US Patent 12,667,575: Resmetirom Dosing, CYP2C8 Inhibitors, Claim Scope, and Patent Landscape
US Patent 12,667,575 covers a narrow method-of-use regimen for resmetirom in adults with NASH-associated liver fibrosis who use a moderate CYP2C8 inhibitor. The central limitation is weight-based dose selection: 80 mg daily for patients weighing at least 100 kg and 60 mg daily for patients weighing less than 100 kg. The patent does not broadly claim resmetirom, Rezdiffra, a resmetirom tablet, or treatment of NASH without the CYP2C8-inhibitor and weight-based dosing limitations.
The commercial significance is high because the claimed regimen tracks FDA-approved dose-adjustment instructions for Rezdiffra, creating potential method-of-use exposure for an ANDA applicant whose labeling directs use of resmetirom with moderate CYP2C8 inhibitors. The principal validity risks are obviousness, written description, enablement, claim construction, and the extent to which the claimed regimen was already disclosed in FDA labeling, clinical pharmacology materials, or earlier resmetirom patent families.
What does US Patent 12,667,575 claim?
The patent contains two parallel claim groups.
| Claim group |
Independent claim |
Claimed therapeutic objective |
Core limitations |
| NASH treatment |
1 |
Treating NASH |
Adult; weight determined; moderate CYP2C8 inhibitor; 80 mg/day at or above 100 kg or 60 mg/day below 100 kg; solid oral dosage form |
| Liver-fibrosis improvement |
16 |
Improving liver fibrosis associated with NASH |
Same weight, inhibitor, dose, adult, and solid oral dosage limitations |
Claims 2-15 depend from claim 1. Claims 17-30 depend from claim 16. The dependency structure creates substantial duplication, but the claims are not legally identical.
Claim 1 requires all of the following:
- An adult human subject in need of treatment.
- NASH.
- Determination of the subject's weight.
- Current use of a moderate CYP2C8 inhibitor.
- Administration of a solid oral dosage form.
- Resmetirom or a pharmaceutically acceptable salt.
- A dose of 80 mg per day if the subject weighs at least 100 kg.
- A dose of 60 mg per day if the subject weighs less than 100 kg.
The weight threshold is a binary limitation. A 100-kg patient falls within the 80-mg branch, not the 60-mg branch. A patient weighing 99.9 kg falls within the 60-mg branch.
How does the patent divide the resmetirom dosing regimen?
The patent claims a dose-adjustment rule based on both body weight and CYP2C8 inhibitor exposure.
| Patient condition |
Claimed daily dose |
| Weight of 100 kg or more and moderate CYP2C8 inhibitor use |
80 mg |
| Weight below 100 kg and moderate CYP2C8 inhibitor use |
60 mg |
The claims do not cover a dose of 100 mg daily, which is the FDA-recommended dose for certain patients weighing at least 100 kg when no dose-reduction condition applies. They also do not expressly cover every possible dose adjustment involving a strong CYP2C8 inhibitor.
The claims require a determination of weight, but they do not specify the weighing device, timing, units, measurement method, or acceptable margin of error. A routine clinical weight measurement should generally satisfy this limitation if it is used to select the dose.
Which CYP2C8 inhibitors are covered?
Claim 8 and claim 23 recite a long list of alleged moderate CYP2C8 inhibitors. Claim 9 and claim 24 narrow the list to five compounds:
- Clopidogrel
- Deferasirox
- Teriflunomide
- Trimethoprim
- Pioglitazone
The broad lists also include compounds such as rosiglitazone, tamoxifen, diltiazem, ketoconazole, rifampicin, verapamil, and others. The breadth creates several claim-construction and validity questions.
First, the claims identify the compounds by name rather than by a quantitative inhibition threshold. That approach can create disputes over whether a listed compound is a "moderate CYP2C8 inhibitor" under the patent's intrinsic disclosure, regulatory definitions, or contemporaneous pharmacology literature.
