US Patent 12,661,330: Mirdametinib Patent Scope, Claims, Exclusivity and Generic Entry Risk
US Patent 12,661,330 covers a specific mirdametinib treatment regimen for patients at least 2 years old with NF1-associated inoperable plexiform neurofibromas. Its core limitation is oral administration of 4 mg twice daily in patients with body surface area of at least 1.5 m². The patent also protects patient selection, diagnostic criteria, tumor characteristics, intermittent dosing, response thresholds, pain outcomes, adverse-event dose reductions and acneiform-event management.
The claims are method-of-treatment claims rather than composition-of-matter claims. They are therefore strongest when an accused product label, clinical protocol or treatment record directs the complete claimed regimen. The patent does not, based on the supplied claims, cover every use of mirdametinib, every NF1 patient, or every dose.
What does US Patent 12,661,330 protect?
The independent claim protects a narrow clinical-use combination:
| Limitation |
Claim 1 requirement |
| Patient |
Human patient |
| Age |
At least 2 years old |
| Disease |
Neurofibromatosis type 1 |
| Tumor |
NF1-associated inoperable plexiform neurofibromas |
| Body surface area |
At least 1.5 m² |
| Dose |
4 mg mirdametinib twice daily |
| Route |
Oral administration |
Claim 1 requires every limitation. A patient with NF1 and inoperable PN who receives 2 mg twice daily would not literally satisfy the claim. Nor would a patient with a body surface area below 1.5 m², unless another claim or patent covers that lower-body-surface-area regimen.
The patent is commercially important because the claimed regimen overlaps with the high-dose end of the FDA-approved mirdametinib dosing framework for NF1-associated inoperable PN. The FDA label describes body-surface-area-based dosing, with a maximum of 4 mg twice daily and a three-weeks-on, one-week-off cycle. [1]
How do claims 2 through 22 narrow the mirdametinib method?
The dependent claims add clinical, diagnostic or operational restrictions. They do not broaden claim 1.
Age and disease-severity limitations
Claims 2 and 20 narrow the population to:
- Patients at least 12 years old; or
- Patients 2 to 15 years old.
Claims 3 through 8 add tumor and morbidity characteristics, including:
- Symptomatic PN;
- Progressive PN;
- PN causing significant morbidity;
- Airway or great-vessel compromise;
- Nerve compression and loss of function;
- Major deformity or significant disfigurement;
- Limb hypertrophy or loss of limb function;
- Painful lesions; and
- Paraspinal lesions.
These claims create alternative infringement positions for treatment populations that are clinically recognizable and likely to appear in medical records, trial protocols and prescribing criteria.
NF1 diagnostic limitations
Claims 9 through 11 address how NF1 is established.
Claim 9 uses the NIH Consensus Conference diagnostic framework and lists café-au-lait macules, axillary or inguinal freckling, optic glioma, Lisch nodules, distinctive bony lesions and a first-degree relative with NF1.
Claim 10 requires a constitutional NF1 mutation documented by a CLIA/CAP-certified laboratory.
Claim 11 uses a more detailed clinical and molecular diagnostic structure, including:
- Café-au-lait macules;
- Axillary or inguinal freckling;
- Neurofibromas or one PN;
- Optic pathway glioma;
- Lisch nodules or choroidal abnormalities;
- Sphenoid dysplasia, tibial bowing or pseudarthrosis; and
- A heterozygous pathogenic NF1 variant with a 50% variant allele fraction in apparently normal tissue.
These claims may be harder to prove in routine litigation than claims based only on age, diagnosis and dose. They require evidence of specific diagnostic findings or laboratory results. They are more relevant to clinical-trial protocols, payer documentation and selected-patient treatment pathways than to broad product-label enforcement.
What dosing schedule and dose-reduction rules are protected?
Claim 12 confirms that 4 mg twice daily is the maximum daily dose expressed in the claim set. Claim 13 protects the intermittent schedule of:
- Treatment during the first three weeks of each four-week period; and
- Discontinuation during the fourth week.
This schedule is commercially significant because it corresponds to the labeled mirdametinib cycle for NF1-associated PN. [1]
Claim 17 protects a dose-reduction matrix following an adverse event:
| Dose at adverse event |
Reduced regimen |
| 1 mg twice daily |
1 mg in the morning only |
| 2 mg twice daily |
2 mg in the morning and 1 mg in the afternoon or evening |
| 3 mg twice daily |
2 mg twice daily |
| 4 mg twice daily |
3 mg twice daily |
Claims 18 and 19 narrow this mechanism to acneiform adverse events and topical clindamycin treatment. These claims are operationally specific. They may be relevant to treatment-support programs, investigator protocols and label-based dose-management instructions.
What clinical outcomes are claimed?
Claim 14 requires at least a 20% reduction in PN volume measured by volumetric MRI analysis.
Claims 15 and 16 require treatment-related reductions in:
- Pain intensity; or
- Pain interference.
Claim 21 covers a pre-treatment selection process in which mirdametinib is selected at least partly because of its objective response rate, with objective response defined as at least a 20% tumor-volume reduction by centrally read MRI volumetric analysis.
Claim 22 narrows this selection process to an objective response rate of at least 70%.
These claims are unusual because they combine treatment with outcome assessment or treatment selection. They may be difficult to enforce against ordinary prescribing unless the selection rationale and response data are documented. They are more likely to matter in clinical trials, treatment algorithms, clinical decision-support systems and promotional materials that expressly rely on the claimed response rate.
What is the likely patent strength of US 12,661,330?
The estate has moderate-to-strong practical value for the labeled high-dose regimen, but claim strength varies materially by claim category.
| Claim category |
Practical strength |
Main reason |
| Claim 1: age, NF1, inoperable PN, BSA ≥1.5 m², 4 mg BID |
Strong |
Closely tracks a commercially relevant regimen |
| Claim 13: three weeks on, one week off |
Strong |
Operational dosing schedule is label-relevant |
| Claim 12: maximum 4 mg BID |
Moderate |
Adds limited protection beyond the core regimen |
| Claims 3-8: symptomatic, progressive or morbid PN |
Moderate to strong |
Clinical facts are likely documented |
| Claims 9-11: diagnostic criteria |
Moderate |
Requires specific medical or laboratory proof |
| Claim 14: ≥20% MRI volume reduction |
Moderate |
Objective but often established after treatment |
| Claims 15-16: pain outcomes |
Moderate to weak |
Requires validated baseline and follow-up evidence |
| Claims 17-19: dose reduction and clindamycin |
Moderate |
Specific, but event-dependent |
| Claims 21-22: selection based on response rate |
Moderate to weak |
Intent and decision-making evidence may be difficult to establish |
The central vulnerability is claim construction. A challenger could argue that the claimed regimen was obvious in view of prior clinical studies, published dosing protocols, FDA materials or earlier MEK-inhibitor treatment approaches. The patent owner would likely rely on the particular patient population, BSA threshold, intermittent schedule, response threshold and tolerability profile as a combined clinical regimen.
What patents protect mirdametinib beyond US 12,661,330?
The mirdametinib estate should be analyzed as a layered portfolio rather than as a single patent.
Composition and foundational compound patents
Mirdametinib, also known as PD-0325901, is a MEK1/2 inhibitor. Foundational compound and pharmaceutical-composition rights are distinct from the treatment-method claims in US 12,661,330. Depending on the priority chain and statutory adjustments, those rights may expire earlier than later clinical-use patents.
Formulation patents
Formulation rights may cover:
- Oral tablets or capsules;
- Specific excipients;
- Solid-state forms;
- Stability characteristics;
- Dissolution profiles;
- Pediatric dose flexibility; and
- Manufacturing processes for the drug product.
The supplied claims do not expressly claim a tablet composition, excipient system, crystal form or manufacturing process. A generic company could therefore avoid US 12,661,330 while still confronting separate formulation, composition or process patents.
Method-of-use patents
US 12,661,330 is a method-of-use patent focused on NF1-associated inoperable PN. Other method patents may target:
- Different patient ages;
- Lower BSA groups;
- Alternative mirdametinib doses;
- Other MEK-driven tumors;
- Combination therapy;
- Response-guided treatment;
- Pain reduction; or
- Specific adverse-event management.
Patent-family analysis is required to determine whether the patent is a continuation, divisional or related application and whether related claims remain pending or issued.
What is the Orange Book status of mirdametinib and US 12,661,330?
Mirdametinib was approved by the FDA under the brand name Gomekli for adults and pediatric patients at least 2 years old with NF1-associated symptomatic, inoperable PN. [1] The approved product is associated with NDA 219430. [2]
A patent’s existence does not establish Orange Book listing. The relevant questions are whether the patent owner submitted the patent for listing, whether FDA accepted it for publication, which claims are identified as covering the approved product or method of use, and whether the listing is active in the current Orange Book edition.
For an ANDA strategy, US 12,661,330 creates potential Paragraph IV exposure if it is listed against the mirdametinib NDA and the proposed generic label or intended use would practice the claimed method. Under the Hatch-Waxman framework, a Paragraph IV certification can trigger patent litigation and, if suit is filed within the statutory period, a 30-month stay of approval. [3]
The key regulatory distinction is between:
- Product or formulation patents, which may be difficult to avoid if they cover the generic dosage form; and
- Method-of-use patents, which may be addressed through a section viii statement or a carved-out label if the patented indication or method can be removed without leaving the generic label promoting the patented use.
For mirdametinib, a carve-out may be commercially difficult if the dominant approved indication is NF1-associated inoperable PN and the patent covers the principal labeled high-dose regimen.
When does mirdametinib lose exclusivity?
Mirdametinib exclusivity has several independent components.
| Exclusivity or patent right |
Relevant endpoint |
| FDA orphan-drug exclusivity |
Seven years from approval for the same disease or condition, subject to statutory exceptions |
| New chemical entity exclusivity |
Potentially five years if FDA classified the active ingredient as an NCE |
| Pediatric exclusivity |
Six-month extension if FDA granted and the sponsor completed qualifying pediatric studies |
| US 12,661,330 |
Runs according to its patent term, including any applicable PTA or PTE |
| Other patents |
Must be assessed separately by patent family and listed claim |
FDA approved Gomekli in February 2025. The orphan exclusivity period would ordinarily extend to approximately February 2032, subject to the precise approval date and FDA regulatory records. [1, 4]
The patent expiration date cannot be derived from the claims alone. It depends on the earliest effective nonprovisional priority date, terminal disclaimers, patent-term adjustment, patent-term extension and any disclaimer or correction recorded by the USPTO. The controlling expiration date should be taken from the USPTO patent record and the current FDA Orange Book listing, not inferred from the grant number.
Which companies are challenging mirdametinib exclusivity?
The relevant competitive set includes generic manufacturers and developers of alternative MEK inhibitors. Publicly established commercial competitors include:
| Company |
Product |
Relevance |
| SpringWorks Therapeutics |
Gomekli, mirdametinib |
Originator and commercial rights holder for the approved NF1-PN product |
| AstraZeneca |
Koselugo, selumetinib |
FDA-approved MEK inhibitor for pediatric NF1-associated symptomatic, inoperable PN |
| Novartis |
Mekinist, trametinib |
MEK inhibitor with broader oncology use, but not the same FDA-approved NF1-PN indication |
| Generic applicants |
Future mirdametinib ANDA products |
Potential Paragraph IV challengers after applicable regulatory exclusivities |
Koselugo is the most direct clinical competitor because it is approved for pediatric NF1-associated symptomatic, inoperable PN. [5] Its patent estate and label differ from mirdametinib’s. The competitive question is not limited to generic mirdametinib entry. A competing MEK inhibitor can reduce the commercial value of the mirdametinib regimen without infringing the mirdametinib patent.
What generic launch scenarios exist?
Scenario 1: No Paragraph IV challenge before orphan exclusivity ends
A generic applicant may wait until the orphan-exclusivity barrier expires. This reduces litigation cost but delays launch until approximately 2032 or later, depending on the applicable exclusivity and patent status.
Scenario 2: Paragraph IV challenge to the method patent
An ANDA applicant may assert that US 12,661,330 is invalid, not infringed or unenforceable. Likely arguments include:
- Obviousness based on prior MEK-inhibitor dosing;
- Lack of written description for the full age and BSA range;
- Lack of enablement for the complete patient population;
- Indefiniteness in terms such as "significant morbidity" or "progressive PN"; and
- Noninfringement based on a label that omits the 4 mg twice-daily regimen or the patented treatment schedule.
Scenario 3: Carved-out labeling
A generic may attempt to omit the patented method from its label. This strategy is strongest where the remaining label supports clinically meaningful noninfringing uses. It is weaker where the patented regimen corresponds to the principal approved use and dose.
Scenario 4: Authorized generic or settlement
The originator could license or authorize an earlier generic launch. Any settlement would require antitrust review under FTC standards and would materially change the expected market-entry date. [6]
What patent litigation affects mirdametinib?
The supplied information identifies the issued patent and claims but does not establish a specific district-court case, Paragraph IV complaint, settlement or judgment involving US 12,661,330. The patent should therefore be treated as an active enforcement risk rather than as a litigated patent with a confirmed court construction.
A litigation review should focus on:
- Orange Book listing;
- NDA patent certifications;
- ANDA litigation filings under 21 U.S.C. § 355(j);
- Patent-family continuations;
- