Patent 11,566,000 scope and claims review: stable sofpironium bromide co-crystal Form CO (US claims, composition and formulation coverage)
United States Patent US 11,566,000 claims a specific stable sofpironium bromide co-crystal polymorph (“Form CO”) defined by (i) a 1:3 stoichiometric ratio of two defined co-formers (formula I-a and I-b), (ii) strict purity and impurity limits, (iii) physicochemical stability and non-hygroscopic behavior, and (iv) an objective DSC and PXRD fingerprint. The claims then extend to a topical pharmaceutical composition containing this Form CO and a manufacturing method for obtaining the active (Form CO) from sofpironium bromide using a specified solvent system (ethyl acetate + methyl t-butyl ether), filtration after stirring.
What does US 11,566,000 claim for sofpironium bromide co-crystal Form CO?
Short answer: Claim 1 defines the protected product as a particular co-crystalline solid form of sofpironium bromide, identified by compositional ratio, purity/impurity thresholds, non-hygroscopic stability, and a set of DSC and PXRD peaks.
Claim 1 structure and required limitations
Claim 1 is a closed, multi-parameter definition. An accused product must meet every enumerated requirement. Key elements:
-
Identity as a co-crystal Form CO
- “A stable co-crystal Form CO of sofpironium bromide”
-
Stoichiometry requirement
- Form CO “comprising in a 1:3 ratio”
- a) compound of formula I-a
- b) compound of formula I-b
-
Purity threshold tied to compound (I)
- “purity of co-crystal Form CO is not less than 98% w/w based on the content of the compound (I)”
- This means the solid must be predominantly the targeted sofpironium bromide-containing co-crystal entity as measured by “content of compound (I)” (as the patent defines).
-
Stability and physical behavior
- “physicochemically stable and non-hygroscopic”
-
DSC thermal fingerprint
- “exhibits a single sharp endothermic peak value of 150°C”
- DSC is “as described in Japanese Pharmacopoeia (17th Edition).”
-
PXRD fingerprint
- “characterized as showing peaks at 5.9 ±0.2, 7.6 ±0.2, 11.0 ±0.2, and 22.2 ±0.2 degrees (2θ)”
- “in a powder X-ray diffraction spectrum.”
Practical reading for enforceability: Claim 1 is a classic “form-by-function” claim where infringement turns on analytical testing of the accused solid. The claim does not merely say “co-crystal”; it requires the exact analytical signatures plus compositional and purity constraints.
Claim 1 infringement trigger tests
An enforcement posture typically tests:
- Co-crystal identity: confirm the presence of both co-former components (I-a and I-b) at the required 1:3 ratio.
- Purity and impurity profiling: confirm the “98% w/w based on content of compound (I)” requirement.
- Non-hygroscopic and stability: confirm behavior under relevant humidity/conditioning used in the patent’s definition.
- DSC: confirm a single sharp endothermic peak at 150°C.
- PXRD: confirm peak positions within the stated tolerances.
Because the claim fixes tolerances (±0.2°) and requires a single DSC feature at 150°C, even small shifts or multiplet melting/endotherms can be asserted as non-infringing.
How do claims 2 and 3 narrow the co-crystal Form CO purity and impurity profile?
Short answer: Claims 2 and 3 add stricter quantitative constraints on minor constituents/impurities, tightening the product scope.
Claim 2: limit for compounds III/IV/V
Claim 2 states Form CO of claim 1 where:
- “a content of each compound represented by formulae III, IV and V is not more than 0.5% w/w based on a content of compound (I).”
This is a specific impurity/composition limitation. Even if an accused solid matches the DSC/PXRD and ratio requirement, failing this impurity threshold can avoid coverage under Claim 2 (but not necessarily avoid Claim 1, depending on whether Claim 2 is an additional dependent limitation only for that dependent claim).
Claim 3: total impurities limit
Claim 3 states:
- “the total content of impurities is not more than 2.0% w/w based on a content of compound (I).”
