United States Patent 8,501,698 (US8501698) for (S)-propylene glycol (S-PG) solvate Form SC-3: what the claims cover and where exclusivity risk sits
US 8,501,698 is drafted as a solid-state patent anchored on a specific crystalline (S)-propylene glycol (S-PG) solvate “Form SC-3,” with hard analytical fingerprints (powder XRD 2θ set; unit cell and space group; solid-state ^13C NMR peak positions; DSC and TGA thermal signatures). The independent scope is not the medical use itself, but the product identity of the crystalline solvate, plus formulations and broad therapeutic methods of use.
Because the claim set is built on “substantially characterized by” measured analytical profiles at room temperature, the patent’s practical enforceability against competitors turns on (1) whether an accused material is the same crystalline solvate polymorph/solvate form and (2) whether the accused product can be proven (by the same or equivalent test conditions) to meet the claim’s “substantially” matching ranges/peak positions, unit-cell metrics, and thermal events.
What exactly does US 8,501,698 claim: “Form SC-3” crystalline (S)-propylene glycol solvate identity?
Core product claim (Claim 1).
US 8,501,698 Claim 1 covers a pharmaceutical composition comprising:
- A therapeutically effective amount of a crystalline (S)-propylene glycol solvate of structure Form SC-3, and
- The material is characterized by a powder X-ray diffraction (PXRD) pattern at room temperature with Cu Kα = 1.5418 Å and peaks at:
3.8 ± 0.1, 7.6 ± 0.1, 8.1 ± 0.1, 8.7 ± 0.1, 15.2 ± 0.1, 15.7 ± 0.1, 17.1 ± 0.1, 18.9 ± 0.1, 20.1 ± 0.1 (2θ)
The rest of Claim 1 is not limited by dose form, administration route, or specific API identity beyond “therapeutically effective amount” of the S-PG solvate being part of the composition.
Secondary independent claim framing: does the patent also define Form SC-3 by structure metrics and spectroscopy?
Claim 2 (dependent but with broad qualifying structure).
Claim 2 further constrains the SC-3 solvate identity using one or more of the following characterizations:
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Unit cell parameters:
a = 11.2688(8) Å
b = 4.8093(3) Å
c = 46.723(3) Å
α = 90°, β = 90°, γ = 90°
Space group = P212121
Molecules/asymmetric unit = 1
Measurement at room temperature
Fractional atomic coordinates “substantially as listed in Table 4.”
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Solid-state ^13C NMR (400 MHz, relative to TMS at zero) with peaks substantially at:
16.2, 17.6, 39.3, 60.9, 63.3, 69.8, 76.9, 78.7, 79.4, 113.8, 123.6, 129.3, 130.5, 132.0, 135.7, 139.1, 158.0 ppm.
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DSC thermogram: an endotherm in about 50°C to 78°C (or as shown in FIG. 7).
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TGA: about 18.7% weight loss from room temperature up to about 240°C (or as shown in FIG. 5).
Claim 7 repeats unit cell parameters constraint with measurement at room temperature and space group P212121 and Z’ = 1.
Claim 12 repeats the ^13C NMR peak list constraint.
Claim 17 repeats the DSC endotherm constraint.
Claim 1’s PXRD fingerprint is the key “first line” identity. It can be used alone without requiring DSC, NMR, or unit cell.
How broad are the “pharmaceutical composition” and formulation limits: are carriers and added therapeutics included?
Claims 1, 7, and 12 set the solvate identity and then broaden the “pharmaceutical composition” concept in dependent claims.
Carriers and “substantially pure form” refinements
The patent repeatedly includes:
- Claim 4 / Claim 9: pharmaceutical composition further comprising a pharmaceutically acceptable carrier or diluent.
- Claim 5 / Claim 10 / Claim 15: solvate is in substantially pure form.
- Claim 6 / Claim 11 / Claim 16: solvate has substantially pure phase homogeneity.
These are standard solid-state claim features that increase enforceability by framing the target as a controlled crystalline product rather than an indistinct mixture.
Combination therapy scope: what therapeutic classes are named?
Claims 3, 8, 13, 14’s structure echoes in other dependents (3, 8, 13, 18, 19 analogues).
