Executive summary: U.S. Patent No. 8,637,540 is an Acura Pharmaceuticals composition patent directed to abuse-deterrent opioid formulations that retain an immediate-release profile. Its broadest independent claims require four elements: an opioid, 3-40 wt% gel-forming polymer, a disintegrant in an amount sufficient to produce immediate release, and a surfactant. Claim 15 narrows the invention to oxycodone hydrochloride. The patent covers composition architecture rather than a particular manufacturing process, clinical indication, or named commercial product.

The principal infringement risk is highest for an immediate-release oxycodone product that combines a gel-forming polymer, a qualifying disintegrant, and a surfactant within the claimed ranges. A conventional generic oxycodone tablet that lacks the gel-forming polymer or uses a non-equivalent excipient system would have a stronger design-around position. The patent’s nominal term runs to approximately December 21, 2027, subject to the USPTO term, adjustment, disclaimer, and maintenance-fee records.

US Patent 8,637,540 Patent Scope, Claims, Expiration, and Opioid Landscape

What does US Patent 8,637,540 protect?

US 8,637,540 protects pharmaceutical compositions containing an opioid and a specific excipient combination designed to provide abuse-deterrent properties while maintaining immediate drug release.

The core combination is:

Required element	Claim requirement
Active ingredient	An opioid
Gel-forming polymer	About 3 to about 40 wt%
Disintegrant	An amount sufficient to produce an immediate-release profile
Surfactant	Required by the independent claims
Dosage form	Not limited in the independent claims
Opioid concentration	0.5-25 wt% only in dependent claims
Disintegrant concentration	2-25 wt% only in dependent claims
Surfactant concentration	1-10 wt% only in dependent claims

The patent is not limited to a single opioid, indication, route of administration, or finished product. Claim 8 expressly identifies a broad Markush group of opioids, including oxycodone, hydrocodone, morphine, fentanyl, methadone, buprenorphine, tramadol, and pharmaceutically acceptable salts.

Claim 15 is commercially important because it independently targets oxycodone hydrochloride. It does not require the broad opioid Markush analysis needed under claim 8.

How are the claims structured?

Claims 1, 8, and 15 are the independent composition claims.

Claim 1: broad opioid composition

Claim 1 requires:

An opioid;
A gel-forming polymer at about 3-40 wt%;
A disintegrant; and
A surfactant.

The disintegrant must be present in an amount sufficient to cause immediate release. The claim does not expressly require the composition to be abuse-resistant, tamper-resistant, or suitable for a particular abuse route. The abuse-deterrent character is inferred from the gel-forming polymer and the specification’s technical disclosure, but the operative claim language is a composition claim.

Claim 8: Markush opioid composition

Claim 8 uses the same formulation architecture as claim 1 but limits the opioid to a specified group. The Markush group includes:

Oxycodone
Hydrocodone
Morphine
Fentanyl
Methadone
Buprenorphine
Codeine
Oxymorphone
Hydromorphone
Tramadol
Meperidine
Pentazocine
Other listed opioid compounds and pharmaceutically acceptable salts

A product containing oxycodone hydrochloride would fall within the recited opioid class, assuming the remaining composition limitations are met.

Claim 15: oxycodone hydrochloride composition

Claim 15 is the most commercially focused independent claim. It requires oxycodone hydrochloride plus:

3-40 wt% gel-forming polymer;
A disintegrant sufficient to produce immediate release; and
A surfactant.

This claim does not require the narrower concentration limitations in claims 18-20. A product can therefore potentially infringe claim 15 even if the opioid, disintegrant, or surfactant concentrations fall outside the dependent-claim ranges, provided the composition still satisfies the independent claim.

What formulations are protected by US 8,637,540?

The patent protects formulations in which the gel-forming polymer, disintegrant, and surfactant operate together in an immediate-release dosage form.

The dependent claims cover:

Claim	Limitation
2, 9, 16	Unit-dose form
3, 10, 17	Suppository, capsule, caplet, pill, gel, soft gelatin capsule, or compressed tablet
4, 11, 18	Opioid at 0.5-25 wt%
5, 12, 19	Disintegrant at 2-25 wt%
6, 13, 20	Surfactant at 1-10 wt%
7, 14, 21	Sodium starch glycolate, crospovidone, or croscarmellose sodium

The patent therefore reaches both solid oral formulations and several non-oral or soft dosage forms. The practical commercial focus is likely immediate-release oral opioid tablets or capsules.

Gel-forming polymers

The claims do not identify a closed list of gel-forming polymers. This broadens the literal scope but creates claim-construction and enablement issues around the meaning of "gel-forming polymer."

