United States Patent 4,517,199: Scope, Claim Strength, and Landscape for Topical Intraocular Pressure Lowering Agents

US Drug Patent 4,517,199 is directed to a topical ocular method for lowering intraocular pressure (IOP) using 2-(trisubstituted phenylimino)-imidazoline derivatives (or pharmaceutically acceptable salts). The independent claim is a method-of-use claim that is constrained by (i) drug structure/formula and (ii) a functional requirement: IOP lowering with CNS sparing at selected concentrations.

What is the core claim scope?

Independent claim 1

Claim 1 covers a method of:

Topical application to the eye of an effective amount for lowering IOP
of a compound defined as 2-(trisubstituted phenylimino)-imidazoline or pharmaceutically acceptable salt
having the formula (rendered in the patent as a structure with variable substituents)
where the substituent sets are defined by one of three regimes: I, II, or III
with a negative structural exclusion under regime III

The claim language is built around a substituent-definition scaffold that is meant to capture a family of analogs rather than a single molecule.

Substituent regimes I, II, III (structural boundaries)

The claim defines allowed variability through the following constraints (as provided in the claim text):

Regime I

R1 = R2 and each can be: methyl, ethyl, trifluoromethyl, chloro, bromo
R1 ≠ R2, and then each = methyl, ethyl, trifluoromethyl, fluoro, chloro, bromo
One of R3 and R4 is H and the other is selected from a marked substituent set (formula shown in claim text)
Substituent constraints include:
- R5 ≠ R6 = H or lower alkyl
- either R5 = R6 and each = H, lower alkyl
- R7 = H with selected allowed options for lower alkyl and hydroxylated alkyl groups:
- lower alkyl
- 2-hydroxyethyl
- 2-hydroxypropyl
- 3-hydroxypropyl
- and constraints on carbon count: the sum of carbon atoms in R5 and R6 or R5 and R7 is 4 or less
- and another optional aryl/alkyl motif for the substituent selection (formula shown in the claim)
R8 = lower alkyl

Regime II

R1 can be methyl, ethyl, trifluoromethyl, chloro, bromo
R2 = H
R3 is selected from a marked substituent set
R4 can be methyl, chloro, bromo
R9 = H or lower alkyl
R10 = H, lower alkyl, 2-hydroxymethyl, 2-hydroxypropyl, or 3-hydroxypropyl
with carbon count constraint:
- sum of carbon atoms in R9 and R10 is 4 or less

Regime III (explicit exclusion)

Claim 1 includes a hard negative limitation:
- “In no event shall said 2-(trisubstituted phenylimino)-imidazoline have the formula:” followed by a specific excluded structure (rendered in the claim text as STR68).

This third regime is typically used to avoid capturing a known compound or a family member excluded from the intended proprietary coverage.

What does “effective amount” cover?

Claim 1 uses a functional exposure: an “effective amount for lowering such intraocular pressure.” In US practice, this typically means the amount that produces the claimed functional effect, while the subsequent dependent claim 3 narrows dosing by CNS impact.

How is topical ocular delivery defined?

Dependent claim 2

Claim 2 narrows claim 1 by requiring:

topical application to the eye
in a pharmaceutically acceptable vehicle

This adds a formulation dimension that can matter in infringement and design-around (vehicle choices typically do not defeat a method-of-use claim unless the vehicle prevents administration or effective delivery).

How does claim 3 narrow concentration and safety?

Dependent claim 3

Claim 3 specifies:

the concentration is selected so that:
- IOP is reduced
- without significantly affecting the central nervous system

This is the major functional safety constraint. It does not define a numerical concentration in the provided claim text, but it introduces a measurable endpoint:

CNS effect must be absent or not significant relative to a baseline (as the patent would define in the specification).

For enforcement and product freedom-to-operate, claim 3 effectively turns the patent from “any concentration that lowers IOP” into “a concentration range/level that lowers IOP without significant CNS impact.”

Which specific compounds are explicitly claimed in dependent claims?

Dependent claims 4 through 14 list specific embodiments. These are not just examples; they are written as alternatives that each independently satisfy claim 3’s concentration constraint.

Enumerated compounds in claims 4-14

Claim	Specific “2-(trisubstituted phenylimino)-imidazoline” species	Claim text description
4	2,6-Dichloro-N1-(2-imidazolidinylidene)-1,4-benzenediamine (or salt)	structure labeled STR69
5	2,6-Dichloro-N1-(2-imidazolidinylidene)-1,3-benzenediamine (or salt)	structure labeled STR70
6	2,6-Diethyl-N1-(2-imidazolidinylidene)-1,4-benzenediamine (or salt)	structure labeled STR71
7	N-[3,5-Diethyl-4-(2-imidazolidinyleneamino)-phenyl]-acetamide (or salt)	structure labeled STR72
8	3,5-Dichloro-4-(2-imidazolidinylideneamino)-phenol and esters (or salt)	structure labeled STR73
9	3-chloro-5-methyl-4-(2-imidazolidinylideneamino)-benzoic acid ethyl ester (or salt)	structure labeled STR74
10	3-chloro-5-ethyl-4-(2-imidazolidinylideneamino)-benzoic acid ethyl ester (or salt)	structure labeled STR75
11	N-[3-chloro-5-methyl-4-(2-imidazolidinylideneamino)-phenyl]-acetamide (or salt)	structure labeled STR76
12	2-chloro-6-methyl-N1-(2-imidazolidinylidene)-1,4-benzenediamine (or salt)	structure labeled STR77
13	2-chloro-6-ethyl-N1-(2-imidazolidinylidene)-1,4-benzenediamine (or salt)	structure labeled STR78
14	3-chloro-5-methyl-4-(2-imidazolidinylideneamino)-benzenecarboxamide (or salt)	structure labeled STR79

Practical significance of these dependent claims

The dependent claim set functions as:

Anchor species: clear reference points for compound identity and enforceable subject matter
Species expansion: the base claim 1 already covers a broader genus, while these claims also lock down at least some specific analogs that fall within the genus definition

What is the likely patent landscape shape around this patent?

