United States Drug Patent 7,387,793: Claim Scope, Amrix Exclusivity, Litigation, and Generic Entry Risk

U.S. Patent No. 7,387,793 protects a multiparticulate, extended-release cyclobenzaprine dosage form, particularly the bead-based formulation commercialized as Amrix. The patent is formulation-focused rather than compound-focused. Its central limitations are cyclobenzaprine-containing cores, water-insoluble polymer-coated beads, specified dissolution behavior, and 24-hour therapeutic exposure. The strongest practical coverage is directed to cyclobenzaprine hydrochloride capsules using ethyl cellulose, diethyl phthalate, and hydroxypropyl methylcellulose, with a 7% to 12% coating weight and the recited in vitro release profile.

The patent does not broadly cover all extended-release cyclobenzaprine products. A competing product that uses a different release technology, a non-bead matrix, a substantially different coating system, or a materially different dissolution profile may avoid literal infringement, although equivalents and other patents in the Amrix estate remain relevant.

What does U.S. Patent 7,387,793 protect?

The patent protects a multiparticulate pharmaceutical dosage form comprising extended-release beads containing cyclobenzaprine or a pharmaceutically acceptable salt or derivative.

Core claim architecture

Independent claim 1 requires all of the following:

Limitation	Required scope
Dosage form	Multiparticulate pharmaceutical dosage form
Active ingredient	Skeletal muscle relaxant selected from cyclobenzaprine, salts, derivatives, or mixtures
Release unit	Population of extended-release beads
Core	Active-containing core particle
Coating	Water-insoluble polymer membrane surrounding the core
Dissolution method	USP Apparatus 2, paddles at 50 rpm, 900 mL of 0.1N HCl, 37°C
Two-hour release	No more than approximately 40%
Four-hour release	Approximately 40% to 65%
Eight-hour release	Approximately 60% to 85%
Clinical effect	Therapeutically effective plasma concentration over 24 hours
Polymer	Listed cellulose, acrylic, methacrylic, polyvinyl acetate, or related water-insoluble polymers
Plasticizer	Listed citrate, phthalate, sebacate, glycol, castor oil, or glyceride plasticizers

The claim uses “comprising,” which generally leaves the formulation open to additional ingredients and processing steps. A product can therefore infringe even if it contains excipients, coatings, capsule materials, or manufacturing elements not expressly identified in claim 1, provided every required limitation is present.

Claim 1 is a combination claim

The claim is not limited to a single excipient combination. It covers multiple polymer and plasticizer alternatives through Markush groupings. The claim’s breadth is narrowed by the combination of:

A bead-based multiparticulate structure;
A water-insoluble membrane;
A specified release profile; and
A 24-hour therapeutic-use limitation.

A formulation using ethyl cellulose but failing the claimed dissolution profile would not literally satisfy claim 1. Conversely, a formulation using a different listed polymer could fall within the claim if the bead structure, release profile, and therapeutic-performance requirements are met.

How do claims 2 through 20 narrow the patent?

Claims 2 through 20 create progressively narrower formulation positions. They are important because generic products frequently design around a broad independent claim while remaining exposed to narrower claims covering the commercial formulation.

Claims	Principal limitation
2	Cyclobenzaprine hydrochloride
3	Cmax, AUC, and Tmax targets after a single 30 mg dose
4	Dose-proportionality relationship between 30 mg and 15 mg
5	Only one extended-release bead population
6	Water-insoluble coating at approximately 7% to 12% of bead weight
7, 10, 13, 14, 20	Addition of a water-soluble polymer
8	Cyclobenzaprine
9	Adds a 12-hour dissolution range of approximately 75% to 85%
11	Ethyl cellulose as the water-insoluble polymer
12	Diethyl phthalate as the plasticizer
15	Hydroxypropyl methylcellulose as the water-soluble polymer
16	Cyclobenzaprine hydrochloride
17	7% to 12% coating weight
18	Full two-, four-, eight-, and 12-hour release profile
19	Narrower polymer group focused on cellulose derivatives and pH-insensitive ammonio methacrylate copolymers

The most commercially relevant dependent chain is claims 11 through 18:

Ethyl cellulose;
Diethyl phthalate;
Hydroxypropyl methylcellulose;
Cyclobenzaprine hydrochloride;
7% to 12% coating weight; and
The specified 12-hour dissolution profile.

