Scope and Claims Analysis for US Patent 11,975,013: Thiotepa Drug Product Compositions in DMSO, PEG400/PEG600, DMA, or NMP with Impurity and Water Controls
Executive summary
US 11,975,013 protects thiotepa compositions defined by (1) specific solvents (DMSO, PEG400, PEG600, DMA, NMP), (2) thiotepa concentration (about 1 to 100 mg/mL), (3) substantially impurity-free constraints with explicit maximum impurity levels (formic acid, acetic acid, formaldehyde, acetaldehyde, peroxide), and (4) optionally water in tightly bounded levels (up to about 30% and down to up to 5%), plus (5) an optional thiosulfate stabilizer at 0.01% to 1.0%. The claim set is structured to cover both neat/solvent-only products and partially aqueous products, and it also creates clear infringement “scorecards” for ANDA/505(b)(2) and compounding-like products that must match solvent identity, thiotepa strength, impurity profile, and water/thiosulfate presence.
What exactly does US 11,975,013 claim: thiotepa composition defined by solvent, concentration, and impurity limits?
Core claim concept: a thiotepa drug product composition defined by solvent selection plus API concentration and an impurity specification.
Claim 1 elements (scope-defining building blocks)
Claim 1 is the independent, broadest anchor and can be treated as a checklist:
- Active: thiotepa.
- Solvent identity (Markush group): solvent is selected from:
- dimethylsulfoxide (DMSO)
- polyethylene glycol 400 (PEG400)
- polyethylene glycol 600 (PEG600)
- dimethylacetamide (DMA)
- N-methylpyrrolidone (NMP)
- Strength: thiotepa present at about 1 to about 100 mg/mL.
- Purity condition: composition is substantially free of impurities, with impurities defined and bounded by explicit ppm limits:
- formic acid < 150 ppm
- acetic acid < 15 ppm
- formaldehyde < 15 ppm
- acetaldehyde < 15 ppm
- peroxide < 35 ppm
- No additional solvent restriction: claim 1 does not require absence of water as written, but it later creates explicit non-water dependent claim (claim 2) and aqueous variants (claims 6–11). Practically, claim 1 reads as allowing water unless excluded by dependent limitations or by “substantially free” plus impurity spec.
Functional meaning of “substantially free”
While “substantially free” is inherently elastic, the claim then supplies concrete numerical impurity ceilings. For validity and infringement analysis, those ppm thresholds do most of the work. A product that meets the explicit impurity ceilings is more likely to land within claim 1 even if other trace impurities exist.
Featured-snippet answer
US 11,975,013 Claim 1 covers thiotepa (1–100 mg/mL) in specified organic solvents (DMSO/PEG400/PEG600/DMA/NMP) with tightly bounded levels of formic/acetic acids, aldehydes, and peroxide, optionally allowing additional dependent features such as absence of water, controlled water content, and thiosulfate.
How do the dependent claims narrow the formulation space? (water-free vs aqueous vs thiosulfate)
The claim family uses a classic dependent-claim strategy to expand coverage across commercially plausible packaging/administration states.
Claim 2: water-free compositions
- “Does not comprise water.”
- Scope impact: removes ambiguity around partial aqueous content.
- Infringement trigger: if a product has zero water (or is formulated such that “comprises water” does not apply), it targets this lane.
Claims 3–5: solvent-specific embodiments (neat organic)
These are direct enumerations:
- Claim 3: thiotepa + PEG400
- Claim 4: thiotepa + PEG600
- Claim 5: thiotepa + DMSO
Scope impact: they convert Markush “selected from” language into explicit, solvent-to-product linkages for litigation. Infringement still requires satisfying the independent claim 1 constraints (thiotepa 1–100 mg/mL and impurity ceilings).
Claims 6–11: controlled water presence (partially aqueous)
- Claim 6: further comprises water.
- Claim 7: water is present at one of several caps:
- up to ~30%
- up to ~25%
- up to ~20%
- up to ~15%
- up to ~10%
- up to ~5%
- Claims 8–10: aqueous variants with solvent:
- claim 8: thiotepa + PEG400
- claim 9: thiotepa + PEG600
- claim 10: thiotepa + DMSO
- Claim 11: water is an aqueous saline solution.
Scope impact:
- These claims capture products that blend water into the organic solvent system, including saline-containing formulations suitable for preparation or stability.
- The water cap ladder (30% down to 5%) creates multiple potential “design-around” pressure points. A competitor can attempt to avoid infringement by exceeding the top water cap, but that may conflict with practical formulation constraints, viscosity, solubility, and dosing volume. Alternatively, a competitor can aim for water absence (claim 2) or avoid the exact solvent identities (Markush avoidance).
Claim 12–13: thiosulfate stabilizer lane
- Claim 12: composition further comprises thiosulfate.
- Claim 13: thiosulfate amount is about 0.01% to about 1.0%.
Scope impact:
- This covers an additional stabilizing strategy. If a competitor uses different antioxidants/reductants, they may avoid claim 12–13 but still risk claim 1 if the thiosulfate is absent and the core solvent/impurity constraints are met.
What is the practical infringement “matrix” for US 11,975,013? (solvent x strength x impurity x water x thiosulfate)
The claim architecture is tight enough to translate into a discrete infringement testing plan.
