
Cyclosporin A	5 to 25 wt% (about 5 to about 25)
Hydrophilic component (lower alkanol, 1-5 C)	0.5 to 90 wt%
Lipophilic component	0.5 to 90 wt% (with subranges in dependents, e.g., 2 to 45)
Surfactant	0.5 to 90 wt% (with subranges in dependents, e.g., 20 to 90)
Dilution solvent condition	1:5 (composition:water) for Claim 1 (and related)
Microemulsion formation	oil-in-water microemulsion spontaneously formed

A key practical consequence: if any one ingredient is outside the claimed weight range, or if the formulation does not “spontaneously” form the microemulsion with the specified particle size under the stated dilution, literal infringement becomes harder.

B) Particle size: average vs maximum, and thresholds

Your claim set uses both “average particle size” and “maximum size” in later claim branches.

Claim set element	Particle size language	Threshold
Claim 1 branch	average particle size	< 1,500 Å
Claim 2 branch	average particle size	150 to < 1,100 Å
Claim 3 branch	average particle size	< 1,000 Å
Claim 45 branch	particles less than	< 2,000 Å
Claim 46-47	maximum size	< 1,500 Å and 100 to 1,000 Å

Design-around attention: droplet-size metrics are not interchangeable. A formulation could meet a “maximum < X” criterion while failing “average < Y,” depending on the distribution.

C) Dilution ratio: 1:5 baseline vs 1:1 dependent

Independent/branch	Dilution ratio	Particle size condition
Claim 1 (core) / Claim 12 method	1:5	oil-in-water microemulsion, avg < 1,500 Å
Claim 4 / Claim 17 / Claim 25 / Claim 62 / Claim 76 / Claim 48 etc.	1:1	still anchored to Claim 1’s microemulsion/size framework in those dependents

Because dilution is specified by weight ratio, not volume ratio, the scope is tied to formulation density effects.

What surfactants are expressly inside the claimed space?

A) Surfactant genera explicitly listed

Claim 33 (composition) and parallel method claims list surfactant options:

polyoxyethylene glycolated natural vegetable oil
polyoxyethylene glycolated hydrogenated vegetable oil
polyoxyethylene-sorbitan-fatty acid ester
polyoxyethylene fatty acid ester

Claim 37/41/55/69/83 list the same families for method/composition.

B) Polyoxyethylene-sorbitan-fatty acid ester: species-level coverage

Claim 36 lists specific PEG-sorbitan fatty acid esters:

polyoxyethylene(20)sorbitanmonolaurate
polyoxyethylene(20)sorbitanmonopalmitate
polyoxyethylene(20)sorbitanmonostearate
polyoxyethylene(20)sorbitanmonooleate
polyoxyethylene(20)sorbitantristearate
polyoxyethylene(20)sorbitantrioleate
polyoxyethylene(4)sorbitanmonolaurate
polyoxyethylene(4)sorbitanmonostearate
polyoxyethylene(5)sorbitanmonooleate

These species claims narrow the surfactant identity and materially reduce ambiguity in enforcement.

C) Polyoxyethylene fatty acid ester emphasis

Multiple dependents focus on “polyoxyethylene fatty acid ester” (Claim 6, Claim 50, Claim 78, Claim 64). This stays within the PEG-fatty ester class but does not enumerate every alkyl/PEG number combination in the portion you provided.

What “extra” coverage exists beyond the basic microemulsion composition?

1) Bioavailability variability reduction

Method claims repeatedly tie the oral administration to reducing variability of cyclosporin A bioavailability during therapy (Claim 12, 59). That ties the utility to the microemulsion composition.

2) Composition overlap: same ranges repeat across composition and method claims

Your claim listing shows repetition in:

independent composition (Claim 1 and Claim 45 and Claim 73)
dependent composition particle size/dilution/ingredient species (2-3, 4-6, 45-58, 74-86)
independent method analogs (12, 14, 59, 73)

This repetition suggests the patent is designed to preserve enforceability across both product and use claims.