That chain corresponds closely to the formulation design associated with Amrix extended-release capsules.

What formulation is most directly exposed to U.S. Patent 7,387,793?

A product is at highest literal-infringement risk if it has the following characteristics:

Cyclobenzaprine hydrochloride;
A capsule containing coated drug-loaded beads;
A single bead population;
Ethyl cellulose as the water-insoluble release-controlling polymer;
Diethyl phthalate as plasticizer;
Hydroxypropyl methylcellulose as a pore-forming or water-soluble coating component;
Approximately 7% to 12% coating weight; and
The claimed release pattern in acidic dissolution media.

Formulation design-around options

Potential design-around strategies include:

Design variable	Potential effect
Matrix tablet instead of beads	Avoids the bead-population limitation
Ion-exchange resin system	May avoid the polymer-membrane limitation
Different insoluble polymer	May avoid claims limited to ethyl cellulose
Different plasticizer	May avoid claim 12 and related dependent claims
Multiple bead populations	May avoid claim 5, but not necessarily claim 1
Coating outside the 7% to 12% range	May avoid claims 6 and 17
Different dissolution profile	May avoid the central performance limitation
Alternative capsule strength or dosing regimen	May avoid pharmacokinetic claims while leaving formulation claims exposed
Non-24-hour release product	May avoid the therapeutic-duration limitation, subject to claim construction

A design change must be evaluated against each claim independently. Avoiding claim 17, for example, does not avoid claim 1 if the broader claim is satisfied.

How significant are the dissolution limitations?

The dissolution profile is a central enforcement feature. Claims 1, 9, and 18 require staged release at defined time points under a specified USP method.

The key profile is:

Time point	Required release
2 hours	No more than approximately 40%
4 hours	Approximately 40% to 65%
8 hours	Approximately 60% to 85%
12 hours	Approximately 75% to 85% for claims 9 and 18

The test conditions matter. A release profile generated using a different apparatus, agitation speed, medium volume, pH, or temperature may not establish literal satisfaction of the claim. For infringement analysis, the relevant question is whether the accused product falls within the claim when tested using the recited conditions.

The terms “about” and “substantially corresponding” introduce claim-construction issues. Courts generally assess those terms in view of the specification, prosecution history, experimental data, and the technical meaning to a skilled person. They do not make the limitations irrelevant. A product with materially faster or slower release could present a strong noninfringement position.

What pharmacokinetic properties does the patent claim?

Claim 3 adds pharmacokinetic limitations for a 30 mg cyclobenzaprine hydrochloride modified-release capsule:

Parameter	Claimed target
Cmax	Approximately 80% to 125% of 20 ng/mL
AUC0-168	Approximately 80% to 125% of 740 ng·hr/mL
Tmax	Approximately 80% to 125% of 7 hours

These ranges correspond approximately to:

Cmax: 16 to 25 ng/mL;
AUC0-168: 592 to 925 ng·hr/mL; and
Tmax: 5.6 to 8.75 hours.

Claim 4 adds a dose-proportionality requirement, requiring the adjusted mean ratio for 30 mg versus 15 mg to exceed approximately 2 for AUC0-168, AUC0-infinity, and Cmax.

Pharmacokinetic claims can be difficult to enforce against a generic because infringement may require access to clinical or bioequivalence data. They can also create validity issues if the claimed ranges are viewed as inherent results of a formulation rather than structural limitations adequately supported by the specification. In practice, claims 3 and 4 are narrower fallback positions rather than the principal commercial barrier.

When did U.S. Patent 7,387,793 lose exclusivity?

U.S. Patent No. 7,387,793 was issued on June 17, 2008. Its term derives from the relevant nonprovisional or international filing chronology and any applicable patent-term adjustment or extension. Public patent and Orange Book records should be reconciled because expiration dates can differ where regulatory patent-term extension, pediatric exclusivity, terminal disclaimers, or record updates apply.[1][2]

The patent was associated with the Amrix product and was part of the Orange Book patent landscape for cyclobenzaprine hydrochloride extended-release capsules. Patent expiry, however, did not necessarily mark the first possible generic launch. Paragraph IV settlements and authorized-generic arrangements can permit entry before the listed patent expiration date.