Where present, the composition can further comprise one or more therapeutic agents selected from:
- antidiabetic agent
- anti-obesity agent
- anti-hypertensive agent
- anti-atherosclerotic agent
- lipid-lowering agent
The clause does not limit to named drug molecules, so it is class-broad. Practically, this supports a licensing and enforcement posture where the S-PG solvate can be paired with existing diabetology, cardiometabolic, and lipid-lowering regimens.
How are the method-of-use claims drafted: what diseases and what population scope are covered?
Method claims are broad and list multiple indications.
The patent includes multiple method-of-treating claims that cover:
- diabetes
- diabetic retinopathy
- diabetic neuropathy
- diabetic nephropathy
- delayed wound healing
- insulin resistance
- hyperglycemia
- hyperinsulinemia
- elevated blood levels of fatty acids or glycerol
- hyperlipidemia
- dyslipidemia
- obesity
- hypertriglyceridemia
- Syndrome X
- diabetic complications
- atherosclerosis
- hypertension
- increasing high density lipoprotein levels in a mammal
Independent method claims in the set
The method claims are tied to different versions of the composition claims:
- Claim 22 method uses Claim 1 formulation/identity (PXRD-based SC-3).
- Claims 23, 25, 27, 29 are for “type II diabetes” and reference Claims 7/12/17 as the composition identity anchors.
- Claims 24, 26, 28 are broader diabetes/multi-indication lists and reference Claims 7/12/17 accordingly.
The result is that even if an accused product argued a different analytical characterization path, the patent provides multiple dependent method pathways tied to alternative characterization sets (PXRD, unit cell, ^13C NMR, DSC).
What patents protect the same idea: where this claim strategy usually overlaps in a solid-state “polymorph/solvate” estate
With only Claim text provided, the landscape below focuses on what this claim structure implies for the typical US prosecution and enforcement pattern in polymorph/solvate families.
Typical overlap areas inside the same family (based on claim architecture)
US 8,501,698 is engineered to capture:
- Identity-by-PXRD (Claim 1)
- Identity-by-crystal structure (unit cell, P212121, Z’=1, Table 4 coordinates) (Claim 2 and 7)
- Identity-by-solid-state NMR (Claim 12)
- Identity-by-thermal signature (DSC endotherm range) (Claim 17)
- Downstream therapeutic use (claims 22 to 29)
In a real family, that often comes with:
- related claims covering preparation methods of the SC-3 solvate,
- other analytical envelopes (Rietveld fits, additional PXRD peaks, different measurement conditions),
- different dosage forms (capsules, tablets, oral liquids) or routes,
- and potentially claims targeting impurities and stability.
However, no additional patent numbers or family members are present in your prompt, so no specific co-listed US patents can be asserted here.
When does US 8,501,698 lose exclusivity: how to calculate term exposure from the patent grant
No filing history, priority date, or maintenance status is provided in the prompt. Without those, the specific expiration date cannot be calculated reliably.
What can be stated from claim scope: the patent’s exclusivity is tied to the crystalline Form SC-3 solvate identity. Even after the hard patent term expires, competitors may still face:
- trade secret/process barriers,
- separate patents on formulation, delivery, or combination therapy,
- and regulatory exclusivities (if applicable to an approved drug product), none of which are determinable from the claim text alone.
What generic entry risks exist: could a competitor design around by changing the solvate form or analytics?
The claim’s “substantially characterized by” language indicates a design-around path exists that is common in polymorph litigation:
Design-around 1: use a different solvate/polymorph than SC-3
If the competitor uses a different crystalline solvate form (different PXRD set, different unit cell, different NMR peaks, different DSC/TGA signature), they can argue non-infringement because the claim requires SC-3.
Design-around 2: preserve performance while shifting “substantially matching” peaks
The PXRD peaks are each given with ±0.1° 2θ tolerances. A competitor could attempt:
- alternative crystallization conditions yielding slightly shifted peak positions,
- amorphous content or mixed phases (though “substantially pure phase homogeneity” is a dependent limitation, not in independent Claim 1),
- or particle-size/measurement condition differences that change apparent 2θ positions.
Litigation risk would then center on how “substantially” is interpreted against the exact test method.
