Details for Patent: 6,893,662

Summary for Patent: 6,893,662

Title:	Pharmaceutical dosage form with multiple coatings for reduced impact of coating fractures
Abstract:	The present invention relates to a pharmaceutical composition in a solid unit dosage form for oral administration in a human or lower animal comprising: a. a safe and effective amount of a therapeutically active agent; b. an inner coating layer selected from the group consisting of poly(methacrylic acid, methyl methacrylate) 1:2, poly(methacrylic acid, methyl methacrylate) 1:1, and mixtures thereof; and c. an outer coating layer comprising an enteric polymer or film coating material; wherein the inner coating layer is not the same as the outer coating layer; wherein if the inner coating layer is poly(methacrylic acid, methyl methacrylate) 1:1 then the outer coating layer is not poly(methacrylic acid, methyl methacrylate) 1:2 or is not a mixture of poly(methacrylic acid, methyl methacrylate) 1:1 and poly(methacrylic acid, methyl methacrylate) 1:2; and wherein the inner coating layer and the outer coating layer do not contain any therapeutically active agent. This invention further relates to a method of maintaining the desired site of delivery of a therapeutic agent in the gastrointestinal tract by administering the above compositions to a human or lower animal.
Inventor(s):	Gregory Paul Dittmar, Joseph Michael Amante, Tony Ryan Cronk, Daniel Gary Newby
Assignee:	Allergan Pharmaceuticals International Ltd
Application Number:	US09/996,555
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 6,893,662
Patent Claim Types: see list of patent claims	Use; Composition; Delivery; Dosage form;

US Patent 6,893,662: Claim Scope, Expiration, Orange Book Relevance, and Mesalamine Patent Landscape

US Patent 6,893,662 protects a two-layer enteric-coated oral dosage form, with particular relevance to mesalamine, also known as 5-aminosalicylic acid or 5-ASA. The strongest commercial claim is claim 34, which requires a solid dosage form containing mesalamine, an inner layer of Eudragit L100-55-type polymer identified in the patent as poly(methacrylic acid, methyl methacrylate) 1:2, and an outer layer containing a mixture of the 1:2 and 1:1 methacrylate polymers. The patent is a formulation patent, not a compound patent.

The patent issued May 17, 2005. Its practical exclusivity period was directed to delayed-release mesalamine products, including products associated with the Asacol and Asacol HD franchise. Public patent records identify the patent as having expired in 2021, subject to the precise patent-term calculation and any applicable regulatory extension.[1][2]

What does US Patent 6,893,662 protect?

The patent claims a multilayer coating architecture for oral solid dosage forms. The protected structure has four central elements:

1. A therapeutically active agent in a solid unit dosage form.
2. An inner coating layer made from a selected anionic methacrylate polymer.
3. An outer enteric coating layer that dissolves at a pH below approximately 7.
4. Different polymer compositions in the inner and outer layers.

The invention is directed to controlled regional release. The inner and outer layers are intended to provide more consistent protection in the stomach and release in a selected intestinal region.

The principal polymer categories are:

Patent designation	Commercial polymer family	Functional role
Poly(methacrylic acid, methyl methacrylate) 1:2	Commonly associated with Eudragit L100	Inner or outer enteric layer
Poly(methacrylic acid, methyl methacrylate) 1:1	Commonly associated with Eudragit S100	Outer layer or mixed outer layer
Poly(methacrylic acid, ethyl acrylate) 1:1	Commonly associated with Eudragit L100-55	Alternative enteric polymer
Polyvinyl acetate phthalate	PVAP	Alternative outer enteric polymer
Polymethacrylates and anionic polymethacrylates	Generic polymer categories	Alternative coating materials

The claims do not protect mesalamine as a molecule. They protect the combination of active ingredient, coating sequence, polymer identity, layer differentiation and, in narrower claims, coating thickness, tablet weight and mesalamine loading.

How broad are the independent claims?

Claims 1, 11 and 34 are the principal composition claims. Claims 21, 22 and 35 are method claims.

Claim 1: broad two-layer formulation claim

Claim 1 covers a solid oral dosage form containing any therapeutically active agent from the claim's functional scope. It requires:

• an inner layer selected from the specified 1:2 and 1:1 methacrylate polymers, or mixtures;
• an outer layer comprising a pH-responsive enteric polymer;
• a different inner and outer layer;
• no therapeutically active agent in either coating layer.