With only the claim text provided, a full cross-patent mapping (other US patents, priority chain, family members, prosecution history, and citation network) cannot be reconstructed into a defensible “who owns what” landscape. Under strict analysis rules, only the following landscape conclusions can be stated from the claim itself.

Landscape signals embedded in the claim

The structure-function approach suggests the patent was built to protect:

a genus of imidazoline-based compounds for ocular IOP reduction
delivered topically
at concentrations that are CNS-sparing

This implies competitor risk concentrates in:

imidazoline phenylimino analogs
with permitted halogen/alkyl/hydroxylated substituents matching regimes I and II
administered as ophthalmic formulations
and dosed to achieve the IOP effect without significant CNS effects

Where competitors can push design-around (claim-text based)

From the wording alone, design-around options cluster into three buckets:

Structural non-infringement
- using substitutions that fall outside regimes I and II
- or into the excluded structure referenced in regime III
Route or delivery non-infringement
- changing from topical ocular administration to an alternative route would break the method elements of claims 1 and 2
Safety endpoint non-infringement
- the concentration must be selected so that IOP decreases without significant CNS effect. A competitor could aim for:
  - lower ocular efficacy and different CNS exposure profile, or
  - a different concentration regime that does not satisfy claim 3’s condition
- In litigation, this turns on how “significantly affecting the CNS” is interpreted against the patent’s disclosure.

Claim-by-claim strength assessment (based strictly on claim structure)

Claim 1 (genus method)

Strength driver: Broad genus definition tied to chemical substituent variables and a functional IOPlowering result.
Vulnerability: Genus boundaries rely on complex substituent rules and the regime III exclusion. A careful structural comparison can defeat coverage even where the compound is functionally similar.

Claim 2 (vehicle)

Strength driver: Adds formulation element.
Vulnerability: Vehicles are usually broad; many ophthalmic formulations will be “pharmaceutically acceptable,” so this claim often does not limit much in practice unless an alternative vehicle disqualifies topical administration or effective delivery.

Claim 3 (CNS sparing concentration)

Strength driver: Adds a safety-limiting functional constraint that can differentiate dosing regimens.
Vulnerability: “Significantly affecting the CNS” is inherently comparative and test-dependent. Still, it is a real limiter for infringement analysis because method claims often require all elements, including concentration selection.

Claims 4-14 (specific compounds)

Strength driver: Species coverage provides clear, enforceable embodiments.
Vulnerability: If a competitor stays outside each enumerated species and also outside the genus boundaries, these dependent claims are less relevant.

Operational guidance for R&D and portfolio work

Given the structure of claims 1 and 3, the key compliance questions for any candidate asset are:

Does the compound meet the 2-(trisubstituted phenylimino)-imidazoline formula boundary?
Is administration topical to the eye?
Is the dosing regimen selected such that IOP decreases without significant CNS effect?

The most defensible way to reduce risk is structural scoping against regimes I/II/III, plus a dosing plan that does not meet the CNS-sparing limitation as construed through the patent’s internal testing definitions.

Key Takeaways

US 4,517,199 is a topical ocular method-of-use patent centered on 2-(trisubstituted phenylimino)-imidazoline compounds and IOP lowering.
The independent claim uses a genus chemical definition with three allowed regimes and an explicit excluded structure (regime III).
The main narrowing element is claim 3, requiring a concentration that reduces IOP without significantly affecting the CNS.
Dependent claims 4-14 explicitly list multiple species (dichloro/diethyl/alkyl-amide/phenol-ester/benzendiamine and related analogs) that sit within the claimed genus.

FAQs

Is this patent compound-focused or method-focused?
It is primarily a method-of-use claim: topical ocular administration of the specified compound family to lower IOP.
What is the biggest limiter on claim scope?
Claim 3: the method requires a concentration selected to lower IOP without significantly affecting the CNS.
Do dependent claims change the route of administration?
No. Claims 2-14 stay within topical application to the eye, with vehicle (claim 2) and concentration/CNS constraint (claim 3).
Can competitors avoid infringement by changing the vehicle?
Vehicle alone is unlikely to avoid claims 1-3 if the administration is still topical ocular and effective. Claim 2 requires a pharmaceutically acceptable vehicle.
Does the patent cover only one chemical entity?
No. It covers a defined genus in claim 1 and also lists multiple specific species in claims 4-14.

References

[1] United States Patent 4,517,199. “Method for lowering intraocular pressure using 2-(trisubstituted phenylimino)-imidazoline derivatives.” Claims 1-14 (as provided in user prompt).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0081924	⤷ Start Trial	SPC/GB93/103	United Kingdom	⤷ Start Trial
Austria	18006	⤷ Start Trial
Canada	1194418	⤷ Start Trial
Canada	1201066	⤷ Start Trial
Germany	3269242	⤷ Start Trial
Japan	H0453846	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,517,199

Summary for Patent: 4,517,199