United States Patent 6,030,643: Oxaprozin Salt Formulations, Claim Scope and Patent Landscape

U.S. Patent No. 6,030,643 protects rapidly dissolving solid oral formulations containing potassium, sodium, or Tris salts of oxaprozin. The central limitation is a dissolution result: approximately 75% of oxaprozin must dissolve within about 30 minutes in pH 7.4 phosphate buffer at 37°C using a paddle apparatus at 75 rpm. The patent also targets lubricant selection, low or absent magnesium stearate, low methylcellulose content, high drug loading, and specific stearic-acid/pregelatinized-starch formulations.[1]

The patent is no longer an enforceable U.S. patent. Its relevant patent term expired in approximately 2017, based on the patent’s 20-year term measured from its earliest effective nonprovisional filing date. The claims therefore have historical and technical relevance but do not create a current U.S. blocking right against generic oxaprozin products.

What does U.S. Patent 6,030,643 protect?

The patent covers pharmaceutical compositions and treatment methods using selected oxaprozin salts in solid oral dosage forms.

Oxaprozin is a nonsteroidal anti-inflammatory drug, or NSAID. The patent does not claim ordinary oxaprozin alone. It focuses on salt forms and formulation conditions intended to improve dissolution and, potentially, oral performance.

The principal protected subject matter has four elements:

A potassium, sodium, or Tris salt of oxaprozin.
A solid dosage form, such as a tablet, pill, or caplet.
A specified lubricant and excipient profile.
A dissolution result showing approximately 75% release within approximately 30 minutes.

Claim 1 is the broadest composition claim in the first claim group. It requires:

potassium, sodium, or Tris oxaprozin;
a solid dosage form;
less than 1% by weight magnesium stearate; and
approximately 75% dissolution within approximately 30 minutes under the stated test conditions.

Claims 2 through 4 narrow claim 1 by selecting potassium, sodium, or Tris oxaprozin. Claims 5 through 8 add drug loading, methylcellulose, metallic-stearate, and dosage-form limitations.

Claim 9 creates a second independent composition category. It requires a salt of oxaprozin and a lubricant selected from water-insoluble or water-soluble lubricants, together with the same dissolution result. This group is broader in lubricant language than claim 1 because it does not initially require less than 1% magnesium stearate.

Claim 23 is the most formulation-specific independent claim. It requires:

70% to 90% oxaprozin salt;
1% to 4% stearic acid;
0.25% to 25% pregelatinized corn starch; and
optionally, 0% to 27% microcrystalline cellulose.

That formulation must also meet the approximately 75% dissolution threshold within 30 minutes.

How are the claims organized?

Claim group	Claim numbers	Primary subject matter	Main narrowing feature
Broad salt formulation	1-8	Solid dosage form containing potassium, sodium, or Tris oxaprozin	Less than 1% magnesium stearate and dissolution performance
Lubricant formulation	9-22	Oxaprozin salt with water-soluble or water-insoluble lubricant	Lubricant identity, amount, binders, and fillers
Defined formulation	23-28	High-load oxaprozin salt formulation	Stearic acid, pregelatinized starch, and optional microcrystalline cellulose
Pain treatment	29-31	Method of treating pain	Administration of qualifying solid dosage form
Inflammation treatment	32-34	Method of treating inflammation or related disorders	Administration of qualifying solid dosage form
Enhanced dissolution	35-36	Composition and treatment claims	Approximately 95% dissolution within 30 minutes

What is the key limitation in the patent?

The dissolution requirement is the central claim limitation.

The claims require approximately 75% of the active agent to dissolve in:

1,000 mL of pH 7.4 phosphate buffer;
at 37°C;
with paddle stirring at 75 rpm; and
within approximately 30 minutes.

Claims 35 and 36 raise the performance threshold to approximately 95% dissolution within the same period.

This limitation materially narrows the patent. A product containing an oxaprozin salt does not necessarily fall within the claims merely because it uses the same active ingredient or a listed lubricant. The product must also satisfy the dissolution test as claimed.

The dissolution language can create infringement and validity issues. Small changes in particle size, compression force, granulation method, excipient grade, tablet hardness, coating, or test execution can affect the result. The words "about" and "approximately" introduce claim-construction questions concerning the permissible range around 75%, 95%, and 30 minutes.

What oxaprozin salts are covered?

The claims identify three salt categories:

Salt	Expressly covered?	Claim references
Potassium oxaprozin	Yes	1-5, 9-10, 23-25, 29-34
Sodium oxaprozin	Yes	1, 3, 5, 9-10, 23, 29-34
Tris oxaprozin	Yes	1, 4-5, 9-10, 23, 29-34
Free-acid oxaprozin	Not expressly covered	Not identified in the supplied claims

The patent is therefore directed to salt-form technology rather than the free acid as such. A formulation using free-acid oxaprozin would not satisfy the express active-agent limitation of these claims.

What formulations are protected by U.S. Patent 6,030,643?

