United States Drug Patent 6,413,549: Claim Scope, Expiration, Litigation Risk, and Patent Landscape

U.S. Patent No. 6,413,549 protects a platform technology for freeze-dried, rapidly disintegrating oral dosage forms containing coated coarse drug particles. Its core limitations are particle size, coating composition, a water-soluble or water-dispersible matrix, and rapid disintegration. The patent is no longer an enforceable barrier in the United States because its statutory patent term expired in 2018. It is not an Orange Book drug patent and does not independently block generic or 505(b)(2) entry.

What does U.S. Patent 6,413,549 protect?

The patent covers a lyophilized oral solid dosage form with the following architecture:

Coarse particles containing the active pharmaceutical ingredient.
Particle size of at least 50 micrometers in independent claim 1, or at least 100 micrometers in independent claim 12.
A polymeric or lipid coating around the active particles.
Incorporation of the coated particles into a matrix.
A water-soluble or water-dispersible carrier.
A structure-forming agent.
Rapid disintegration, expressly less than 10 seconds in claim 1.

The invention addresses a formulation problem: a dosage form must disintegrate quickly in the mouth while preventing unpleasant taste, premature drug release, or loss of dose uniformity from exposed drug particles.

Claim element	Claim 1	Claim 12
Freeze-dried oral solid	Required	Required
Pharmaceutically active material	Required	Required
Coarse particles	50-400 micrometers	At least 100 micrometers
Polymer or lipid coating	Required	Required
Carrier material	Water-soluble or water-dispersible	Water-soluble or water-dispersible
Structure-forming agent	Required	Required
Disintegration in less than 10 seconds	Required	Not expressly stated
Closed particle-size upper limit	400 micrometers	No upper limit stated

Claim 12 is structurally broader than claim 1 in two respects. It does not recite the less-than-10-second performance limitation, and it has no express 400-micrometer maximum. Claim 12 still requires the same basic freeze-dried matrix and coated-particle construction.

When did U.S. Patent 6,413,549 lose exclusivity?

U.S. Patent 6,413,549 issued on July 2, 2002. Its effective patent term ended in 2018, based on the 20-year term applicable to the underlying nonprovisional filing. The patent therefore does not create current U.S. exclusivity.

Event	Date or status
U.S. patent issued	July 2, 2002
Patent type	Utility patent
Technology	Freeze-dried, rapidly disintegrating oral dosage forms
Statutory term	20 years from the applicable nonprovisional filing date
U.S. exclusivity	Expired in 2018
Current enforcement value	No live U.S. patent exclusion right
Regulatory listing	Not an Orange Book listing by itself

The expiration analysis is separate from any protection that could have existed for a particular commercial drug. A product using the formulation may have been covered by other patents, including active-ingredient, polymorph, salt, formulation, dosage, or method-of-use patents.

The U.S. Patent and Trademark Office determines patent term under 35 U.S.C. § 154, including any applicable patent-term adjustment. A patent that has expired cannot support a new infringement action for post-expiration conduct, although historical damages and other procedural issues can depend on the litigation record and timing. [1]

How broad are the independent claims?

Claim 1: rapid-disintegration formulation claim

Claim 1 is a combination claim. Each required feature must be present for literal infringement. A potentially covered product must contain:

A freeze-dried oral solid dosage form.
Coarse particles consisting of a pharmaceutically active material.
Particle sizes within 50 to 400 micrometers.
A coating made from polymer or lipid material.
A matrix containing both a carrier and a structure-forming agent.
A water-soluble or water-dispersible carrier.
Disintegration in water in less than 10 seconds.

The claim does not limit the active ingredient to a particular therapeutic class. It can therefore read across analgesics, antihistamines, antiemetics, psychiatric drugs, cardiovascular agents, and other active materials if the formulation architecture is present.

The phrase “coarse particles consisting of a pharmaceutically active material” is important. It may narrow the particle core to active material rather than a broad mixture of active ingredient and excipients. The precise interpretation depends on the specification, prosecution history, and claim-construction record. “Consisting of” generally operates as a closed transitional phrase, subject to established patent-law exceptions for components that do not materially affect the basic and novel characteristics.

Claim 12: alternative independent claim

Claim 12 removes the express sub-10-second disintegration requirement and replaces the particle-size range with a lower threshold of at least 100 micrometers. That structure can capture particles larger than 400 micrometers, provided the other elements are met.

The absence of a numerical disintegration-time limitation makes claim 12 potentially more difficult to avoid through performance testing. It also makes the claim more dependent on construction of “rapidly disintegrating,” “freeze-dried,” “coated,” and “matrix.”

