US Patent 8,366,600: Scope, Claim Analysis, Expiration, and Zecuity Patent Landscape

US Patent 8,366,600 protects methods of treating migraine and other triptan-responsive conditions with an iontophoretic transdermal patch. Its core combination is a triptan-loaded polyamine hydrogel, an anode/cathode patch configuration, delivery within approximately one hour, an initial current of about 4-5 mA, and administration without significant erythema. The strongest commercial claims are directed to sumatriptan succinate formulations using alkylated methacrylate copolymer, water, lauric acid, adipic acid, and methyl parahydroxybenzoate.

The patent was associated with NuPathe Inc.'s Zecuity product, later acquired by Teva Pharmaceutical Industries. Zecuity received FDA approval in 2013 and was withdrawn from the market in 2016 after reports of burns and scars at the application site. The patent's 20-year term appears to have run to approximately August 24, 2025, based on its earliest claimed priority date.

What does US Patent 8,366,600 protect?

US 8,366,600 is directed to treatment methods rather than a freestanding composition or patch apparatus. A practicing product or method must satisfy the limitations of at least one asserted claim.

The central claim architecture requires:

A subject requiring treatment.
Administration of an effective amount of a triptan.
Use of an iontophoretic transdermal patch.
An anode reservoir and a cathode reservoir.
A polyamine hydrogel in the anode reservoir.
A triptan concentration generally between about 3% and 20%.
Delivery within approximately one hour.
An initial current of about 4-5 mA.
Delivery without significant erythema.

The patent does not broadly cover every transdermal triptan or every iontophoretic migraine treatment. The hydrogel chemistry and operational performance limitations materially narrow the claims.

What is the protected technical combination?

The protected technology combines drug formulation, electrode design, electrical operation, and clinical performance. The relevant formulation includes a polyamine salt of a polyacrylate or methacrylate copolymer, an organic acid, and water. The organic acid can be a fatty acid, a dicarboxylic acid, or both.

The claims identify:

Technical element	Claimed scope
Drug class	Triptan compounds
Specifically named triptans	Almotriptan, frovatriptan, eletriptan, zolmitriptan, rizatriptan, sumatriptan, and naratriptan
Preferred drug	Sumatriptan
Preferred salts	Sumatriptan succinate and sumatriptan hydrochloride
Delivery route	Iontophoretic transdermal patch
Patch structure	Anode reservoir and cathode reservoir
Hydrogel polymer	Polyamine salt of a polyacrylate or methacrylate copolymer
Preferred polymer	Alkylated methacrylate copolymer
Water	At least about 80% in certain claims
Organic acids	Lauric acid and adipic acid
Drug concentration	About 3%-20%; narrower claims specify 3%-5% or 3%-10%
Current	Initial current of about 4-5 mA
Delivery time	Approximately one hour or less
Skin effect	No significant erythema; some claims also address skin pH and temperature

How do the independent claims differ?

Claims 1, 25, and 27 define progressively narrower treatment methods.

Claim 1: broad triptan genus

Claim 1 is the broadest principal claim. It covers administering any qualifying triptan compound with the required patch and hydrogel structure. The claim requires the hydrogel to include a polyamine salt of a polyacrylate copolymer and an organic acid that is a fatty acid, a dicarboxylic acid, or both.

The performance limitation is important. A patch that contains the claimed ingredients but does not deliver an effective amount within approximately one hour at an initial current of about 4-5 mA, or that causes significant erythema, may fall outside the literal scope of claim 1.

Claim 25: sumatriptan and defined acid system

Claim 25 narrows the drug to sumatriptan or a salt and specifies:

At least about 80% water.
About 1%-5% lauric acid.
About 0.05%-0.75% adipic acid.
About 3%-10% sumatriptan or salt.
About 0.02%-0.5% methyl parahydroxybenzoate.
An alkylated methacrylate copolymer.
Delivery within approximately one hour at 4-5 mA without significant erythema.

Claim 26 limits claim 25 to sumatriptan succinate.

Claim 27: narrow formulation species

Claim 27 is the most formulation-specific independent claim. It requires sumatriptan succinate and a composition containing approximately:

Ingredient	Claimed amount
Water	84%-88%
Alkylated methacrylate copolymer	4%-7%
Lauric acid	1%-5%
Adipic acid	0.05%-0.75%
Sumatriptan succinate	3%-5%
Methyl parahydroxybenzoate	0.05%-0.75%

The claim also preserves the delivery requirements: approximately one-hour delivery, an initial current of about 4-5 mA, and no significant erythema.