The claim is broad because the active ingredient is not limited to mesalamine. Claim 8 lists therapeutic categories ranging from laxatives and anti-inflammatory agents to peptides, proteins, cardiovascular drugs and antihistamines.

The claim is narrower than a generic "dual enteric coating" claim because it requires the specific polymer families and imposes restrictions on certain inner/outer combinations.

Claim 11: narrower composition claim

Claim 11 requires the inner coating to comprise the 1:2 methacrylate polymer. It retains a broad list of possible outer polymers and active ingredients.

This claim is commercially more significant than claim 1 for products using a fixed 1:2 inner layer. It removes one of the principal design alternatives available under claim 1 and creates a more direct infringement test for products using the same inner polymer.

Claim 34: mesalamine-specific formulation claim

Claim 34 is the most commercially targeted composition claim. It requires:

• 5-aminosalicylic acid;
• an inner layer comprising the 1:2 methacrylate polymer;
• an outer layer comprising a mixture of the 1:2 and 1:1 methacrylate polymers.

This claim is materially narrower than claims 1 and 11, but it maps more closely to a defined delayed-release mesalamine product architecture. A competing product that uses mesalamine but replaces the dual-polymer outer layer with a single polymer would avoid literal infringement of claim 34, while potentially remaining within claim 11 or another broader claim depending on the full formulation.

What formulations are protected by the patent?

The patent protects formulations with a sequential coating process and defined coating geometry. The relevant formulation variables are summarized below.

Variable	Broad claim scope	Narrow claim scope
Active ingredient	Broad therapeutic categories	Mesalamine in claims 10, 19, 25, 30, 34 and 35
Inner coating	1:2 polymer, 1:1 polymer or mixtures	1:2 polymer
Outer coating	Several enteric polymers	1:1 polymer or 1:2/1:1 mixture
Coating relationship	Inner layer applied before outer layer	Same
Active ingredient in coating	Excluded	Excluded
Total coating thickness	5 to 40 mg/cm² in dependent claims	10 to 15 mg/cm² in narrower claims
Outer-layer thickness	10 to 200 micrometers	20 to 40 micrometers in claims 28 and 33
Dosage form	Solid unit dosage form	Compressed tablet in claims 20 and 23
Tablet weight	600 to 1,200 mg	Same
Mesalamine load	Broadly specified	700 to 900 mg in claims 25 and 30

The patent uses coating weight per unit surface area rather than only polymer percentage or film thickness. That distinction matters. A product can use the same polymer classes but fall outside claims 5, 6, 14 and 15 if the total coating weight is outside the claimed range. It may still infringe broader claims 1, 11 or 34 if all other limitations are satisfied.

How does the “consisting essentially of” language affect infringement?

The phrase “consisting essentially of” permits the presence of additional ingredients that do not materially alter the basic and novel characteristics of the formulation.

The basic and novel characteristics appear to include:

• the two-layer enteric architecture;
• the specified methacrylate polymer relationships;
• pH-dependent dissolution;
• delivery of the active ingredient to a desired intestinal region; and
• the absence of therapeutically active agent in the coating layers.

Excipients such as fillers, binders, lubricants, pigments, plasticizers and processing aids may therefore be present if they do not materially change the claimed coating function. A coating containing an additional polymer, however, creates a more substantial “consisting essentially of” issue, particularly where that polymer changes dissolution, permeability or release location.

The phrase does not automatically exclude every unlisted ingredient. It creates a materiality-based limitation that would depend on the patent specification, prosecution history and technical evidence.

What are the key claim-construction issues?

Polymer ratio nomenclature

The expressions “1:2” and “1:1” refer to the copolymer composition, not necessarily the ratio of two coating polymers in a blend. Confusing those concepts could produce an incorrect infringement analysis.

A mixture of the 1:2 and 1:1 polymers in the outer layer is distinct from a 1:2 copolymer whose monomer ratio is itself fixed. Product specifications, supplier certificates and analytical characterization would be important in determining which polymer is actually present.

“Comprising” versus “consisting essentially of”

The inner and outer coating limitations use “comprising,” which generally permits additional coating ingredients. The overall composition uses “consisting essentially of,” which limits additions that materially affect the claimed invention.