What do the dependent claims add?

Claims 2 through 11 narrow claim 1.

Claims	Added limitation	Commercial significance
2-3	Gelatin carrier and mannitol or sorbitol structure-forming agent	Targets conventional lyophilized dosage matrices
4	Coating delays release beyond disintegration on the tongue	Addresses taste masking and oral release control
5-7	Polymeric coating materials	Covers cellulose derivatives, acrylic derivatives, PLGA, PVA, gelatin, collagen, PEG and polymethacrylates
8-9	Lipid coating materials	Covers waxes, lanolin, stearic acid, stearic-acid derivatives, phospholipids, glycolipids and related fats
10	Structure-forming agent at 1-5% by weight	Creates a quantitative formulation limitation
11	Particle size of 100-400 micrometers	Narrows the particle-size range

Claims 4 through 9 are directed to taste masking and release separation. A tablet may disintegrate rapidly in the mouth while the coated drug particles release the active ingredient later. That distinction is technically important: tablet disintegration is not the same as dissolution or drug release.

Claim 10 is vulnerable to design-around through concentration outside the 1-5% range, although the limitation applies only to that dependent claim and does not avoid claim 1 or claim 12.

What formulations are protected by U.S. Patent 6,413,549?

The disclosed claim categories include the following formulation combinations:

Gelatin-mannitol and gelatin-sorbitol matrices

Claims 2 and 3 target freeze-dried matrices using gelatin as the carrier and mannitol or sorbitol as the structure-forming agent. These excipients are associated with lyophilized oral dosage forms because they support cake structure, porosity, and rapid wetting.

A formulation using a different carrier, such as a starch derivative, sugar alcohol other than mannitol or sorbitol, or another water-dispersible polymer may fall outside claims 2 and 3 while remaining potentially relevant to claim 1.

Polymeric taste-masking coatings

Claims 5 through 7 cover coatings using:

Cellulose
Ethylcellulose
Hydroxyethylcellulose
Hydroxypropylmethylcellulose
Hydroxypropylcellulose
Methylcellulose
Cellulose acetate
Cellulose acetate phthalate
Hydroxypropylmethylcellulose phthalate
Acrylic derivatives
Polymethacrylates
Polyvinyl alcohol
Polyethylene glycol
Gelatin
Collagen
Polyglycolic-polylactic acid

The breadth is functional as well as compositional. The coating must be associated with the coarse active particles and, under claim 4, must delay release beyond the point at which the dosage form disintegrates on the tongue.

Lipid and wax coatings

Claims 8 and 9 cover lipid-based particle coatings, including:

Wax
Lanolin
Stearic acid
Glycerol esters
Fixed oils
Fats
Phospholipids
Glycolipids

A coating outside the listed categories could avoid the dependent claims but would still require analysis under claim 1's broader “polymer or lipid material” language.

How can a competing product design around the claims?

A competitor could reduce claim exposure by changing one or more required elements. Potential design-around paths include:

Use uncoated active particles.
Use drug particles below 50 micrometers for claim 1 and below 100 micrometers for claim 12.
Use a non-freeze-dried orally disintegrating tablet.
Use a matrix that is not water-soluble or water-dispersible.
Use a dosage form that does not contain the claimed structure-forming agent.
Use a coating that is neither polymeric nor lipid-based.
Use a particle core that contains active ingredient in a composition materially different from the claimed “particles consisting of” active material.
Use a conventional compressed tablet, orally disintegrating tablet, film, granule, capsule, or spray-dried dosage form.
For claim 1, produce a formulation that does not disintegrate in water in less than 10 seconds.

A design-around is not automatically safe under the doctrine of equivalents. The strength of an equivalence argument would depend on prosecution-history estoppel, the technical interchangeability of the substituted element, and whether the substitution would vitiate a claim limitation.

What is the Orange Book status of U.S. Patent 6,413,549?

U.S. Patent 6,413,549 is not, by itself, an Orange Book patent listing. The FDA Orange Book lists patents submitted by an NDA holder for a specific approved drug product, including eligible patents covering the drug substance, drug product, or approved method of use. A formulation-platform patent is not automatically listed merely because it could cover multiple drugs. [2]

The practical consequences are:

The patent does not independently create a Paragraph IV filing obligation.
A generic applicant would not certify to this patent unless it appeared in the relevant NDA’s patent listing.
The patent does not independently delay ANDA approval.
Any current Paragraph IV issue would arise from other patents listed against the specific reference-listed drug.

Are there Paragraph IV challenges or generic litigation tied to this patent?

