Details for Patent: 7,906,489

Which drugs does patent 7,906,489 protect, and when does it expire?

Patent 7,906,489 protects DIFICID and is included in two NDAs.

Protection for DIFICID has been extended six months for pediatric studies, as indicated by the *PED designation in the table below.

This patent has one hundred and twenty-six patent family members in twenty-nine countries.

Summary for Patent: 7,906,489

Title:	18-membered macrocycles and analogs thereof
Abstract:	The present invention relates generally to the 18-membered macrocyclic antimicrobial agents called Tiacumicins, specifically, OPT-80 (which is composed almost entirely of the R-Tiacumicin B), pharmaceutical compositions comprising OPT-80, and methods using OPT-80. In particular, this compound is a potent drug for the treatment of bacterial infections, specifically C. difficile infections.
Inventor(s):	Youe-Kong Shue, Chan-Kou Hwang, Yu-Hung Chiu, Alex Romero, Farah Babakhani, Pamela Sears, Franklin Okumu
Assignee:	Merck Sharp and Dohme LLC
Application Number:	US11/882,219
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 7,906,489
Patent Claim Types: see list of patent claims	Use; Composition; Dosage form;

United States Drug Patent 7,906,489: Fidaxomicin Claim Scope, Expiration, Orange Book Status, and Generic Risk

US Patent 7,906,489 protects the oral use of stereomerically pure fidaxomicin, also known as OPT-80 and lipiarmycin, for treating diarrhea caused by a gastrointestinal infection with Clostridioides difficile.[1] The patent does not broadly claim fidaxomicin as a chemical compound. Its enforceable scope is concentrated in method-of-treatment claims requiring oral administration, a human patient, C. difficile-associated diarrhea, and a specified stereochemical purity.

The patent issued March 15, 2011, and has an original 20-year term measured from its earliest nonprovisional priority date. Public patent records identify an expiration date of February 4, 2025, subject to any applicable patent-term adjustment or extension recorded by the USPTO.[2] The patent was one of the principal Orange Book protections associated with DIFICID tablets.

What drug does US Patent 7,906,489 protect?

US 7,906,489 protects fidaxomicin treatment methods.

Fidaxomicin is a minimally absorbed macrocyclic antibacterial approved by the FDA under the brand name DIFICID for treatment of C. difficile-associated diarrhea in adults and pediatric patients aged six months and older.[3] The patent refers to fidaxomicin through chemical formula IV rather than consistently using the generic name in the claims.

Attribute	Patent-relevant information
Active ingredient	Fidaxomicin
Other names	OPT-80; lipiarmycin; tiacumicin B
Drug class	Macrocyclic antibacterial
Approved product	DIFICID
FDA indication	C. difficile-associated diarrhea
Route	Oral
Dosage forms	Tablets and oral suspension; the patent expressly claims tablets and capsules
Patent owner or commercial rights chain	Optimer Pharmaceuticals originated the product; U.S. commercialization rights moved through Cubist Pharmaceuticals and Merck
Patent at issue	US 7,906,489
Patent type	Method-of-treatment patent
Principal limitation	Fidaxomicin above specified stereochemical-purity thresholds

The claims provided identify formula IV as the therapeutic compound and impose stereomeric-purity limitations. The claim language is consistent with fidaxomicin’s stereochemically complex macrocyclic structure.

What are the independent claims in US 7,906,489?

Claims 1 and 9 are the two independent claims.

Claim 1 requires:

1. A human patient.
2. Diarrhea caused by a C. difficile gastrointestinal infection.
3. Oral administration.
4. A therapeutically effective amount of formula IV or a pharmaceutically acceptable salt.
5. One or more pharmaceutically acceptable carriers.
6. More than 90% by-weight stereomeric purity.

Claim 9 is narrower because it requires:

1. The same disease and patient setting.
2. Oral administration.
3. Formula IV or a pharmaceutically acceptable salt.
4. More than 93% by-weight stereomeric purity.
5. Administration consisting of the claimed treatment.

The distinction between claims 1 and 9 is material. Claim 1 begins at greater than 90% purity, while claim 9 independently begins above 93% purity and uses “consisting of” language.

