United States Drug Patent 4,904,769: Acarbose Purification Claims, Patent Scope, Expiration, and Landscape

U.S. Patent No. 4,904,769 protected a purified acarbose composition and a chromatographic process for producing it. The patent was assigned to Bayer AG and issued on February 27, 1990. Its original 17-year U.S. patent term expired on February 27, 2007, absent a term adjustment or extension that is not reflected in the patent’s basic term. The claims are no longer enforceable against generic acarbose products or manufacturing processes.

The patent’s commercial relevance was strongest before FDA approval of acarbose products in the United States and during the early life of Bayer’s Precose franchise. Its principal technical contribution was control of acarbose purity and removal of sugar-like secondary components using a weakly acidic cation-exchange column eluted only with degassed, distilled water.[1]

What does U.S. Patent 4,904,769 cover?

U.S. Patent 4,904,769 covers two related subject-matter categories:

A purified acarbose composition defined by acarbose content and the level of sugar-like secondary components.
A process for purifying acarbose through a specific aqueous ion-exchange procedure.

The patent does not broadly claim all acarbose, all acarbose tablets, or every process for making acarbose. Its composition claims are limited by purity ranges. Its process claims contain several narrow operational limitations.

Claim group	Covered subject matter	Principal limitations
Claim 1	Purified acarbose composition	About 93% to 98% acarbose by weight, excluding water
Claim 2	Composition of claim 1	2% to 5% sugar-like secondary components
Claim 3	Composition of claim 1	Less than 2% sugar-like secondary components
Claim 4	Purification process	Aqueous acarbose feed, pH 3.5-7, weakly acidic carboxyl cation exchanger, water-only elution
Claims 5-6	Loading conditions	Full column filling volume or less than 60% of column volume
Claims 7-8	Feed pH	Narrowed to 3.5-6.0 or 4.0-5.5
Claims 9-10	Temperature sequence	Low-temperature loading followed by column heating after removal of salts and coloring materials
Claim 11	Pharmaceutical composition	Effective amount of qualifying acarbose plus pharmaceutically acceptable excipient

The claim language supplied for the process claims uses “weekly acid cation exchanger.” In the technical context, this is almost certainly intended to read “weakly acid cation exchanger,” referring to a resin with carboxyl groups. The patent’s enforceable interpretation would depend on the issued patent text, prosecution history, and applicable claim-construction principles.

What composition does claim 1 protect?

Claim 1 covers a purified acarbose composition containing approximately 93% to 98% acarbose by weight, calculated apart from water.

This is a product-by-composition claim. A product is potentially within the claim if it has the claimed composition, regardless of whether it was made by the patented process. A competitor could therefore face literal infringement exposure from making or selling an acarbose material with the claimed purity profile even if it used a different purification process.

The phrase “apart from water” is material. The percentages are calculated on a substantially dry basis or on the composition excluding water. A wet acarbose solution is not evaluated by simply comparing the total wet formulation to the 93%-98% range.

The claim does not require a particular dosage form, excipient, particle size, crystalline form, manufacturing site, or therapeutic use. It is directed to the purified active ingredient composition itself.

How do claims 2 and 3 divide the impurity range?

Claims 2 and 3 narrow claim 1 according to the content of sugar-like secondary components:

Claim 2: 2% to 5% sugar-like secondary components.
Claim 3: less than 2% sugar-like secondary components.

These claims create two distinct impurity profiles within the broader 93%-98% acarbose range. Claim 3 is the stronger purity limitation because it requires less than 2% of the specified secondary components.

The claims do not expressly define every non-acarbose constituent as a sugar-like secondary component. The scope therefore depends on how the patent specification identifies and measures those materials. In a dispute, analytical methodology, sampling, water correction, and the identity of the measured impurities would be central issues.

What process does claim 4 protect?

Claim 4 is a combination process claim. Every listed limitation must be met for literal infringement. The principal limitations are:

Starting with prepurified acarbose.
Preparing a 1%-20% by-weight aqueous solution.
Maintaining the solution at pH 3.5-7.
Applying the solution to a column.
Using a weakly acidic cation exchanger with carboxyl groups.
Using a packing material based on dextran, agarose, cellulose, or derivatives of those materials with added polyamide.
Eluting exclusively with degassed, distilled water.
Isolating purified acarbose from the eluate.