Second, a defendant may argue that certain listed compounds were not properly supported as moderate inhibitors at the relevant priority date. A compound's presence in the Markush list does not eliminate written-description or enablement issues if the specification lacks technical support across the full list.
Third, claims 9 and 24 are more commercially focused. They identify five named inhibitors and reduce the factual dispute over inhibitor classification. A generic label that expressly addresses clopidogrel, trimethoprim, or pioglitazone presents a clearer infringement theory than a label referring only to an undefined moderate CYP2C8 inhibitor.
What fibrosis stages are protected?
The claims cover three fibrosis categories:
| Claims |
Fibrosis category |
| 6 and 21 |
F2 or F3 fibrosis |
| 7, 15, and 22 |
F4, or cirrhotic NASH |
| 1-5, 8-14, 16-20, 23-30 |
No separate fibrosis stage unless inherited from a dependent claim |
The F2/F3 claims align more closely with the FDA-approved Rezdiffra population. FDA approved resmetirom with diet and exercise for adults with noncirrhotic NASH with moderate-to-advanced liver fibrosis consistent with stages F2 and F3. The approved indication does not establish approval for cirrhotic F4 NASH. [2]
The F4 claims may still be enforceable if supported by the patent specification and otherwise valid. Patent scope is not limited automatically to the FDA-approved indication. However, the F4 claims may face stronger arguments concerning clinical support, enablement, written description, and the relationship between cirrhosis and the claimed liver-fibrosis improvement.
What do the prior-use claims cover?
Claims 4, 13, 19, and 28 cover a patient who used the moderate CYP2C8 inhibitor before beginning resmetirom.
Claims 5, 14, 20, and 29 cover the reverse sequence: the patient was taking resmetirom before starting the moderate CYP2C8 inhibitor.
These claims attempt to capture both clinically relevant prescribing sequences:
| Sequence |
Covered claims |
| CYP2C8 inhibitor first, resmetirom second |
4, 13, 19, 28 |
| Resmetirom first, CYP2C8 inhibitor second |
5, 14, 20, 29 |
The sequence limitations may be useful in infringement analysis, but they also narrow the claims. A regimen in which both drugs are initiated simultaneously may not satisfy the specific prior-use limitations. Claims 1 and 16 do not impose a particular sequence unless a dependent claim is asserted.
How strong is the patent estate for resmetirom?
US Patent 12,667,575 appears strategically important but narrow. Its strongest commercial characteristic is alignment with a labeled dose-adjustment scenario. Its weakness is that it does not protect the basic resmetirom molecule or ordinary treatment of NASH.
| Estate segment |
Coverage represented by this patent |
Commercial importance |
| Active ingredient |
No broad molecule claim shown |
Low for molecule exclusivity |
| Standard NASH treatment |
No, absent inhibitor and weight limitations |
Limited |
| Weight-based dosing |
Yes, at 60 mg and 80 mg |
High if reflected in labeling |
| CYP2C8 drug interaction |
Yes |
High for co-medication scenarios |
| Solid oral dosage form |
Yes |
Supports tablet or similar oral product |
| F2/F3 NASH |
Yes through dependent claims |
High for approved population |
| F4 cirrhotic NASH |
Yes through dependent claims |
Commercially narrower and clinically more exposed |
| Manufacturing process |
No claims provided |
No apparent manufacturing barrier |
| Composition or formulation |
No independent composition claims provided |
Limited formulation protection |
The patent is therefore best characterized as a clinical-use and dose-management patent, not a composition-of-matter or manufacturing patent.
What is the FDA and Orange Book status?