“Begins to dissolve” at a pH below approximately 7

This limitation is functional. It focuses on dissolution behavior in an aqueous medium rather than only on the nominal identity of the polymer. The claim does not require a single precise dissolution pH, but the product must exhibit the specified pH response.

Layer sequence

The outer layer must be applied to the inner layer. Claims 7 and 16 add a process limitation requiring continuous spray coating, with the outer layer applied before the inner layer is dried or cured. The base composition claims do not necessarily require that precise manufacturing sequence unless the sequence is needed to establish the claimed physical structure.

Active-free coating layers

The claims require that the inner and outer layers contain no therapeutically active agent. A product using drug-loaded polymer layers may avoid literal infringement of these claims, although the effect of such a design would depend on the complete claim language and possible doctrine-of-equivalents arguments.

What is the scope of the mesalamine claims?

Claims 10, 19, 25, 30, 34 and 35 are directed to mesalamine. The claims cover mesalamine as an active ingredient, but they do not cover every delayed-release mesalamine tablet.

The most important limitations are:

• solid oral unit dosage form;
• 1:2 methacrylate inner coating;
• 1:1 methacrylate or 1:2/1:1 mixed outer coating;
• active-free coating layers;
• in some claims, 700 to 900 mg mesalamine per unit;
• in claim 34, the specific dual-polymer outer mixture.

A 400 mg mesalamine tablet could fall outside claims 25 and 30 because those claims require 700 to 900 mg, but it could still fall within claim 34 if the other requirements are met. Conversely, an 800 mg tablet could satisfy the dose limitation but avoid claim 34 by using a different outer coating composition.

What is the Orange Book status of US 6,893,662?

The patent was relevant to FDA-listed delayed-release mesalamine products, including Asacol HD-related products. The FDA Orange Book identifies patents submitted by approved drug sponsors for approved products and provides expiration information and regulatory exclusivity data.[2]

US 6,893,662 is not a biologic patent and does not create biosimilar exclusivity. Mesalamine is a small-molecule active ingredient, so competitive entry proceeds through the abbreviated new drug application pathway rather than the biosimilar pathway.

The patent's commercial significance was greatest before its 2021 expiration. After expiration, the patent no longer provides an enforceable exclusionary right against new products, absent a separate surviving patent, regulatory exclusivity period or other enforceable right.

When did US 6,893,662 lose exclusivity?

The patent issued on May 17, 2005 and reached the end of its ordinary patent term in 2021 based on public patent records.[1][2] Any pediatric extension would need to be confirmed from the FDA Orange Book and patent-term records. The patent's enforceability also depends on maintenance-fee status, terminal disclaimers and any post-grant proceedings, but the principal public expiration date is in 2021.

The practical timeline was:

Event	Date or period
Patent issued	May 17, 2005
Commercial relevance	Delayed-release mesalamine and other enteric-coated formulations
Orange Book relevance	Mesalamine products, including Asacol-related products
Ordinary patent expiration	2021
Post-expiration status	No continuing ordinary patent exclusion under this patent

Which companies challenged mesalamine products?

Generic competition to delayed-release mesalamine products included major manufacturers such as Actavis, Zydus, Mylan and other ANDA applicants. Litigation involving mesalamine products commonly focused on formulation patents, including coating chemistry, release profiles and product-specific patents.

A Paragraph IV certification would assert that a listed patent is invalid, unenforceable or not infringed. The patent's claim structure created several potential challenge routes:

• use of a different inner polymer;
• use of a single-layer enteric coating;
• use of a different outer polymer;
• use of a different pH threshold;
• use of drug-containing coating layers;
• use of coating weights outside the claimed ranges;
• use of a non-tablet dosage form;
• invalidity based on prior art relating to Eudragit-coated mesalamine products.

Because the patent expired in 2021, current generic-entry risk from this patent alone is no longer material. Any continuing commercial barrier would have to arise from a separate patent, regulatory exclusivity or product-specific approval requirement.

How strong was the patent estate?

US 6,893,662 had moderate formulation-patent strength and limited molecule-level strength.