No current Paragraph IV barrier arises from U.S. Patent 6,413,549 because the patent expired and is not an independent Orange Book-listed drug patent.

A Paragraph IV certification under the Hatch-Waxman Act applies when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or will not be infringed. The mechanism is product-specific rather than platform-patent-specific. [3]

The patent could have been relevant to historical litigation if a branded product used a claimed freeze-dried formulation and the patent had been listed or asserted before expiration. That possibility does not create present exclusivity. Current generic-entry risk must be assessed against live patents covering the relevant active ingredient, dosage form, strength, formulation, or method of use.

What patent landscape surrounds rapidly disintegrating freeze-dried dosage forms?

The broader landscape has several overlapping patent families.

Zydis and lyophilized dosage-form patents

R.P. Scherer, later associated with Catalent’s Zydis technology, developed an important portfolio around freeze-dried oral dosage forms. Earlier patents generally addressed porous freeze-dried units, excipient matrices, manufacturing processes, and rapid oral disintegration. U.S. Patent 6,413,549 occupies a narrower technical position focused on coated coarse drug particles within the freeze-dried matrix.

Earlier platform patents may have expired before U.S. Patent 6,413,549. Later patents may have covered specific manufacturing controls, packaging, taste-masking systems, active ingredients, or commercial products.

Compressed orally disintegrating tablets

The Cima, Fuisz, Elan, and related portfolios generally concern compressed or molded orally disintegrating dosage forms rather than the specific freeze-dried architecture claimed here. Such patents may be relevant to product competition but do not necessarily overlap claim 1 or claim 12.

Particle-coating and taste-masking patents

Taste-masking portfolios often claim:

Coated drug crystals or granules.
Polymer thickness or weight gain.
pH-dependent release.
Saliva-resistant coatings.
Controlled gastric release.
Fluid-bed coating processes.
Multiparticulate dosage forms.

Those patents may overlap the coating concept but avoid the claims if the final dosage form is not freeze-dried or lacks the claimed carrier matrix.

Manufacturing and process patents

Manufacturing barriers can remain relevant after a composition patent expires. Relevant process categories include:

Preparation of uniform coarse drug particles.
Fluid-bed or spray coating.
Suspension preparation.
Mold filling.
Controlled freezing.
Lyophilization cycle design.
Removal from blister packaging.
Moisture-protective packaging.

A commercial product may therefore have manufacturing know-how or later process patents even though U.S. Patent 6,413,549 has expired.

How strong was the patent estate, and what is its current strength?

At issuance, the patent had meaningful platform breadth because the independent claims were not limited to one active ingredient. Its strongest features were:

Coverage across multiple therapeutic products.
Both polymer and lipid coating categories.
Alternative independent claims.
Explicit particle-size limitations that could be measured analytically.
A functional taste-masking and release-delay concept.

Its weaknesses included:

Dependence on a specific freeze-dried matrix architecture.
Particle-size limitations that could support design-around.
The need to prove the coating, matrix, and particle structure in the finished product.
A potential dispute over “consisting of” and the relationship between the particle core and coating.
Expiration of the patent term.

Risk category	Current assessment
Direct infringement risk from the expired patent	None for new U.S. activity
Historical infringement exposure	Potentially relevant only to conduct before expiration
Orange Book impact	None as a standalone patent
Generic approval delay	None
Formulation design-around risk	Low from this patent alone
Biosimilar risk	Not applicable
Manufacturing know-how risk	May remain relevant through other IP or trade secrets
Need to review product-specific patents	High

Does biosimilar law apply to this patent?

No. Biosimilar applications concern biological products under the Public Health Service Act. U.S. Patent 6,413,549 claims an oral solid dosage-form architecture and does not claim a biologic molecule or biologic manufacturing process.

The relevant competitive pathway is an ANDA, a 505(b)(2) application, or, for a non-biologic product requiring a different regulatory route, an applicable NDA pathway. The expired patent does not block any of those routes.

What licensing deals are associated with this patent?

The patent is associated with the broader commercial field of freeze-dried oral dosage technology developed by R.P. Scherer and later commercialized through Catalent. Commercial licensing and technology-transfer arrangements in this field have often been negotiated at the platform or product level rather than through a single patent license.

U.S. Patent 6,413,549 alone does not establish:

A continuing royalty obligation.
A product-specific license.
A current exclusivity arrangement.
A right to use a trademarked delivery platform.
Freedom to operate under later patents.

Patent ownership, licensing, and technology access must be separated. Expiration removes the patent exclusion right but does not terminate contractual confidentiality, manufacturing, trademark, or know-how obligations.