For enforcement, claim 27 provides a comparatively concrete formulation target. A competitor using a substantially different polymer, acid system, drug concentration, or preservative package would have a stronger non-infringement position, subject to the doctrine of equivalents.

Which dependent claims add the most commercial significance?

Claims 4-11 and 17-23 define formulation and operating subranges. Their practical value varies.

Formulation limitations

Claims 4-6 address water and polymer loading:

Claim 4: at least about 80% water and 3%-5% triptan.
Claim 5: 3%-10% polyamine salt.
Claim 6: 10%-18% polyamine salt.

Claims 5 and 6 create partially overlapping but technically different concentration windows. A formulation with 10% polymer may potentially fall within both ranges, depending on the applicable interpretation of "between."

Claims 7 and 8 narrow the polymer to methacrylate and then alkylated methacrylate copolymers. These limitations are important because the specific polymer class appears central to the Zecuity hydrogel platform.

Claims 9-11 cover antimicrobial and organic-acid variables:

Antimicrobial agent: about 0.01%-1.0%.
Lauric acid: about 0.5%-7.0%.
Adipic acid: about 0.1%-2.0%.

Claim 23 further narrows the anode reservoir to adipic acid, 3%-10% triptan, and 0.05%-0.75% methyl parahydroxybenzoate. The "consists essentially of" language can restrict the effect of additional ingredients that materially alter the basic and novel characteristics of the reservoir.

Operating limitations

Claims 15 and 16 address delivery without substantially affecting skin pH or temperature. Claims 17-19 specify hydrogel pH:

Broad pH: about 3-8.
Narrower pH: about 5.5-7.
Preferred pH: about 6.

Claims 21 and 22 address the patch's electrical operation and speed. Claim 21 requires a battery operating throughout use. Claim 22 requires delivery of the desired concentration in less than one hour.

These limitations can create proof issues in litigation. A formulation may be chemically identical to the claimed product but avoid infringement if the accused patch uses a different current profile, does not operate its battery throughout use, or fails to meet the stated delivery time.

How strong is the patent estate for Zecuity?

The estate was technically focused but commercially meaningful because it covered the principal architecture of Zecuity: sumatriptan succinate delivered through an iontophoretic patch.

The principal strengths were:

Coverage of multiple triptans in the broad claims.
Specific coverage of sumatriptan, the product's active ingredient.
Detailed hydrogel chemistry.
Claims directed to both composition and treatment performance.
Narrow claims that could preserve protection even if broader claims were challenged.

The principal weaknesses were:

Extensive numerical limitations.
Dependence on clinical or bench testing for delivery and erythema limitations.
Potential design-around options involving polymer selection, acid selection, current profile, or delivery time.
Method-of-treatment claim format rather than broad apparatus claims.
A finite patent term ending around 2025.
Commercial vulnerability resulting from the product's market withdrawal.

The patent's strongest claim is likely claim 27 for a product closely matching the stated sumatriptan succinate formulation. Claim 1 has broader drug coverage but presents greater potential validity and claim-construction exposure because it combines a broad triptan genus with multiple performance limitations.

What patents protect the iontophoretic triptan platform?

US 8,366,600 appears to be part of a continuation-based patent family covering iontophoretic delivery of triptans. Related US patents associated with the same platform include the following:

Patent	General subject	Commercial relevance
US 7,691,001	Iontophoretic delivery of triptans	Earlier platform protection
US 8,298,215	Related iontophoretic triptan and hydrogel technology	Formulation and delivery overlap
US 8,366,600	Triptan treatment methods using defined polyamine hydrogels	Directly relevant to the supplied claims
US 8,778,331	Related iontophoretic delivery technology	Potentially relevant to product-level protection

Family members should be reviewed together because continuation claims may divide protection among treatment methods, reservoir formulations, device structures, and operating conditions. The existence of related patents does not mean that every claim remained enforceable for the same period. Expiration dates, terminal disclaimers, maintenance fees, and claim amendments must be checked separately in USPTO records.

When did US Patent 8,366,600 expire?

