United States Patent 11,040,023 (Enalapril Stable Oral Liquid): What Is Claimed and How Broad Is the Patent Estate?

What does US 11,040,023 claim, in plain scope terms?

US 11,040,023 claims a stable enalapril oral liquid formulation with a tight control set around (1) enalapril concentration, (2) sweetener type and amount, (3) preservative identity and amount, (4) storage stability at refrigerator temperature, and (5) impurity/assay retention at end of storage. The invention is not a generic enalapril syrup; it is a formulation that is stable under defined 5 ± 3°C storage and meets defined assay and impurity thresholds.

Core claim structure (Claim 1)

Claim 1 is the independent claim and reads as a “stable formulation” with a product-by-function stability requirement plus composition-by-component.

Claim 1 elements (required):

Active: about 0.6 to about 1.2 mg/mL enalapril (or pharmaceutically acceptable salt/solvate).
Sweetener: any “sweetener” (dependent claims narrow).
Preservative: comprises sodium benzoate, a paraben, or mixture of parabens.
Vehicle: water.
Optional: flavoring agent.
Stability: stable at about 5 ± 3°C for at least 12 months.
Quality at end of storage:
- ≥ 95% w/w of initial enalapril amount, and
- ≤ 5% w/w total impurity/related substances at end of storage period.

Claim 1 defines the “win condition” as both (a) time-at-temp stability and (b) analytical acceptance criteria (assay and impurities).

Dependent claims define narrower sub-ranges and stability windows

Longer stability (Claims 2-3):
- 18 months at 5 ± 3°C (Claim 2)
- 24 months at 5 ± 3°C (Claim 3)
pH window (Claims 4-5):
- maintains pH 3 to 4 for at least 3 months (Claim 4)
- maintains pH 3 to 4 for at least 12 months (Claim 5)
Sweetener-specific (Claims 6-9):
- sucralose (Claim 6) with 0.5 to 0.9 mg/mL (Claim 7)
- saccharin (or salt) at about 2 mg/mL (Claims 8-9)
pH/buffer positioning (Claim 11):
- enalapril (or salt/solvate) “functions as a buffer”
Active at a specific point (Claim 12):
- about 1.0 mg/mL enalapril
Preservative specificity (Claims 13-18):
- mixture of parabens (Claim 13)
- methylparaben, ethylparaben, propylparaben, butylparaben (Claim 14)
- methylparaben + propylparaben (Claim 15)
- preservative present 0.1 to 2 mg/mL (Claim 16)
- sodium benzoate (Claim 17) at 0.2 to 1.2 mg/mL (Claim 18)
“consisting essentially of” fallback formulations (Claims 19-20):
- Claim 19: active about 1.0 mg/mL; sweetener is sucralose or sodium saccharin; preservative is mixture of parabens present 0.1 to 2 mg/mL; water; optional flavor
- Claim 20: active about 1.0 mg/mL; sweetener is sucralose or sodium saccharin; preservative is sodium benzoate at 0.2 to 1.2 mg/mL; water; optional flavor

Practical read: If an accused product meets the same analytical stability criteria at refrigerated storage and uses the same core composition logic (enalapril concentration range + specific sweetener/preservative categories + pH control), it is difficult to avoid the claim by “minor” excipient changes.

How broad is the scope? Where are the real boundaries for infringement?

US 11,040,023 has breadth in the identity of sweeteners and salts/solvates (Claim 1), but it narrows substantially through dependent claims and through the stability-and-analytical “guardrails.”

1) Active concentration range is the first key boundary

Claim 1: 0.6 to 1.2 mg/mL enalapril
Claim 12: about 1.0 mg/mL
“Consisting essentially of” claims 19-20 are anchored at about 1.0 mg/mL

Design-around pressure point: Products with enalapril outside 0.6–1.2 mg/mL may avoid Claim 1, but depending on “about” interpretation, the effective carve-out is not exact and would hinge on the patent’s construction.

2) Preservative identity is constrained to benzoates/parabens families

Claim 1 permits preservative comprises:

sodium benzoate, or
a paraben, or
mixture of parabens

Design-around pressure point: Switching to non-benzoate, non-paraben preservation systems may be the most direct route to avoiding the explicit preservative limitation. However, because Claim 1 is “consisting essentially of” in dependent claims, excipient substitution is not unlimited.

3) pH control and buffering can matter for stability proof

Claims 4-5 add a pH stability requirement (3–4 over specified times at 5 ± 3°C). Claim 11 frames enalapril as a buffer.

Design-around pressure point: Even if preservative/sweetener categories match, an accused formulation that does not maintain pH in the 3–4 band over the required period may not satisfy dependent claims.