Claim	Status	Core limitation
1	Independent	Oral treatment of C. difficile diarrhea with formula IV above 90% stereomeric purity
2	Dependent	Claim 1 compound formulated as a tablet
3	Dependent	Claim 1 compound formulated as a capsule
4	Dependent	Greater than 93% purity
5	Dependent	Greater than 95% purity
6	Dependent	Greater than 97% purity
7	Dependent	Substantially free of other diastereomers
8	Dependent	Method consisting of administering the claimed compound and carrier
9	Independent	Oral treatment with formula IV above 93% purity
10	Dependent	Claim 9 compound formulated as a tablet
11	Dependent	Claim 9 compound formulated as a capsule
12	Dependent	Greater than 95% purity
13	Dependent	Greater than 97% purity
14	Dependent	Substantially free of other diastereomers

How broad is the claim scope of US 7,906,489?

The patent’s scope is narrower than a basic compound patent but potentially significant against a fidaxomicin generic product.

Disease limitation

The method must treat diarrhea caused by a C. difficile gastrointestinal infection. A product used for another infection, another gastrointestinal disease, or a non-diarrheal manifestation would not fall within the literal disease limitation unless the use also satisfies the claimed C. difficile diarrhea requirement.

Patient limitation

The claims require treatment of a human patient. Animal use is outside the literal scope.

Route limitation

The drug must be orally administered. Intravenous, intramuscular, topical, or other nonoral administration is outside the literal language.

Purity limitation

The purity thresholds are central:

• Claim 1: greater than 90%.
• Claim 4: greater than 93%.
• Claim 5: greater than 95%.
• Claim 6: greater than 97%.
• Claim 9: greater than 93%.
• Claim 12: greater than 95%.
• Claim 13: greater than 97%.

A fidaxomicin product with 98% stereomeric purity would satisfy the purity limitations of claims 1, 4, 5, 6, 9, 12, and 13, assuming it also satisfies the formula, disease, patient, route, dosage, and carrier requirements.

The patent does not require the accused product to be labeled with a particular purity statement. Purity may be established through manufacturing records, analytical testing, batch specifications, regulatory submissions, or other evidence.

“Substantially free of other diastereomers”

Claims 7 and 14 add a qualitative limitation. The phrase may require claim construction in litigation because “substantially free” does not establish a single numerical threshold in the claim text. Claims 7 and 14 are therefore useful as fallback claims but less predictable than the express numerical purity claims.

Formulation limitation

Claims 2, 3, 10, and 11 specifically cover tablets and capsules. These claims do not broaden the patent to all dosage forms. They narrow the independent methods to particular formulations.

DIFICID tablets are commercially important because the FDA-approved product historically relied on an oral tablet presentation. The capsule claims could become relevant to an alternative generic dosage form even if the reference product is marketed primarily as a tablet.

How do the “comprising” and “consisting of” limitations affect infringement risk?

Claims 1 through 7 use “comprising” or depend from a claim using that open-ended transition. Those claims generally tolerate the presence of additional treatment steps or ingredients, subject to ordinary claim-construction principles.

Claims 8 and 9 use “consisting of” language. This creates a narrower formulation of the claimed method:

• Claim 8 depends on claim 1 and requires that the method consist of administering the claimed compound or salt with carriers.
• Claim 9 is an independent method claim requiring treatment with formula IV above 93% purity.
• Claims 10 through 14 depend from claim 9.

A generic label that instructs oral fidaxomicin treatment for C. difficile diarrhea could create method-of-use exposure even if the product manufacturer does not itself administer the drug. The legal analysis would depend on the exact label, marketing conduct, induced-infringement standards, and the patent’s enforceability at the relevant time.

What patents protect DIFICID and fidaxomicin?

DIFICID has been associated with a broader patent estate than US 7,906,489. The relevant categories include the active compound, stereochemical purity, formulations, solid forms, and treatment methods.