As of 2025, the principal economic issue is historical enforcement and the effect of related patents, settlements, and regulatory exclusivity rather than a new standalone blocking period under the 7,387,793 patent.

What was the FDA and Orange Book status of the patent?

Amrix is an FDA-approved extended-release capsule containing cyclobenzaprine hydrochloride. The product was approved for relief of muscle spasm associated with acute, painful musculoskeletal conditions and is administered once daily.[3]

The relevant regulatory framework is:

NDA 021777 for Amrix;
Active ingredient: cyclobenzaprine hydrochloride;
Dosage form: extended-release capsule;
Strengths: 15 mg and 30 mg;
Reference product sponsor: originally associated with Cephalon and subsequently commercialized within the Teva portfolio;
Regulatory category: small-molecule drug, not a biologic.

The Orange Book identifies patents submitted by the NDA holder for approved drug products. Listing creates a statutory framework for ANDA applicants, including certification requirements and potential Paragraph IV litigation. It does not itself establish that every claim is valid, enforceable, or infringed.[1]

Which companies challenged Amrix patents?

The generic-drug challenge landscape included ANDA applicants seeking approval for cyclobenzaprine hydrochloride extended-release capsules. Public litigation records identify disputes involving generic manufacturers, including Watson/Actavis and other ANDA applicants, over patents associated with Amrix.[4][5]

The primary challenge mechanism was Paragraph IV certification. An applicant filing a Paragraph IV certification represents that the listed patent is invalid, unenforceable, or not infringed. The NDA or patent holder may then file an infringement action within the statutory period, triggering a regulatory stay of approval, generally for up to 30 months under the Hatch-Waxman framework.[6]

The commercial result in this product class was shaped by patent settlements and negotiated generic-entry dates. A settlement can create a date-certain launch right without requiring the patent holder to litigate through final judgment. The precise terms of individual agreements may include licenses, authorized-generic commitments, supply arrangements, or restrictions on launch timing.

What patent litigation affects cyclobenzaprine extended-release capsules?

The principal litigation risk has historically involved:

Whether an ANDA formulation uses coated beads rather than another extended-release technology;
Whether the generic’s dissolution profile falls within the claimed ranges;
Whether the generic uses the same or equivalent coating polymers and plasticizers;
Whether pharmacokinetic claims are infringed;
Whether the asserted claims are enabled and sufficiently definite; and
Whether related patents provide additional formulation or method-of-use coverage.

A generic applicant can challenge claim validity through lack of novelty, obviousness, written description, enablement, indefiniteness, or improper claim scope. The likely validity pressure is greatest against claims that combine known excipients and conventional coating processes with a target dissolution profile. The patent holder’s strongest response is usually the asserted relationship between the specific coating architecture and the 24-hour clinical pharmacokinetic result.

How strong is the patent estate for Amrix?

The 7,387,793 patent is commercially meaningful but structurally narrow compared with a basic compound patent. Its strength is concentrated in the specific multiparticulate formulation and release behavior.

Factor	Assessment
Compound protection	Weak; cyclobenzaprine was known before this patent
Bead formulation protection	Stronger; central to claim 1
Polymer coverage	Broad in claim 1, narrower in dependent claims
Dissolution limitation	Important for infringement and validity
Pharmacokinetic coverage	Narrow and data-dependent
Manufacturing barrier	Moderate; coated-bead production is technically reproducible
Generic design-around potential	Meaningful
Biosimilar relevance	None; product is a small molecule
Geographic coverage	U.S. rights only for this patent
Commercial value	Linked to the Amrix extended-release product and generic substitution timing

The patent does not prevent competitors from selling immediate-release cyclobenzaprine products. It also does not automatically block all modified-release formulations.

How does U.S. Patent 7,387,793 compare with competing protection?

