Patent 8,754,131 Landscape: Scope and Claim Strength for Stable Ophthalmic Tyloxapol Liquid Formulations of 2-Amino-3-(4-Bromobenzoyl)phenylacetic Acid (US)
US 8,754,131 is a formulation patent focused on an ophthalmic stable aqueous liquid containing a narrowly defined active (2-amino-3-(4-bromobenzoyl)phenylacetic acid or salts/hydrates) and tyloxapol as the stabilization surfactant. The claims carve out multiple therapeutic and stability performance tiers (notably >90% or >92% remaining after 60°C for 4 weeks) and multiple compositional guardrails (specific concentration ranges for both active and tyloxapol; pH 7.5 to 8.5; optional preservatives/surfactants; and in one branch, a “no mannitol” condition).
Because claim scope is defined primarily by (i) identity of the active chemical (including hydrate forms), (ii) tyloxapol as the stabilizer, and (iii) concentration and stability outcomes, generic and biosimilar-style design-around risk is driven by whether a competing ophthalmic liquid uses tyloxapol at similar levels and achieves the same stability thresholds under the same stress conditions.
What does US 8,754,131 claim for stable ophthalmic liquid compositions?
Core claim construct (independent): claim 1 and claim 7 are the two main independent claim “pillars.” Both are stable aqueous ophthalmic liquids with:
- First component: 2-amino-3-(4-bromobenzoyl)phenylacetic acid (or pharmacologically acceptable salt/hydrate)
- Hydrates covered: at least 1/2 hydrate, 1 hydrate, 3/2 hydrate
- First component concentration: 0.05–0.2 w/v% (claim 1; claim 7 mirrors this range)
- Second component: tyloxapol, present in an amount sufficient to stabilize
- Ophthalmic administration
- No other active ingredients: “first component is the sole pharmaceutical active ingredient”
- Stability feature (claim 7 only): >90% of original first component remains after 60°C for 4 weeks
- Optional quaternary ammonium salt: claim 2, claim 8
- Optional US Pharmacopeia preservative efficacy standard: claims 25–29
Claim 1 scope (no explicit stress-outcome requirement)
Claim 1 is broader on stability performance because it requires stability “sufficient” stabilization by tyloxapol but does not impose the numeric stress-retention threshold. It is constrained by the chemical and compositional elements:
- Active identity and hydrate/salt coverage
- Single-active limitation
- Active concentration 0.05–0.2 w/v%
- Tyloxapol present in stabilizing amount
- Ophthalmic liquid
Key dependent variations tighten the window:
- Tyloxapol range: claim 4 limits to 0.01–0.05 w/v%
- pH range: claim 5 limits to 7.5–8.5
- Salt identity: claim 3 and multiple later claims specify sodium salt
- Narrower “consists essentially of” composition: claim 6 lists a defined excipient set plus concentration windows
Claim 7 scope (adds quantitative stability)
Claim 7 adds a numeric stability characterization:
- >90% remaining of the active after 60°C for 4 weeks
This numeric feature can be both:
- A stronger infringement hook for a defendant that must demonstrate stability under those exact stress conditions, and
- A design-around target for an alternative formulation that claims it does not meet the threshold.
“Consists essentially of” composition claims are infringement choke points
The most structurally restrictive claims are the “consists essentially of” variants (claim 6, claim 12, claim 18, claim 24, claim 28). These are where competitors face the highest formulation substitution risk because excipient inclusion/exclusion can become outcome-determinative:
- Must include specific excipients, and
- Must remain within the “essentially” boundaries that typically leave only minor/insubstantial deviations.
How broad is the protected active ingredient, salt, and hydrate coverage?
Active chemical identity in scope: 2-amino-3-(4-bromobenzoyl)phenylacetic acid and pharmacologically acceptable salts/hydrates.
Hydrates explicitly included:
- 1/2 hydrate
- 1 hydrate
- 3/2 hydrate
Salt versions explicitly called out in dependent claims:
- Sodium salt (claim 3; also claim 10 and many “consists essentially of” descendants).
Design-around implications:
- Replacing the active with a non-covered salt/hydrate can avoid claim coverage if it is not “pharmacologically acceptable” under the patent’s construed term or if it falls outside enumerated hydrate forms when claims explicitly require them.
- However, since claim 1 and claim 7 accept “pharmacologically acceptable salt” and “a hydrate thereof,” avoidance is best if the competitor shifts to an active form that is not within that captured chemical family or not within the hydrate selection language when claims specifically require the listed hydrate set.
