Patent 5,438,072 Scope, Claim-by-Claim Coverage, and US Patent Landscape for Taxane Perfusion Injectable Gel-Control Formulations

US Patent 5,438,072 protects a specific class of injectable taxane perfusion solutions and storage concentrates that avoid gel formation when diluted/mixed with aqueous solutions, using (i) a defined surface-active agent (selected from polysorbates, ethylene oxide esters-ethers, and fatty acid glycerides), and (ii) a defined “dilution additive” (selected from small organic hydroxyl/amine compounds under MW<200, including sodium chloride or amino acids). The claims broaden beyond a single taxane by covering “taxane derivatives” and specifying a gel control mechanism tied to mixing with aqueous media.

Which taxane perfusion formulations are covered by US Patent 5,438,072?

Short answer: It covers injectable compositions configured for storage of taxane derivatives in surfactant systems, paired with a specific dilution additive solution (small hydroxyl/amine organics or amino acids, or NaCl) to prevent or break gelled phases during mixing with aqueous perfusion solutions.

What is the core claim structure (independent claim 1)?

Claim 1 is a system-level formulation claim with functional gel-control language and compositional constraints. It is built from three interacting elements:

Drug class element: “taxane derivatives”
Storage vehicle element: a solution convenient for storage in a surface active agent selected from:
- polysorbates, or
- ethylene oxide esters-ethers, or
- fatty acid glycerides
Dilution additive element: a water solution of an “effective amount” of at least one dilution additive selected from:
- organic compounds having a hydroxyl group and/or an amine functional group and
- molecular weight < 200, or
- sodium chloride
Performance element: when the stored composition is mixed with an aqueous solution (for perfusion), gel formation is avoided or any gelled phase can be broken during mixing.

Practical reading: Infringement hinges on (a) using a taxane derivative in a surfactant storage concentrate chosen from the recited classes, and (b) including a recited dilution additive in aqueous form that changes the mixing/dilution behavior so gels do not persist or do not form.

Claim 1 limitation map (what must be present)

Claim 1 is not just “taxane + surfactant + additive.” The wording requires a configuration for dilution with aqueous solutions and explicit gel control:

Taxane derivative: covered broadly by “taxane derivatives” (no single specified molecule is required by claim 1)
Surface-active agent scope:
- “selected from polysorbates, ethylene oxide esters-ethers and fatty acids glycerides”
Dilution additive definition:
- “organic compounds having a hydroxyl group an amine functional group and a molecular weight of less than 200”
- plus NaCl as an alternate enumerated additive
Mixing outcome:
- avoid gelled phase during mixing with an aqueous solution or break any gelled phase formed during mixing.

What does “gelled phase during mixing” capture?

The claim language is directed to dilution/transition-phase behavior. A gelled phase “formed during mixing” implies that the patent is concerned with what happens when a concentrate meets an aqueous perfusion/infusion diluent.

So, the technical scope is not limited to preventing precipitation in the final solution only. It also covers systems where a transient gel occurs but is later broken by the additive during mixing.

Which dependent claims narrow the formulation options?

Claim 2: Additive is an amino acid

Short answer: Claim 2 narrows claim 1 to amino-acid dilution additives.

This creates a clear infringement lane: using an amino acid (as the MW<200, hydroxyl/amine class falls within) as the dilution additive in the claimed system.

Claims 3 and 4: Additive-to-surfactant weight ratios

Claim 3: weight ratio between additive and surface-active agent > 6%
Claim 4: weight ratio > 15%

Short answer: These claims define quantitative boundaries. If a formulation uses too little additive relative to the surfactant, it may fall short of dependent-claim coverage even if it prevents gel formation under some conditions.

Key legal implication: Because claim 1 does not contain a numeric ratio requirement, a system can still infringe claim 1 even if it does not meet the dependent ratios, so long as the gel-control function and other structural elements are satisfied. Claims 3 and 4 strengthen fallback positions.

Claim 5: Specific enumerated dilution additives

Claim 5 lists examples of dilution additives that map into the functional definition of claim 1 (small organics with relevant hydroxyl/amine features and/or compatibility with the gel-control mechanism). The listed additives:

glucose
glycerol
sorbitol
mannitol
glycine
polyethylene glycols
propylene glycol
benzyl alcohol
ethanol

Short answer: This is an explicit “laundry list” of candidate additives for the claimed system. The presence of PEG, glycols, sugars/polyols, and amino acids (glycine) suggests the inventors targeted humectants/osmolytes and compatible co-solutes that modulate surfactant hydration and dilution behavior.

