United States Patent 11,957,681 Scope and Claims Analysis for Imatinib Mesylate Liquid Dosage Forms
United States Patent 11,957,681 claims a specific flavored liquid oral dosage formulation of imatinib mesylate with defined w/v concentration ranges for key excipients (glycerin, sodium benzoate, liquid maltitol) plus specified ingredients (citric acid, acesulfame potassium, strawberry flavor, water). The claim scope is strongest for formulations that fall inside the claimed quantitative ranges and include the listed organoleptic system. Design-arounds that shift concentrations outside ranges, substitute different sweeteners/preservatives, or omit the flavor system are the principal freedom-to-operate variables.
What does US 11,957,681 claim for imatinib mesylate liquid formulations?
Core claim structure (Claim 1 as provided):
A liquid dosage form comprising, by concentration in w/v, and containing the following components:
- Imatinib mesylate: about 0.01% to about 25% w/v
- Glycerin: about 25% to about 60% w/v
- Sodium benzoate: about 0.01% to about 10% w/v
- Liquid maltitol: about 0.01% to about 10% w/v
- Citric acid (amount not numerically constrained in provided claim text)
- Acesulfame potassium (amount not numerically constrained)
- Strawberry flavor (amount not numerically constrained)
- Water (solvent)
Claim 1 is a composition claim, not a process claim. It does not recite manufacturing steps, pH targets, viscosity ranges, particle size, stability criteria, or dosing-unit rules. That makes the claim’s enforceability and infringement focus heavily on formulation composition and whether an accused product uses a composition that falls within the claimed ranges and includes the listed ingredients.
What is the practical claim “center of gravity” for infringement?
The most infringement-relevant constraints are the four concentration-defined ingredients:
- imatinib mesylate within 0.01%–25% w/v
- glycerin within 25%–60% w/v
- sodium benzoate within 0.01%–10% w/v
- liquid maltitol within 0.01%–10% w/v
A second-tier scope element is inclusion of the flavor/sweetener/preservative system via:
- citric acid
- acesulfame potassium
- strawberry flavor
Water is inherently present in a “liquid dosage form.”
How broad is the numerical range coverage?
On face value, the numeric windows are wide for formulation chemistry:
- Imatinib mesylate range spans three orders of magnitude boundaries (from 0.01% up to 25% w/v). That is unusually broad for an API content limitation; it can capture low-dose and higher-concentration suspensions/solutions, depending on actual solubility strategy.
- Glycerin range of 25%–60% w/v is a major formulation anchor: many sweetened glycerin-based oral liquids will fall within or near this range.
- Sodium benzoate at 0.01%–10% w/v overlaps typical preservative levels.
- Liquid maltitol at 0.01%–10% w/v covers low-to-moderate polyol sweetener concentrations used to mask taste and improve stability.
What must the accused product contain, beyond concentration ranges?
Because the claim explicitly lists other ingredients without numerical limits, the accused liquid dosage form would need to include:
- citric acid
- acesulfame potassium
- strawberry flavor
- water
- plus the API and the excipients in claimed ranges
If an accused product omits any of those listed ingredients, infringement risk drops materially because the claim requires them.
How do the concentration ranges interact: is this claim “all elements” rigid or does it allow tolerance?
Element-by-element requirement: The claim text requires the formulation to consist of the listed ingredients and ranges. It is a “liquid dosage form consisting of” statement, which (if construed strictly) can be interpreted to exclude ingredients not listed, unless the “consisting of” is treated with accepted claim-construction leeway for incidental components (such as impurities or buffering minor adjustments). In practice, oral liquids often include additional excipients (e.g., viscosity modifiers, surfactants, preservatives, buffering agents). If the accused product includes additional deliberate ingredients, “consisting of” becomes a key litigation issue.
What are likely construction issues for “consisting of” in infringement?
- Whether “liquid dosage form consisting of” allows trace impurities outside the recited list.
- Whether functional substitutions (e.g., different flavor system, different acidifier) count as “citric acid” or whether equivalents could be argued under doctrine of equivalents.
- Whether the asserted “strawberry flavor” must be the exact flavor component or whether a formulation marketed as “strawberry flavored” suffices.
The claim’s structure supports an infringement theory that accused products must match the listed ingredient set and at least include these exact ingredient categories.
What patents typically surround a composition like US 11,957,681 in imatinib liquid oral development?