Design-around 3: avoid “therapeutically effective amount” framing by changing intended use
The method claims capture therapeutic uses. A competitor could try to sell a composition without targeting the listed therapeutic indications, but that typically does not remove product-claim infringement exposure if they still manufacture/sell the infringing composition for therapeutic use, and method-of-use infringement turns on evidence of labeling/marketing/clinical intent.
How strong is the patent estate for enforcement: claim definiteness and proof burden
The patent is drafted to be enforceable via analytical comparison:
- PXRD peak list is explicit and finite.
- Unit cell and space group are numeric.
- ^13C NMR peaks are listed.
- DSC and TGA are tied to defined event ranges and mass loss/temperature windows.
- The structure is identified as “SC-3” with fractional atomic coordinates in Table 4.
Consequence for infringement and invalidity posture
In enforcement, the patentee can build an evidentiary record by running:
- room-temperature PXRD under Cu Kα,
- solid-state NMR at 400 MHz referenced to TMS,
- DSC and TGA as described,
- plus unit cell determination.
The accused infringer can respond by:
- showing a different solvate form,
- showing measurement discrepancies that prevent matching “substantially” criteria,
- or attacking validity (anticipation/obviousness) against prior art crystalline characterizations.
But no prior-art references are included in the prompt, so the validity strength cannot be scored against specific references.
What to expect in litigation: likely contested issues tied to these claims
Non-infringement likely focuses on analytical identity
Given the tight PXRD and NMR fingerprints, the dispute often becomes:
- whether the accused sample is truly SC-3,
- whether the testing conditions match “room temperature” and the stated instrument settings,
- and whether “substantially equal” tolerances are met.
Validity likely focuses on whether SC-3 was known or obvious
Polymorph/solvate validity battles typically hinge on whether:
- SC-3 was disclosed in prior art (with enough detail to identify it),
- or whether it is an obvious crystallization outcome from a known system.
No prior art is provided here.
Orange Book status, FDA pathway, and Paragraph IV: what can and can’t be concluded from the claim text alone
Nothing in the prompt provides:
- the drug name,
- FDA application number,
- dosage form approval,
- Orange Book listing,
- regulatory exclusivity expiry,
- or whether any ANDA/BLA challenges have been filed.
So a Paragraph IV and Orange Book timeline cannot be produced from the provided information.
Key Takeaways
- US 8,501,698 is an identity-driven solid-state patent targeting a specific crystalline (S)-propylene glycol solvate “Form SC-3.”
- The independent composition claim is anchored to an explicit PXRD peak set (2θ values with ±0.1° tolerances at room temperature).
- Dependent claims multiply the identity proofs with unit cell/space group (P212121, Z’=1), solid-state ^13C NMR peak list, and DSC/TGA signatures.
- The patent also covers method-of-use across broad diabetes and cardiometabolic indications, including type II diabetes.
- Design-around is most plausibly achieved by using a different crystalline solvate/polymorph or by producing a material that fails the claimed analytical envelopes.
FAQs
1) Does Claim 1 require the solvate to be in “substantially pure form”?
No. “substantially pure form” appears in dependent claims (e.g., Claim 5) rather than being stated in Claim 1.
2) Can a competitor infringe if they match the DSC but not the PXRD peaks in Claim 1?
Claim 1 requires PXRD characterization. A product that matches DSC alone would not satisfy Claim 1’s PXRD requirement, though it could still be evaluated against other dependent claims tied to DSC/^13C NMR/unit cell.
3) Is “room temperature” a material claim limitation?
Yes. The PXRD and crystallographic measurement constraints explicitly refer to characterization at room temperature.
4) Do the method claims require a specific dosage form or route of administration?
The claim text provided does not limit route or dosage form; it requires administering a therapeutically effective amount of the claimed composition.
5) What is the main litigation proof file for infringement of this patent?
Analytical characterization of the accused material against the claim’s fingerprints: PXRD (Cu Kα, listed 2θ peaks), unit cell/space group, solid-state ^13C NMR peaks, and DSC/TGA thermal events.
References (APA)
- Provided by user: Claim text for United States Patent US 8,501,698 (Form SC-3 crystalline (S)-propylene glycol solvate) including claims 1–29.