Claim scope scoring table
| Dimension |
Claim language |
Direct pass/fail risk |
| Solvent identity |
DMSO, PEG400, PEG600, DMA, or NMP |
High: change solvent likely avoids |
| Thiotepa concentration |
~1 to ~100 mg/mL |
High: strength outside range avoids |
| “Substantially free” |
plus explicit impurity limits |
High: analytical mismatch can defeat |
| Formic acid |
< ~150 ppm |
Quantitative trigger |
| Acetic acid |
< ~15 ppm |
Quantitative trigger |
| Formaldehyde |
< ~15 ppm |
Quantitative trigger |
| Acetaldehyde |
< ~15 ppm |
Quantitative trigger |
| Peroxide |
< ~35 ppm |
Quantitative trigger |
| Water presence |
absent (claim 2) or present (claim 6) |
High: water content matters |
| Water level |
up to ~30%, 25%, 20%, 15%, 10%, or 5% |
High: water percentage is key |
| Water identity |
aqueous saline solution (claim 11) |
Medium: depends on product |
| Thiosulfate |
present (claim 12) |
Medium: optional feature |
| Thiosulfate amount |
~0.01% to ~1.0% (claim 13) |
Medium: depends on use |
Key litigation-relevant point
Because the independent claim includes explicit ppm ceilings and concentration ranges, infringement analysis will likely center on QC batch release testing data for impurity profile and solvent system, not only on generic composition descriptors.
How does US 11,975,013 compare with typical thiotepa formulation IP? (solvent choice + impurity specifications)
This patent’s differentiator is the combination of:
- specific polar aprotic solvents (DMSO, NMP, DMA) and PEG-based solubilizers (PEG400/PEG600),
- bounded API concentration (1–100 mg/mL), and
- numerical impurity limits for degradation-related species (formic/acetic acid, aldehydes, peroxide).
Many thiotepa-related patents and patents for cytotoxic injectables focus on method-of-use, lyophilized forms, unit-dose presentation, or broad excipient inclusion without such tight impurity quantification. Here, the claim is engineered to protect release-spec-defined drug products, not just “a thiotepa solution.”
What patent landscape risks exist for thiotepa generics or 505(b)(2) products under this claim?
Within the limited information provided, the risk profile is determined by whether an applicant’s candidate product must be:
- DMSO/PEG400/PEG600/DMA/NMP-based, and
- within thiotepa concentration 1–100 mg/mL, and
- manufactured to impurity limits for the specific five impurity classes, and
- optionally: water content within the dependent bounds or thiosulfate within 0.01%–1.0%.
Design-around levers implied by the claims
- Solvent substitution: using solvents outside the five listed (and not qualifying under “selected from”) avoids core claim 1.
- Concentration shift: shifting below 1 mg/mL or above 100 mg/mL can avoid claim 1, but may break dosing and administration constraints.
- Impurity management mismatch: if any of the five impurity classes exceed the ppm ceilings, claim 1 fails.
- Water strategy: a “water-free” product avoids claim 6–11 while still potentially falling into claim 1 (unless claim 1 product does not meet “substantially free” criteria).
- Thiosulfate exclusion: avoid claim 12–13 by omitting thiosulfate or using an out-of-range amount.
Where do claim gaps likely matter? (what is not covered by the provided claims text)
Based only on the claims provided in the prompt, the following are not explicitly part of the protected matter in these claims:
- dosage form presentation details (vial type, freeze-dried vs liquid),
- container closure system claims,
- manufacturing steps (mixing order, sterilization method, process controls),
- method-of-use claims (indication, regimen),
- particle size, reconstitution steps, or pH specifications (unless embedded elsewhere in a fuller claim set not provided here).
This matters commercially because many thiotepa competition barriers are process- or administration-based. Here, the visible claim set is product-composition centered.
What is the claim strength relative to typical formulation patents?
Based on claim structure alone:
-
Strength indicators
- Explicit solvent list.
- Explicit thiotepa concentration band.
- Explicit impurity ppm ceilings for multiple analytes.
- Optional branches for water and saline, plus thiosulfate stabilization.
-
Strength vulnerabilities
- If a challenger uses a different solvent system outside the listed Markush options, the core claim 1 may not read on the composition.
- If a product is outside concentration limits or has impurity levels above ceilings, claim 1 may not read on it even if the solvent is identical.
Key Takeaways
- US 11,975,013 Claim 1 protects thiotepa compositions defined by (i) solvent identity (DMSO/PEG400/PEG600/DMA/NMP), (ii) thiotepa concentration 1–100 mg/mL, and (iii) impurity ceilings for formic acid, acetic acid, formaldehyde, acetaldehyde, and peroxide.
- Claims 2–5 carve out water-free and specific solvent embodiments.
- Claims 6–11 cover partially aqueous formulations with water caps (up to 30% to 5%) and a specific aqueous saline limitation.
- Claims 12–13 add a thiosulfate stabilization lane at 0.01%–1.0%.
- For competitive assessment, the decision tree is straightforward: match solvent + match strength + meet all five impurity ppm limits + control water/thiosulfate as required.
FAQs
1) Does US 11,975,013 require “substantially free of impurities” and also specific ppm limits?
Yes. Claim 1 combines a general “substantially free” qualifier with explicit numerical limits for five named impurities.
2) Can a product still infringe if it uses DMSO but has higher peroxide than the claim allows?
No. Claim 1 requires peroxide below about 35 ppm (and the other impurity ceilings as well).
3) Is water presence always required to infringe?
No. Water is only expressly limited by dependent claims (claim 2 excludes water; claims 6–11 require water with caps). Claim 1 itself does not require water.
4) Does thiosulfate inclusion automatically mean infringement of the thiosulfate claims?
Thiosulfate inclusion is required only for claims 12–13. Infringement of claim 12–13 also requires matching the thiosulfate amount (about 0.01% to 1.0%) plus claim 1 constraints.
5) What is the fastest likely design-around if reformulation is allowed?
Using a solvent system outside the listed five solvents is the most direct avoidance lever, assuming other constraints (concentration and impurity limits) are also satisfied for non-infringement.
References
- United States Patent 11,975,013.