Practical infringement reading: If a competitor’s perfusion concentrate uses one of these additives as the dilution additive in the claimed surfactant class, it is easier to argue coverage.

Claims 6-8: Specific taxane derivatives using Formula (I) substituents

Claims 6-8 narrow the “taxane derivative” element to derivatives of formula (I) with defined substituent options:

Claim 6: taxane derivative selected from derivatives of formula (I)
- R is hydrogen or acetyl
- R1 is tert-butoxycarbonylamino or benzoylamino
Claim 7: R = acetyl; R1 = benzoylamino
Claim 8: R = hydrogen; R1 = tert-butoxycarbonylamino

Short answer: These dependent claims restrict coverage to specific chemical structures within the taxane derivative family. They create a stronger patent position if a competitor uses those exact prodrug/derivative substituent patterns.

How broad is the coverage in practice?

Breadth drivers:

Claim 1 uses “taxane derivatives” generically.
Claim 1 allows broad surfactant selection within three classes.
Claim 1 covers a broad set of dilution additives through a functional definition (hydroxyl/amine-containing organics with MW<200) plus NaCl.

Narrowing drivers:

Gel behavior during mixing with aqueous solutions is a required functional element.
Claim 2 (amino acids) and Claims 3-4 (ratio thresholds) narrow dependent coverage.
Claims 6-8 constrain taxane derivative structures to formula (I) substituent patterns.

What patent landscape surrounds US 5,438,072 in the US for taxane injection gel-control?

What the landscape typically contains in this technical niche US taxane injection formulations in the gel/precipitation/infusion stability space commonly converge on:

surfactant-based solvent systems (polysorbates; ethoxylated surfactants; glycerides)
co-solvents and tonicity/osmolality agents (polyols, amino acids, sugars, glycols)
formulation strategies addressing dilution-induced phase transitions

Expected claim interplay in enforcement US 5,438,072’s claim pattern suggests it is primarily a formulation/procedure-by-outcome patent for mixing behavior (gel avoidance or gel breakability). In litigation and licensing, this type of patent is often paired against:

patents covering solvent systems for taxanes (choice of surfactant)
patents covering specific additive species and concentration ranges
patents covering specific taxane derivatives and prodrugs
patents covering dilution methods or infusion compatibility

What are the infringement risk “design-around” vectors?

The claim structure points to several high-leverage modifications competitors can use (legally and practically) to move away from the claim boundaries.

1) Keep the taxane and surfactant, remove/additive element

If a competitor removes the MW<200 hydroxyl/amine class additive (or NaCl) and instead uses additives outside that definition, claim 1 and claim 2/5 coverage weakens.
Substituting larger molecules or additives without the relevant hydroxyl/amine features could be a path, depending on actual composition and function.

2) Maintain additive class but alter surfactant selection

Claim 1 requires a surface-active agent selected from polysorbates, ethylene oxide esters-ethers, or fatty acid glycerides. Using a different class of surfactant could avoid the literal surface-active agent requirement.

3) Avoid gel control outcome dependence

Claim 1 includes a functional outcome tied to gel avoidance or gel breaking during mixing. If an alternative formulation forms persistent gels or cannot break any gelled phase during mixing, literal infringement of claim 1 could be harder even if components overlap.

4) Quantitative avoidance for dependent claims only

Even if claim 1 is met, Claims 3 and 4 require additive-to-surfactant weight ratios >6% and >15%. A competitor could target ratio avoidance to reduce risk on dependent claims, while still potentially litigating claim 1.

How does the claim scope map to typical taxane products and compendial practices?

This patent is formulated around two-step behavior:

a “solution convenient for storage” in the surfactant class
an aqueous dilution step that uses an additive solution to control gel formation.

Modern taxane infusions often involve staged preparation, and the “gelled phase during mixing” language aligns with compatibility concerns when concentrates are combined with diluents in clinical settings.

Accordingly, the strongest enforcement scenario usually involves:

a stored concentrate with taxane in a surfactant system within the claimed class
a defined dilution additive species (amino acid, sugar/polyol, glycerol, PEG, glycols, etc.)
evidence that the formulation’s mixing behavior avoids gel formation or allows breakage.

What is the litigation posture likely associated with a patent like US 5,438,072?