4) “Stability at 5 ± 3°C” plus impurity/assay retention is the core proving element

Claim 1 requires:

≥ 12 months stability at 5 ± 3°C
≥ 95% enalapril remaining
≤ 5% total impurities/related substances at end of storage

This makes the claim outcome-determinative. Even if a product’s ingredient list matches, infringement can turn on whether the formulation actually meets the analytical thresholds under the claimed storage conditions.

5) Dependent claims create narrower “landing pads” that map to common formulation selections

Sucralose at 0.5–0.9 mg/mL (Claims 6-7)
Saccharin/salt at ~2 mg/mL (Claims 8-9)
Sodium benzoate at 0.2–1.2 mg/mL (Claims 17-18)
Parabens mixture at 0.1–2 mg/mL with methylparaben + propylparaben (Claims 13-16)

Business implication: The patent is structured so that many plausible “standard syrup” choices for sweetener and preservative fall directly into dependent claims. That reduces the space for routine reformulation.

How do the “consisting essentially of” claims affect scope and potential workarounds?

Claims 19 and 20 are “consisting essentially of” formulations, with specified ingredient categories and ranges.

Claim 19 (“consisting essentially of”): enalapril ~1.0 mg/mL + sweetener (sucralose or sodium saccharin) + preservative (parabens mixture 0.1–2 mg/mL) + water + optional flavor.
Claim 20 (“consisting essentially of”): enalapril ~1.0 mg/mL + sweetener (sucralose or sodium saccharin) + preservative (sodium benzoate 0.2–1.2 mg/mL) + water + optional flavor.

Effect on design-around:

It tightens permissible “other” excipients relative to Claim 1’s broader “stable formulation” with “optionally” flavoring.
If an accused product adds significant stabilizers, chelators, antioxidants, or buffers beyond what is considered acceptable under “consisting essentially of,” it may fall outside these dependent claims even if it still could fall within Claim 1.

However: Claim 1 is not “consisting essentially of” in the text provided; it uses “consisting essentially of” only in the dependent “fallback” claims. That means an accused product could still be tested against Claim 1 even if it introduces additional components, so long as it uses the required categories and meets the storage/impurity/assay criteria.

What does the claim set imply about the patent’s likely experimental scope?

Even without the specification text, the claim language implies the inventors built stability data around:

refrigerated storage (5 ± 3°C),
long-term stability (12, 18, 24 months),
controlled pH range (3–4) and/or buffering by enalapril salt/solvate,
specific sweetener concentrations (sucralose 0.5–0.9 mg/mL; saccharin ~2 mg/mL),
preservative concentration windows (parabens 0.1–2 mg/mL; sodium benzoate 0.2–1.2 mg/mL),
acceptance criteria: ≥95% assay and ≤5% impurities.

From a landscape standpoint, that means the enforceable “center of gravity” is the intersection of: 1) enalapril oral liquid at roughly 1 mg/mL,
2) refrigerator storage stability,
3) the selected preservative family, and
4) formulation-validated analytical outcomes.

Where does this patent sit inside the broader US enalapril product and formulation landscape?

Using the claim language alone, US 11,040,023 targets a narrow but commercially relevant niche: stable pediatric- or convenience-oriented oral liquids that avoid degradation and maintain shelf-life in refrigerated conditions.

Competitive filing patterns this claim is likely to collide with

In US practice, FDA-competitive product development for oral liquids frequently uses:

standard sweeteners (sucralose; saccharin salts),
standard preservatives (sodium benzoate; parabens),
pH tuning with buffer systems or API as buffer.

US 11,040,023 maps those common levers directly into dependent claims with explicit ranges and time-based stability outcomes.

Claim-by-claim landscape relevance (what competitors should map to)

Below is a mapping table that shows what a generic or competitor would need to replicate (or avoid) to fall inside each claim tier.