How broad is the claim in real-world formulation space? (Scope gradients)

1) Broad where identity is generic; narrow where function is strict

Broad: hydrophilic component is “lower alkanol 1-5 C,” giving room for multiple alkanols (ethanol explicitly covered, but not exclusive unless you infer from the claim language).
Narrow: the microemulsion must form spontaneously at a defined dilution ratio and achieve droplet size targets.

2) Broad because ranges are wide; narrow because the microemulsion outcome is not

The compositional ranges allow wide formulation flexibility:

cyclosporin A: 5-25 wt%
hydrophilic component: 0.5-90 wt%
lipophilic component: 0.5-90 wt%
surfactant: 0.5-90 wt%

But the droplet size constraints convert that wide compositional space into a functional boundary. A formulation could be within all weight % bands and still fall outside if the microemulsion formation under water dilution does not yield the required particle size.

3) Measurability is a scope lever

The patent includes:

“average particle size” thresholds (e.g., <1,500 Å; <1,100 Å; <1,000 Å)
and “maximum size” thresholds in the alternate particle-size branch (e.g., <1,500 Å maximum; 100-1,000 Å maximum)

For enforcement and freedom-to-operate, the exact measurement definition and method used to quantify particle size becomes central, because the claims distinguish metrics.

What the “scope map” looks like as claim clusters

Cluster 1: Baseline microemulsion formulation

Composition: Claim 1
Method: Claim 12 and Claim 14
Key constraints: 5-25% cyclosporin A; lower alkanol 1-5 C; oil-in-water microemulsion spontaneously formed at 1:5 dilution; average particle size <1,500 Å

Cluster 2: Particle size refinement (sub-1,100 Å and sub-1,000 Å)

Composition: Claims 2-3
Method: Claims 15-16, 23-24, 31? (as listed)

Cluster 3: Dilution ratio variant

Composition: Claim 4
Method: Claim 17, 25, 62, 76, 48

Cluster 4: Ethanol + PEG surfactant family

Ethanol: Claim 5 (composition) and Claim 18 (method) and Claim 49/77 (composition/method branches)
PEG fatty acid ester: Claims 6, 50, 78, 64, 83? (depending on listing)

Cluster 5: Specific surfactant species

PEG-sorbitan fatty acid ester species enumerated in Claim 36 (composition) and corresponding method dependents (Claims 40, 44, 72, 86)

Cluster 6: “Less than 2,000 Å” alternate particle-size ceiling

Composition: Claim 45 and dependents 46-48
Method: Claim 59 and dependents 60-62

This alternate branch expands coverage to formulations that produce microemulsions under the functional umbrella with less stringent size caps (but still constrained by maxima for some dependents).

Patent landscape: what matters for freedom-to-operate around US 5,741,512

1) Landscape driver is not cyclosporin itself; it is the specific microemulsion architecture

US 5,741,512 is not a claim on cyclosporin A as a molecule; it is a claim on:

an oral composition,
with precise excipient functional classes and weight ranges,
that yields microemulsions with defined droplet sizes under defined dilution conditions.

In a landscape sense, the enforceability threat typically comes from competing “microemulsion-based” cyclosporin oral products that can match both:

excipient architecture (lower alkanol + lipophilic component + PEG surfactant family), and
microemulsion droplet size under water dilution.

2) Expect overlap between product development and “use” claims

Because the patent includes both composition claims and method claims tied to reduced variability, challengers must address both:

product composition design around the microemulsion criteria; and
claimed use for bioavailability variability.

In practice, “use” claims are harder to evade if you sell a product whose administration inherently meets the claimed composition limits.

3) The explicit surfactant enumerations reduce uncertainty

Enumerated surfactants (PEG(20)sorbitan monolaurate, etc.) create clearer infringement vectors. If a formulation uses those exact surfactant species and meets the microemulsion behavior and particle size conditions, the claim set is comparatively easier to map.