This provides another quantitative gate. In practice, impurity profiling is often the dispute driver in co-crystal form patents because analytical methods, reference standards, and thresholds matter.
What is protected beyond the co-crystal itself: topical composition claim 4?
Short answer: Claim 4 covers a topical pharmaceutical composition comprising the protected Form CO plus a pharmaceutically acceptable carrier.
Claim 4 requirements
- “A stable topical pharmaceutical composition”
- Made by mixing:
- “a pharmaceutically effective amount of sofpironium bromide co-crystal Form CO according to claim 1”
- with “a pharmaceutically acceptable carrier.”
Key scope points:
- It is not limited by concentration range of active ingredient in the text you provided.
- It is not limited by specific topical vehicle type in the claim language shown; it is broadly “carrier.”
- It is limited by the requirement that the API is Form CO as defined in Claim 1.
Infringement risk for formulators: If a generic or competitor uses a different solid form, or Form CO that fails one of the Claim 1 analytical thresholds, then Claim 4 coverage can be avoided (assuming no separate claims cover alternate forms or polymorphs).
What manufacturing method is claimed in claim 5, and what does it cover?
Short answer: Claim 5 claims a method to prepare the active Form CO using a specific solvent system for a sofpironium bromide suspension, with at least 1 hour stirring and then filtration to obtain the crystalline form.
Claim 5 step-by-step scope
Claim 5 states Claim 4 where the active agent (Form CO) is prepared by:
- “preparing a suspension of sofpironium bromide in a solvent comprising ethyl acetate and methyl t-butyl ether”
- “stirring the suspension for at least 1 hour”
- “and filtering the suspension to obtain the crystalline form of the active pharmaceutical agent.”
Implications:
- The claim is method-forming, so a competitor manufacturing Form CO via a different solvent pair, different stirring time, or different isolation step may avoid Claim 5 while still potentially infringing Claim 1/4 if the resulting solid is the same protected Form CO.
- The claim does not specify ratios of ethyl acetate to methyl t-butyl ether in the text provided; it only requires the solvent comprising both.
Design-around pathway: Using the same end product (Form CO) could still risk Claim 1/4 exposure even if Claim 5 is avoided. Conversely, using the same process but altering the produced solid so it fails the PXRD/DSC fingerprints can reduce product claim risk.
How strong is the patent estate around analytical-defined co-crystal solid forms?
Short answer: The claims you supplied rely on objective analytics (DSC and PXRD) plus quantitative composition constraints, which often improves proof in litigation but also makes non-infringement possible through controlled variation in crystallization outcome and impurity management.
Key strengths
- Analytical specificity: PXRD peak positions with tolerances and a DSC single endotherm at 150°C create concrete identity criteria.
- Purity and impurity thresholds: Claim 2 (0.5% w/w each for compounds III/IV/V) and Claim 3 (≤2.0% total impurities) provide additional measurable gates.
- Composition and formulation coverage: Claim 1 covers the solid; Claim 4 covers topical formulations containing it.
- Process hook: Claim 5 adds an additional independent infringement theory tied to manufacturing.
Key vulnerability
- Form-by-form definition is testable. If a competitor obtains a different polymorph, amorphous content, or a co-crystal with shifted PXRD peaks or different DSC behavior, it can argue non-infringement.
- Impurity testing variability: If Claim 2/3 become central, disputes can arise around impurity method, standards, and sample preparation.
What generic or competitor entry risks exist for sofpironium bromide topical products?
Short answer: The risk concentrates on competitors that use or generate exactly the claimed Form CO API and then formulate it into a topical product.
Risk scenarios
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Generic topicals using the same Form CO API
- High risk for Claim 4 exposure.
- High risk for Claim 1 if product form is challenged directly.
-
Competitors producing Form CO by the same solvent method
- Adds Claim 5 exposure if method steps are mirrored (ethyl acetate + methyl t-butyl ether; ≥1 hour stirring; filtration).
-
Competitors using a different co-crystal form or polymorph
- Potentially avoids Claim 1/4 if DSC and PXRD fingerprints differ enough to fall outside stated tolerances.
- Must also manage purity/impurity profiles if aiming to still fall within Claim 2/3 ranges.
What analytical results matter most
- PXRD peak positions (5.9, 7.6, 11.0, 22.2 degrees 2θ within ±0.2°)
- DSC: a single sharp endothermic peak at 150°C
- Purity ≥98% w/w based on compound (I) content
- Impurity limits: individual ≤0.5% w/w and total ≤2.0% w/w
What patent “landscape” can be inferred from this claim set (within the limits of provided text)?
Short answer: Based on the claim architecture, the broader landscape most likely clusters around:
- solid form patents for co-crystal/polymorph variants,
- process patents for producing those solids,
- and formulation patents for topical vehicles.
But the actual breadth, priority chain, and whether US 11,566,000 is part of a larger family set across jurisdictions cannot be confirmed from the claim text alone.
Inferred family structure by claim type
- Product form claim (Claim 1): analytical fingerprint co-crystal Form CO.
- Product form dependent claims (Claims 2-3): impurity control layers.
- Formulation claim (Claim 4): topical composition.
- Manufacturing method claim (Claim 5): solvent-based crystallization route.
This pattern aligns with typical strategies by originators: secure enforceable protection on the crystalline API identity, then extend to downstream product and upstream synthesis.
Claim-by-claim scope table for US 11,566,000 (based on supplied claim language)
| Claim |
What it protects |
Essential limitations (must all be met) |
Key analytical gate |
| 1 |
Stable sofpironium bromide co-crystal Form CO |
1:3 ratio of I-a:I-b; purity ≥98% w/w; physicochemically stable; non-hygroscopic; DSC single sharp endotherm at 150°C; PXRD peaks at 5.9±0.2, 7.6±0.2, 11.0±0.2, 22.2±0.2 (2θ) |
DSC at 150°C; PXRD peak matching |
| 2 |
Same as Claim 1 plus impurity ceiling per compounds III/IV/V |
Each of III/IV/V ≤0.5% w/w (based on compound I content) |
Quantitative impurity profiling |
| 3 |
Same as Claim 1 plus total impurity ceiling |
Total impurities ≤2.0% w/w (based on compound I content) |
Total impurity profiling |
| 4 |
Topical pharmaceutical composition |
Contains “pharmaceutically effective amount” of Form CO (Claim 1) + pharmaceutically acceptable carrier |
Identity of API Form CO |
| 5 |
Method to make the active Form CO used in Claim 4 |
Suspend sofpironium bromide in solvent comprising ethyl acetate + methyl t-butyl ether; stir ≥1 hour; filter to obtain crystalline form |
Resulting solid must match Claim 1 if litigated under product claims |
Key Takeaways
- US 11,566,000 protects a highly specific crystalline entity: sofpironium bromide co-crystal Form CO defined by 1:3 stoichiometry (I-a:I-b), ≥98% w/w purity, non-hygroscopic stability, and tight DSC/PXRD fingerprints.
- Dependent claims add impurity controls: ≤0.5% w/w each for compounds III/IV/V and ≤2.0% w/w total impurities.
- Downstream protection includes topical formulations containing the claimed Form CO and a process for producing the Form CO via ethyl acetate + methyl t-butyl ether suspension crystallization with ≥1 hour stirring and filtration.
- Competitor/generic risk centers on whether the API used in the topical product matches the precise analytical identity (DSC and PXRD) and meets the compositional/impurity thresholds; process differences can avoid Claim 5 but may still leave product-form claims at risk.
FAQs
- Can a competitor avoid infringement by shifting PXRD peaks slightly outside ±0.2° tolerances?
- How do impurity limits in Claims 2 and 3 affect design-around strategies for co-crystal Form CO?
- If a topical product uses Form CO obtained by a different solvent system than ethyl acetate + methyl t-butyl ether, does Claim 5 still apply?
- Does Claim 4 cover any topical dosage form or only specific vehicle types?
- What analytical sequence is most persuasive for confirming the claimed Form CO identity (PXRD versus DSC)?
