US Patent 10,993,952: What Is the Scope of the Claims and How Broad Is the Landscape?
United States Patent 10,993,952 claims a specific, stable liquid parenteral cyclophosphamide formulation defined by tightly bounded composition ranges and a defined stability/impurity-performance test after storage. The claim set is built around a solvent system (ethanol plus mixed polyethylene glycol/propylene glycol) and a narrow window for impurity formation under stress.
What Does Claim 1 Actually Cover?
Core product: “stable liquid parenteral formulation of cyclophosphamide”
Claim 1 defines the formulation by six independent elements: (i) drug concentration, (ii) ethanol level, (iii) dual glycol system with a ratio, (iv) PEG mass %, (v) PG mass %, and (vi) impurity limitation after a defined stress condition.
Composition limits (by total formulation weight)
- Cyclophosphamide: about 12% to about 23%
- Ethanol: about 70% to about 75%
- Polyethylene glycol (PEG): about 3.4% to about 8.8%
- Propylene glycol (PG): about 3.4% to about 4.4%
- PEG:PG mass ratio: between approximately 1.0:1.0 and 2.0:1.0
Stability/impurity-performance limitation
After 7 days at 40°C / 75% RH, decomposition must form each listed impurity at < 0.5%:
- a) bis(2-chloroethyl)amine hydrochloride
- b) 3-(2-chloroethyl)-2-oxo-2-hydroxy-1,3,6,2-oxadiazaphosphonane
- c) 3-[2-(2-chloroethylamino)ethyl amino] propyl dihydrogen phosphate dihydrochloride
Scope implications
- Liquid parenteral narrows the field to injectable, solution-like systems, excluding solid forms and excluding dry/lyophilized presentations.
- The combination of high ethanol (70-75%) with specific PEG and PG windows creates a “composition-defined” scope that is difficult to design around without missing at least one constraint.
- The stress test with a numerical impurity cap (<0.5%) converts the claim from purely compositional to compositional + functional. Even a near-match composition can fall outside if impurities exceed the cap.
Where Is the Claim Narrowest?
Claim 1 is most restrictive at the intersection of:
- PG: 3.4% to 4.4% (a tight band)
- PEG:PG ratio: 1.0:1.0 to 2.0:1.0 (constrains PEG relative to PG)
- Ethanol: 70% to 75% (high and bounded)
- Cyclophosphamide: 12% to 23% (bounded)
The PEG and PG ranges are interlocked via the ratio. For a competitor formulation, it is not enough to match PEG and PG ranges independently; it must also satisfy the ratio.
What Additional Scope Do Claims 2 and 3 Add?
Claim 2
Claim 2 adds: the formulation of claim 1 further comprises an antioxidant.
This shifts scope from “no antioxidant required” to “antioxidant present” but does not specify the antioxidant type in Claim 2.
Claim 3
Claim 3 tightens the antioxidant specification:
- antioxidant = monothioglycerol
- monothioglycerol concentration: about 0.01% to about 0.02% by total formulation weight
Scope effect: Claim 3 is a narrow subset of Claim 2. It is only infringed if the formulation both (1) meets Claim 1 composition and stability constraints and (2) uses monothioglycerol at that level.
What Does Claim 4 Lock In? (A Singleton Composition)
Claim 4 provides a specifically enumerated formulation matching a single point (or extremely narrow point) on the parameter space.
Explicit composition in Claim 4
- Cyclophosphamide: about 23%
- Ethanol: about 70%
- PEG:PG ratio: about 1.0:1.0
- PEG: about 3.4% to 8.8%
- PG: about 3.4% to 4.4%
- Monothioglycerol: about 0.02%
Notable: Claim 4 hard-codes cyclophosphamide at the top of the Claim 1 window and ethanol at the low end (70%), plus PEG:PG at 1:1. It also pins monothioglycerol at 0.02% (upper end of Claim 3’s range).
Scope effect: Claim 4 can be treated as a “design point” claim. If a competitor matches Claim 1 but shifts ethanol upward (e.g., >70% by meaningful amount) or shifts PEG:PG ratio away from 1:1, it may still avoid Claim 4 while still potentially falling into Claim 1.
How Likely Is Infringement? (Design-Around Sensitivities)
A competitor would have to satisfy all of the following simultaneously to come within Claim 1:
- Cyclophosphamide at 12% to 23%
- Ethanol at 70% to 75%
- PEG and PG each within their stated ranges
- PEG:PG ratio within 1.0:1.0 to 2.0:1.0
- Impurity control after 7 days at 40°C / 75% RH with each listed impurity below 0.5%
The functional stability constraint is the hardest to “engineer around” by mere substitution because:
- Even if a competitor hits all numeric ranges, impurity formation can vary based on micro-parameters (drying, trace water, mixing, container interaction, processing conditions).
