United States Patent 6,358,986: Telmisartan Polymorph Claims, Scope, Expiration, and Patent Landscape

U.S. Patent 6,358,986 protects a defined mixture of two crystalline telmisartan polymorphs, Form A and Form B, when the Form A-to-Form B ratio is 10:90 to 60:40. Claim 2 extends that protection to pharmaceutical compositions containing the claimed mixture and a pharmaceutically acceptable carrier. The patent was assigned to Boehringer Ingelheim and has expired. It no longer creates an enforceable U.S. barrier to generic telmisartan entry, although its technical disclosure remains relevant to solid-state characterization, formulation development, and historical Hatch-Waxman disputes.

What does U.S. Patent 6,358,986 cover?

The patent covers a specific polymorphic composition rather than telmisartan generally.

Claim element	Requirement
Active compound	Telmisartan
First polymorph	Form A
Form A characterization	DSC endothermic maximum at 269 ± 2°C
Second polymorph	Form B
Form B characterization	DSC endothermic maxima at 183 ± 2°C and 269 ± 2°C
Composition	Mixture of Forms A and B
Ratio	Form A:Form B from 10:90 to 60:40
Claim 2 additional limitation	Pharmaceutically acceptable carrier

Claim 1 is a composition claim defined partly by analytical properties. It does not claim every crystalline form of telmisartan, every telmisartan formulation, or telmisartan as an active pharmaceutical ingredient in the abstract.

Claim 2 is dependent in substance on the limitations of Claim 1. A tablet, capsule, powder, suspension, or other dosage form would fall within the claim only if it contains the claimed Form A/Form B mixture within the specified ratio and also contains a pharmaceutically acceptable carrier.

How should the Form A and Form B limitations be interpreted?

The claims use differential scanning calorimetry, or DSC, to identify the polymorphs. Form A is characterized by a single relevant endothermic maximum at approximately 269°C. Form B has two relevant maxima, approximately 183°C and 269°C.

The shared 269°C event is important. It does not independently distinguish the forms. The approximately 183°C event identifies the additional thermal behavior associated with Form B. A formulation containing both forms could therefore show overlapping or combined thermal signals, depending on sample preparation, heating rate, instrument calibration, water content, excipients, and the relative proportion of each form.

The principal claim-construction issues are:

Whether the DSC values are mandatory identity limitations or merely descriptive characteristics.
Whether the ratio is measured by weight, molar quantity, or another analytical basis.
Whether the ratio applies to the bulk active ingredient before formulation or to the active ingredient recovered from the finished dosage form.
Whether a mixture that changes polymorphic state during manufacturing or storage remains within the claim.
How much analytical deviation is permitted by the ±2°C ranges.

The claim language makes the thermal characteristics central to identity. A party alleging infringement would generally need to establish both the presence of the two claimed polymorphs and the claimed ratio. Testing would likely include DSC, powder X-ray diffraction, and quantitative solid-state analysis. DSC alone may show thermal events but may not reliably quantify the relative amount of each polymorph in a complex formulation.

What is the scope of Claim 1?

Claim 1 is narrow in composition but potentially broad in the forms of material that can contain the mixture.

The claim does not limit:

The final dosage form
The amount of telmisartan
The identity or concentration of excipients
Particle size
Crystallization solvent
Manufacturing process
Milling conditions
Storage conditions
Therapeutic indication
Route of administration

It does limit the composition to a two-polymorph mixture with a defined ratio. A material containing only Form A would not meet the express mixture requirement. A material containing only Form B would also fall outside the claim. A Form A/Form B mixture outside the 10:90 to 60:40 range would not literally satisfy the ratio limitation.

The ratio endpoints are ordinarily read as inclusive unless the specification or prosecution history establishes otherwise. Thus, 10:90 and 60:40 are within the stated range.

The claim is not limited to a particular level of purity. It does not state that the material must contain only Forms A and B. A formulation could contain additional amorphous telmisartan, another polymorph, or non-telmisartan components, subject to the ordinary interpretation of the word "mixture" and the remaining claim limitations.

What formulations are protected by U.S. Patent 6,358,986?

Claim 2 can cover conventional oral telmisartan formulations if the active ingredient contains the claimed polymorph mixture.

Potentially relevant dosage forms include:

Immediate-release tablets
Film-coated tablets
Capsules
Granules
Powders
Solid oral dosage forms containing excipients
Pharmaceutical compositions using binders, disintegrants, lubricants, diluents, or coating materials

The carrier limitation is broad. Common excipients such as lactose, mannitol, cellulose derivatives, starches, povidone, magnesium stearate, and coating polymers would generally qualify as pharmaceutically acceptable carriers when used in an approved pharmaceutical composition.

The key limitation remains the solid-state composition of the telmisartan. A tablet does not infringe merely because it contains telmisartan. The accused product must contain the claimed Forms A and B in the claimed proportion.