Claim	What must match	Direct “hook” for enforcement	Practical avoid point
1	Enalapril 0.6–1.2 mg/mL; sweetener; preservative is sodium benzoate/paraben/parabens; water; optional flavor; stable at 5 ± 3°C ≥12 months; ≥95% assay and ≤5% impurities at end	Stability outcome + analytical acceptance at refrigerated temp	Use different preservative family and/or fail storage/impurity thresholds
2	Claim 1 + ≥18 months at 5 ± 3°C	Longer stability extension	Shorter stability claims or failure to meet acceptance criteria
3	Claim 1 + ≥24 months at 5 ± 3°C	Long-term extension	Again, cannot reach these stability outcomes
4	Claim 1 + pH 3–4 for ≥3 months at 5 ± 3°C	pH stability window	Maintain different pH regime or fail retention time
5	Claim 1 + pH 3–4 for ≥12 months at 5 ± 3°C	Extended pH control	Change pH behavior
6	Claim 1 + sucralose	Sweetener identity	Use a different sweetener
7	Claim 6 + sucralose 0.5–0.9 mg/mL	Sweetener concentration	Shift sucralose concentration outside range
8	Claim 1 + saccharin/salt	Sweetener identity	Use different sweetener
9	Claim 8 + saccharin/salt ~2 mg/mL	Sweetener concentration	Shift concentration
10	Claim 1 + flavoring agent included	Optional inclusion	If no flavoring and this is asserted as limiting, avoid by formulation without flavor
11	Claim 1 + enalapril acts as buffer	Functional formulation role	Use separate buffering agent and argue different functional attribution
12	Claim 1 + enalapril about 1.0 mg/mL	Tight active concentration landing	Move outside “about 1.0” range
13	Claim 1 + preservative is mixture of parabens	Preservative family	Use single preservative or different family
14	Claim 13 + methyl/ethyl/propyl/butyl parabens or combo	Paraben species	Use different preservative system
15	Claim 13 + methylparaben + propylparaben	Common paraben combo	Change paraben species combination
16	Claim 1 + parabens mixture 0.1–2 mg/mL	Paraben concentration	Change concentration outside range
17	Claim 1 + preservative comprises sodium benzoate	Preservative family	Use parabens (or other family)
18	Claim 17 + sodium benzoate 0.2–1.2 mg/mL	Sodium benzoate concentration	Shift outside range
19	“Consisting essentially of” with: enalapril ~1.0; sweetener sucralose or sodium saccharin; parabens mixture 0.1–2; water; optional flavor	Tight formulation carveout	Add excipients that are not allowed under “consisting essentially of” or change preservative
20	“Consisting essentially of” with: enalapril ~1.0; sweetener sucralose or sodium saccharin; sodium benzoate 0.2–1.2; water; optional flavor	Tight formulation carveout	Change preservative family or sweetener

How should an investor or developer assess “freedom to operate” risk from this patent alone?

From the claim structure, the most material exposure arises if a candidate product:

uses enalapril oral liquid at roughly 1 mg/mL,
uses sucralose or saccharin salts at the stated levels,
uses sodium benzoate or parabens within the claimed concentration windows,
and achieves the claimed analytical stability at 5 ± 3°C for at least 12 months while keeping impurity levels low.

Risk is highest for products designed explicitly for refrigerated pediatric shelf-life using standard syrup ingredients, because the dependent claims track those ingredient selections.

Key Takeaways

US 11,040,023 claims a specific stable enalapril oral liquid defined by enalapril concentration (0.6–1.2 mg/mL), preservative family (sodium benzoate/parabens), optional flavor, and refrigerated stability performance (≥12 months at 5 ± 3°C) with ≥95% assay and ≤5% impurities.
Dependent claims tighten scope into sucralose and saccharin concentration targets, paraben or sodium benzoate concentration ranges, and pH stability (pH 3–4) for defined time periods.
“Consisting essentially of” claims 19-20 narrow ingredient allowances around ~1.0 mg/mL enalapril plus either parabens mixture or sodium benzoate, making standard syrup excipient swaps more difficult to defend.
The enforceable hook is not just the ingredient list; it is formulation stability at 5 ± 3°C with defined assay and impurity outcomes.

FAQs

Is US 11,040,023 limited to sucralose?
No. Claim 1 covers “a sweetener.” Sucralose is one dependent option (Claim 6-7). Saccharin (Claim 8-9) is another.
What is the key stability temperature and time requirement?
About 5 ± 3°C for at least 12 months (Claim 1), with extensions to 18 and 24 months in Claims 2 and 3.
What analytical thresholds are required at end of storage?
About 95% w/w or greater of initial enalapril amount and about 5% w/w or less total impurity/related substances at the end of the storage period (Claim 1).
Does the patent require pH control?
Not in Claim 1. pH 3–4 for defined durations is required in dependent claims (Claims 4 and 5).
How do the “consisting essentially of” claims differ from Claim 1?
Claims 19-20 set a tighter composition set anchored to about 1.0 mg/mL enalapril, specific sweetener options, a defined preservative family with specific ranges, water, and optional flavor.

References

[1] United States Patent Application / Patent US 11,040,023: claims provided in user prompt (Claim 1-20).

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Azurity	EPANED	enalapril maleate	SOLUTION;ORAL	208686-001	Sep 20, 2016	AB	RX	Yes	Yes	11,040,023	⤷ Start Trial	Y				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Brazil	112018068960	⤷ Start Trial
European Patent Office	3429581	⤷ Start Trial
World Intellectual Property Organization (WIPO)	2017161339	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,040,023

Which drugs does patent 11,040,023 protect, and when does it expire?

Summary for Patent: 11,040,023