Magnesium-stearate limitations

Several claims restrict magnesium stearate:

Claims 1 and 12 require less than 1% magnesium stearate.
Claim 23’s dependent claim 26 adds the same less-than-1% limitation.
Claims 7, 13, and 27 require the composition to be substantially free of metallic stearates.

These limitations are commercially relevant because magnesium stearate is a common tablet lubricant. The patent attempts to capture formulations that avoid the dissolution impairment allegedly associated with conventional metallic-stearate lubrication.

A formulation with 0.5% magnesium stearate could potentially satisfy a less-than-1% limitation, assuming all other claim elements are met. A formulation with 1% or more would not satisfy that literal numerical limitation, although claim construction and equivalents issues could remain relevant in litigation.

Water-insoluble lubricants

Claim 16 identifies:

calcium stearate;
zinc stearate;
stearic acid;
hydrogenated vegetable oil; and
talc.

The list is important because claim 9 uses a broader lubricant category, while claim 16 narrows the scope to specified water-insoluble lubricants.

Water-soluble lubricants

Claim 17 identifies:

sodium lauryl sulfate; and
sodium stearyl fumarate.

These ingredients can be important design-around options because they differ from conventional magnesium stearate in water solubility and may support faster dissolution.

Binders and fillers

Claims 18 through 22 add:

binders at 0.25% to 30%;
cornstarch;
pregelatinized cornstarch;
sucrose;
polyvinylpyrrolidone;
methylcellulose;
sodium carboxymethyl cellulose;
ethylcellulose; and
microcrystalline cellulose as a filler.

Claim 6 and claim 14 restrict methylcellulose to less than 2%. The patent therefore combines broad excipient categories with narrower dependent-claim selections.

How strong is the patent estate?

The patent’s historical strength came from combining composition identity with measurable product performance. A claim directed only to an oxaprozin salt or only to a conventional tablet excipient would likely have been easier to design around. The dissolution requirement creates a more product-specific boundary.

Its principal strengths were:

coverage of three selected oxaprozin salts;
claims directed to tablets, pills, and caplets;
high drug-load embodiments;
lubricant-specific alternatives;
method-of-use claims for pain and inflammation; and
a defined formulation using stearic acid and pregelatinized corn starch.

Its principal weaknesses were:

dependence on a particular in vitro dissolution test;
relatively narrow excipient and percentage limitations in important dependent claims;
potential design-around options using different salts, lubricants, binders, or manufacturing processes;
possible difficulty proving infringement when dissolution results vary between batches; and
patent expiration, which eliminates current U.S. enforcement value.

The patent does not appear, from the supplied claims, to contain broad claims covering every oxaprozin dosage form, every oxaprozin salt, or every immediate-release formulation.

When did U.S. Patent 6,030,643 lose exclusivity?

The patent’s enforceable term expired approximately 20 years after its earliest effective nonprovisional filing date, placing expiration in approximately 2017.[1] Patent expiration ends the exclusionary right created by the patent. It does not remove the patent from historical records, FDA submissions, litigation files, or freedom-to-operate analyses.

The commercial exclusivity analysis must also distinguish patent protection from FDA regulatory exclusivity. Oxaprozin was approved before the modern period in which many small-molecule products received substantial statutory exclusivity. Any applicable FDA exclusivity would have expired long before the patent term ended.[2]

Exclusivity timeline

Event	Approximate timing	Commercial effect
Oxaprozin development and original approval	Before issuance of U.S. 6,030,643	Established the product and active ingredient
Patent application and prosecution	Before 2000	Created the formulation patent position
Patent issuance	February 29, 2000	U.S. patent rights began on issued claims
FDA generic competition period	Before patent expiration	Depended on Orange Book patents and generic certifications
Patent expiration	Approximately 2017	Removed current U.S. patent exclusivity
Current position	After expiration	No active U.S. exclusion based on this patent

What is the Orange Book status of U.S. Patent 6,030,643?

U.S. Patent 6,030,643 is not a current blocking Orange Book patent because its patent term has expired. Orange Book listing status is product-specific and depends on whether the patent was submitted and listed for a particular approved drug product, not merely on the existence of a patent relating to the active ingredient.

For a historical Orange Book analysis, the relevant questions are:

whether the patent was submitted by the NDA holder;
whether FDA accepted it for listing;
whether it was listed for drug substance, drug product, or method of use;
whether the listing was active when an ANDA was filed; and
whether any subsequent delisting or expiration occurred.

The supplied claim set is directed primarily to drug product formulations and methods of use. It does not establish, by itself, that the patent was listed in the Orange Book for a specific oxaprozin NDA.[3]

What Paragraph IV challenges and generic-entry risks existed?

A Paragraph IV certification would have been relevant only while the patent was listed and unexpired. An ANDA applicant could challenge the patent by asserting that:

the proposed product does not meet the salt limitation;
the formulation does not meet the claimed dissolution threshold;
the product uses a lubricant outside the claimed category;
the product exceeds a stated excipient limit;
the claims are invalid for anticipation or obviousness;
the claims are indefinite because of terms such as "about," "approximately," or "substantially free"; or
the claimed subject matter lacks adequate written description or enablement.

