United States Patent 5,296,504: Scope, Claim Coverage, and US Landscape for Topical Ocular PGF2α Isopropyl Ester
US Patent 5,296,504 claims topical ophthalmic formulations and treatment methods built around a specific prostaglandin analog: 13,14-dihydro-17-phenyl-18,19,20-trinor PGF2α isopropyl ester, delivered in an ophthalmologically compatible vehicle and dosed to reduce intraocular pressure while avoiding substantial ocular irritation.
What is the claimed technology?
The patent’s core invention is a two-part construct:
- Active: 13,14-dihydro-17-phenyl-18,19,20-trinor PGF2α isopropyl ester
- Ocular delivery system: an ophthalmologically compatible vehicle, optionally including:
- a solubilizing agent (claims 2, 10)
- an aqueous saline solution containing benzalkonium chloride (claims 3, 11)
The claims then lock in indication scope (ocular hypertension and glaucoma) and usage scope (topical treatment methods with defined dosing ranges and application frequency).
What exactly do the claims cover?
Independent claims
The claim set is structured as two composition claims (ocular hypertension, glaucoma) plus method claims tied to each composition.
| Claim |
Claim type |
Indication |
Composition must include |
Key limitations |
| 1 |
Composition |
Ocular hypertension |
Active + vehicle |
“amount sufficient to reduce intraocular pressure” and “without causing substantial ocular irritation” |
| 4 |
Method |
Ocular hypertension |
Topical application of claim 1 composition |
Uses topical treatment framing |
| 9 |
Composition |
Glaucoma |
Active + vehicle |
Same performance/irritation framing |
| 12 |
Method |
Glaucoma |
Topical application of claim 9 composition |
Uses topical treatment framing |
Dependent claim add-ons (vehicle and dosing)
Dependent claims narrow the vehicle and operational dosing parameters.
| Dependent claims |
Adds limitation to what? |
Narrowing effect |
| 2, 10 |
Vehicle comprises a solubilizing agent |
Requires solubilization strategy in the carrier |
| 3, 11 |
Vehicle comprises aqueous saline + benzalkonium chloride |
Forces a particular preservative/excipient system |
| 5, 13 |
Method applies once or twice a day |
Defines frequency envelope |
| 6, 14 |
Contains 0.1 μg to 30 μg active per dose |
Defines broad dose range |
| 7, 15 |
Contains 1.0 μg to 10 μg active per dose |
Defines narrower dose sub-range |
| 8, 16 |
Applied twice a day; 1.0 μg to 10 μg in 10–50 μL |
Adds volume and double-daily regimen coupling |
What is the functional claim language and how it shapes scope?
The independent compositions rely on two functional limitations:
- Efficacy function: “amount sufficient to reduce intraocular pressure”
- Safety/compatibility function: “without causing substantial ocular irritation”
These elements do not enumerate excipients beyond “ophthalmologically compatible vehicle,” but they do set enforceability boundaries: an accused product needs to be topical, to incorporate the claimed active, and to plausibly achieve the stated performance/safety profile.
What is the dosing and regimen scope in measurable terms?
Dose ranges
The patent provides two explicit active-per-application bands:
- Broad band (claims 6, 14): 0.1 μg to 30 μg active per application
- Focused band (claims 7, 15): 1.0 μg to 10 μg active per application
Regimen constraints
- Once or twice daily: claims 5, 13
- Twice daily with volume coupling: claims 8, 16
- regimen: twice a day
- active: 1.0 μg to 10 μg per application
- volume: 10 to 50 μL per application
This coupling matters for design-around. A product that uses the same active but changes volume outside 10–50 μL while keeping frequency and mg dose could potentially avoid claims 8/16 while still falling under claims 6/7/14/15 depending on dose.
How does benzalkonium chloride narrow claim coverage?
Claims 3 and 11 require the vehicle to include benzalkonium chloride in an aqueous saline solution.
This means:
- A formulation using the same active and saline but using a different preservative does not satisfy the “benzalkonium chloride” limitation for those dependent claims.
- However, the independent claims 1 and 9 do not require benzalkonium chloride; they only require an “ophthalmologically compatible vehicle.” That keeps the broad composition coverage open even if benzalkonium chloride is replaced, depending on the vehicle’s compatibility and performance.
For method claims: claims 4 and 12 are tethered to “the therapeutic composition of claim 1/9,” so vehicle-dependent differences can affect dependent method claim scope via reliance on the corresponding composition claims.
What is the effective claim hierarchy? (How infringement is likely to be argued)
A typical infringement analysis for this patent would proceed as follows:
-
Composition path
- Does the accused product contain 13,14-dihydro-17-phenyl-18,19,20-trinor PGF2α isopropyl ester?
- Is it formulated for topical ocular use?
- Does it use a vehicle that is “ophthalmologically compatible” and claims’ functional efficacy and irritation profile?
-
Vehicle path
- If aiming for dependent claims: does it contain a solubilizing agent (claims 2/10)?
- Does it specifically use aqueous saline + benzalkonium chloride (claims 3/11)?
-
Method path
- For use claims: does the labeled or practiced regimen match “once or twice a day” (claims 5/13)?
- Does the per-dose active mass fall in the claimed microgram ranges (claims 6/7/14/15)?
- If twice daily: is volume in the 10–50 μL band (claims 8/16)?
What does “scope” look like as a claim matrix?