The process claim is narrower than a generic chromatography claim. It does not cover every ion-exchange resin, every aqueous eluent, or every acarbose purification process.

Why is the resin limitation important?

The resin limitation identifies a weakly acidic cation exchanger containing carboxyl groups and based on specified natural or modified polymeric materials. A process using a strong-acid sulfonated resin, a synthetic resin outside the stated material classes, silica chromatography, reverse-phase chromatography, or a membrane process would not literally satisfy this limitation.

The phrase “or exchangers which are derived from the latter with the addition of polyamide” expands the material category but remains tied to the listed dextran, agarose, and cellulose bases. The claim does not appear to cover every mixed-polymer ion exchanger.

Why is water-only elution important?

Claim 4 requires elution “exclusively with degassed, distilled water.” This is a substantial limitation. A competing process using a buffer, salt solution, organic solvent, acidified water, or another eluent would have a strong noninfringement position under the literal claim language.

The term “degassed” may also create an evidentiary issue. A process using purified water without documented degassing could dispute whether the claim limitation is met. The practical relevance would depend on whether degassing is treated as a material process step or as a process condition with little effect on the final product.

How do claims 5 through 10 narrow the purification process?

Claims 5-10 add operational restrictions to claim 4.

Claim	Additional limitation	Commercial significance
5	Feed-solution volume corresponds to the column filling volume	Covers near-full column loading
6	Feed-solution volume is less than 60% of column volume	Covers a lower-loading operating mode
7	Feed pH is 3.5-6.0	Narrows the pH window
8	Feed pH is 4.0-5.5	Creates the narrowest pH limitation
9	Feed is applied at up to room temperature; column heated to 25-95°C after salts and coloring materials are eluted	Adds a staged temperature profile
10	Feed is applied at 4-25°C; column heated to 40-70°C	Narrows claim 9’s temperature ranges

Claims 5 and 6 should be read carefully. They describe alternative loading volumes and are not cumulative requirements. A process generally cannot satisfy both “corresponds to the filling volume” and “less than 60% of the column volume” unless the terms are given unusual meanings.

Claims 9 and 10 target a staged operation. The acarbose solution is applied at a relatively low temperature, salts and coloring constituents are removed, and the column is then heated before or during later elution. This sequence distinguishes the claimed process from a process operated at a constant temperature.

What does claim 11 protect?

Claim 11 covers a pharmaceutical composition containing:

An effective amount of the claimed acarbose composition;
Less than 10% sugar-like secondary components, apart from water; and
A pharmaceutically acceptable excipient.

The claim is dependent on claim 1 but adds a secondary-component limitation. Because claim 1 already requires 93%-98% acarbose, claim 11 is directed to a pharmaceutical formulation using relatively purified acarbose.

Claim 11 does not require a particular tablet strength, excipient, release profile, indication, or dosage regimen. It could theoretically cover tablets, capsules, powders, or other dosage forms if the acarbose composition and excipient limitations are satisfied.

The claim’s “less than 10%” threshold is broader than claim 3’s “less than 2%” threshold. It can therefore encompass compositions with 2%-10% sugar-like secondary components, subject to the inherited claim 1 limitations and the meaning of “sugar-like secondary components.”

When did U.S. Patent 4,904,769 expire?

The patent issued on February 27, 1990. For a U.S. patent governed by the pre-Uruguay Round patent term, the basic term was 17 years from issue. On that basis, the patent expired on February 27, 2007.[1]

Event	Date
U.S. patent issue	February 27, 1990
Basic statutory term	17 years from issue
Basic expiration date	February 27, 2007
Current enforceability	Expired

The patent was issued before the June 8, 1995 transition to a 20-year term measured from the earliest effective nonprovisional filing date. Accordingly, the basic 17-year-from-issue rule applies unless a specific term adjustment, terminal disclaimer, or statutory extension altered the term.[2]

No current freedom-to-operate restriction should be based solely on U.S. Patent 4,904,769. Expiration eliminates infringement liability for conduct occurring after expiration, although it does not eliminate potential exposure for acts committed while the patent was in force.

What was the FDA and Orange Book status of the acarbose franchise?

