U.S. Patent 5,641,803: Taxol Three-Hour Infusion Claims, Expiration, and Patent Landscape

U.S. Patent 5,641,803 covered a specific paclitaxel treatment regimen: parenteral administration of approximately 135 to 175 mg/m² over about three hours to reduce hematologic toxicity, and in some claims, neurotoxicity. The patent was a method-of-use patent, not a basic paclitaxel compound or formulation patent. Its enforceable term expired on June 24, 2014. It does not create a current U.S. exclusivity barrier for generic paclitaxel products.

What does U.S. Patent 5,641,803 cover?

U.S. Patent 5,641,803, titled “Method for reducing toxicity of Taxol,” covers the clinical administration of Taxol, meaning paclitaxel, by parenteral delivery at specified dose and infusion-duration parameters.[1]

The central limitation is the combination of:

Claim element	Scope
Active ingredient	Taxol, commercially understood as paclitaxel
Route	Parenteral administration
Dose range in claims 1, 4 and 6	About 135 to 175 mg/m²
Dose in claims 2, 3 and 5	About 135 mg/m²
Administration time	About three hours
Therapeutic result	Reduced hematologic toxicity, or reduced hematologic toxicity and neurotoxicity
Patient population	Cancer patients; certain claims specify solid tumors, leukemias or ovarian cancer

The patent does not claim:

The paclitaxel molecule itself
A paclitaxel formulation as a composition
Cremophor EL or another excipient
A manufacturing process for paclitaxel
Albumin-bound paclitaxel
A specific dosage form such as a vial or prefilled syringe

Its protection was directed to how paclitaxel was administered in clinical practice.

How do the six claims differ?

The six claims divide into general cancer-treatment claims and ovarian-cancer claims.

Claims 1 and 6: three-hour dosing to reduce hematologic toxicity

Claim 1 covers administering approximately 135 to 175 mg/m² of Taxol over approximately three hours to reduce hematologic toxicity.

Claim 6 narrows claim 1 by limiting the patients to those suffering from solid tumors or leukemias.

A regimen of 135, 150, 160 or 175 mg/m² over approximately three hours falls within the numerical dosing range, assuming the other claim elements are met.

Claims 2 and 3: 135 mg/m² to reduce two toxicities

Claim 2 covers approximately 135 mg/m² over approximately three hours where the intended therapeutic result is reduction of both hematologic toxicity and neurotoxicity.

Claim 3 narrows claim 2 to patients with solid tumors or leukemias.

These claims are narrower than claim 1 because they require both toxicity-reduction outcomes and a dose centered on approximately 135 mg/m².

Claims 4 and 5: ovarian-cancer regimens

Claim 4 applies the 135 to 175 mg/m², three-hour regimen to patients with ovarian cancer.

Claim 5 covers approximately 135 mg/m² over approximately three hours for ovarian cancer while requiring reduction of both hematologic toxicity and neurotoxicity.

Claims 4 and 5 therefore overlap substantially with claims 1 and 2 but add the ovarian-cancer limitation.

What is the practical scope of infringement under Patent 5,641,803?

The practical scope depended on four factors:

The product had to be Taxol or paclitaxel.
Administration had to be parenteral.
The dose had to fall within approximately 135 to 175 mg/m², or approximately 135 mg/m² for the narrower claims.
Administration had to occur over approximately three hours.

A standard paclitaxel regimen of 175 mg/m² over three hours would historically have presented the clearest literal overlap with claims 1, 4 and 6. A 135 mg/m², three-hour regimen would have implicated the broader claims and the toxicity-specific claims.

The functional language concerning reduced hematologic toxicity and neurotoxicity added a potential evidentiary issue. A method claim generally requires performance of the claimed steps with the required therapeutic purpose or result. A product label, prescribing information, clinical protocol, physician instruction or ANDA labeling could have been relevant to proving induced or direct infringement during the patent term.

The claim language also uses approximate terms such as “about” and “approximately.” Those terms generally provide numerical flexibility rather than limiting coverage to a single exact dose. The precise scope would have depended on intrinsic evidence, prosecution history and expert testimony.

When did U.S. Patent 5,641,803 expire?

The patent issued on June 24, 1997. Its U.S. patent term expired on June 24, 2014, based on the pre-1995 patent-term framework applicable to the application.[1] The FDA Orange Book identified the patent as a Taxol-related patent during the relevant period.[2]

Milestone	Date or status
Patent issued	June 24, 1997
Patent type	Method-of-use patent
Primary subject	Paclitaxel dose and three-hour infusion duration
FDA product associated with the patent	Taxol injection
Orange Book relevance	Historical listed method-of-use patent
Patent expiration	June 24, 2014
Current enforceability	Expired

No current patent exclusivity remains under Patent 5,641,803. An expired patent cannot support a present-day injunction, damages claim for post-expiration conduct or a current Paragraph IV litigation strategy.