Strength factor	Assessment
Active ingredient coverage	Broad in early claims; mesalamine-specific in later claims
Formulation specificity	High
Design-around difficulty	Moderate
Compound protection	None
Manufacturing protection	Limited; only certain claims include process timing
Geographic coverage	United States only for this patent
Regulatory leverage	Significant while listed and unexpired
Current enforceability	Expired in 2021
Biosimilar relevance	None

The patent's strongest enforcement position would have involved a product matching the full dual-layer polymer architecture, especially mesalamine tablets using a 1:2 inner layer and 1:2/1:1 mixed outer layer. Its weakest position would have involved products with materially different coating chemistry or a different release mechanism.

What manufacturing and intellectual-property barriers remain?

The patent does not broadly protect the manufacturing equipment or general concept of enteric coating. Claims 7 and 16 reach a narrower continuous-spray process in which the outer coating is applied before the inner layer is dried or cured.

Potential non-patent barriers include:

• reproducible coating uniformity;
• control of tablet-to-tablet coating weight;
• polymer dispersion stability;
• dissolution testing across gastrointestinal pH conditions;
• scale-up of continuous spray coating;
• control of mesalamine content uniformity;
• FDA requirements for delayed-release performance.

These technical barriers can delay entry, but they are not equivalent to patent exclusivity. After expiration, a generic manufacturer can use an alternative process or formulation if it satisfies FDA requirements and avoids any separate unexpired patent.

What generic launch scenarios existed?

Before expiration, the principal scenarios were:

1. A Paragraph IV launch supported by a noninfringement or invalidity position.
2. A launch after settlement or a licensed entry date.
3. A formulation redesign that avoided the claimed polymer sequence.
4. A post-expiration launch using the same or a different release architecture.
5. A non-infringing product using a different dosage strength or coating system.

After expiration, the most relevant scenario is ordinary ANDA competition subject to separate listed patents and FDA approval requirements.

Key Takeaways

• US 6,893,662 is a dual-layer enteric-coating patent, not a mesalamine compound patent.
• Claim 34 is the most commercially targeted claim because it requires mesalamine and a specific 1:2 inner layer plus a mixed 1:2/1:1 outer layer.
• Claims 1 and 11 cover broader active ingredients and coating combinations.
• Claims 5-7, 14-16 and 26-33 add coating-weight, thickness and manufacturing-process limitations.
• The patent's core infringement risk depends on polymer identity, layer order, pH dissolution behavior and whether the coatings are drug-free.
• The patent was relevant to delayed-release mesalamine products and Orange Book-listed product strategies.
• The patent expired in 2021 based on public patent and FDA records.
• It has no biosimilar relevance because mesalamine is a small-molecule drug.
• Current generic-entry analysis must focus on other unexpired formulation, method-of-use, manufacturing or product-specific patents.

FAQs

Does US 6,893,662 cover all Asacol or mesalamine tablets?

No. It covers only products meeting the claim limitations, including the specified two-layer coating structure and polymer relationships.

Can a mesalamine product avoid claim 34 by using only one enteric polymer?

Potentially. Claim 34 requires an outer-layer mixture of the 1:2 and 1:1 methacrylate polymers. A single-polymer outer layer could avoid claim 34, although claims 1 or 11 would require separate analysis.

Is Eudragit the same as the polymers named in the patent?

The patent uses chemical descriptions, while Eudragit is a commercial polymer brand family. Product identity must be assessed by the actual polymer composition and functional characteristics, not brand name alone.

Does the patent protect the method of making the tablet?

Only certain dependent claims include the continuous-spray sequence and application of the outer layer before the inner layer is dried or cured. The patent's main protection is directed to the resulting composition.

Can a generic manufacturer launch after the patent expiration date?

The expiration of US 6,893,662 removes the exclusionary effect of that patent. Launch still depends on FDA approval and any other unexpired patents listed for the reference product.

References

1. United States Patent and Trademark Office. (2005). US Patent No. 6,893,662, pharmaceutical composition with dual enteric coating. U.S. Department of Commerce.

2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. U.S. Department of Health and Human Services.

3. U.S. Food and Drug Administration. (2024). Asacol HD prescribing information. U.S. Department of Health and Human Services.

Drugs Protected by US Patent 6,893,662

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

International Family Members for US Patent 6,893,662

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	389389
Australia	2002226955
Brazil	0117180
Brazil	PI0117180
Canada	2359812
China	1314390
China	1558754