Scope and claims analysis for US Patent 5,612,367: amorphous solid form of N-[4-[5-(cyclopentyloxycarbonyl)amino-1-methylindol-3-yl-methyl]-3-methoxybenzoyl]-2-methylbenzenesulphonamide (oral bioavailability and stabilization) with polyvinylpyrrolidone
What does US 5,612,367 claim for oral bioavailability of the specific amorphous indole sulphonamide?
Answer: US 5,612,367 claims methods that hinge on (i) using a defined amorphous physical form of the named active ingredient that is substantially free of other physical forms, (ii) verifying that physical form via a specific IR pattern (KBr, 0.5%), and (iii) formulating the composition for oral administration in combination with polyvinylpyrrolidone (PVP), optionally with conventional carriers and excipients.
Claim 1 (core independent claim) is a physical-form + excipient method claim
Claim 1 requires all of the following:
- Active ingredient identity: the named compound
N-[4-[5-(cyclopentyloxycarbonyl)amino-1-methylindol-3-yl-methyl]-3-methoxybenzoyl]-2-methylbenzenesulphonamide.
- Amorphous physical form only: amorphous solid state that is “substantially free of other physical forms.”
- IR fingerprint: infra-red spectrum (0.5% in KBr) with sharp peaks at
1690, 1530, 1490, 1420, 1155, 1060, 862, 550 cm⁻¹.
- Formulation/excipient: the amorphous form is formulated in a pharmaceutical composition with polyvinylpyrrolidone.
- Route: administered orally to living mammals.
- Bioavailability enhancement: the method is framed as “enhancing bioavailability upon oral administration,” but in claim structure the operative limitations are the physical form + IR + PVP formulation.
Practical meaning for infringement/validity: the claim’s enforceability will track whether an accused product uses the same amorphous form as characterized by the IR peaks and whether it includes PVP as recited.
Claim 2 is the stabilization mirror image of Claim 1
Claim 2 requires:
- The same amorphous physical form and the same IR peak set,
- A pharmaceutical composition for administration to mammals,
- Formulated with PVP,
- Purpose recast as stabilizing the amorphous form.
Functional difference: Claim 1 is “enhancing bioavailability”; Claim 2 is “stabilizing amorphous form.” In practice, both converge on the same physical-form limitations and the same PVP combination, so product-mapping is similar.
How is the “amorphous physical form” scope defined, and what are the key limiting features?
Answer: The claim defines the amorphous state through a purity constraint (“substantially free of other physical forms”) and a spectroscopic boundary (IR sharp peaks at a fixed list). These two features are the strongest determinants of claim scope.
“Substantially free of other physical forms” scope
This is a relative term. For freedom-to-operate analysis, it creates a factual question: whether an accused amorphous powder contains significant crystalline or other polymorphic phases. Even low-level inclusion can be argued both ways depending on measurement method.
IR peak list functions as a claim-drawing technical boundary
Claim 1/2 require sharp peaks at:
- 1690 cm⁻¹
- 1530 cm⁻¹
- 1490 cm⁻¹
- 1420 cm⁻¹
- 1155 cm⁻¹
- 1060 cm⁻¹
- 862 cm⁻¹
- 550 cm⁻¹
Claim impact:
- Any formulation that uses a different amorphous form that does not generate that same IR signature is outside the literal claim.
- Conversely, a product with an amorphous form that matches that IR signature could fall in even if the manufacturer argues “similar amorphous.”
Why KBr and “0.5% in KBr” matters
The claim specifies the measurement setup: IR spectrum (0.5% in KBr). That matters for reproducibility, because IR peak appearance can shift with sample preparation, concentration, and instrumentation. Claim scope is therefore tied to that test condition.
What do the dependent claims add: carriers, weight ranges, excipients, and dosage form?
Answer: Dependent claims narrow Claim 1/2 with specific formulation parameters and add optional excipient classes. They also expand coverage to certain dosage forms (notably tablets).
