United States Patent 4,826,821 Lung Surfactant: Scope, Claim Construction, and US Patent Landscape
US Patent 4,826,821 claims an improved synthetic lung surfactant that keeps the core DPPC (dipalmitoyl phosphatidyl choline) + C14–C18 fatty alcohol framework while adding a specific non-ionic alkyl aryl polyether alcohol surface-active agent (optionally tyloxapol) and minor sodium chloride, with explicit quantitative ranges designed to improve dispersibility in aqueous suspension and (for dependent claims) performance after lyophilization.
The claim set is tight on (i) the identity and quantitative composition of each component and (ii) the surface-active agent structure and parameters (m, n, R, R’). That combination narrows literal infringement risk for close substitutes that change the surfactant class, the polyether length parameters, or the DPPC:fatty-alcohol ratio.
What does US Patent 4,826,821 claim for synthetic lung surfactant dispersant properties?
Core independent claim (Claim 1) covers a specific multi-component composition for lung surfactant with improved dispersant properties in water compared to a baseline DPPC + C14–C18 fatty alcohol formulation.
Claim 1: Elements and built-in limitations
A. Baseline comparator
- The claimed “improved surfactant” is compared to a prior art “lung surfactant composition consisting essentially of dipalmitoyl phosphatidyl choline and a fatty alcohol having from 14 to 18 carbon atoms.”
- That “consisting essentially of” comparator is not the literal scope, but it sets the technical point: adding a specific additional surface-active agent improves dispersibility.
B. “Consists essentially of” formulation (claimed composition backbone)
Claim 1 recites that the improved surfactant consists essentially of:
- DPPC
- Present in at least 80% by weight of the total weight of:
- Fatty alcohol
- Carbon range: C14–C18
- Present as 7–10% by weight relative to the sum of weights of:
- DPPC + fatty alcohol + surface active agent.
- Non-ionic polyether surface active agent (structure-limited)
- Physiologically acceptable, non-toxic
- Alkyl aryl polyether alcohol type with the structure shown in the claim:
- R = –CH2CH2O(CH2CH2O)mCH2CH2OH
- R’ = –C(CH3)2CH2C(CH3)2CH3 (a bulky branched alkyl aryl portion, consistent with tyloxapol-type motifs)
- m = 6 to 8
- n = 4 or 5
- Presence: 6–11% by weight of the organic components of the composition.
- Sodium chloride
- Present as a minor component by weight.
C. Functional limitation
- “Improved dispersant properties in aqueous suspension” is included at the preamble/intro, but the literal scope is still constrained by the specific composition elements above.
Featured-scope bottom line for Claim 1
Literal scope requires all of:
- DPPC:fatty alcohol core with DPPC ≥80% of the DPPC+fatty alcohol fraction.
- Fatty alcohol is C14–C18 and falls into a 7–10 wt% allocation tied to the three-component denominator (DPPC + fatty alcohol + surface active agent).
- Surface active agent must match the alkyl aryl polyether alcohol structure with m = 6–8 and n = 4 or 5, and must be present in 6–11 wt% of organic components.
- Sodium chloride present at minor level.
How is tyloxapol treated in US 4,826,821 claims and what does that do to claim scope?
Claim 2 and Claim 6 lock the surface active agent to tyloxapol.
- Claim 2: “The composition of claim 1 wherein the surface active agent is tyloxapol.”
- Claim 6: “The composition of claim 5 wherein the surface active agent is tyloxapol.”
Practical scope effect
- If tyloxapol fits the structure/parameter limitations of Claim 1, Claim 2 is narrower but likely aligns closely with Claim 1’s structural gate.
- If a different alkyl aryl polyether alcohol matches the structural formula with the same m/n but is not tyloxapol, Claim 1 can cover it, while Claim 2/6 cannot.
Infringement risk framing
- A product that uses a different non-ionic surfactant (even one described as “polyether alcohol”) may fall outside Claim 1 if it fails the m/n parameters or structural elements.
- A tyloxapol product that maintains the DPPC ≥80% and the specific wt% allocations should be within the Claim 2/6 dependent scope (and likely also within Claim 1 if all parameters are satisfied).
What is the quantitative formulation scope in claim 1 (DPPC %, fatty alcohol %, surface active agent %, NaCl)?
Claim 1 quantitative map
| Component |
Identity restriction |
Quantitative requirement |
Denominator definition (as claimed) |
| DPPC |
dipalmitoyl phosphatidyl choline |
≥80 wt% |
of (DPPC + fatty alcohol) |
| Fatty alcohol |
C14–C18 |
7–10 wt% |
of (DPPC + fatty alcohol + surface active agent) |
| Surface active agent |
alkyl aryl polyether alcohol |
6–11 wt% |
of organic components |
| Sodium chloride |
minor component |
“minor by weight” |
no numeric range stated |
Claim 3 tightens DPPC
- Claim 3: DPPC is ≥90 wt% of the total weight of (DPPC + fatty alcohol).
Scope impact of tighter DPPC
- A formulation with DPPC at 80–89% may still fall under Claim 1 but not Claim 3.
- A formulation with DPPC ≥90% aligns with Claim 3 and reduces variability on the core phospholipid/fatty alcohol ratio.
What does claim 4 cover about saline suspension?
- Claim 4: “The composition of claim 1 wherein is suspended in saline solution.”
This introduces a presentation/dosing medium limitation. A composition with the same formulation but delivered in a different vehicle could avoid Claim 4 while still potentially falling under Claim 1 (composition claims are not always vehicle-limited unless the claim explicitly requires suspension in saline).
What is claimed in claim 5 about lyophilized powdered lung surfactant?
Claim 5 covers a powdered lyophilized version of the improved composition, again with enhanced dispersant properties after reconstitution.
Claim 5: Key differences versus Claim 1
- Lyophilized, powdered
- Requires a lyophilized powdered lung surfactant.
- Specific wt% refinements
Claim 5 uses narrower/shifted numeric ranges:
- DPPC: ≥80 wt% of (DPPC + fatty alcohol)
- Fatty alcohol allocation:
- “present relative to the sum of the weights of the components of DPPC, fatty alcohol and surface active agent in between about 9 and 10 wt%”
- Surface active agent allocation:
- 6–11 wt% of the sum of organic components (as in Claim 1)
- Sodium chloride: minor by weight
- Surface active agent identity is still structural
- It keeps the “alkyl aryl polyether alcohol type of structure” definition, rather than directly tying to tyloxapol (tyloxapol appears in Claim 6).
Claim 6 and Claim 7
- Claim 6: surface active agent is tyloxapol.
- Claim 7: DPPC is ≥90 wt% of (DPPC + fatty alcohol).
How should “consisting essentially of” be interpreted for US 4,826,821 in scope and design-around?
All compositions are framed as “consists essentially of” which generally:
- includes the listed ingredients, and
- allows other ingredients only if they do not materially affect the claimed properties/limitations.
In practice for this patent’s claim drafting, the most salient scope guardrails are not “other ingredients,” but the explicit, quantitative, component identity and structural formula limits:
- Non-ionic surface agent class and formula parameters (m, n, R, R’).
- Fatty alcohol chain length (C14–C18) and quantitative allocation.
- DPPC minimum weight fraction.
- Sodium chloride described only as “minor” (leaves room for low-level salt but avoids high salt loads).
Design-around opportunities typically arise by changing one of the strict gates:
- switch away from the alkyl aryl polyether alcohol with the specified m/n parameters, or
- move the fatty alcohol allocation outside 7–10 wt% (Claim 1) or outside 9–10 wt% (Claim 5), or
- move DPPC below 80% (or 90% for dependent claims), or
- avoid saline suspension / lyophilized powdered form depending on which dependent claims matter.
What prior art and comparator formulation is embedded in the claims?
Claim language uses a comparator “lung surfactant composition consisting essentially of dipalmitoyl phosphatidyl choline and a fatty alcohol having from 14 to 18 carbon atoms.”
That baseline is not necessarily the exact prior art composition used during examination, but it indicates the claimed novelty is the addition of the specified non-ionic alkyl aryl polyether alcohol (and salt), producing better aqueous dispersibility.
The landscape implication:
- If a competing product uses DPPC + C14–C18 fatty alcohol but omits the specified polyether surfactant, it likely avoids the key novelty element.
- If it uses a different surfactant type (non-ionic surfactants are broad), the structural and parameter limitations in Claim 1 become the primary infringement test.
What is the US patent landscape around DPPC + fatty alcohol synthetic lung surfactants (and where does 4,826,821 fit)?
US 4,826,821 is best treated as a formulation-optimization patent inside a broader class of synthetic lung surfactants that combine:
- DPPC (primary surface-active phospholipid),
- fatty alcohol (often to modulate stability/phase behavior), and
- water-compatible formulation excipients and surfactants to manage dispersibility.
How 4,826,821 differentiates
- It adds a specific non-ionic alkyl aryl polyether alcohol with explicit structural parameters and quantity limits.
- It separately claims lyophilized powdered presentation with modified fatty alcohol range (9–10 wt% allocation).
