US Patent 12,138,248 (bendamustine/PEG liquid): What is claimed, what is covered, and where competitors still have room
What are the claim-level boundaries in US 12,138,248?
US 12,138,248 claims a sterile, liquid bendamustine formulation packaged in a sterile container, with tight control of: (i) bendamustine concentration, (ii) the vehicle (PEG with optional co-solvents), (iii) antioxidant identity and level, and (iv) stability/impurity limits measured by HPLC at 223 nm after at least 15 months under 5 °C to 25 °C storage.
Independent claim
Claim 1 (sterile container + formulation) is the only independent claim provided. It requires all of the following:
- Sterile container containing a liquid bendamustine-containing composition comprising
- Bendamustine (or a pharmaceutically acceptable salt).
- Bendamustine concentration: “about 25 mg/mL”.
- A pharmaceutically acceptable fluid consisting of
- Polyethylene glycol (PEG), and optionally one or more of:
propylene glycol, ethanol, benzyl alcohol, glycofurol.
- A stabilizing amount of an antioxidant.
- Impurity threshold: “total impurities resulting from the degradation of the bendamustine is less than about 5% peak area response”
- Method: HPLC
- Wavelength: 223 nm
- Time/temperature: after at least 15 months at about 5 °C to about 25 °C.
Dependent claims that narrow within Claim 1
- Antioxidant identity
- Claim 2: antioxidant is monothioglycerol.
- Claim 3: monothioglycerol at about 5 mg/mL.
- Stability statements
- Claim 4: composition stable for at least about 15 months at 5 °C or at least about 15 months at 25 °C.
- Vehicle sub-sets
- Claim 5: vehicle consists of PEG and one or more of the listed co-solvents.
- Claims 13–17: sterile container variants where the vehicle consists of PEG plus a specific one (or glycofurol) among the listed co-solvents:
- PEG only (Claim 13)
- PEG + propylene glycol (Claim 14)
- PEG + ethanol (Claim 15)
- PEG + benzyl alcohol (Claim 16)
- PEG + glycofurol (Claim 17)
- Dose/amount language
- Claims 6 and 7: “about 100 mg of bendamustine” (as salt or as free base).
- Note that these depend from Claim 1, but do not appear to change the 25 mg/mL concentration requirement inherited from Claim 1.
- Parallel composition claims
- Claims 8–12 recast the formulation as a standalone “liquid bendamustine-containing composition,” with the same core constraints as Claim 1:
- 25 mg/mL bendamustine in PEG-based fluid (PEG plus optional listed co-solvents)
- antioxidant-stabilized
- total degradation impurities <5% peak area at 223 nm after at least 15 months at 5–25 °C
- Claims 9–10: monothioglycerol and at about 5 mg/mL.
- Claims 11–12: vehicle consisting of PEG plus one or more listed co-solvents; benzamustine concentration about 25 mg/mL.
- More vehicle sub-sets
- Claims 18–22: composition variants matching Claim 11’s vehicle subsets:
- PEG only (Claim 18)
- PEG + propylene glycol (Claim 19)
- PEG + ethanol (Claim 20)
- PEG + benzyl alcohol (Claim 21)
- PEG + glycofurol (Claim 22)
What is the practical claim “shape”?
The patent is not a broad “any bendamustine liquid.” It is a narrow formulation claim with a technical performance gate:
- Composition: bendamustine + antioxidant in PEG-based fluid
- Concentration: about 25 mg/mL bendamustine
- Stability/quality: degradation impurities capped at <5% peak area (HPLC, 223 nm) after 15 months at 5–25 °C
- Sterility packaging: “sterile container” is required in the container claims
This structure means a competitor can avoid infringement only by changing at least one mandatory element, typically one of the following:
1) Bendamustine concentration (not “about 25 mg/mL”),
2) Vehicle system (not PEG with the defined optional co-solvents and “consists of” boundaries),
3) Antioxidant identity/level (if the asserted claim depends on monothioglycerol at ~5 mg/mL),
4) Stability performance such that impurities exceed the <5% peak area cap, or
5) Form factor (for the “sterile container” claims) if sterility is not met as claimed.
How broad is “about 25 mg/mL” and “about 5% peak area” in enforceable scope?
The claims use “about” in multiple places:
- Bendamustine concentration: about 25 mg/mL
- Impurities: “less than about 5% peak area response”
- Antioxidant concentration in dependent claims: “about 5 mg/mL” for monothioglycerol
From a landscape perspective, the scope hinges on how “about” is construed. Practically, enforcement risk will cluster around formulations that are:
- near the same concentration (operationally close to 25 mg/mL),
- demonstrate the claimed impurity limit by HPLC at 223 nm,
- are stored for the same duration and temperature range.
Even small deviations can matter because the claims tie infringement to a specific analytical readout after a specific accelerated/real-time stability regimen.
What do the dependent vehicle claims do to competitors?
The vehicle in Claim 1 is stated as:
- “polyethylene glycol and optionally one or more of propylene glycol, ethanol, benzyl alcohol and glycofurol.”