How does U.S. Patent 6,413,549 compare with competing dosage-form patents?

Technology	Typical dosage form	Main protection focus	Relationship to U.S. 6,413,549
Freeze-dried Zydis-type systems	Lyophilized oral solid	Porous matrix, rapid disintegration, manufacturing	Closest technical field
Compressed ODTs	Compressed tablet	Compression excipients, porosity, taste masking	Usually different dosage-form architecture
Oral films	Thin polymeric film	Film-forming polymers and drug loading	Generally outside freeze-dried matrix claims
Coated multiparticulates	Granules or pellets	Coating, release profile, taste masking	May overlap coating concepts
Effervescent systems	Tablet or granule	Acid-base reaction and rapid dispersion	Usually lacks the claimed freeze-dried matrix
Spray-dried particles	Powder or tablet	Particle engineering and dissolution	Not necessarily freeze-dried

What generic launch scenarios exist?

Because the patent expired, three practical scenarios apply:

Immediate formulation entry

A generic or 505(b)(2) applicant can use a similar freeze-dried, coated-particle formulation without infringing an enforceable claim of U.S. Patent 6,413,549. The applicant still must satisfy FDA requirements for pharmaceutical equivalence, bioequivalence, stability, manufacturing, packaging, and labeling.

Entry using a different dosage form

A competitor can use a compressed orally disintegrating tablet, oral film, conventional tablet, capsule, or multiparticulate product. This may avoid the expired patent and reduce dependence on lyophilization equipment.

Delayed entry because of other patents

The principal remaining delay risk would come from patents covering the specific active ingredient, formulation, strength, dosage regimen, method of use, or manufacturing process. Those patents must be reviewed in the relevant FDA product record and patent-family databases.

Key Takeaways

U.S. Patent 6,413,549 claims freeze-dried oral dosage forms containing coated coarse active particles in a water-soluble or water-dispersible matrix.
Claim 1 requires 50-400 micrometer particles and disintegration in water in less than 10 seconds.
Claim 12 requires particles of at least 100 micrometers but does not expressly include the 400-micrometer ceiling or sub-10-second limitation.
Claims 2-11 narrow the formulation through gelatin, mannitol, sorbitol, polymeric coatings, lipid coatings, and a 1-5% structure-forming-agent range.
The patent expired in 2018 and does not create current U.S. market exclusivity.
It is not an Orange Book patent by itself.
No current Paragraph IV or biosimilar barrier follows from this patent.
Current freedom-to-operate analysis should focus on later drug-specific, formulation, method-of-use, manufacturing, and packaging patents.

FAQs About U.S. Patent 6,413,549

Can a company launch a freeze-dried orally disintegrating product after expiration of U.S. 6,413,549?

Yes. The expired patent does not prevent launch. The product must still avoid infringement of other unexpired patents and meet FDA requirements.

Does a coated particle automatically infringe this patent?

No. The product must satisfy all limitations of at least one enforceable claim. Particle size, freeze-dried structure, coating material, matrix composition, carrier type, and applicable disintegration limitations must be assessed together.

Does claim 12 cover particles larger than 400 micrometers?

Potentially, yes. Claim 12 requires particles of at least 100 micrometers and does not state an upper limit. The remaining claim elements still apply.

Can an expired formulation patent support a Paragraph IV certification?

An expired patent can appear in historical patent records, but it does not provide a current approval stay or enforceable exclusion right. Paragraph IV analysis concerns listed patents associated with the reference-listed drug.

Is Catalent’s Zydis platform still protected by this patent?

No. U.S. Patent 6,413,549 no longer provides enforceable U.S. patent protection. Catalent or other platform owners may retain separate patents, trademarks, know-how, contractual rights, or foreign rights.

References

United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure § 2710: Patent term. https://www.uspto.gov/web/offices/pac/mpep/mpep-2710.html
U.S. Food and Drug Administration. (2024). 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. (2024). ANDA submissions: Patent certification and 30-month stay provisions. https://www.fda.gov/drugs/abbreviated-new-drug-application-anda/abbreviated-new-drug-application-anda
U.S. Patent and Trademark Office. (2002). U.S. Patent No. 6,413,549: Rapidly disintegrating solid oral dosage form. https://patents.google.com/patent/US6413549B1/en
U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, Pub. L. No. 98-417, 98 Stat. 1585.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	8399298	⤷ Start Trial
Japan	2001509478	⤷ Start Trial
Japan	4943581	⤷ Start Trial
World Intellectual Property Organization (WIPO)	9902140	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,413,549

Summary for Patent: 6,413,549