A formulation patent for an oncology drug like imatinib mesylate often clusters with:
- related liquid composition claims (different excipient systems, different sweeteners/preservatives),
- method-of-use claims (often pediatric dosing administration),
- and/or solid oral dosage claims for stability and dose uniformity.
Given only the single claim description provided, a full patent landscape cannot be enumerated without bibliographic data. This analysis therefore focuses on claim scope mechanics and landscape vectors that are directly implicated by the claim content you provided.
Landscape vectors created by this particular excipient combination
The combination of:
- glycerin (high content polyol),
- sodium benzoate (preservative),
- liquid maltitol (polyol sweetener),
- citric acid + acesulfame potassium (acid-sweet taste system),
- strawberry flavor (organoleptics)
tends to create multiple adjacent claim opportunities by competitors seeking to make an “imatinib oral liquid” that is:
- palatable for pediatric use,
- preservable against microbial growth,
- and stable for shipping.
This means the strongest competitive pressure risk is from patents claiming alternative excipient matrices that still aim to preserve solubility and taste while shifting one or more required claim elements.
Which design-arounds are most relevant for freedom-to-operate against US 11,957,681?
Because the claim is composition-based and uses “consisting of,” the most meaningful design-arounds are composition-level.
1) Move one of the four concentration-limited ingredients outside the claimed range
The simplest quantitative non-infringement strategy is to ensure at least one of:
- imatinib mesylate is below 0.01% w/v or above 25% w/v
- glycerin is below 25% w/v or above 60% w/v
- sodium benzoate is below 0.01% w/v or above 10% w/v
- liquid maltitol is below 0.01% w/v or above 10% w/v
From a commercial feasibility standpoint, shifting glycerin is typically more constrained because it drives viscosity, mouthfeel, and solubilization behavior, but glycerin is also frequently used as a carrier. Sodium benzoate and maltitol are more tunable.
2) Remove or replace a “must-have” ingredient
Because citric acid, acesulfame potassium, and strawberry flavor are listed without range, omission or substitution can reduce infringement risk:
- Replace acesulfame potassium with another sweetener (e.g., sucralose, saccharin, or another polyol system) and remove acesulfame potassium entirely.
- Replace strawberry flavor with a non-strawberry flavor system while removing “strawberry flavor” as an ingredient.
- Replace citric acid with another acidulant (e.g., malic acid) while not including citric acid.
3) Add other ingredients that break “consisting of” scope
If the claim is construed strictly, a product that intentionally includes other formulation ingredients not enumerated could fall outside the “consisting of” limitation. Typical additions that could be relevant include:
- surfactants,
- suspending agents,
- viscosity modifiers,
- alternative buffers,
- co-solvents beyond the listed system.
This is a high-stakes area because litigation turns on claim construction and whether courts treat additional ingredients as “incidental” or deliberate.
What patent expiration and exclusivity timing matters for generic or liquid-solution entry?
No expiration or exclusivity timeline can be computed from the information provided. To do so, the patent’s key bibliographic fields are required (filing date, priority, and any terminal disclaimers), and Orange Book exclusivity would require the specific imatinib product NDA/ANDA listing and exclusivity identifiers. Those data are not included in your prompt, so a timing-based risk map cannot be produced without fabricating facts.
How strong is the patent estate for this formulation, based on claim structure alone?
Strength indicators:
- The claim is not limited to a narrow API dose strength or a particular dosing frequency.
- It provides broad API and excipient quantitative ranges.
- It includes organoleptic components (citric acid, acesulfame potassium, strawberry flavor), which increases the probability that a marketed “strawberry flavored imatinib oral liquid” with glycerin and those preservatives will match.
Potential weaknesses:
- If “consisting of” is enforced strictly, many real-world liquid formulations may use additional ingredients (buffers, stabilizers, solubilizers) and could avoid the claim.
- Large composition ranges can increase prior art overlap risk, but the novelty determination depends on the patent’s specification and the actual prior art record.
Net: the claim is likely strong against closely matching “strawberry glycerin-benzoate maltitol” formulations, and weaker against formulations that reconfigure the taste system or omit listed components or add additional deliberate ingredients.
What is the infringement theory for generic entrants under this claim?
To infringe Claim 1, a challenger would need to show that an accused product is:
- a liquid oral dosage form,
- that “consists of” the claimed ingredient set, and
- that the concentrations of imatinib mesylate, glycerin, sodium benzoate, and liquid maltitol fall within the specified w/v windows.