The dependent claims then create “consists of” variants that lock the permissible vehicle inventory. Examples:
- Claim 13: vehicle consists of PEG (no co-solvent)
- Claim 14: PEG + propylene glycol
- Claim 15: PEG + ethanol
- Claim 16: PEG + benzyl alcohol
- Claim 17: PEG + glycofurol
The “consists of” language is a sharper boundary than “comprises,” which generally allows additional components. If asserted claims rely on the “consists of” limitations, competitors with extra solvents, buffers, or stabilizers outside the enumerated list can face design-around difficulty.
The antioxidant is also a stabilizing element but is not limited in Claim 1 beyond “a stabilizing amount.” The scope tightens if an asserted claim is dependent on monothioglycerol (Claims 2 and 3, or 9 and 10).
What is the likely infringement test structure?
If a formulation is alleged to infringe, the claim elements imply this analytical test flow:
1) Is it bendamustine (or a pharmaceutically acceptable salt)?
2) Is concentration about 25 mg/mL?
3) Is the vehicle PEG plus only the optional enumerated co-solvents (or only PEG in the “consists of PEG” variants)?
4) Is there an antioxidant in a stabilizing amount?
5) Does it meet the stability performance gate?
- HPLC at 223 nm
- after at least 15 months at about 5 °C to 25 °C
- degradation impurities < about 5% peak area
6) For container claims: is the formulation in a “sterile container”?
The stability test can be the decisive element because it is both time- and temperature-conditioned and uses a quantified impurity threshold.
What is the patent landscape implication given claim structure alone?
With only the claims provided (no prosecution history, no cited art list, no specification disclosure), the defensible landscape conclusion is limited to claim-scope-driven mapping rather than a full prior-art validity analysis.
Still, the claims indicate that the novelty and/or commercial value the applicant asserted is tied to achieving:
- a PEG-based liquid formulation of bendamustine at ~25 mg/mL, and
- low degradation impurity levels under defined storage conditions, with an antioxidant stabilization strategy (with monothioglycerol singled out in dependent claims).
This tends to concentrate competition around:
- alternative antioxidants (if permitted under “a stabilizing amount of an antioxidant” but may fail the impurity threshold), or
- alternative vehicle systems (non-PEG, or PEG systems with additional co-solvents beyond the enumerated list, depending on which dependent claims are asserted), or
- alternative concentrations (not “about 25 mg/mL”),
- and separate stability outcomes (impurities above the <5% peak area cap).
Where are the likely design-around “pressure points”?
Using only the provided claim text, the most straightforward design-around levers are:
-
Vehicle swap away from PEG
- If a competitor uses a different liquid excipient system (not PEG), Claim 1’s “consisting of PEG and optionally listed co-solvents” becomes a mismatch.
-
Concentration shift away from 25 mg/mL
- Moving concentration outside the “about” range can break element 1.
-
Antioxidant substitution
- Claim 1 does not require monothioglycerol. Only the dependent claims do. So using a different antioxidant keeps the competitor in Claim 1’s “a stabilizing amount” space, unless the formulation fails the impurity threshold.
-
Purity/stability outcome change
- If degradation impurities exceed “less than about 5% peak area response” after at least 15 months (5–25 °C) using HPLC at 223 nm, then even a near match in composition may avoid infringement.
-
For “sterile container” claims
- If the competitor’s product packaging or sterility status does not meet the claim’s sterile container requirement, that can matter. (In practice, commercial products almost always meet sterility expectations, so this is typically a weaker lever.)
Key Takeaways
- US 12,138,248 claims a PEG-based liquid bendamustine formulation with ~25 mg/mL bendamustine, an antioxidant, and a measured stability gate: total degradation impurities < ~5% peak area by HPLC at 223 nm after at least 15 months at ~5 °C to 25 °C.
- The patent’s scope is constrained by “consists of” vehicle limitations in dependent claims, enumerating PEG and optionally propylene glycol, ethanol, benzyl alcohol, and glycofurol.
- Monothioglycerol at ~5 mg/mL is covered in dependent claims, but Claim 1 covers any antioxidant that achieves the impurity limit.
- Competitors’ highest-probability design-around paths are: change vehicle, change concentration, change stability outcome, or, for narrower dependent claims, avoid monothioglycerol at ~5 mg/mL.
- Landscape conclusions from claims alone are composition- and performance-driven; a full prior-art and validity map requires prosecution and patent-family data not included in the claim text.
FAQs
1) Does the patent require monothioglycerol?
No. Claim 1 only requires “a stabilizing amount of an antioxidant.” Monothioglycerol is required only in dependent claims (Claims 2–3 and 9–10).
2) What measurement defines infringement risk in Claim 1?
The key gate is “total impurities resulting from the degradation of the bendamustine” < ~5% peak area response measured by HPLC at 223 nm after at least 15 months at ~5 °C to 25 °C.
3) Is PEG mandatory?
Yes. The vehicle in Claim 1 is “polyethylene glycol and optionally” specific co-solvents. Dependent claims use “consists of,” narrowing vehicle composition further.
4) What concentration is covered?
The bendamustine concentration in the composition is about 25 mg/mL in the independent framework (Claim 1) and in composition-dependent claims (Claims 8 and 12).
5) Are there both product-form and formulation claims?
Yes. The patent includes a sterile container claim set (Claims 1–7, plus container vehicle subsets) and a parallel set of liquid composition claims (Claims 8–12, plus composition vehicle subsets).
References
[1] US Patent 12,138,248. Claims 1-22 (provided claim text).