Patent category	Relevance to fidaxomicin	Relationship to US 7,906,489
Compound patents	Protect fidaxomicin or related macrocyclic structures	Potentially broader chemical protection
Stereochemical-purity patents	Protect purified or stereomerically enriched fidaxomicin	US 7,906,489 uses purity as a treatment-method limitation
Formulation patents	Protect tablets, capsules, suspension, excipients, or release characteristics	Claims 2, 3, 10, and 11 provide dosage-form limitations
Method-of-use patents	Protect treatment of C. difficile infection or associated diarrhea	Core category of US 7,906,489
Manufacturing patents	Protect purification, crystallization, isolation, or process conditions	May create non-Orange Book manufacturing barriers
Solid-form patents	Protect crystalline or polymorphic forms	May restrict active-ingredient sourcing or finished-product manufacture

Public regulatory and patent databases have associated DIFICID with US patents including US 7,456,180, US 7,906,489, and US 8,455,468, although the scope and expiration of each patent must be assessed separately.[2,4] Patent listing does not itself establish validity or infringement.

What is the Orange Book status of US 7,906,489?

US 7,906,489 was listed in connection with DIFICID in the FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations, commonly called the Orange Book.[4] The relevant patent type is a method-of-use patent rather than a simple active-ingredient composition patent.

The Orange Book listing has several commercial consequences:

• An ANDA applicant may need to make a Paragraph III certification that it will wait for patent expiration.
• It may make a Paragraph IV certification alleging that the patent is invalid, unenforceable, or not infringed.
• A Paragraph IV notice can trigger patent litigation under the Hatch-Waxman Act.
• A method-of-use listing may be addressed through a permitted carve-out if the protected indication can be omitted from the generic label.
• A carve-out may be difficult where C. difficile diarrhea is the principal or only approved use.

The Orange Book does not determine whether the claims are valid. It records FDA-listed patent information and regulatory exclusivity relevant to abbreviated approval pathways.

When did US 7,906,489 expire?

The reported patent expiration date for US 7,906,489 is February 4, 2025.[2] The effective date must be confirmed against the USPTO patent-term-adjustment record and any applicable extension.

Event	Date
Earliest relevant priority date	February 4, 2004, as reflected in public patent records
Patent issued	March 15, 2011
Reported nominal expiration	February 4, 2025
FDA product approval for DIFICID	May 27, 2011
Pediatric approval expansion	Later FDA approval action; current labeling must be checked separately
Patent status after nominal expiration	No ordinary enforceable patent term remains unless a recorded adjustment or extension applies

Patent expiry does not eliminate other patents in the fidaxomicin estate. A generic applicant could face separate composition, formulation, solid-form, process, or later-filed patent barriers.

Did US 7,906,489 provide FDA regulatory exclusivity?

Patent protection and FDA regulatory exclusivity are separate.

DIFICID received FDA approval in 2011 under the drug approval pathway for a new chemical entity. New chemical entity exclusivity generally blocks submission of an ANDA for five years, subject to statutory exceptions. That period was distinct from the 2025 patent term.[3,5]

DIFICID also received pediatric regulatory actions. Pediatric exclusivity, when granted, can add six months to qualifying FDA exclusivity or patent exclusivity periods. The exact effect depends on the listed product, completed pediatric studies, and FDA’s exclusivity records.[5]

The 7,906,489 patent itself did not create FDA exclusivity. It created patent rights enforceable under the Patent Act.

Are there Paragraph IV challenges to fidaxomicin?

A Paragraph IV challenge is an ANDA certification asserting that a listed patent is invalid, unenforceable, or not infringed. The existence, timing, and outcome of a challenge must be assessed from FDA correspondence, district-court dockets, and patent records.

For US 7,906,489, the key diligence issue is whether an ANDA applicant challenged the method-of-use listing before the February 2025 expiration date and whether litigation produced a stay, settlement, consent judgment, or launch agreement. A patent challenge to a different DIFICID patent would not necessarily resolve the claims of US 7,906,489.