Rezdiffra, containing resmetirom, received FDA approval in March 2024 for adults with noncirrhotic NASH with moderate-to-advanced liver fibrosis, used with diet and exercise. The approved tablet strengths are 60 mg, 80 mg, and 100 mg. [2, 3]
The FDA label provides weight-based dosing and dose-reduction information for patients taking moderate CYP2C8 inhibitors. That labeling relationship materially increases the patent's relevance to generic substitution and ANDA strategy. [3]
A patent number alone does not establish whether US Patent 12,667,575 is listed in the Orange Book. Orange Book listing depends on the NDA holder's submission, FDA review, timing, and whether the patent claims an approved drug, formulation, or method of use that qualifies for listing. The authoritative status is the current FDA Approved Drug Products with Therapeutic Equivalence Evaluations database. [4]
If listed as a method-of-use patent, the likely effect would be a use code tied to dose adjustment or administration of resmetirom with moderate CYP2C8 inhibitors. Such a listing would not necessarily block every ANDA for resmetirom. It would principally affect an ANDA that seeks or carries labeling for the patented use.
When does resmetirom lose exclusivity?
Resmetirom has several distinct exclusivity layers:
| Exclusivity type |
Relevance |
| New chemical entity exclusivity |
FDA approval of a new active ingredient generally provides five years, subject to statutory exceptions |
| Orphan-drug exclusivity |
Not the principal basis of the NASH approval described in the FDA approval materials |
| Patent term |
Depends on each patent's earliest effective nonprovisional filing date, patent-term adjustment, terminal disclaimers, and any patent-term extension |
| Pediatric exclusivity |
Adds six months only if statutory requirements are satisfied |
| Method-of-use patent protection |
Can delay or complicate approval for a generic seeking the patented use |
The expiration date of US Patent 12,667,575 cannot be calculated reliably from the patent number or claim text alone. The relevant calculation requires the patent's earliest effective nonprovisional priority date, any continuation relationship, terminal disclaimer, patent-term adjustment, and any applicable patent-term extension. Under 35 U.S.C. § 154, the ordinary patent term is generally 20 years from the earliest effective nonprovisional filing date, subject to statutory adjustments. [5]
FDA regulatory exclusivity and patent expiration are separate. A generic may become eligible for approval after regulatory exclusivity ends while remaining exposed to unexpired method-of-use patents.
What Paragraph IV risks exist?
A generic applicant could pursue several strategies under the Hatch-Waxman framework.
Paragraph IV certification
A Paragraph IV certification could assert that the patent is invalid, unenforceable, or not infringed. The most likely arguments would be:
- The claimed weight-based dosing regimen was obvious from resmetirom pharmacokinetic data and known CYP2C8 interaction principles.
- The FDA label or earlier clinical disclosures anticipated the claimed regimen.
- The specification does not adequately support the entire list of moderate CYP2C8 inhibitors.
- Certain listed drugs were not properly characterized as moderate CYP2C8 inhibitors.
- The generic's proposed label does not induce performance of the patented method.
- The claims do not cover administration without the specified treatment sequence.
- The claims lack adequate written description or enablement for F4 cirrhotic NASH.
A Paragraph IV notice would expose the ANDA applicant to patent litigation under 35 U.S.C. § 271(e)(2). [6]
Section viii carve-out
If the patent is listed with a method-of-use code, an ANDA applicant may attempt a section viii statement that omits the patented use. That strategy is less attractive if the FDA-approved label necessarily instructs the weight-based dose adjustment for moderate CYP2C8 inhibitors.
The practical question is whether the patented use can be cleanly removed while preserving a commercially viable label. If the dose-reduction instruction remains necessary for safe use of resmetirom, a carve-out may be difficult.
Which companies are challenging resmetirom exclusivity?
The supplied information does not identify a filed Paragraph IV notice, ANDA applicant, district-court complaint, settlement, or license involving US Patent 12,667,575. No specific challenger or settlement should be treated as established from the claim text alone.
The competitive threat is likely to come from generic manufacturers rather than biosimilar developers. Resmetirom is a small molecule, so future competitors would ordinarily use the ANDA pathway. Biosimilar approval under section 351(k) is not the expected pathway for a chemically synthesized active ingredient such as resmetirom.
