United States Patent 8,597,272: What Is Claimed, Where It Fits, and How It Stacks Up
What does US 8,597,272 claim at a technical level?
US Patent 8,597,272 claims an iontophoretic patch for delivering sumatriptan (including sumatriptan succinate) using a two-stage current profile to produce targeted exposure metrics (AUC and Cmax). The claim set is structured as a core method/patch concept (independent claim 1) followed by increasingly specific dependent claims on current density, surface area, delivered dose, reservoir composition, and pharmacokinetic (PK) ranges.
Independent claim 1: the core treatment-current profile
Claim 1 recites an iontophoretic patch for delivering sumatriptan with a defined current regime:
- High current treatment period: current of about 4 mA for about 1 hour
- Subsequent low current treatment period: current of about 2.0 mA for about 3 hours
This defines the central differentiator: stepwise iontophoretic current dosing for extended administration rather than a single constant current.
Integrated patch (claim 2)
- The patch is integrated (claim 2).
Current density and iontophoretically active area
Claims 3 to 6 narrow the delivery geometry and current intensity per area:
- At least a portion of the high-current period uses current density ≥ about 0.10 mA/cm² (claim 3)
- The high-current current density is between about 0.10 and 0.5 mA/cm² (claim 4)
- Patch iontophoretically active surface area is ≥ about 10 cm² (claim 5)
- Surface area is about 30 cm² (claim 6)
Amount delivered
- Delivered sumatriptan amount is about 10 mg (claim 7)
Reservoir formulation details
Claims 8 to 12 specify an electrode/reservoir architecture and specific excipient levels:
- Patch has cathode reservoir and anode reservoir (claim 8)
- Cathode reservoir comprises 2% hydroxypropyl cellulose (HPC) and sodium chloride (claim 8)
- Cathode reservoir comprises 2% HPC in an amount of about 3.0 g (claim 9)
- Anode reservoir comprises sumatriptan or pharmaceutically acceptable salt in a gel solution (claim 10)
- Gel solution comprises 4% sumatriptan succinate (claim 11)
- Gel solution further comprises 10% polyamine (claim 12)
Target PK ranges: AUC and Cmax
Claims 13 to 20 tightly bind performance to exposure metrics and statistical confidence intervals:
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AUC0-inf (95% CI) between about 67 and about 158 hr·ng/mL (claim 13)
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Narrower AUC0-inf (95% CI) between about 99 and about 128 hr·ng/mL (claim 14)
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AUC0-inf between about 67 and 158 hr·ng/mL (claim 15)
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AUC0-inf between about 99 and 128 hr·ng/mL (claim 16)
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Cmax (95% CI) between about 14 and about 38 ng/mL (claim 17)
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Narrower Cmax (95% CI) between about 20 and about 28 ng/mL (claim 18)
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A specific performance expression: Cmax about 23-25 ng/mL and plasma concentrations sustained for at least three hours (claim 19)
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Joint constraint: AUC0-inf about 99 to 128 hr·ng/mL and Cmax about 20 to 28 ng/mL (claim 20)
Drug identity
- Sumatriptan is sumatriptan succinate (claim 21)
What is the practical scope of the claim set (what you would infringe)?
US 8,597,272 is not limited to “iontophoresis of sumatriptan” in the abstract. It is constrained by a stack of technical requirements that collectively define a relatively narrow product concept, with multiple ways to meet claim limitations due to dependent claims that still capture variants within specified bands.
Core “must-have” elements
To fit within the claim family’s scope, a patch would need at least the independent-claim features:
- Iontophoretic patch for sumatriptan
- Two-stage current regimen:
- ~4 mA for ~1 hour
- ~2 mA for ~3 hours
If a product deviates from this current step structure (for example, swaps durations, changes high/low current levels materially, or uses a different current waveform), infringement risk against claim 1 drops sharply because claim 1 is the backbone.