The FDA approved Precose, Bayer’s acarbose product, for use in patients with type 2 diabetes as an adjunct to diet and exercise. Acarbose is an alpha-glucosidase inhibitor that delays carbohydrate digestion and reduces postprandial glucose increases.[3]

Regulatory item	Status
Active ingredient	Acarbose
Reference product	Precose
Sponsor	Bayer
Dosage forms	Oral tablets
Therapeutic category	Alpha-glucosidase inhibitor
FDA pathway	New Drug Application
U.S. patent at issue	U.S. 4,904,769
Patent status today	Expired
Current Orange Book relevance	No blocking force from this expired patent

The Orange Book is relevant to listed patents and regulatory exclusivity associated with approved drug products. An expired process or purity patent cannot block approval or commercial launch merely because it was historically associated with the reference product. FDA approval of an acarbose generic would be governed by the applicable abbreviated new drug application requirements, including bioequivalence and pharmaceutical-equivalence standards.[4]

The supplied patent claims do not appear to be method-of-use claims under the Hatch-Waxman framework. They claim a composition, manufacturing process, and pharmaceutical composition. They do not claim treatment of diabetes, a specific dosing schedule, or a patient population.

Did the patent create Paragraph IV risk?

During its enforceable period, a generic applicant could have addressed the patent through a Paragraph IV certification if the patent was listed for the reference product and the applicant asserted that the patent was invalid, unenforceable, or not infringed.[5]

The principal Paragraph IV arguments would have included:

The generic acarbose does not contain 93%-98% acarbose on the claimed water-excluded basis.
The product does not contain the claimed level of sugar-like secondary components.
The manufacturing process does not use the specified weakly acidic carboxyl cation exchanger.
The process uses an eluent other than degassed, distilled water.
The process does not use the required pH, loading volume, or temperature sequence.
The claims are invalid for anticipation or obviousness based on prior purification methods.
The composition claims lack adequate written description or enablement for the full purity range.

Because the patent expired in 2007, a present-day Paragraph IV strategy directed to this patent has no commercial blocking value. Any historical litigation or settlement involving this patent would have to be assessed against the expiration date and the timing of the generic filing.

How strong was the patent estate for acarbose?

The patent estate represented by U.S. 4,904,769 was technically focused rather than broad. Its strongest features were the combination of:

A defined purity range;
A defined impurity profile;
A specified weak-acid ion-exchange medium;
Water-only elution;
Narrow pH, loading, and temperature parameters.

Its main weaknesses were the narrow process limitations and the potential difficulty of proving composition infringement through analytical testing. Acarbose manufacturers could seek noninfringing routes using different chromatographic media, different elution systems, alternative purification technologies, or impurity profiles outside the claimed ranges.

The patent did not prevent competitors from pursuing acarbose as a molecule, nor did it cover all pharmaceutical formulations containing acarbose. It primarily protected a particular quality specification and a disclosed purification approach.

What generic entry risks exist for acarbose?

Current generic entry risk from U.S. Patent 4,904,769 is zero because the patent expired. Historical risk depended on whether a competitor’s product used acarbose within the claimed purity range or whether its manufacturing process copied the chromatography limitations.

Risk category	Historical risk	Current risk from U.S. 4,904,769
Purified acarbose composition	Moderate	None
Sugar-like secondary-component profile	Moderate	None
Specified ion-exchange process	Moderate to high if copied exactly	None
Alternative purification process	Lower	None
Acarbose tablet formulation	Limited unless claim 11 met	None
Method of treating diabetes	Not claimed	None
Biosimilar risk	Not applicable	Not applicable

Acarbose is a small-molecule drug, not a biologic. Biosimilar pathways and biosimilar litigation do not apply. Competitive entry would proceed through generic-drug mechanisms rather than biosimilar approval.

What licensing and litigation issues affect this patent?

The patent was assigned to Bayer AG, the company associated with the U.S. Precose product. The patent record should be treated as the primary source for ownership, inventorship, priority, prosecution, and assignment information.[1]

The supplied information does not establish a license, covenant not to sue, patent settlement, Paragraph IV notice, or reported U.S. litigation involving U.S. Patent 4,904,769. The patent’s expiration also removes the need for a current license to practice the claimed subject matter in the United States.