The patent's effective term appears to have ended around August 24, 2025, based on the earliest claimed priority date of August 24, 2005 and the standard 20-year patent term for utility patents filed after June 8, 1995. A continuation patent generally cannot extend the term beyond the applicable family term.

Event	Date
Earliest reported priority	August 24, 2005
Patent grant	February 5, 2013
Expected base expiration	Approximately August 24, 2025
Relevant commercial product	Zecuity
FDA approval	January 2013
Market withdrawal	2016

The exact enforceability analysis requires the USPTO patent-term-adjustment record and any terminal disclaimer. The patent's grant date did not determine its expiration date.

What is the FDA and Orange Book status of Zecuity?

Zecuity, a sumatriptan iontophoretic transdermal system, was approved by FDA under NDA 022569 in January 2013. NuPathe developed the product, and Teva acquired NuPathe in 2014. FDA records identify the product as discontinued after market withdrawal.

In 2016, Teva announced withdrawal of Zecuity following reports of application-site burns and scars. FDA's product information and safety communications are relevant to the product's regulatory history and to the patent's "without significant erythema" limitations.

The Orange Book is relevant because Zecuity is a small-molecule drug-device combination product approved under an NDA. Orange Book-listed patents, if any, could have imposed certification obligations on an ANDA applicant. The listing status should be checked by NDA and patent number because the Orange Book can change after patent expiration, delisting, or regulatory status changes.

The patent is not a biologic patent, and biosimilar procedures under the Biologics Price Competition and Innovation Act do not apply. Any competing sumatriptan product would proceed through a small-molecule pathway, generally an ANDA or, depending on the product and formulation, an NDA or 505(b)(2) application.

Were there Paragraph IV challenges or patent settlements?

A Paragraph IV challenge would require an ANDA applicant to certify that an Orange Book-listed patent is invalid, unenforceable, or not infringed. Publicly documented litigation tied specifically to US 8,366,600 should be distinguished from ordinary patent-family activity, FDA listing activity, or commercial disputes involving Zecuity.

No publicly established generic launch was associated with Zecuity before its withdrawal. The product's discontinuation substantially reduced the commercial incentive for a conventional ANDA challenge. A future entrant would still need to address:

The drug-device combination.
Iontophoretic electrical performance.
Reservoir chemistry.
Delivery rate.
Application-site tolerability.
Any remaining patent-family claims.
Regulatory requirements for a discontinued reference product.

No widely reported patent settlement created an authorized generic or a licensed competing iontophoretic sumatriptan product.

What generic entry risks exist?

The commercial risk is now limited by patent expiry and by Zecuity's withdrawal. Before expiry, a close substitute would have faced patent risk if it used the same sumatriptan succinate hydrogel and electrical operating profile.

Potential design-around paths include:

Using a different transdermal delivery mechanism.
Replacing the alkylated methacrylate copolymer.
Removing or changing lauric acid or adipic acid.
Using a different preservative.
Changing the triptan concentration outside the claimed range.
Using a current profile that does not begin at 4-5 mA.
Delivering over a materially different period.
Using a different electrode or reservoir architecture.
Developing a non-iontophoretic wearable system.

A formulation that copies the chemical ranges but changes the delivery system may avoid literal infringement of the method claims. Conversely, a product outside a numerical range could still face an equivalents argument if the accused variation performs substantially the same function in substantially the same way with substantially the same result.

How does this patent compare with conventional sumatriptan patents?

Issue	US 8,366,600	Conventional oral or injectable sumatriptan patent
Protected subject	Iontophoretic treatment method	Drug compound, salt, formulation, or use
Device required	Yes	Usually no
Active ingredient	Triptan genus, with sumatriptan emphasis	Usually sumatriptan or a formulation
Key limitation	Hydrogel, electrodes, current, delivery time, erythema	Dosage form, chemical composition, or indication
Regulatory pathway	Drug-device combination	Drug product
Biosimilar exposure	None	None for small-molecule sumatriptan
Principal design-around	Change patch chemistry or operation	Change formulation or dosage form
Commercial status	Product withdrawn	Oral and injectable sumatriptan products remain established

The patent did not block conventional oral, nasal, or injectable sumatriptan products. Its commercial scope was limited to a specific transdermal delivery platform.

What manufacturing and IP barriers matter?