Based on the claim content, US 5,438,072 is well-suited to:

be asserted against generic or reformulated taxane injections when their excipient system and dilution behavior are similar
be used as a settlement anchor for composition-of-matter and “mixing/gel control” features
be attacked with invalidity theories focused on whether the combination of taxane surfactant storage with small polyols/amino acids for dilution compatibility was disclosed earlier, and whether the functional “gel avoidance” is supported and novel.

(Notes: this section describes typical enforcement patterns for this technical claim style, not the specific docket history for 5,438,072.)

Key claim coverage table for US 5,438,072

Claim	What must be present	What it covers tightly	Main risk if competitor changes
1	Taxane derivative + storage surfactant (polysorbates/EO esters-ethers/fatty glycerides) + aqueous dilution additive (MW<200 hydroxyl/amine organics or NaCl) + gel avoidance or gel break during aqueous mixing	Core system-level “gel control” formulation	Removing additive, changing surfactant class, or failing gel-break behavior
2	Claim 1 + dilution additive is amino acid	Amino-acid co-additives	Using non-amino-acid additives
3	Claim 1 + additive/surfactant weight ratio >6%	Quantitative additive level	Lowering additive amount
4	Claim 1 + additive/surfactant weight ratio >15%	Higher quantitative threshold	Lowering additive amount
5	Claim 1 + additive is one of listed compounds (glucose, glycerol, sorbitol, mannitol, glycine, PEG, propylene glycol, benzyl alcohol, ethanol)	Explicit additive species	Substituting other allowed additives not listed, or not meeting definition
6	Claim 1 + taxane derivative is formula (I) with R=H or acetyl; R1=Boc-amino or benzoylamino	Chemical-structure constrained taxane derivatives	Using a different derivative outside formula (I)
7	Claim 1 + formula (I): R=acetyl; R1=benzoylamino	Specific derivative	Changing substituents
8	Claim 1 + formula (I): R=H; R1=Boc-amino	Specific derivative	Changing substituents

What freedom-to-operate issues arise from the formula (I) taxane derivative limitation?

Because Claims 6-8 constrain R and R1 substituents, a taxane derivative outside that structural set may avoid dependent claim coverage even if claim 1 is implicated. That creates a bifurcated risk profile:

If a competitor uses taxane derivative structures outside formula (I), the infringement risk shifts primarily to claim 1 (because claim 1 is broader on taxane derivatives).
If a competitor uses formula (I) derivatives, the patent estate strengthens on both structural and formulation grounds (claims 6-8 in addition to claim 1).

Key Takeaways

US 5,438,072 is a formulation patent centered on gel control during aqueous mixing of taxane derivative concentrates.
The enforceable system core (claim 1) requires: taxane derivative + recited surfactant class + MW<200 hydroxyl/amine small molecule or NaCl + gel avoidance or gel breaking during mixing.
Dependent claims add: amino acid restriction (claim 2), ratio thresholds (claims 3-4), explicit additive list (claim 5), and taxane derivative structural limits (claims 6-8).
The main design-around levers are: changing the dilution additive class/species, changing the surfactant class, altering concentrations to miss ratio thresholds, or failing the functional gel avoidance/breaking requirement.

FAQs

1) Does US 5,438,072 require a specific taxane drug molecule?
Claim 1 requires “taxane derivatives” generally; specific structural constraints appear in dependent claims 6-8.

2) Can a formulation infringe claim 1 if a gel forms initially during mixing but later breaks?
Yes. Claim 1 covers systems where any gelled phase formed during mixing can be broken.

3) Which excipients are explicitly named as dilution additives?
Glucose, glycerol, sorbitol, mannitol, glycine, polyethylene glycols, propylene glycol, benzyl alcohol, and ethanol (claim 5), plus NaCl by definition in claim 1.

4) What quantitative thresholds exist in the patent?
Claims 3 and 4 require additive-to-surface-active agent weight ratios greater than 6% and greater than 15%, respectively.

5) What is the strongest way to reduce infringement risk?
Operate outside the claimed dilution additive definition/species or surfactant class, and demonstrate that mixing does not meet the gel avoidance/gel-breaking functional requirement.

References

US Patent 5,438,072.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
France	92 14501	Dec 02, 1992

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	190838	⤷ Start Trial
Australia	5566994	⤷ Start Trial
Australia	691476	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,438,072

Summary for Patent: 5,438,072