Potentially relevant polymer classes include:

Polyethylene oxide;
High-viscosity cellulose derivatives;
Carbomers;
Polyvinyl alcohol or related hydrophilic polymers;
Other polymers that hydrate and form a viscous matrix in an abuse-relevant medium.

A candidate product should not be assessed solely by whether its excipient is commonly described as a controlled-release polymer. The relevant question is whether the polymer forms the claimed gel under the conditions disclosed in the patent and whether its concentration falls within the claimed range.

Disintegrants

Claims 7, 14, and 21 specifically identify:

Sodium starch glycolate;
Crospovidone; and
Croscarmellose sodium.

These dependent claims are narrower than the independent claims. A product using another disintegrant could still implicate claims 1, 8, or 15 if the disintegrant satisfies the functional immediate-release limitation.

Surfactants

The independent claims require a surfactant, but they do not provide a closed surfactant list in the claims supplied. The 1-10 wt% limitation appears only in dependent claims 6, 13, and 20.

A formulation using a low level of surfactant below 1 wt% may avoid the dependent claims but remain within an independent claim. Conversely, eliminating the surfactant entirely is a direct design-around strategy, subject to whether another ingredient is legally characterized as a surfactant.

How should “immediate release” be interpreted?

The immediate-release limitation is a central infringement issue.

The claims do not recite a fixed dissolution threshold, time point, apparatus, medium, or pharmacopoeial method. That creates two competing effects:

The limitation may cover a wide range of formulations that release the drug promptly.
The functional wording creates evidentiary disputes over the applicable test and whether the composition actually exhibits immediate release.

The patent owner would likely rely on dissolution data, formulation composition, and the patent specification to establish that the disintegrant is present in an amount sufficient to produce immediate release. A challenger would examine:

Dissolution testing method;
Test medium and pH;
Agitation speed;
Tablet hardness;
Particle size;
Compression force;
Release percentage at specified time points;
Whether the polymer causes delayed or extended release.

The claim does not require a separate abuse-deterrence test. Crushing, extraction, snorting, injection, heating, and gelling behavior may be relevant to the specification and validity analysis, but they are not expressly recited as claim limitations in the supplied claims.

When does US 8,637,540 lose exclusivity?

The earliest claimed priority date is generally reported as December 21, 2007. On a conventional 20-year term calculation, the patent’s nominal expiration date is approximately December 21, 2027. The enforceable term must be confirmed against the USPTO patent-term calculation, including any patent-term adjustment, terminal disclaimer, maintenance-fee status, or other record affecting enforceability. [1]

The patent issued on January 28, 2014. The issuance date does not determine expiration for a modern utility patent. The controlling baseline is generally 20 years from the earliest effective nonprovisional filing date, subject to statutory adjustments. [2]

Exclusivity timeline

Event	Approximate date
Earliest claimed priority	December 21, 2007
Patent grant	January 28, 2014
Nominal 20-year expiration	December 21, 2027
Post-expiration entry	Potentially available after expiration, subject to other patents and regulatory requirements

Patent expiration would not automatically eliminate all market barriers. Related Acura or successor-company patents, formulation patents, method-of-use patents, manufacturing patents, and regulatory exclusivities could create separate barriers.

What is the FDA and Orange Book status?

The commercial relevance of US 8,637,540 is associated with Acura’s abuse-deterrent immediate-release oxycodone technology and the product later marketed as Oxecta and subsequently associated with the Oxaydo brand.

FDA-approved abuse-deterrent oxycodone products are distinct from conventional generic oxycodone hydrochloride immediate-release tablets. FDA’s product-specific labeling and abuse-deterrence determinations do not, by themselves, establish patent infringement. Patent scope must be evaluated against the actual formulation and the Orange Book-listed patents for the relevant NDA. [3]

Orange Book considerations

For an NDA product, the Orange Book may list:

Drug-substance patents;
Drug-product formulation patents;
Method-of-use patents;
Patent-use codes;
Patent expiration dates.

An Orange Book listing does not mean that every generic oxycodone product infringes the listed patent. It means that an ANDA applicant may need to address the listing through a Paragraph I, II, III, or IV certification, depending on patent status and the proposed labeling.

The supplied claims are composition claims. They would generally be evaluated as drug-product patents rather than method-of-use patents. The precise Orange Book listing for any NDA must be checked against the current FDA Orange Book database and the relevant NDA patent certification history. [3]

Are there Paragraph IV challenges to US 8,637,540?