Common dependent-claim “lock-ins”
Even if claim 1 is met, scope often hinges on dependent limitations:
- Current density band: at least part of high current at ≥ 0.10 mA/cm², and high current specifically 0.10 to 0.5 mA/cm²
- Surface area: ≥10 cm², with a target of ~30 cm²
- Dose: ~10 mg delivered
- Reservoir composition:
- Cathode reservoir: 2% HPC + sodium chloride, with a cited formulation mass (about 3.0 g reservoir containing 2% HPC)
- Anode reservoir: gel with 4% sumatriptan succinate and 10% polyamine
PK-driven constraints
Claims 13 to 20 introduce an exposure-based gate. That matters in two ways:
- It increases the difficulty of designing around by substituting different patch engineering while still achieving the same systemic profile.
- It also creates proof pathways in enforcement and litigation where testing and bioequivalence-style studies can be used to map a product’s PK to the claim windows.
What are the likely claim construction pressure points?
1) “About” ranges
The claims repeatedly use “about” (for mA values, durations, current density, surface area, AUC/Cmax bands, and dose). Courts typically interpret “about” in a range guided by intrinsic evidence, but the net effect is to capture a window rather than a single point.
Key “about” anchors:
- Current: about 4 mA and about 2.0 mA
- High period: about 1 hour; low period: about 3 hours
- Current density: ≥ about 0.10 mA/cm², high band about 0.10 to 0.5 mA/cm²
- Surface area: about 30 cm² and ≥ about 10 cm²
- Dose: about 10 mg
- PK: “about” appended to exposure values and confidence intervals
2) Two-stage regimen as a structural concept
The independent claim ties together the high-current period and low-current period in sequence. A design that uses a single constant current or a different step pattern is likely non-infringing relative to claim 1, even if the average current is similar.
3) Current density depends on effective area
Claims 3 to 6 use current density and iontophoretically active surface area. For enforcement and validity analysis, “active surface area” becomes technical and potentially contentious:
- A device can mechanically have larger electrode area but a smaller effective active area.
- Claim 5 requires ≥10 cm², and claim 6 anchors ~30 cm², so area determination matters.
4) Reservoir composition precision
Dependent claims 8 to 12 are explicit:
- 2% HPC + sodium chloride in cathode reservoir
- 2% HPC with about 3.0 g reservoir amount
- 4% sumatriptan succinate gel solution
- 10% polyamine
These are formulation-specific enough that substituting a different polymer level or different polyamine class may be outside dependent claim scope, even if current profile is the same.
5) PK confidence interval language
Claims recite PK ranges “within a 95% confidence interval between about X and about Y.” This can raise issues around:
- how PK is measured (study design, sample size, analytical method)
- the definition of AUC0-inf
- statistical computation
For a competing patch, this acts as a performance signature.
How does this patent sit in the broader US sumatriptan iontophoresis landscape (what are the usual neighbors)?
Within US drug delivery patent landscapes, you typically see clusters that fall into four buckets:
- Drug selection and route claims (sumatriptan delivered transdermally or otherwise)
- Iontophoretic device architecture (patch format, electrodes, current sources, reservoirs)
- Iontophoretic operating parameters (current magnitude, current density, duty cycle, duration)
- Formulation and performance targets (specific reservoir excipients, penetration enhancers, PK endpoints)
US 8,597,272 is concentrated at the intersection of (3) operating parameters, (4) formulation detail, and (4) PK outcomes, with the strongest scope anchored by the staged current schedule in claim 1 and specific excipient levels in claims 8 to 12.
From a competitive strategy standpoint:
- A product that matches claim 1’s staged current profile but uses different reservoir excipients could still be captured by claim 1 (and possibly by other performance claims, depending on PK).
- A product that matches formulation and PK but uses a different current schedule is more likely to avoid claim 1 but can still be caught if the PK and current-density limitations are independently met.
What does a “design-around” assessment look like against the claim stack?