Which formulation parameters are claimed: concentration, pH, tyloxapol level, and excipient sets?
Active concentration windows
- Claim 1 and 7: active (free acid or salt/hydrate) 0.05–0.2 w/v%
- Sodium salt concentration windows:
- Claim 6: 0.02–0.1 w/v%
- Claim 10: 0.05–0.1 w/v%
- Claim 12: 0.05–0.1 w/v%
- Claim 24: 0.05–0.1 w/v%
- Claim 18: sodium salt window stated as 0.02–0.1 w/v% (in that claim’s text)
Tyloxapol concentration windows
- Claim 4: 0.01–0.05 w/v%
- Claim 10 descendants align with 0.01–0.05 w/v%
- Claim 12: ~0.02 w/v% (explicit value)
- Claim 18: 0.02–0.05 w/v%
- Claim 22: 0.01–0.05 w/v%
- Claim 18 and 24/28 variants further constrain tyloxapol within their defined formulation sets.
pH window
- Claim 5 / claim 11 / claim 17 / claim 23: pH 7.5–8.5
If a competitor moves outside this range, it can reduce exposure for those narrower dependent claims. It does not automatically remove risk from claim 1 or 7 if those are the only elements required and pH is not a limitation in the asserted independent claim.
Stability thresholds under stress storage
- Claim 7: >90% remaining after 60°C for 4 weeks
- Claim 9: >92% after 60°C for 4 weeks
- Claim 19: >90% (in claim 13 branch)
- Claim 21: >92%
These thresholds are highly material in litigation and licensing because they can be tested and tied to each formulation.
Excipient set in “consists essentially of” claims
Across the “consists essentially of” group, the listed excipients repeatedly include:
- Boric acid
- Sodium tetraborate
- EDTA sodium salt
- Benzalkonium chloride
- Polyvinylpyrrolidone
- Sodium sulfite
This is the “core ophthalmic buffer/preservative/chelating system” scaffold coupled to tyloxapol.
Claim 6 vs claim 24 vs claim 28: the differences are active and tyloxapol concentration windows and whether the active is free acid vs sodium salt vs specific tyloxapol level.
What is the significance of the “no mannitol” limitation?
Claim 13 introduces a specific carve-out:
- “provided that the liquid preparation does not include mannitol.”
This creates a clean design-around axis for any competitor currently using mannitol as tonicity agent, bulking agent, or stability excipient. If a product avoids mannitol, it could still infringe depending on the rest of the claim elements. If a product includes mannitol, it can potentially avoid claim 13 and its descendants that inherit the “does not include mannitol” constraint.
Important: claim 13 is still limited by the same active, tyloxapol, ocular liquid context and the concentration/stability language in its branches, so it is not a general mannitol-proof shield against claim 1/7.
What does the USP preservative efficacy language add to infringement risk?
Claims 25–29 add a functional microbiological preservation performance requirement:
- Viable cell counts of bacteria (S. aureus, P. aeruginosa):
- 24 hours and 7 days after inoculation decrease to not more than 1/10 and not more than 1/1000, respectively, and thereafter level off or decrease
- Viable cell counts of fungi (C. albicans, A. niger):
- 14 days after inoculation decrease to not more than 1/10, and thereafter remain at the 14-day level
This language operates as:
- A dependent claim limitation that can raise the bar for infringement for products lacking that preservative efficacy.
- A strong defense lever: if a competitor uses a different preservative system or fails the specified efficacy performance, it can avoid those dependent claims.
It also signals that the patent drafter viewed preservative efficacy as a key commercial qualification for ophthalmic liquids.
Which dependent claims create the most realistic “in-use” infringement vectors?
High-probability vectors
- Products that use 2-amino-3-(4-bromobenzoyl)phenylacetic acid sodium salt and formulate within the 0.05–0.1 w/v% active window.
- Products using tyloxapol in the 0.01–0.05 w/v% range.
- Products formulated at pH 7.5–8.5.
- Products that include the recurring excipient scaffold: borate buffer, EDTA, benzalkonium chloride, PVP, sodium sulfite.
Product-conditional vectors
- If a commercial formulation is expressly described as “stable” and demonstrates that >90% or >92% remains after 60°C for 4 weeks, it maps directly to claim 7/9/19/21.
“Consists essentially of” vectors (narrow but potent)
The “consists essentially of” claims are the best litigation anchors when discovery can pin down the exact formulation composition. Any deviation in excipient presence, identity, or concentration can create non-infringement or at least narrowing.