Any historical transaction analysis should distinguish between:

A license to the acarbose active ingredient or manufacturing technology;
A license to the purified composition claims;
A settlement of generic litigation;
A supply agreement for pharmaceutical-grade acarbose; and
A patent assignment or security interest.

These instruments have different effects on control, royalty obligations, and launch timing. Expiration of the patent does not necessarily terminate contractual obligations, but it eliminates the patent exclusionary right.

How does U.S. Patent 4,904,769 compare with other acarbose protection?

Protection type	Covered by U.S. 4,904,769?	Relevance
Acarbose molecule itself	No broad molecule claim shown	Requires separate composition-of-matter protection
Purity specification	Yes	Core protection
Impurity profile	Yes, through claims 2, 3, and 11	Analytical infringement issue
Manufacturing process	Yes	Limited to specified chromatography
Tablet formulation	Yes, only through claim 11’s broad formulation language	No specific excipient or tablet design required
Treatment method	No	No direct use patent protection shown
Crystalline form	No	No polymorph limitation appears
Combination therapy	No	No combination claim appears
Biologic or biosimilar protection	No	Acarbose is a small molecule

The estate was therefore more relevant to active-ingredient manufacture than to lifecycle management. It did not create a durable barrier around dosing, formulation engineering, or new therapeutic uses.

Key Takeaways

U.S. Patent 4,904,769 claimed purified acarbose compositions containing approximately 93%-98% acarbose, excluding water.
Claims 2 and 3 divided the composition into impurity profiles containing 2%-5% or less than 2% sugar-like secondary components.
Claim 4 required a specific purification process using a weakly acidic carboxyl cation exchanger and degassed, distilled water as the exclusive eluent.
Claims 5-10 narrowed loading volume, pH, and temperature conditions.
Claim 11 covered pharmaceutical compositions using qualifying acarbose and a pharmaceutically acceptable excipient.
The patent issued February 27, 1990, and its basic 17-year term expired February 27, 2007.
The patent is not a current barrier to generic acarbose entry.
Biosimilar analysis is irrelevant because acarbose is a small-molecule drug.
The patent’s historical strength was concentrated in manufacturing and purity control, not in the acarbose molecule, diabetes treatment, or broad tablet formulation protection.

FAQs About U.S. Patent 4,904,769

Could a generic acarbose tablet infringe claim 11?

Historically, yes, if the tablet used an acarbose composition meeting claim 1 and containing less than 10% sugar-like secondary components. The patent’s expiration eliminates current infringement risk.

Does the patent cover acarbose API made outside the United States?

During the patent term, importation into the United States of an API meeting the composition claims could have raised infringement issues. A foreign manufacturing process could also have implicated process-patent remedies if the statutory requirements were met. The patent is now expired.

Is a purification process using a different resin covered?

Not literally if the resin does not satisfy the claim 4 requirement for a weakly acidic carboxyl cation exchanger based on the specified materials. Expiration makes the distinction commercially immaterial today.

Could the patent support a current U.S. patent-infringement lawsuit?

No. An expired patent cannot support a new infringement action for post-expiration conduct. Historical claims may remain subject to applicable limitation periods and procedural rules, but they do not create current market exclusivity.

Does U.S. Patent 4,904,769 block acarbose use in combination with metformin?

No method-of-treatment or combination-therapy claim appears in the supplied claims. The patent does not claim metformin, combination therapy, or a specific diabetes-treatment regimen.

References

Bayer AG. (1990). U.S. Patent No. 4,904,769: Purified acarbose and process for its preparation. U.S. Patent and Trademark Office.
United States Code. (2023). 35 U.S.C. §§ 154, 156.
U.S. Food and Drug Administration. (1995). Precose (acarbose) tablets prescribing information.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations.
United States Code. (2023). 21 U.S.C. § 355(j)(2)(A)(vii)(IV).

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	3543999	Dec 13, 1985

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	71951	⤷ Start Trial
Bulgaria	49497	⤷ Start Trial
Canada	1288768	⤷ Start Trial
China	1013866	⤷ Start Trial
China	86108259	⤷ Start Trial
Germany	3543999	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,904,769

Summary for Patent: 4,904,769