Landscape risk areas for competitors
Competitors most directly exposed are those whose:
- surfactant excipient is tyloxapol or a tyloxapol-like polyether alcohol meeting the claimed m/n parameters, and
- DPPC:fatty alcohol and allocation denominators match the claimed ranges, and
- product presentation aligns (saline suspension vs lyophilized powder).
What generic or biosimilar entry risks exist for products covered by US 4,826,821?
For lung surfactant therapeutics, “generic” typically means:
- same active ingredient(s) and substantially similar formulation and performance, with regulatory pathways depending on product classification.
The key patent-driven exclusion risk under 4,826,821 is formulation-driven:
- If the marketed product uses a non-ionic polyether alcohol matching the claimed structural parameters and amounts, generic-style substitution risks literal infringement of Claim 1/2 (or Claim 5/6 for lyophilized products).
Because the claims are composition-limited with tight numeric ranges, a generic or authorized substitute could reduce exposure by moving formulation parameters outside the claimed ranges or switching the surfactant class.
The patent’s structure/quantity constraints make design-around possible, but not guaranteed:
- some marketed formulations are commercially standardized (which can keep them within the asserted ranges),
- and reconstitution and dispersibility targets can pressure formulators toward similar excipients and ratios.
Which jurisdictions are implicated? What about international coverage?
The claims you provided are for United States Patent 4,826,821. The infringement and exclusivity landscape for other jurisdictions turns on whether corresponding filings exist in those countries, and on their claim sets.
No international family information is supplied in your prompt, and a full, accurate cross-jurisdiction map cannot be produced from the claim text alone.
What to litigate: likely construction and infringement focal points
Claim construction hotspots
- “consists essentially of” in combination with explicit quantitative limits
- “alkyl aryl polyether alcohol type of the structure” with parameters:
- m=6–8, n=4 or 5
- R and R’ structural features
- allocation denominators:
- Claim 1 fatty alcohol 7–10 wt% relative to (DPPC + fatty alcohol + surface active agent)
- Claim 5 fatty alcohol about 9–10 wt% in the same denominator
- “minor component by weight” for sodium chloride
- saline suspension requirement (Claim 4)
- lyophilized powdered presentation (Claim 5)
Likely infringement proof themes
- component identification: DPPC identity and purity,
- fatty alcohol chain distribution (confirm C14–C18),
- tyloxapol presence (if relying on Claims 2/6),
- analytic confirmation of polyether structure and the m/n parameters (or validated equivalence if argued),
- wt% quantification using the claim denominators,
- product presentation and reconstitution medium.
Key Takeaways
- US 4,826,821 claims an improved synthetic lung surfactant built on DPPC + C14–C18 fatty alcohol, plus a specific alkyl aryl polyether alcohol (tyloxapol optional via dependent claims) and minor NaCl.
- Claim scope is narrowed by hard composition math:
- DPPC ≥80 wt% of (DPPC + fatty alcohol) in Claim 1; ≥90 wt% in Claim 3.
- Fatty alcohol 7–10 wt% allocation in Claim 1; ~9–10 wt% allocation in Claim 5.
- Polyether surfactant 6–11 wt% of organic components.
- The patent differentiates on aqueous dispersibility and explicitly adds a lyophilized powdered variant with tighter fatty alcohol allocation.
- Design-around efforts are most likely to succeed by altering one of the strict gates: surfactant class/structure (m/n parameters), fatty alcohol allocation range, DPPC fraction, or product presentation (saline suspension vs lyophilized powder).
FAQs
1) What happens if a lung surfactant uses DPPC and a C14–C18 fatty alcohol but omits tyloxapol?
If the formulation omits the claimed alkyl aryl polyether alcohol (or uses one outside the defined structure/parameters), it is unlikely to meet Claim 1’s surface active agent limitation.
2) Does US 4,826,821 cover saline suspension only or also other delivery media?
Claim 4 is limited to saline suspension. Independent Claim 1 is a composition claim and does not require saline suspension, based on the claim wording provided.
3) What is the difference between Claim 1 and Claim 5 for lyophilized products?
Claim 5 requires a powdered lyophilized formulation and narrows the fatty alcohol allocation to about 9–10 wt% (versus 7–10 wt% in Claim 1).
4) How narrow are the polyether alcohol parameters m and n?
They are narrow by design: m is 6 to 8 and n is 4 or 5, tied to the specified structure elements R and R’.
5) Can a competitor change sodium chloride levels and avoid the claims?
Claim 1/5 only require sodium chloride as a minor component by weight; avoiding the claims would require moving outside what is considered “minor” by the relevant construction and performance-linked “consists essentially of” context.
References (APA)
- United States Patent No. 4,826,821. “Improved synthetic lung surfactant composition.” (Claims provided in prompt text).