Relevant legal questions include:

• Whether the generic label induces use for C. difficile diarrhea.
• Whether the generic product has the claimed stereomeric purity.
• Whether the listed claims were properly submitted for Orange Book purposes.
• Whether a section viii statement or label carve-out can omit the protected use.
• Whether the patent was valid and enforceable.
• Whether the ANDA applicant could launch at risk before final judgment.

No biosimilar pathway applies. Fidaxomicin is a small-molecule drug, so competition proceeds through the ANDA process rather than the biosimilar pathway under the Public Health Service Act.

What generic entry risks exist for fidaxomicin?

The principal generic-entry risks are now different from those that existed before February 2025.

Method-of-use risk

Before expiration, an ANDA applicant needed to address the claimed C. difficile treatment method. After expiration, those claims generally no longer block launch, assuming no surviving patent-term adjustment, extension, injunction, or separate patent.

Formulation risk

Tablet and capsule claims can create separate exposure if the claims remain enforceable. A generic tablet may be vulnerable to claims 2 or 10 if it satisfies all underlying treatment and purity limitations.

Purity risk

The patent’s purity thresholds are commercially important because ordinary pharmaceutical manufacturing may produce fidaxomicin with purity levels well above 90%. A generic manufacturer cannot avoid the claim merely by omitting purity information from its label if the manufactured active ingredient satisfies the limitation.

Manufacturing risk

Separate process or purification patents may affect the ability to make fidaxomicin economically. These patents can be more difficult to identify through the Orange Book because not all manufacturing patents are listed for an approved drug.

Regulatory-label risk

The generic label must state the approved indication unless a valid carve-out is available. If C. difficile-associated diarrhea is the core indication, a meaningful carve-out may be difficult.

How strong is the patent estate for fidaxomicin?

US 7,906,489 is a focused but commercially meaningful method patent.

Strength factor	Assessment
Claim breadth	Moderate to narrow
Disease specificity	Narrow; limited to C. difficile-associated diarrhea
Route limitation	Narrow; oral administration required
Patient limitation	Narrow; human patient required
Purity limitation	Potentially strong if generic purity is above the thresholds
Dosage-form claims	Narrow but relevant to tablets and capsules
Chemical compound coverage	Not provided by the claims quoted
Design-around potential	Possible through indication carve-out, alternative use, or challenge to purity applicability
Biosimilar relevance	None
Post-expiration value	Limited for this patent, but the broader estate may remain relevant

The strongest feature is the overlap between the purity limitations and commercial fidaxomicin manufacturing. The principal weakness is the number of required limitations. An accused product or use must satisfy the disease, patient, route, compound, carrier, therapeutic-effect, and purity requirements.

What licensing deals affect DIFICID commercialization?

Optimer Pharmaceuticals developed fidaxomicin and commercialized DIFICID through a U.S. collaboration with Cubist Pharmaceuticals. Merck acquired Cubist in 2015 and obtained Cubist’s commercial rights and assets, including DIFICID-related operations.[6]

These transactions affect commercial control and product revenue but do not automatically transfer every patent right. Patent ownership, exclusive licenses, field restrictions, sublicenses, and prosecution-control provisions must be verified in the relevant assignment and license records.

The principal commercial entities associated with the product are:

• Optimer Pharmaceuticals, the original developer.
• Cubist Pharmaceuticals, the U.S. commercial partner.
• Merck, after its acquisition of Cubist.
• Generic manufacturers entering through the ANDA pathway.

What revenue exposure is associated with US 7,906,489?

The patent protected a product with premium pricing in the C. difficile antibiotic market. Its economic value derived from limiting oral fidaxomicin competition during the patent term, not from broad control of all C. difficile therapies.

Revenue exposure depends on:

• DIFICID tablet and suspension sales.
• Hospital and outpatient use.
• Recurrent C. difficile treatment demand.
• Generic approval timing.
• Net price after rebates and government discounts.
• Remaining protection from other DIFICID patents.
• Market substitution by oral vancomycin and other therapies.

Because US 7,906,489 is an indication-specific method patent, its value is highest when the generic must carry the C. difficile diarrhea indication and cannot rely on a commercially workable label carve-out.

How does US 7,906,489 compare with a compound patent?