Scope matrix for compositions
Let A = active identity; V = vehicle identity; D = dose; F = frequency; Vol = volume.
| Dimension |
Independent claims (1, 9) |
Dependent narrowing (2, 3, 10, 11) |
Method narrowing (4, 12, 5, 13, 8, 16) |
| Active (A) |
Required |
Required |
Required |
| Vehicle compatibility |
Required (broad) |
Solubilizing agent required (2/10) or benzalkonium chloride required (3/11) |
Determines which composition is being practiced |
| Dose (D) |
Implicit through “amount sufficient” |
Express microgram bands in dependent method claims |
Express microgram bands (6/7/14/15) |
| Frequency (F) |
Not specified |
Not in composition claims |
Once/twice daily in method dependent claims (5/13) |
| Volume (Vol) |
Not specified |
Not specified |
Express twice-daily volume band (8/16) |
How strong is coverage against likely formulation variations?
Vehicle substitution
- Solubilizer changes: claims 2 and 10 require “a solubilizing agent,” so eliminating solubilization could avoid those dependent claims, but independent claims can still be asserted because they only require compatibility and topical efficacy/safety.
- Preservative change: swapping benzalkonium chloride likely avoids claims 3/11 and any method claims anchored to them, but not necessarily claims 1/9.
Dose and administration changes
- Moving outside 0.1–30 μg per application could avoid claims 6/14, but independent composition claims still require a dose “sufficient” to reduce intraocular pressure without substantial irritation, which may still be met by typical effective dosing.
- Moving outside 1.0–10 μg avoids claims 7/15 (and also the per-application constraints inside 8/16).
- Changing the administered volume outside 10–50 μL can reduce exposure to claims 8/16, but claims 5/6/7/13/14/15 remain relevant if the dose and frequency still land within those limits.
US patent landscape implications (what this patent blocks and what it leaves open)
This patent is an ocular active + topical delivery + microdose regimen claim
The claims are not directed to:
- novel chemical scaffolds beyond the specific active identity
- dosing platforms other than conventional ophthalmic topical application
- specific manufacturing steps or stability technologies
That means the landscape impact is concentrated in:
- formulation containing this exact prostaglandin isopropyl ester
- ophthalmic delivery using compatible vehicles
- use regimens that fall into the microgram/dose-volume windows
Design-around pressure points
To reduce risk of infringement, a product would typically alter at least one of the claim-essential elements:
- Active identity: use a different prodrug, ester, or prostaglandin analog
- Vehicle: avoid benzalkonium chloride if targeting claims 3/11 exposure
- Dosing/volume regimen: move outside microgram bands or outside 10–50 μL while keeping efficacy
The key practical point is that independent claims remain broad on vehicle composition (as long as compatibility and functional outcomes are met), so complete avoidance often requires active or functional/dosing separation rather than only a preservative switch.
How to read the claim set for freedom-to-operate (FTO) decisions
Product-formulation FTO
A clearance assessment should treat this patent as covering:
- a topical ocular formulation where the active is exactly 13,14-dihydro-17-phenyl-18,19,20-trinor PGF2α isopropyl ester
- a compatible ophthalmic carrier that allows reduction in intraocular pressure without substantial irritation
Dependent claims then add:
- solubilizer requirement (narrow)
- benzalkonium chloride requirement (narrow)
- dose and administration method constraints (for use)
Label/use-direction FTO
Even if a company argues a product is “different,” method claims can still be implicated if the market uses the regimen:
- once or twice daily
- within microgram active per dose windows
- with twice-daily dosing within the specific 10–50 μL volume band
Key Takeaways
- Core coverage: US 5,296,504 claims topical ocular hypertension and glaucoma treatments using 13,14-dihydro-17-phenyl-18,19,20-trinor PGF2α isopropyl ester in an ophthalmologically compatible vehicle, with efficacy and irritation performance limitations.
- Vehicle narrowing: Benzalkonium chloride in saline is required only for dependent composition claims (3, 11), while solubilizer is required only for dependent composition claims (2, 10).
- Method exposure is dosing-driven: once/twice daily (claims 5, 13), microgram dose bands (claims 6, 7, 14, 15), and twice-daily dosing with 10–50 μL volume (claims 8, 16).
- Design-around: safe positioning typically requires changing active identity and/or moving outside the claimed dose-volume regimen; a preservative-only change mainly affects dependent claim scope.
FAQs
1. Does the patent require benzalkonium chloride to infringe?
Not for the independent composition claims (1 and 9). Benzalkonium chloride is required only for dependent composition claims (3 and 11) that specify an aqueous saline vehicle containing benzalkonium chloride.
2. Are dosing amounts explicitly claimed?
Yes in the method-dependent claims: 0.1–30 μg (claims 6 and 14) and 1.0–10 μg (claims 7 and 15), with a further twice-daily requirement that includes 10–50 μL volume (claims 8 and 16).
3. What regimens are covered for use?
Once or twice daily is covered for the method dependent claims (claims 5 and 13). Twice daily with constrained volume is covered for claims 8 and 16.
4. Does the patent cover both ocular hypertension and glaucoma?
Yes. Composition claims exist for ocular hypertension (claim 1) and glaucoma (claim 9), with parallel method claims (claims 4 and 12).
5. What is the main claim vulnerability for competitors?
Products using the same active can still face exposure under broad independent composition coverage, while dependent claim exposure increases if dosing and vehicle match the specified microgram ranges and benzalkonium chloride conditions.
References
- US Patent 5,296,504. “Therapeutic compositions for topical treatment of ocular hypertension and glaucoma.” Claims as provided in the prompt.