What manufacturing and formulation barriers remain?
The claims supplied do not cover:
- A particular crystalline form.
- A specific excipient system.
- A tablet coating.
- A dissolution profile.
- A manufacturing process.
- A polymorph.
- A salt-selection process.
- A specific release mechanism.
The "solid oral dosage form" limitation is broader than a named tablet formulation but narrower than administration of any resmetirom product. A generic tablet could potentially satisfy that limitation if the remaining method elements are present. Conversely, a formulation patent or process patent elsewhere in the resmetirom portfolio could create separate barriers not addressed by US Patent 12,667,575.
What litigation and settlement issues matter?
The key litigation risk is label-based inducement. If a generic label directs use of 60 mg or 80 mg resmetirom in patients taking a moderate CYP2C8 inhibitor, the patent owner may argue that the label encourages performance of every element of claims 1 or 16.
The generic would likely focus on three defenses:
- The label does not require determination of patient weight in the manner claimed.
- The label does not instruct use of the patented NASH or fibrosis population.
- The listed CYP2C8 inhibitors and dosing rule were anticipated or obvious.
A settlement could involve a delayed launch date, a license limited to certain uses, or a label carve-out. No settlement terms are established here for this patent.
Key Takeaways
- US Patent 12,667,575 is a narrow resmetirom method-of-use patent.
- Its central rule is 80 mg daily at or above 100 kg and 60 mg daily below 100 kg when the patient uses a moderate CYP2C8 inhibitor.
- The claims cover both treatment of NASH and improvement of NASH-associated liver fibrosis.
- F2/F3 claims track the FDA-approved Rezdiffra population; F4 claims extend beyond the principal approved population.
- Claims 9 and 24 create narrower protection for clopidogrel, deferasirox, teriflunomide, trimethoprim, and pioglitazone.
- The patent does not, based on the supplied claims, cover resmetirom's active ingredient, ordinary NASH treatment, a specific formulation, or a manufacturing process.
- Paragraph IV exposure is greatest for an ANDA label that retains dose-adjustment instructions for moderate CYP2C8 inhibitors.
- The patent's expiration date and Orange Book status require review of the official patent and FDA records rather than inference from the claims.
FAQs
Does US Patent 12,667,575 cover the 100-mg Rezdiffra dose?
No. The supplied claims cover 80 mg daily for patients weighing at least 100 kg when they use a moderate CYP2C8 inhibitor, and 60 mg daily for patients below 100 kg. They do not recite 100 mg daily.
Does taking clopidogrel with resmetirom create patent risk?
Potentially. Clopidogrel is expressly identified in dependent claims 9 and 24. Infringement would still require the other limitations, including the applicable weight threshold, dose, adult patient, NASH-related condition, and solid oral dosage form.
Is a generic resmetirom tablet automatically infringing?
No. The claims are method claims. A tablet alone does not establish infringement. Risk depends on whether the generic's label, instructions, or conduct causes performance of the claimed dosing method.
Are F4 cirrhotic NASH patients covered by the patent?
Yes. Claims 7, 15, and 22 expressly recite cirrhotic NASH with F4 fibrosis. That patent coverage is separate from whether FDA has approved the product for that population.
Is a resmetirom biosimilar expected?
No. Resmetirom is a small-molecule drug. A competing product would ordinarily pursue an ANDA, not a biosimilar application under section 351(k).
References
- United States Patent and Trademark Office. (n.d.). US Patent No. 12,667,575. USPTO Patent Center.
- U.S. Food and Drug Administration. (2024, March 14). FDA approves first treatment for patients with liver scarring due to fatty liver disease.
- U.S. Food and Drug Administration. (2024). Rezdiffra (resmetirom) prescribing information. Madrigal Pharmaceuticals, Inc.
- U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations.
- Patent Act, 35 U.S.C. § 154.
- Patent Act, 35 U.S.C. § 271(e)(2).