What was the Orange Book status of Taxol and Patent 5,641,803?

Taxol was approved by the FDA under NDA 020262 for multiple oncology indications, including ovarian cancer, breast cancer and non-small-cell lung cancer.[3] The FDA-approved labeling described paclitaxel administration by intravenous infusion, including three-hour and longer infusion schedules depending on the indication and treatment protocol.[3]

Patent 5,641,803 was relevant to the Orange Book because it claimed a method of using Taxol. Method-of-use patents are generally listed with an associated FDA use code identifying the approved indication or method covered by the patent.

The listing did not convert the patent into a product patent. It also did not prevent FDA approval of a generic paclitaxel product for uses outside the patented method, provided that applicable labeling and statutory requirements were satisfied.

After patent expiration, the Orange Book listing no longer created an operative Hatch-Waxman delay or an enforceable use-patent barrier.

What Paragraph IV challenges affected paclitaxel?

During the patent term, an ANDA applicant seeking approval for a use covered by a listed method-of-use patent could have filed a Paragraph IV certification asserting that the patent was invalid, unenforceable or would not be infringed.

The commercial effect of a Paragraph IV filing would have depended on:

Whether the patent was still listed and unexpired
Whether the ANDA included the patented three-hour dosing method
Whether the applicant used a section viii statement to carve out the patented use
Whether the NDA holder filed suit within the statutory period
Whether a 30-month stay applied

Today, Patent 5,641,803 cannot generate a new 30-month stay because its term has expired. Generic applicants no longer need to defeat this patent to obtain or maintain approval for paclitaxel injection.

The remaining commercial risk is therefore regulatory and commercial rather than patent-based. A generic applicant can compete against Taxol and other paclitaxel products without resolving this expired patent.

How does Patent 5,641,803 compare with formulation and compound patents?

Patent 5,641,803 was narrower than a compound patent and narrower than a broad formulation patent.

Patent category	Typical protection	Relationship to U.S. 5,641,803
Compound patent	Paclitaxel molecule or chemical class	Not covered by 5,641,803
Formulation patent	Solubilized paclitaxel, excipient system or dosage form	Not covered by 5,641,803
Manufacturing patent	Extraction, purification or synthesis	Not covered by 5,641,803
Method-of-use patent	Dose, duration, indication or treatment outcome	Core subject of 5,641,803
Delivery-system patent	Albumin-bound or other specialized delivery	Generally outside the claimed three-hour Taxol regimen

The patent was commercially important because the three-hour infusion schedule became a recognized paclitaxel administration approach. Its legal scope, however, remained limited to the claimed administration method.

Albumin-bound paclitaxel products, such as nab-paclitaxel, are technically and clinically distinct from conventional solvent-based Taxol formulations. A typical nab-paclitaxel regimen uses a different formulation, dose expression and infusion duration. A 30-minute administration would not literally satisfy the approximately three-hour limitation.

Does Patent 5,641,803 cover Abraxane or biosimilars?

No biosimilar framework applies to conventional paclitaxel in the way it applies to biologic products. Paclitaxel is a chemically synthesized or semi-synthesized small-molecule drug, and competing products are generally approved through the ANDA pathway rather than the biosimilar pathway.

The patent also does not directly cover Abraxane, the albumin-bound paclitaxel product, where the administration protocol and formulation differ from the claimed Taxol regimen.

A product could have faced historical method-of-use issues if its labeling instructed physicians to administer conventional paclitaxel at 135 to 175 mg/m² over approximately three hours during the patent term. That issue ended with patent expiration.

What manufacturing and intellectual-property barriers remain for paclitaxel?

Patent 5,641,803 presents no current manufacturing barrier. Paclitaxel manufacturers instead face operational and regulatory requirements involving:

Active pharmaceutical ingredient quality
Control of impurities and degradation products
Sterility assurance
Solubilization and excipient compatibility
Container-closure integrity
Stability
Validated aseptic manufacturing
FDA ANDA requirements
Supply-chain reliability

Conventional paclitaxel injection historically presented formulation challenges because paclitaxel has poor aqueous solubility. Solvent systems and infusion-related safety requirements remain relevant to product development, but those issues are not protected by Patent 5,641,803.

What patent litigation and settlement risks remain?

No current litigation risk arises from Patent 5,641,803 because the patent expired in 2014. Historical litigation, if any, could have involved an ANDA applicant’s Paragraph IV certification, a use carve-out, infringement allegations based on labeling or a challenge to validity and enforceability.