Protection type	7,387,793 position
Active pharmaceutical ingredient	Does not protect cyclobenzaprine as a molecule
Immediate-release tablet	Generally outside the claimed multiparticulate architecture
Extended-release bead capsule	Primary target
Matrix-based extended release	Potential design-around
Method of treating muscle spasm	Present as a functional context, but formulation limitations dominate
Manufacturing process	No broad standalone process monopoly in the supplied claims
Biologic or biosimilar protection	Not applicable
Other jurisdictions	Requires separate national patent analysis

The patent estate should therefore be assessed as a formulation and product-by-process risk, not as a broad therapeutic monopoly.

What generic launch scenarios exist?

Three scenarios are commercially relevant:

Early launch under settlement

An ANDA applicant launches on a negotiated date before or near patent expiry. This is common where litigation risk is material but both parties prefer a defined market-entry timetable.

Delayed launch after patent expiry

Generic approval is obtained, but launch occurs after the listed patent term or related exclusivity expires. This reduces litigation exposure but can leave substantial value on the table if the incumbent retains switching advantages.

Design-around launch

The applicant uses a different extended-release architecture, polymer system, coating weight, bead population, or dissolution profile. The product may avoid 7,387,793 while remaining subject to other patents or regulatory requirements.

Key Takeaways

U.S. Patent 7,387,793 is a formulation patent covering multiparticulate cyclobenzaprine extended-release beads.
Claim 1 requires a coated bead structure, specified polymers and plasticizers, staged dissolution, and 24-hour therapeutic exposure.
Claims 11 through 18 provide the most commercially relevant narrow coverage for ethyl cellulose, diethyl phthalate, hydroxypropyl methylcellulose, cyclobenzaprine hydrochloride, coating weight, and release profile.
The patent does not broadly protect cyclobenzaprine, immediate-release products, or every extended-release formulation.
The main generic risk factors are bead architecture, coating composition, dissolution testing, and related Amrix patents.
Paragraph IV certifications and Hatch-Waxman litigation were central to the product’s generic-entry pathway.
Biosimilar risk is irrelevant because cyclobenzaprine is a small-molecule drug.
A complete freedom-to-operate analysis must include related Amrix patents, Orange Book records, settlement agreements, and foreign counterparts, not 7,387,793 alone.

FAQs

Does U.S. Patent 7,387,793 cover a 15 mg cyclobenzaprine extended-release capsule?

Potentially. The broad claims are not limited to 30 mg. Claims 3 and 4 add specific 30 mg and 15 mg pharmacokinetic relationships, but a 15 mg product may still be exposed to claims 1, 2, 5 through 20 if its formulation and dissolution profile satisfy those claims.

Can a generic use ethyl cellulose without infringing the patent?

Yes, potentially. Ethyl cellulose alone does not establish infringement. The product must also satisfy the bead, cyclobenzaprine, coating, plasticizer, dissolution, and other applicable limitations. Claims 11 through 18 create greater risk where the full dependent-claim combination is present.

Is a different capsule shell enough to avoid infringement?

Usually not. The claims focus on the extended-release beads and their coating, not the outer capsule shell. Changing gelatin, capsule color, shell composition, or capsule size generally would not avoid the relevant formulation limitations.

Does the patent cover once-daily treatment of all muscle spasms?

No. The claims are tied to a particular modified-release dosage form containing cyclobenzaprine and defined performance characteristics. They do not create unrestricted protection for every once-daily muscle-spasm treatment.

Are foreign patents equivalent to U.S. Patent 7,387,793?

No. Foreign counterparts are examined and enforced under national laws. Priority, claim scope, patent-term rules, opposition proceedings, supplementary protection rights, and litigation outcomes can differ materially by jurisdiction.

References

U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
United States Patent and Trademark Office. (2008). U.S. Patent No. 7,387,793: Modified release dosage forms of cyclobenzaprine. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2007). Amrix prescribing information. FDA.
Cephalon, Inc. v. Watson Pharmaceuticals, Inc., patent litigation concerning Amrix extended-release cyclobenzaprine capsules.
Teva Pharmaceuticals USA, Inc. v. generic ANDA applicants, litigation concerning patents listed for Amrix.
Drug Price Competition and Patent Term Restoration Act, 21 U.S.C. § 355(j).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
World Intellectual Property Organization (WIPO)	2005048996	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,387,793

Summary for Patent: 7,387,793