Claim 3: pharmaceutically acceptable carrier
- Requires that the composition further comprises a pharmaceutically acceptable carrier.
- This is an “optional limitation” in the sense it only applies if the claim depends, but it signals that carriers are contemplated in practice and may be needed to establish a complete product map.
Claim 4: amorphous content by weight (1–90%)
- “amorphous physical form… present in an amount of from 1 to 90% by weight.”
Scope consequence: a product where the amorphous API is outside that range (eg, only trace-level amounts) would avoid this dependent layer, though Claim 1 could still be asserted if Claim 1 is read independently of Claim 4.
Claim 5: PVP content (1–20%)
- PVP is present at 1 to 20% by weight.
Scope consequence: If an accused formulation uses PVP outside that range, it may avoid Claim 5 but still potentially meet Claim 1/2 if PVP is present at any amount and other limitations are met.
Claim 6: carrier selection list
- Carrier selected from:
mannitol, lactose, sorbitol, glucose, sucrose, dextrose, fructose, xylitol, microcrystalline cellulose, powdered cellulose, hydroxypropylmethylcellulose.
Scope consequence: this list matters for validity-to-infringement mapping where the asserted claim is this dependent claim. Using carriers outside the list could avoid Claim 6.
Claim 7: processing adjuvant list
- Processing adjuvant selected from:
croscarmellose sodium, sodium starch glycolate, starch, magnesium stearate, stearic acid, talc, powdered vegetable stearine.
Claim 8: tablet dosage form
- “composition is in the form of a tablet.”
Scope consequence: product presentation as a capsule, film, suspension, or other dosage form would avoid Claim 8, while still potentially meeting Claim 1/2 unless those claims are asserted in combination.
What is the likely patent landscape structure around US 5,612,367 (how many “layers” of protection does it create)?
Answer: Even without external bibliographic expansion here, the claim text itself indicates that US 5,612,367 creates protection in at least three layers:
- Solid-state form layer: the amorphous form defined by IR peaks plus “substantially free of other physical forms.”
- Formulation-excipient layer: required combination with PVP.
- Composition tailoring layers: dependent claims for carriers, excipients, weight ranges, and tablet form.
Claim drafting pattern that narrows entry paths
This patent is not a broad “any amorphous form + any binder” composition patent. It is a specific amorphous physical form + specific IR fingerprint + specific polymer excipient patent. That drafting typically forces generics to either:
- use the same form and PVP system, or
- switch to a different solid form / different polymer system that avoids IR matching or avoids PVP.
How does a generic or competitor avoid infringement risk on the amorphous IR fingerprint?
Answer: The two primary “escape routes” in claim language are avoiding the IR signature or avoiding PVP.
Escape route A: use a different amorphous form that fails the IR peak requirement
To avoid Claim 1/2 literal scope, an accused API lot would need an amorphous form whose IR (0.5% in KBr) lacks one or more of the listed sharp peaks at the required positions.
Escape route B: formulate without PVP
Because PVP is a required component in Claim 1 and Claim 2, substituting another polymer (eg, HPMC-based matrices or other binder systems) could avoid at least the “PVP combination” limitation.
Escape route C: avoid dependent claim parameters
Even if the product meets Claim 1/2, dependent-claim differences can reduce exposure:
- PVP outside 1–20 wt% could avoid Claim 5.
- Carriers outside the Claim 6 list could avoid that dependent layer.
- Dosage form not a tablet could avoid Claim 8.
How does this patent interact with regulatory pathways (ANDA vs 505(b)(2))?
Answer: As a method-of-enhancing-bioavailability and stabilization-by-formulation patent, US 5,612,367 is most likely to be implicated in Orange Book listing and dispute scenarios where an applicant’s proposed product uses:
- the same API solid-state form and IR-defined amorphous material, and
- a PVP-containing formulation.