- The claim ties success to a specific impurity set and threshold, not just “stable” in general.
What Is the Practical Claim Coverage Shape?
A “matrix” claim
The claim behaves like a constrained matrix:
- Solvent system axis: ethanol 70-75%
- Co-solvent axis: PEG 3.4-8.8% and PG 3.4-4.4%
- Relative co-solvent axis: PEG:PG 1-2
- Drug load axis: 12-23%
- Performance axis: impurity formation <0.5% after stress
Antioxidant add-on coverage
Claims 2 and 3 add a separate “antioxidant layer”:
- antioxidant included (Claim 2)
- monothioglycerol at 0.01-0.02% (Claim 3)
- monothioglycerol at 0.02% and other fixed parameter choices (Claim 4)
How Does This Map Into the Broader Cyclophosphamide Formulation Landscape?
Likely non-infringement routes
Given claim construction, the main avoidance strategies are typically:
- Change the solvent system outside the bounded windows
- Ethanol outside 70-75%
- PEG outside 3.4-8.8%
- PG outside 3.4-4.4%
- PEG:PG ratio outside 1.0:1.0 to 2.0:1.0
- Use a different impurity-control strategy that does not meet the performance test
- Even with similar composition, failing the <0.5% impurity threshold for the specific impurities may avoid literal coverage (assuming the formulation does not meet the functional limitation).
- Avoid the antioxidant layer
- If a product does not include an antioxidant, it can still potentially fall under Claim 1 (since Claim 1 does not require an antioxidant).
- But it would avoid Claims 2-4 if antioxidants are absent or monothioglycerol is outside the stated range.
What is protected beyond composition?
The listed impurities and the numerical threshold after the defined stress condition mean the patent protects a formulation that is not just “similar” but demonstrably “stable” by the stated metrics.
This tends to make “equivalence-style” design around more difficult because the claim is already tied to measurable outcomes, not just ingredient presence.
Competitive Read: How Broad Is This Relative to a Typical Drug Product Patent?
Relative to many drug product patents that are either:
- broad composition ranges without functional limits, or
- broad method claims for manufacturing,
this one is more specific:
- tight solvent and excipient bands
- a defined co-solvent mass ratio window
- a specific forced-degradation storage condition
- a defined impurity panel with numeric caps
That combination generally supports narrower but enforceable coverage focused on a particular formulation class.
Key Takeaways
- Claim 1 defines a liquid parenteral cyclophosphamide formulation with tightly bounded ethanol (70-75%), cyclophosphamide (12-23%), PEG (3.4-8.8%), PG (3.4-4.4%), and PEG:PG ratio (1-2), plus a quantified stability requirement: after 7 days at 40°C/75% RH, each specified impurity must be <0.5%.
- Claims 2-3 add an antioxidant requirement; Claim 3 narrows to monothioglycerol at 0.01%-0.02%.
- Claim 4 locks a near “single point” within the claim space: cyclophosphamide ~23%, ethanol ~70%, PEG:PG ~1:1, and monothioglycerol ~0.02%, while preserving the PEG and PG range language.
- The stability/impurity clause is the main practical enforcement lever and raises the cost of design-arounds that rely only on adjusting compositions.
FAQs
1) Does Claim 1 require an antioxidant?
No. Claim 1 is fully satisfied by the specified cyclophosphamide, ethanol, PEG/PG and ratio, plus the impurity-performance requirement.
2) What impurity endpoints are explicitly controlled?
The claim lists three specific impurities (bis(2-chloroethyl)amine hydrochloride; 3-(2-chloroethyl)-2-oxo-2-hydroxy-1,3,6,2-oxadiazaphosphonane; and 3-[2-(2-chloroethylamino)ethyl amino] propyl dihydrogen phosphate dihydrochloride) each at <0.5% after the defined stress.
3) If a formulation matches Claim 1 ranges but fails the impurity threshold, is it covered?
It would not satisfy Claim 1 as written because Claim 1 includes the impurity-performance limitation after the stated storage condition.
4) What does Claim 4 add that Claim 1 does not?
Claim 4 anchors a specific formulation point: cyclophosphamide about 23%, ethanol about 70%, PEG:PG about 1:1, and monothioglycerol about 0.02%.
5) How do Claims 2 and 3 change the infringement picture?
They add an antioxidant requirement, with Claim 3 narrowing to monothioglycerol in a specified concentration band. A formulation can potentially fall under Claim 1 while avoiding Claims 2-4 if it uses no antioxidant or uses monothioglycerol outside the defined range.
References (APA)
[1] User-provided claim text for US Patent 10,993,952 (claims 1-4).