Design-around and risk-reduction levers implicit in the claim language

Levers that can avoid literal infringement

Change the dilution ratio so that under water dilution the system does not “spontaneously form” the required oil-in-water microemulsion with the claimed droplet size/average size.
Shift droplet size distribution so the formulation’s measured “average particle size” or “maximum size” exceeds the claimed thresholds (for the applicable claim branch).
Replace the surfactant family/species so it falls outside the expressly covered polyoxyethylene fatty acid ester and PEG-sorbitan-fatty acid ester selections (unless equivalent is argued in doctrine-of-equivalents analysis).
Use a hydrophilic component not limited to lower alkanols 1-5 C (the claim defines this component as the lower alkanol with from one to five carbon atoms).
Move cyclosporin A content outside 5-25 wt% (if the product is formulated around different strength levels).

Where “equivalents” may still create exposure

Even if you change one excipient within the surrounding classes, the functional constraints (microemulsion formation and droplet size upon dilution at defined ratios) remain the biggest enforcement hook. If the alternative formulation is engineered to reproduce the same microemulsion performance, the risk stays high.

Key Takeaways

US 5,741,512 claims oral cyclosporin A compositions that, upon water dilution at 1:5 by weight, spontaneously form an oil-in-water microemulsion with average particle size < 1,500 Å, plus dependent claim variations down to <1,100 Å and <1,000 Å.
The scope is defined by both (i) wide excipient weight ranges (cyclosporin A 5-25 wt%, lower alkanol 1-5 C hydrophile 0.5-90 wt%, lipophilic 0.5-90 wt%, surfactant 0.5-90 wt%) and (ii) a functional microemulsion particle-size outcome under specified dilution conditions.
Dependent claims narrow onto ethanol and PEG-based surfactant families, including explicitly listed polyoxyethylene-sorbitan-fatty acid ester species (PEG(20) and PEG(4)/(5) sorbitan fatty esters across multiple fatty acid chain types).
The patent adds method-of-use claims to reduce bioavailability variability and to administer the composition, so product design that matches the composition and microemulsion criteria typically carries method exposure too.
The principal freedom-to-operate lever is not cyclosporin A content alone; it is whether an alternative formulation reproduces the claimed microemulsion droplet-size performance under the claimed dilution ratios using excipient families outside the enumerated surfactant species.

FAQs

1) Does the patent require the microemulsion to form without energy input?

Yes. The claims require the microemulsion to be “spontaneously formed” upon dilution with water at the specified ratios.

2) What is the key droplet-size parameter used in the broadest claim set?

The broadest composition claim (Claim 1) uses average particle size with a threshold of less than about 1,500 Å after dilution at 1:5 (composition:water by weight).

3) Are ethanol and specific PEG-sorbitan esters optional or required?

In the broadest claims, the hydrophilic component is any lower alkanol (1-5 carbons), but dependent claims expressly require ethanol and expressly cover particular polyoxyethylene-sorbitan-fatty acid ester species.

4) What changes in the alternate branch that references particles less than 2,000 Å?

The independent branch (Claim 45) uses a higher ceiling (particles less than 2,000 Å) and then introduces dependents with maximum size limits (such as <1,500 Å and 100-1,000 Å).

5) Do method claims protect against competitors selling a matching formulation?

They protect against oral administration of a composition meeting the claimed microemulsion criteria, including use aimed at reducing bioavailability variability, so a matching product can create both composition and method exposure.

References (APA)

[1] US Patent No. 5,741,512. (n.d.). Oral pharmaceutical compositions of cyclosporin A forming microemulsions upon dilution. United States Patent and Trademark Office.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	8821754	Sep 16, 1988
United Kingdom	8902900	Feb 09, 1989
United Kingdom	8902903	Feb 09, 1989

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	403435	⤷ Start Trial
Austria	A214289	⤷ Start Trial
Australia	4140089	⤷ Start Trial
Australia	627220	⤷ Start Trial
Belgium	1003105	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 5,741,512