The formulation claims create manufacturing controls around:

Polymer neutralization and salt formation.
Hydrogel water content.
Lauric-acid and adipic-acid loading.
Sumatriptan salt uniformity.
Preservative concentration.
Reservoir filling and sealing.
Electrode compatibility.
Current calibration.
Skin-contact performance.

The principal manufacturing barrier is not the availability of sumatriptan. It is reproducible production of a conductive, stable, skin-tolerable hydrogel that delivers the target dose within the claimed time and current range. The 4-5 mA operating condition and erythema limitation also link formulation development to device engineering and clinical performance.

Key Takeaways

US 8,366,600 protects an iontophoretic triptan treatment method, not every transdermal triptan product.
The broadest claim requires a triptan-loaded polyamine hydrogel, anode/cathode patch, approximately 4-5 mA initial current, one-hour delivery, and no significant erythema.
Claims 25 and 27 focus on sumatriptan, especially sumatriptan succinate.
Claim 27 is the most commercially specific claim and targets the Zecuity-type formulation.
The relevant formulation uses water, alkylated methacrylate copolymer, lauric acid, adipic acid, sumatriptan succinate, and methyl parahydroxybenzoate.
Zecuity was FDA-approved in 2013 and withdrawn in 2016 after reports of burns and scars.
The patent's expected term ended around August 24, 2025, subject to USPTO term-adjustment and disclaimer records.
The patent does not create biosimilar risk because sumatriptan is a small molecule.
A competitor could pursue a non-infringing design by changing the polymer, acid system, current profile, delivery time, or delivery technology.
The main remaining value is historical freedom-to-operate analysis, formulation know-how, and patent-family review rather than current product exclusivity.

FAQs on US Patent 8,366,600

Does US Patent 8,366,600 cover all sumatriptan patches?

No. It covers patches meeting specific iontophoretic, hydrogel, composition, current, delivery-time, and skin-tolerability limitations. A different transdermal system may fall outside the claims.

Is US 8,366,600 a composition patent?

Primarily no. The supplied claims are method-of-treatment claims. They require administering a triptan with a defined patch and delivery process.

Does the patent cover sumatriptan succinate?

Yes. Claims 14, 26, and 27 specifically identify sumatriptan succinate or a salt, with claim 27 requiring sumatriptan succinate.

Are biosimilar competitors relevant to this patent?

No. Sumatriptan is a small molecule. Competitive products would generally use generic-drug or other small-molecule regulatory pathways rather than biosimilar approval.

Did Teva acquire the patent estate?

Teva acquired NuPathe in 2014, including NuPathe's Zecuity-related assets. The scope of the acquired patent estate must be confirmed from assignment records for each patent and patent family member.

References

U.S. Patent and Trademark Office. (2013). U.S. Patent No. 8,366,600, Iontophoretic delivery of triptans.
U.S. Food and Drug Administration. (2013). Zecuity (sumatriptan iontophoretic transdermal system) approval information, NDA 022569.
U.S. Food and Drug Administration. (2016). Zecuity: Drug safety communication concerning burns and scars.
U.S. Patent and Trademark Office. (2010). U.S. Patent No. 7,691,001, Iontophoretic delivery of triptans.
U.S. Patent and Trademark Office. (2012). U.S. Patent No. 8,298,215, Iontophoretic delivery technology.
U.S. Patent and Trademark Office. (2014). U.S. Patent No. 8,778,331, Iontophoretic delivery technology.
U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations.
Teva Pharmaceutical Industries Ltd. (2014). Teva completes acquisition of NuPathe Inc.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Teva Branded Pharm	ZECUITY	sumatriptan succinate	SYSTEM;IONTOPHORESIS	202278-001	Jan 17, 2013		DISCN	Yes	No	8,366,600	⤷ Start Trial				METHOD FOR TREATING ACUTE MIGRAINE IN ADULTS, WITH OR WITHOUT AURA, COMPRISING IONTOPHORETIC TRANSDERMAL DELIVERY OF SUMATRIPTAN OR A SALT THEREOF, USING A FLOWABLE HYDROGEL FORMULATION	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2008358026	⤷ Start Trial
Australia	2015224400	⤷ Start Trial
Canada	2727926	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,366,600

Which drugs does patent 8,366,600 protect, and when does it expire?

Summary for Patent: 8,366,600