An expired patent can remain relevant to historical damages analysis, prior settlement terms or market-entry disputes involving conduct before expiration. It cannot provide a current exclusionary right.

There is no current settlement-related launch restriction attributable to this patent. Any historical agreement must be analyzed separately for contractual provisions, licensed rights, launch dates and releases.

How strong was the patent estate for the three-hour paclitaxel regimen?

The patent had moderate historical commercial strength but limited breadth.

Strengths

It covered a clinically meaningful three-hour paclitaxel regimen.
The 135 to 175 mg/m² range captured common conventional paclitaxel dosing.
Claims covered general oncology populations and ovarian cancer.
The patent was tied to an FDA-approved therapy and administration schedule.
Labeling and physician instructions could have created useful evidence in an infringement case.

Limitations

It did not cover paclitaxel itself.
It did not cover all paclitaxel doses or infusion durations.
It did not cover non-paclitaxel drugs.
It did not broadly cover alternative formulations.
The toxicity-reduction limitations could have created proof and claim-construction disputes.
The patent expired in 2014.

The estate was therefore valuable as a historical lifecycle-management asset but did not provide durable product-level exclusivity.

What generic launch scenarios existed?

During the patent term, the principal scenarios were:

Scenario	Patent impact
Generic label excluded the patented use	Potential section viii pathway
Generic label included 135 to 175 mg/m² over three hours	Potential Paragraph IV exposure
Generic used a different dose or infusion duration	Possible design-around, subject to claim construction
Generic supplied conventional paclitaxel with broad oncology labeling	Greater method-of-use risk during the term
Product launched after June 24, 2014	No remaining 5,641,803 patent barrier

The current scenario is straightforward: generic paclitaxel products compete without this patent restricting the three-hour infusion regimen.

What is the geographic coverage of Patent 5,641,803?

The patent provided protection only in the United States. It did not automatically protect the same regimen in Canada, Europe, Japan or other markets.

International protection would have required separate national or regional patent filings. Expiration, prosecution history, claim scope and litigation status could have differed by jurisdiction. U.S. Patent 5,641,803 cannot be used to establish foreign exclusivity.

Key Takeaways

U.S. Patent 5,641,803 covered parenteral paclitaxel at approximately 135 to 175 mg/m² over approximately three hours.
Claims 2, 3 and 5 focused on approximately 135 mg/m² and reduction of both hematologic toxicity and neurotoxicity.
Claims 4 and 5 specifically covered ovarian-cancer treatment.
The patent was a method-of-use patent, not a compound, formulation or manufacturing patent.
Its U.S. term expired on June 24, 2014.
The patent no longer creates an Orange Book, Paragraph IV or generic-launch barrier.
Conventional paclitaxel and albumin-bound paclitaxel must be analyzed separately because their formulations and administration schedules differ.
Current commercial barriers are regulatory, manufacturing and supply-chain related rather than based on this patent.

FAQs About U.S. Patent 5,641,803

Does a 175 mg/m² paclitaxel dose over three hours fall within the patent?

Historically, yes. A 175 mg/m², three-hour conventional paclitaxel regimen fell within the 135 to 175 mg/m² range in claims 1, 4 and 6, subject to the remaining claim limitations. The patent is now expired.

Did Patent 5,641,803 cover 24-hour paclitaxel infusions?

No. The claims require administration over approximately three hours. A 24-hour infusion would not literally satisfy that duration limitation.

Did the patent cover paclitaxel for breast cancer?

The broad claims could cover cancer patients receiving the claimed regimen, while other claims focused on solid tumors or leukemias. The patent was not limited exclusively to ovarian cancer, although claims 4 and 5 were ovarian-cancer specific.

Can an expired method-of-use patent block an FDA-approved generic today?

No. An expired patent cannot support a current injunction or statutory approval stay. FDA labeling and other unexpired patents may still affect approval, but Patent 5,641,803 does not.

Is Patent 5,641,803 relevant to paclitaxel licensing negotiations?

Only as historical background unless a transaction includes pre-expiration conduct, legacy indemnities, litigation releases or representations concerning past patent rights. It has no current standalone exclusivity value.

References

U.S. Patent No. 5,641,803. (1997). Method for reducing toxicity of Taxol. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2024). Taxol (paclitaxel) injection prescribing information. Bristol-Myers Squibb Company.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	152910	⤷ Start Trial
Australia	3216893	⤷ Start Trial
Australia	4207096	⤷ Start Trial
Australia	641894	⤷ Start Trial
Australia	704393	⤷ Start Trial
Belgium	1006497	⤷ Start Trial
Canada	2086874	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,641,803

Summary for Patent: 5,641,803