Below is a practical claim-coverage matrix based strictly on the limitations you provided.
| Design element |
Claim linkage |
Typical design-around lever |
| High/low current values and durations |
Claim 1 |
Change step schedule so it no longer uses ~4 mA for ~1 hour and ~2 mA for ~3 hours |
| High-period current density |
Claims 3-4 |
Adjust effective active area/current so density exits 0.10 to 0.5 mA/cm² for the high stage |
| Electrode active area |
Claims 5-6 |
Reduce effective active area below ~10 cm² or move away from ~30 cm² (if claim 5/6 asserted) |
| Delivered dose |
Claim 7 |
Deliver substantially different mg or use different dosing schedule such that delivered amount is not ~10 mg |
| Cathode reservoir formulation |
Claims 8-9 |
Change HPC percentage or remove sodium chloride or use materially different reservoir mass/composition |
| Anode reservoir formulation |
Claims 10-12 |
Change succinate concentration, remove/replace polyamine, alter gel base to exit specific percentages |
| Systemic exposure profile |
Claims 13-20 |
Target different AUC/Cmax outcomes by changing delivery kinetics and thereby step parameters |
What are the most enforceable claim points for litigation or licensing?
Claim 1 is the primary enforcement anchor
If a patch uses:
- staged current: ~4 mA for ~1 hour then ~2 mA for ~3 hours, and
- delivers sumatriptan
then the patent’s core coverage is in play, regardless of whether the other dependent limitations are met.
Claims 8 to 12 are formulation “proof multipliers”
These are highly specific. If product records or device inspection show:
- cathode contains 2% HPC + sodium chloride
- anode gel contains 4% sumatriptan succinate + 10% polyamine
then infringement arguments strengthen, because the claims require particular formulation compositions, not only performance.
Claims 13 to 20 are PK “performance multipliers”
They can be used to correlate a competitor’s clinical data with the patent claim windows:
- AUC0-inf between 67 and 158 hr·ng/mL, with narrower band at 99 to 128
- Cmax between 14 and 38 ng/mL, with narrower band at 20 to 28
- A combined signature: AUC0-inf ~99 to 128 and Cmax ~20 to 28
- Cmax about 23-25 ng/mL and sustained levels for at least 3 hours
In licensing negotiations, these can operate as measurable differentiators.
Key Takeaways
- US 8,597,272 claims a sumatriptan iontophoretic patch with a two-stage current regimen: ~4 mA for ~1 hour, then ~2 mA for ~3 hours.
- The patent scope tightens via dependent claims on current density (0.10 to 0.5 mA/cm² during high stage), active surface area (≥10 cm²; ~30 cm²), and dose (~10 mg).
- It adds device formulation specificity: cathode contains 2% HPC + sodium chloride, and anode gel contains 4% sumatriptan succinate + 10% polyamine.
- It further locks coverage to PK endpoints using AUC0-inf and Cmax confidence-interval bands and a joint exposure window (AUC0-inf ~99 to 128; Cmax ~20 to 28).
- For competition strategy, the most direct infringement lever is matching claim 1’s stepwise current schedule; the highest proof leverage typically comes from matching reservoir compositions and PK outcomes.
FAQs
1) Is the patent limited to sumatriptan succinate specifically?
No. Claim 1 broadly covers sumatriptan, while claim 21 specifies that sumatriptan is sumatriptan succinate.
2) What is the central technical differentiator in claim 1?
The staged iontophoretic dosing: ~4 mA for ~1 hour followed by ~2.0 mA for ~3 hours.
3) What current density limits are recited?
High-stage current density is constrained to ≥ about 0.10 mA/cm² (at least a portion of the high-current period) and specifically about 0.10 to 0.5 mA/cm² during the high-current period.
4) What reservoir compositions are explicitly claimed?
Cathode reservoir includes 2% hydroxypropyl cellulose (HPC) and sodium chloride; anode reservoir is a gel with 4% sumatriptan succinate and 10% polyamine.
5) How do the claims use pharmacokinetics?
They recite AUC0-inf and Cmax ranges expressed with 95% confidence intervals, plus a combined AUC/Cmax window and a Cmax target with sustained exposure for at least 3 hours.
References
- United States Patent 8,597,272 (claims as provided by user).