A compound patent generally prevents making, using, selling, offering to sell, or importing the claimed molecule, subject to claim scope and validity. US 7,906,489 instead requires a particular therapeutic use.

Issue	Compound patent	US 7,906,489
Protects	Chemical compound or composition	Treatment method
Requires C. difficile indication	Usually no	Yes
Requires oral use	Usually no	Yes
Requires human patient	Usually no	Yes
Requires purity threshold	Not necessarily	Yes
Direct product infringement	More likely	Usually requires use-related conduct
Label-carve-out relevance	Lower	High
Manufacturing relevance	High	Limited unless use is proven
Generic challenge path	Paragraph IV	Paragraph IV or section viii analysis

Key Takeaways

• US 7,906,489 covers oral fidaxomicin treatment of C. difficile-associated diarrhea in humans.
• The claims require formula IV, corresponding to fidaxomicin, with stereomeric purity above 90%, 93%, 95%, or 97%, depending on the claim.
• Claims 2, 3, 10, and 11 specifically address tablets and capsules.
• Claims 7 and 14 cover material substantially free of other diastereomers.
• The reported patent expiration date is February 4, 2025.
• The patent was associated with DIFICID’s Orange Book listing as a method-of-use patent.
• It is a small-molecule patent; biosimilar analysis does not apply.
• Generic risk before expiration focused on Paragraph IV challenges, label carve-outs, purity, and induced infringement.
• Patent expiry does not eliminate separate risks from composition, formulation, solid-form, or manufacturing patents.
• The commercial rights history runs from Optimer to Cubist and then Merck.

FAQs

Is US 7,906,489 a patent on fidaxomicin itself?

No. The quoted claims are method-of-treatment claims. They require use of formula IV for oral treatment of C. difficile-associated diarrhea.

Does a fidaxomicin capsule infringe the patent?

A capsule could fall within claims 3 or 11 if all other limitations are met, including the disease indication, oral human use, formula IV identity, carrier requirement, therapeutic amount, and applicable purity threshold.

Can a generic avoid US 7,906,489 by making lower-purity fidaxomicin?

Potentially, but only if the product genuinely falls below the relevant claim threshold and does not satisfy another claim. Manufacturing and analytical evidence would control the assessment.

Does FDA approval of a fidaxomicin generic prove that US 7,906,489 is invalid?

No. FDA approval and patent validity are separate issues. Approval may proceed after patent expiry, through a successful patent challenge, through a settlement, or through a legally sufficient label carve-out.

Does US 7,906,489 cover treatment of recurrent C. difficile infection?

The quoted claims do not expressly require or exclude recurrence. Treatment of recurrent infection could fall within the claims if the patient has diarrhea caused by C. difficile gastrointestinal infection and all other limitations are satisfied.

References

1. United States Patent No. 7,906,489. (2011). Methods of treating Clostridium difficile infection. U.S. Patent and Trademark Office.

2. United States Patent and Trademark Office. (n.d.). Patent Center: U.S. Patent No. 7,906,489. https://patentcenter.uspto.gov/

3. U.S. Food and Drug Administration. (2011). DIFICID (fidaxomicin) prescribing information. https://www.accessdata.fda.gov/

4. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/

5. U.S. Food and Drug Administration. (n.d.). Regulatory exclusivity and pediatric exclusivity information. https://www.fda.gov/

6. Merck & Co., Inc. (2015). Merck completes acquisition of Cubist Pharmaceuticals. https://www.merck.com/insights/

Drugs Protected by US Patent 7,906,489

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Cubist Pharms Llc	DIFICID	fidaxomicin	FOR SUSPENSION;ORAL	213138-001	Jan 24, 2020		RX	Yes	Yes	7,906,489*PED				Y
Cubist Pharms Llc	DIFICID	fidaxomicin	TABLET;ORAL	201699-001	May 27, 2011	AB	RX	Yes	Yes	7,906,489*PED				Y

International Family Members for US Patent 7,906,489

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	1539977		C300727	Netherlands
European Patent Office	1539977		CA 2015 00020	Denmark
European Patent Office	1539977		92684	Luxembourg