That means typical generic entry via ANDA for a reformulated oral liquid (if supported by a bioequivalence strategy) would face high infringement risk if the generic formulation matches these ingredient ranges and includes citric acid + acesulfame potassium + strawberry flavor.
How does this claim compare with typical liquid oncology formulation patent approaches?
Common approaches in formulation patenting include:
- narrow recitations of exact concentrations, or
- recitations of solubility enhancers or viscosity modifiers with tight ranges, or
- structural constraints tied to stability outcomes.
This claim is atypical in how broad the API and excipient concentration ranges appear, while still mandating a specific sweetener/preservative/acid/flavor system. That pattern often targets a specific commercially used taste and preservation matrix rather than a purely solubility-driven formulation.
What formulation and process claims would most likely be “companion” claims to US 11,957,681?
Without the full patent document, the companion-claim set cannot be listed. However, based on the provided Claim 1 and typical claim families, the most likely adjacent claim scopes include:
- alternative sweetener systems while keeping glycerin and sodium benzoate,
- alternative flavors (non-strawberry) while keeping citric acid and acesulfame potassium,
- alternative preservatives while keeping sodium benzoate range,
- method claims for preparing the liquid formulation,
- pediatric dosing regimen claims (if the patent family ties to pediatric use).
These are common because they preserve the business objective of covering commercial “ways to make it” while offering multiple barriers to generic mimicry.
What regulatory pathway risks exist for a generic “imatinib oral liquid” given this claim scope?
A generic formulation that seeks FDA approval for an oral liquid version must also satisfy chemistry and manufacturing controls, stability, and bioequivalence or reference product comparisons (depending on the approval route). The patent risk exists regardless of regulatory success if the formulation matches the patented composition.
The patent-specific regulatory exposure is a function of:
- whether the listed branded product in the Orange Book is the same imatinib oral liquid formulation, and
- whether the generic must list the patent under 21 U.S.C. §355(b)(2) (Orange Book patent certifications).
No Orange Book listing data was provided, so claim-trigger certification risk cannot be mapped.
Key Takeaways
- US 11,957,681 Claim 1 is a liquid oral composition claim requiring imatinib mesylate plus a defined glycerin/sodium benzoate/maltitol quantitative matrix and explicitly listed taste and acid components: citric acid, acesulfame potassium, strawberry flavor, and water.
- The primary infringement levers are the four concentration ranges: imatinib mesylate (0.01%–25% w/v), glycerin (25%–60% w/v), sodium benzoate (0.01%–10% w/v), and liquid maltitol (0.01%–10% w/v), plus inclusion of citric acid + acesulfame potassium + strawberry flavor.
- The most practical freedom-to-operate approaches are (a) shifting at least one concentration outside the claimed window, (b) removing a mandatory ingredient (acesulfame potassium/citric acid/strawberry flavor), or (c) leveraging the “consisting of” limitation by structuring the formulation to include non-listed deliberate ingredients.
- A complete timing and Orange Book exclusivity map cannot be produced from the provided claim text alone.
FAQs
1) Does US 11,957,681 cover imatinib mesylate oral solutions without strawberry flavor?
No, based on Claim 1’s explicit requirement for “strawberry flavor,” a strawberry-free formulation does not read on the claim element as written.
2) If a formulation matches all ingredient ranges but uses a different acid than citric acid, is it likely outside the claim?
Yes, because Claim 1 explicitly requires citric acid as an ingredient in the “consisting of” list.
3) Can a generic avoid infringement by using the same excipients but changing glycerin concentration?
Yes. Moving glycerin outside 25%–60% w/v creates a straightforward non-infringement path if the formulation is otherwise within scope and still meets the claim’s “consisting of” ingredient set.
4) Is the claim process-limited or composition-limited?
Composition-limited. The claim is directed to the formulation composition of a liquid dosage form, not manufacturing steps.
5) What is the most likely evidentiary dispute in an infringement case for this claim?
Testing and documentation of actual w/v concentrations of imatinib mesylate, glycerin, sodium benzoate, and liquid maltitol in the accused product, plus ingredient verification for citric acid, acesulfame potassium, and strawberry flavor.
References (APA)
- United States Patent 11,957,681 (claim 1 as provided).