Practical risk framing: If a generic applicant relies on a different solid form or different polymer excipient system, it can position the proposed product as outside the claim’s “amorphous IR + PVP” construction. If it relies on the same amorphous form technology and PVP, infringement exposure increases.
What litigation issues typically arise from claim structure like this (method claims tied to characterization and formulation)?
Answer: The claim’s proof burden typically centers on two factual axes: (i) characterization of the accused amorphous material by IR under specified conditions and (ii) formulation composition proving PVP presence and levels.
Axis 1: IR testing and sample preparation
- Whether peaks are “sharp” and present at the claimed wavenumbers.
- Whether the spectrum is obtained “0.5% in KBr.”
- Whether there are other physical forms present and whether the sample is “substantially free” of them.
Axis 2: formulation composition and PVP identification
- Whether PVP is present.
- Whether the amount falls within dependent claim ranges (Claim 5 for 1–20 wt%).
- Whether the product uses a tablet dosage form (Claim 8).
Key claim scope matrix for US 5,612,367 (what must be present vs what is optional)
| Feature |
Claim 1 |
Claim 2 |
Dependent refinements |
| Named active ingredient |
Required |
Required |
n/a |
| Amorphous physical form |
Required |
Required |
n/a |
| Substantially free of other physical forms |
Required |
Required |
n/a |
| IR peaks at 1690, 1530, 1490, 1420, 1155, 1060, 862, 550 cm⁻¹ (0.5% in KBr) |
Required |
Required |
n/a |
| PVP included |
Required |
Required |
Claim 5: 1–20 wt% |
| Oral administration to mammals |
Required |
Required |
n/a |
| Purpose: enhance bioavailability |
Required (framing) |
n/a |
stabilization purpose in Claim 2 |
| Pharmaceutically acceptable carrier |
Not required in Claim 1 |
Not required in Claim 2 |
Claim 3; Claim 6 list applies if pleaded |
| Processing adjuvants |
Not required |
Not required |
Claim 7 list applies if pleaded |
| Tablet dosage form |
Not required |
Not required |
Claim 8 |
| Amorphous API wt% range |
Not required in Claim 1 |
Not required in Claim 2 |
Claim 4: 1–90 wt% |
Key takeaways
- US 5,612,367 is a solid-form and formulation method patent: it protects using a specific amorphous form of the named indole sulphonamide, defined by a fixed IR peak set and low contamination by other physical forms.
- PVP is mandatory in both independent claims, making polymer substitution a principal design-around lever.
- Dependent claims add narrow ranges and specific excipient lists (PVP 1–20 wt%; carriers from a defined list; tablet format), which can reduce overlap but do not eliminate Claim 1/2 risk if those dependent limitations are not asserted.
- In any enforcement or litigation posture, the central technical battleground is IR characterization under “0.5% in KBr” conditions and proof of PVP presence in the accused formulation.
FAQs
1) What are the two independent claim limitations that most directly control infringement for US 5,612,367?
The product must use the IR-defined amorphous physical form (with the listed peaks at 1690, 1530, 1490, 1420, 1155, 1060, 862, 550 cm⁻¹ in 0.5% KBr) and must include polyvinylpyrrolidone.
2) Can an accused product avoid US 5,612,367 by using a different excipient binder instead of PVP?
If PVP is omitted, it avoids the required “in combination with polyvinylpyrrolidone” limitation in Claims 1 and 2.
3) Does the patent require the composition to be a tablet?
No. Tablet form is only required in Claim 8, which is dependent.
4) What weight parameters does the patent impose in dependent claims?
Dependent Claims 4 and 5 impose: amorphous form 1–90 wt% (Claim 4) and PVP 1–20 wt% (Claim 5).
5) What is the role of “substantially free of other physical forms” in claim construction?
It limits the claimed amorphous material by requiring it not contain significant amounts of other physical forms (eg, crystallinity), supporting an infringement argument based on phase purity.
References
- United States Patent 5,612,367.