When did U.S. Patent 6,358,986 expire?

U.S. Patent 6,358,986 expired in approximately June 2019 under the applicable twenty-year patent-term framework. The relevant term is based on the patent family’s filing history and any applicable adjustments or extensions reflected in USPTO records.[1]

The patent therefore does not provide current U.S. patent exclusivity. Any pediatric exclusivity attached to an FDA product or related patent would have been temporary and would not restore enforceable rights today.

Event	Date or status
Patent	U.S. 6,358,986
Title	Crystalline forms of telmisartan
Patent holder	Boehringer Ingelheim-related entity
Grant	March 19, 2002
Subject matter	Telmisartan Forms A and B and pharmaceutical compositions
U.S. expiration	Approximately June 2019
Current status	Expired
Current blocking effect on generic entry	None from this patent

The expiration of this patent does not eliminate any separate rights under later patents covering formulations, combinations, manufacturing processes, or other therapeutic uses.

What is the Orange Book status of telmisartan?

Telmisartan was approved by the FDA in Micardis, an oral tablet marketed by Boehringer Ingelheim. The FDA Orange Book historically listed patents associated with Micardis, including the telmisartan compound patent and U.S. Patent 6,358,986.[2]

The relevant distinction is between:

The original compound patent, which covered telmisartan or a related class of compounds.
The polymorph patent, which covered the Form A/Form B mixture.
Later patents, if any, covering formulations, combinations, manufacturing methods, or specific uses.

The Orange Book listing of U.S. 6,358,986 did not convert the patent into a product-wide monopoly. An ANDA applicant challenging the patent could focus on whether its active ingredient was a single polymorph, a different polymorph, or a mixture outside the claimed ratio.

Because the patent has expired, it is no longer a current Orange Book obstacle to approval or launch. FDA approval of generic telmisartan depends on the ANDA applicant meeting bioequivalence, quality, labeling, manufacturing, and other regulatory requirements, not on obtaining a license from Boehringer Ingelheim.

Were Paragraph IV challenges relevant to this patent?

Yes. As an Orange Book-listed patent, U.S. 6,358,986 could be challenged through a Paragraph IV certification before expiration. A generic applicant could assert that the patent was invalid, unenforceable, or would not be infringed.

The most direct non-infringement positions would have involved:

Use of a single telmisartan polymorph.
Use of a Form A/Form B ratio outside the claimed range.
Use of a different crystalline or amorphous form.
Failure of the material to exhibit the claimed DSC profile.
Absence of the claimed mixture from the final pharmaceutical composition.
Lack of proof that the alleged product contained both forms at the claimed ratio.

Validity arguments could have addressed anticipation, obviousness, enablement, written description, claim indefiniteness, and the reproducibility of the DSC-defined forms. Polymorph patents often face obviousness analysis based on the predictability of solid-state screening and the ability of a skilled person to identify crystalline forms, although the outcome depends on the patent record and evidence of unexpected properties.

The patent’s expiration makes any historic Paragraph IV dispute commercially moot as a current launch barrier. Publicly available FDA and USPTO records do not indicate an ongoing enforceable dispute based solely on U.S. Patent 6,358,986.[1,2]

How strong was the patent estate for telmisartan?

The estate was stronger for the active molecule than for the specific polymorph mixture.

Patent category	Scope	Commercial significance
Compound patent	Telmisartan chemical entity and related compounds	Primary early exclusivity
Polymorph patent	Forms A and B in a defined ratio	Secondary solid-state protection
Formulation patents	Excipients, release profile, stability, or dosage form	Potential product-specific barriers
Method-of-use patents	Treatment of hypertension or cardiovascular conditions	Often vulnerable where use is inherent or label-driven
Process patents	Crystallization, purification, or manufacturing steps	Relevant only when the accused process is covered
Regulatory exclusivity	NDA and pediatric exclusivity periods	Time-limited and separate from patent rights

The 6,358,986 patent had meaningful historical value because a polymorph mixture can be embedded in the marketed active ingredient and may be difficult to distinguish without solid-state testing. Its weakness was claim specificity. The requirement for two particular forms and a bounded ratio created multiple design-around routes.

A generic manufacturer could seek to:

Manufacture substantially pure Form A.
Manufacture substantially pure Form B.
Use another polymorph.
Produce an amorphous or differently crystallized material.
Control the mixture ratio outside the claimed range.
Demonstrate that the finished product no longer contains the claimed ratio.

Those approaches could create manufacturing and regulatory complications, but they also reduce literal infringement exposure.

How does the patent compare with the main telmisartan compound patent?

The compound patent had broader chemical scope and was commercially more important during the initial Micardis exclusivity period. U.S. Patent 6,358,986 was a secondary patent directed to solid-state form and formulation composition.