A Paragraph IV certification would assert that the patent is invalid, unenforceable, or will not be infringed by the proposed ANDA product. The certification could target:

Lack of written description;
Lack of enablement across the full opioid and polymer scope;
Obviousness based on known abuse-deterrent polymers, disintegrants, surfactants, and immediate-release opioid tablets;
Indefiniteness of "about," "gel-forming polymer," and "sufficient to cause ... immediate release";
Non-infringement based on the absence of a claimed surfactant or gel-forming polymer;
Failure to meet the functional immediate-release limitation.

A Paragraph IV challenge to a listed patent can trigger patent litigation and, for a qualifying first applicant, potentially a 180-day generic exclusivity period. [4]

There is no basis in the supplied material to conclude that a specific ANDA applicant challenged US 8,637,540. Generic oxycodone applicants may avoid the patent through a formulation that does not include the claimed gel-forming polymer, surfactant, or excipient combination. Conventional oxycodone hydrochloride immediate-release products should not be presumed to infringe merely because they contain the same active ingredient.

Which companies are associated with the patent estate?

Acura Pharmaceuticals is the principal company associated with the Aversion abuse-deterrent technology and the patent family surrounding abuse-deterrent opioid compositions. Commercial rights and product responsibilities for Acura’s oxycodone products have changed over time through corporate transactions and licensing arrangements.

Relevant commercial entities include:

Company	Relevance
Acura Pharmaceuticals	Original developer and assignee associated with Aversion technology
Egalet Corporation	Associated with the Oxaydo commercial product after acquisition or licensing transactions
Successor or acquiring entities	May hold product, patent, or commercialization rights depending on asset transfers
Generic manufacturers	Potential ANDA applicants, subject to Orange Book certification and formulation design

The patent assignment record, rather than product branding, determines the current patent owner. The USPTO assignment database should be used to identify post-grant transfers. [5]

How strong is the patent estate for abuse-deterrent oxycodone?

US 8,637,540 has meaningful formulation coverage but is not a complete exclusivity barrier by itself.

Strengths

Claim 15 directly targets oxycodone hydrochloride.
The independent claims combine active ingredient and excipient architecture.
The gel-forming polymer range is broad.
The claims reach multiple dosage forms.
The disintegrant requirement supports immediate release rather than limiting the invention to an extended-release matrix.
The claims do not require a specific abuse route.

Weaknesses

"Gel-forming polymer" may require technical evidence and construction.
"About 3 to about 40 wt%" creates boundary questions.
"Sufficient to cause ... immediate release" is functional and may be contested.
The broad opioid claim may face enablement and obviousness attacks.
A generic can potentially remove or replace one required excipient.
The claims do not expressly require a measured abuse-deterrence result.

The patent is stronger against a formulation that copies the complete architecture than against a conventional generic oxycodone tablet. Its practical value depends on whether the commercial product’s formulation, manufacturing specifications, and dissolution profile fall within the claims.

What patent litigation and settlements affect the patent?

The supplied claim text does not establish a litigation history, settlement agreement, consent judgment, or license covering US 8,637,540. Those facts must be determined from PACER, district-court dockets, ANDA litigation records, and the USPTO assignment database.

For diligence purposes, the relevant litigation questions are:

Was the patent listed against the applicable oxycodone NDA?
Did an ANDA applicant make a Paragraph IV certification?
Was a 30-month stay triggered?
Was the case dismissed, settled, or resolved by judgment?
Did the settlement permit an authorized generic or licensed launch?
Did the settlement restrict launch until patent expiration or another date?

A patent settlement may resolve one ANDA dispute without clearing the entire patent estate. It may also include confidential manufacturing, licensing, or authorized-generic provisions that are not visible in the patent record.

What generic launch risks exist?

Low-risk design-around scenario

A generic formulation may reduce risk by:

Omitting the gel-forming polymer;
Omitting the surfactant;
Using a conventional disintegrant and standard tablet excipients;
Demonstrating immediate release through a non-infringing composition;
Avoiding the claimed concentration architecture.

Higher-risk scenario

Risk increases where the proposed product:

Contains oxycodone hydrochloride;
Includes polyethylene oxide or another gel-forming polymer at 3-40 wt%;
Uses crospovidone, croscarmellose sodium, or sodium starch glycolate;
Contains a surfactant;
Is an immediate-release tablet or capsule;
Has an excipient profile materially similar to the protected product.

Biosimilar risk

Biosimilar risk is not relevant to this patent because the claims cover small-molecule opioid compositions, not biologic products. The applicable pathway is an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act, not the biosimilar pathway under section 351(k) of the Public Health Service Act.

What manufacturing and geographic barriers remain?

The patent is a U.S. composition patent. Its direct exclusionary effect is limited to the United States and activities having a U.S. statutory nexus. Corresponding foreign patents, if any, must be reviewed separately by jurisdiction.

Manufacturing risk can arise even where a final formulation appears different. Relevant issues include:

Polymer grade and molecular weight;
Excipient supplier specifications;
Wet or dry granulation;
Compression force;
Tablet porosity;
Particle-size distribution;
Surfactant concentration;
Dissolution performance;
Batch-to-batch composition variation.

A U.S. manufacturer, importer, or ANDA sponsor should assess both literal infringement and potential equivalents. A product that replaces one claimed excipient may still face an equivalents argument if the replacement performs substantially the same function in substantially the same way to achieve substantially the same result. [6]

How does US 8,637,540 compare with conventional oxycodone patents?

Issue	US 8,637,540	Conventional oxycodone tablet patent
Primary focus	Abuse-deterrent composition architecture	Dosage strength, formulation, or use
Active ingredient	Broad opioids and specifically oxycodone HCl	Usually oxycodone or oxycodone salt
Polymer requirement	Required in independent claims	Often absent
Surfactant requirement	Required in independent claims	Often absent
Immediate release	Expressly required	May be implicit or not claimed
Abuse-deterrence limitation	Not expressly required in supplied claims	Usually absent
Design-around route	Remove or replace a required excipient	Depends on claim scope
Biosimilar relevance	None	None

Key Takeaways

US 8,637,540 is a composition patent covering opioid formulations with a gel-forming polymer, disintegrant, and surfactant.
Claim 15 is the principal oxycodone hydrochloride claim.
The broadest practical infringement risk is for immediate-release oxycodone products using the claimed excipient architecture.
The patent does not expressly require a measured abuse-deterrence result.
The key claim-construction disputes concern "gel-forming polymer," "about," and the immediate-release functional limitation.
The nominal patent term is approximately December 21, 2027, subject to the official USPTO term and enforceability records.
Conventional generic oxycodone tablets are not automatically covered.
Biosimilar litigation is irrelevant because oxycodone is a small molecule.
A complete launch assessment requires review of the Orange Book listing, patent assignments, FDA certifications, ANDA litigation, and related patent families.

FAQs about US Patent 8,637,540

Does US 8,637,540 cover all oxycodone tablets?

No. It covers oxycodone hydrochloride compositions containing the claimed gel-forming polymer, disintegrant, surfactant, and immediate-release characteristics.

Can a generic avoid US 8,637,540 by changing the disintegrant?

Potentially. Replacing the disintegrant may avoid the dependent claims naming sodium starch glycolate, crospovidone, and croscarmellose sodium, but the independent claims may still cover another disintegrant if it produces immediate release.

Is Oxaydo the same as a conventional oxycodone generic?

No. Oxaydo was developed as an abuse-deterrent immediate-release oxycodone product. Conventional oxycodone immediate-release products generally have different formulation objectives and excipient systems.

Does a Paragraph IV certification automatically invalidate US 8,637,540?

No. A Paragraph IV certification is an ANDA applicant’s legal position that the patent is invalid, unenforceable, or not infringed. The patent remains enforceable unless it expires, is canceled, or is held invalid or unenforceable.

Are foreign patents equivalent to US 8,637,540?

Not automatically. Foreign family members may have different claims, expiration dates, prosecution histories, and enforceability outcomes. Each jurisdiction requires a separate analysis.

References

United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term calculation resources. https://www.uspto.gov/patents/laws/american-inventors-protection-act-1999/patent-term-adjustment
United States Code. (2024). 35 U.S.C. § 154: Contents and term of patent; provisional rights. https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title35-section154
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
U.S. Food and Drug Administration. (n.d.). ANDA submissions: Refuse-to-receive standards and Paragraph IV certifications. https://www.fda.gov/drugs/abbreviated-new-drug-application-anda
United States Patent and Trademark Office. (n.d.). Patent assignment search. https://assignment.uspto.gov/
United States Code. (2024). 35 U.S.C. § 271: Infringement of patent. https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title35-section271

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2004294953	⤷ Start Trial
Australia	2010200979	⤷ Start Trial
Australia	2013206525	⤷ Start Trial
Australia	2015264950	⤷ Start Trial
Australia	2017239544	⤷ Start Trial
Canada	2547334	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,637,540

Summary for Patent: 8,637,540