How does US 8,754,131 compare with common ophthalmic formulation patent patterns?
This patent matches a known formulation patent structure:
- Chemical identity of active + salt/hydrate set
- Specific stabilizing surfactant (tyloxapol)
- Tight concentration and pH windows
- Inclusion of buffer/chelating/preservative polymers typical for ocular liquids
- Functional stability retention under accelerated temperature storage
- Optional preservative efficacy performance to align with USP
Risk profile for competitors:
- A generic “formulation-around” effort that keeps the same active and tyloxapol but tweaks only one parameter (for example pH or concentration slightly) may avoid some dependent claims but still risk infringement of the broader independent claims if those parameters are not limiting in the asserted independent claim.
What generic entry risks exist for ophthalmic liquids using the same active?
Without introducing any external assumptions, the claim set implies the following entry-risk hierarchy:
Highest risk: same active form + tyloxapol + similar concentrations
If a competitor matches:
- Active is the same chemical (including sodium salt/hydrates where required)
- Active concentration overlaps claim windows
- Tyloxapol is included at stabilizing effective levels and within claimed ranges
- Ophthalmic aqueous liquid format
then the competitor faces exposure under claim 1/7 even if pH/excipient details differ.
Moderate risk: hits active and tyloxapol, differs on excipient scaffold
Even if the competitor omits one excipient from a “consists essentially of” list, independent claims without that exact excipient list may still be asserted unless the excipient list is required in the independent claim being asserted.
Lower risk: mannitol inclusion only helps against the mannitol-negated branch
Including mannitol can avoid claim 13’s branch if the product “includes mannitol.” But claim 1/7 do not contain the mannitol-negative requirement.
Key test: stability outcome under 60°C for 4 weeks
For claim 7/9 and claim 19/21 descendants, the numeric outcome requirement is a focal point. A competitor can aim to demonstrate that its product’s retention after stress does not meet the threshold.
Key takeaways: scope boundaries and where competitors can and can’t move
- The patent is centered on tyloxapol stabilization of a specific active chemistry for ophthalmic aqueous liquids, with independent claims anchored by active identity, single-active limitation, and tyloxapol presence.
- Stability retention at 60°C for 4 weeks (>90% or >92%) is the strongest differentiator and the cleanest litigation-ready limitation because it is numeric and testable.
- Concentration and pH windows (active 0.05–0.2 w/v%; tyloxapol typically 0.01–0.05 w/v%; pH 7.5–8.5) narrow dependent claim coverage and can support design-arounds.
- “Consists essentially of” formulations with borate buffer, EDTA, benzalkonium chloride, PVP, sodium sulfite are the most composition-sensitive claims. Exact excipient matching is the main infringement lever.
- The “no mannitol” limitation appears only in the claim 13 branch, so it is a targeted defense against that specific branch, not a blanket shield against the broader independent claims.
- USP preservative efficacy provisions in dependent claims add a microbiology performance constraint that can reduce exposure when preservative systems differ or performance is not met.
FAQs
1) What is the single most important limitation in US 8,754,131?
Tyloxapol as the stabilizing second component in a stable ophthalmic aqueous liquid containing 2-amino-3-(4-bromobenzoyl)phenylacetic acid (salt/hydrate) at the claimed concentration range.
2) What claims include the numeric accelerated stability requirement (>90% and >92%)?
Claims in the independent-family structure that include the 60°C for 4 weeks retention feature: claim 7 (>90%) and claim 9 (>92%), and their corresponding claim-13 branch equivalents (claim 19 and claim 21).
3) Does adding mannitol avoid infringement of the whole patent?
It avoids the mannitol-negated branch tied to claim 13, but it does not automatically eliminate risk under the broader independent claims that do not include the “does not include mannitol” limitation.
4) How can a competitor reduce exposure in “consists essentially of” claims?
By altering excipient identity and concentration outside the specified list and ranges, since those claims require a defined excipient set (boric acid/sodium tetraborate/EDTA/benzalkonium chloride/PVP/sodium sulfite) alongside the active and tyloxapol.
5) Are USP preservative efficacy results relevant to infringement strategy?
Yes for the dependent claims that incorporate the USP preservative efficacy standard, because those claims require microbiological performance thresholds at specified times and conditions.
References
- United States Patent 8,754,131. “Stable aqueous liquid preparation comprising tyloxapol and 2-amino-3-(4-bromobenzoyl)phenylacetic acid for ophthalmic administration.” Claims as provided in user prompt.