Issue	Compound patent	U.S. 6,358,986
Protected subject matter	Telmisartan chemical entity or related compounds	Specific Form A/Form B mixture
Claim breadth	Broad chemical coverage	Narrower solid-state coverage
Design-around difficulty	Higher before expiry	More manageable through polymorph control
Relevance to API manufacturing	Direct	Dependent on crystalline form
Relevance to finished dosage forms	Broad	Requires claimed mixture in the product
Current status	Expired	Expired

The compound patent and polymorph patent should not be treated as interchangeable. A company could avoid the polymorph patent while still facing the compound patent before that earlier patent expired. Conversely, after compound-patent expiry, the polymorph patent could still have delayed or complicated generic entry until its own expiration.

What manufacturing and intellectual-property barriers remain?

The patent is expired, but polymorph control remains a technical issue.

Telmisartan has limited aqueous solubility and solid-state properties that affect powder handling, dissolution, stability, and batch consistency. Manufacturers must control:

Solvent and antisolvent conditions
Temperature profile
Seeding
Drying
Milling
Humidity exposure
Storage temperature
Excipient interactions
Conversion between polymorphs

These controls are manufacturing risks, not current patent barriers created by U.S. Patent 6,358,986. Trade secrets, regulatory data, process patents, and quality systems may still affect development cost and launch timing.

Does telmisartan have biosimilar risk?

No. Telmisartan is a synthetic small-molecule active ingredient. It is subject to the abbreviated new drug application pathway for generics, not the biosimilar pathway under the Public Health Service Act.

The relevant competitive threats are generic telmisartan tablets, fixed-dose combination products, and alternative angiotensin II receptor blockers such as losartan, valsartan, irbesartan, candesartan, and olmesartan.

What is the current commercial impact of U.S. Patent 6,358,986?

The current direct revenue exposure is zero from enforceable exclusivity under this patent because it expired in 2019. Its historical revenue significance was tied to Micardis sales and the timing of generic telmisartan entry.

The patent may still have residual commercial relevance in:

Freedom-to-operate opinions
Historical litigation analysis
Patent-term and launch strategy studies
Solid-state analytical method development
Product quality investigations
Foreign-family review
Assessment of later formulation or process patents

No license is required from Boehringer Ingelheim to practice the expired U.S. patent. Any commercial license question would relate to separate unexpired patents, know-how, trademarks, regulatory rights, or private technology-transfer agreements.

Key Takeaways

U.S. Patent 6,358,986 covers a telmisartan mixture containing Forms A and B.
Form A is defined by a DSC endotherm at 269 ± 2°C.
Form B is defined by DSC endotherms at 183 ± 2°C and 269 ± 2°C.
The Form A-to-Form B ratio must be 10:90 to 60:40.
Claim 2 covers pharmaceutical compositions containing that mixture and a pharmaceutically acceptable carrier.
Pure Form A, pure Form B, a different polymorph, or a mixture outside the ratio is outside the literal claim scope.
The patent expired in approximately June 2019.
It creates no current U.S. patent barrier to generic telmisartan entry.
Telmisartan is a small-molecule drug and faces generic, not biosimilar, competition.
Remaining risks must be assessed against separate formulation, process, use, foreign, trademark, and regulatory rights.

FAQs

Is U.S. Patent 6,358,986 a telmisartan compound patent?

No. It is a solid-state patent directed to a mixture of two crystalline telmisartan forms. It does not broadly claim the telmisartan molecule itself.

Can a generic use a telmisartan polymorph outside the claimed ratio?

Yes, from the standpoint of literal infringement of U.S. Patent 6,358,986, a composition outside the 10:90 to 60:40 Form A/Form B range does not meet the express ratio limitation.

Does the patent cover a tablet containing only Form A telmisartan?

No. Claim 1 requires a mixture of Forms A and B. Claim 2 depends on that mixture requirement.

Does expiration of the patent eliminate all telmisartan patent risk?

No. It eliminates the enforceable U.S. barrier created by this patent. Separate patents covering formulations, combinations, manufacturing methods, or uses must be analyzed independently.

Is DSC alone sufficient to prove infringement?

Not necessarily. DSC can identify thermal events consistent with the claimed forms, but quantitative proof of the Form A/Form B ratio may require complementary solid-state and compositional testing.

References

United States Patent and Trademark Office. (2002). U.S. Patent No. 6,358,986, Crystalline forms of telmisartan.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs, Micardis telmisartan tablets.
U.S. Food and Drug Administration. (2018). Guidance for industry: ANDAs for certain highly soluble, highly permeable drugs.
United States Code, 35 U.S.C. § 154. (2024). Contents and term of patent; provisional rights.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	199 01 921	Jan 19, 1999

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	035475	⤷ Start Trial
Austria	252564	⤷ Start Trial
Australia	2288100	⤷ Start Trial
Australia	765081	⤷ Start Trial
Bulgaria	105654	⤷ Start Trial
Bulgaria	65027	⤷ Start Trial
Brazil	0007584	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,358,986

Summary for Patent: 6,358,986