The main generic design-around paths would have included:

Using free-acid oxaprozin rather than a claimed salt.
Using a different salt form.
Using magnesium stearate at or above the claimed threshold, if acceptable from a formulation perspective.
Selecting a lubricant not covered by the relevant claim.
Modifying the formulation so that it does not achieve the claimed dissolution result.
Using a dosage form outside the claimed tablet, pill, or caplet categories where relevant.

After expiration, these Paragraph IV issues no longer create a current patent-entry barrier in the United States.

What litigation status affects the patent?

The supplied information identifies the patent and claims but does not establish a current infringement action, settlement agreement, consent judgment, or appellate decision involving U.S. Patent 6,030,643. The patent’s expiration means that any historical litigation would have limited present-day exclusionary effect unless it produced damages, contractual obligations, or a continuing settlement provision.

A complete litigation review would ordinarily examine:

district court docket records;
Federal Circuit decisions;
ANDA litigation complaints;
claim-construction rulings;
invalidity judgments;
settlement terms;
covenant-not-to-sue provisions; and
any post-expiration damages proceedings.

No current litigation consequence can be assigned solely from the claim text.

What manufacturing and intellectual-property barriers did the patent create?

The patent could have restricted formulation development in several technical areas:

selection of oxaprozin salt form;
tablet lubrication;
granulation and blending;
compression conditions;
drug loading;
use of pregelatinized starch;
use of microcrystalline cellulose;
methylcellulose concentration;
tablet disintegration; and
dissolution performance.

The practical barrier was not merely ingredient selection. A manufacturer could avoid a literal claim while using similar excipients if its product failed one required limitation, particularly the dissolution requirement or a numerical concentration range.

The patent did not expressly claim a manufacturing process. Its risk was therefore primarily product-based. A process could still create indirect risk if it consistently produced tablets that met all composition and dissolution limitations.

How does this patent compare with ordinary oxaprozin protection?

Issue	U.S. 6,030,643	Basic oxaprozin composition patent
Active agent	Potassium, sodium, or Tris salt	May cover oxaprozin or broader salt chemistry
Dosage form	Solid dosage form	May be broader or unspecified
Dissolution test	Required in central claims	Not necessarily required
Lubricant limitations	Extensive	May be absent
High drug loading	Covered in dependent claims and claim 23	Not necessarily covered
Method of treatment	Pain and inflammation	May or may not be included
Current enforceability	Expired	Depends on separate patent term
Main design-around	Change salt, excipient, percentage, or dissolution profile	Depends on separate claim language

Key Takeaways

U.S. Patent 6,030,643 covers solid oral formulations containing potassium, sodium, or Tris oxaprozin salts.
The central technical limitation is approximately 75% dissolution within approximately 30 minutes under specified pH, temperature, volume, and paddle-stirring conditions.
Claims 35 and 36 raise the dissolution requirement to approximately 95%.
The patent addresses magnesium stearate, metallic stearates, methylcellulose, water-soluble lubricants, water-insoluble lubricants, pregelatinized starch, and microcrystalline cellulose.
Claim 23 is the most commercially specific formulation claim, requiring high oxaprozin loading, stearic acid, and pregelatinized corn starch.
The patent’s term expired approximately in 2017 and does not currently block U.S. generic entry.
The claims do not expressly cover free-acid oxaprozin.
The main historical design-around strategies involved changing the salt, lubricant, excipient percentages, dosage form, or dissolution profile.
The claim text alone does not establish current Orange Book listing, Paragraph IV litigation, or settlement status.

FAQs

Is U.S. Patent 6,030,643 still enforceable?

No. Its U.S. patent term expired approximately in 2017.

Does the patent cover free-acid oxaprozin?

No. The supplied claims require potassium, sodium, or Tris salts of oxaprozin.

Does a tablet infringe merely because it contains potassium oxaprozin?

No. The applicable claim also requires the specified solid dosage form, excipient or lubricant limitations where applicable, and the claimed dissolution performance.

Can a generic use magnesium stearate?

The answer depends on the applicable claim. Several claims require less than 1% magnesium stearate or substantial absence of metallic stearates, while other claims use broader lubricant language. Because the patent has expired, these limitations no longer create a current U.S. patent barrier.

Is the 95% dissolution requirement present in every claim?

No. Claims 35 and 36 add approximately 95% dissolution within approximately 30 minutes. The principal independent claims use the approximately 75% threshold.

References

United States Patent and Trademark Office. (2000). U.S. Patent No. 6,030,643, Pharmaceutical compositions containing oxaprozin salts.
U.S. Food and Drug Administration. (n.d.). Drug approval package and labeling resources for oxaprozin products.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	299699	⤷ Start Trial
Australia	3059797	⤷ Start Trial
Australia	718030	⤷ Start Trial
Brazil	9710448	⤷ Start Trial
Canada	2255064	⤷ Start Trial
China	1129429	⤷ Start Trial
China	1225580	⤷ Start Trial
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Details for Patent: 6,030,643

Summary for Patent: 6,030,643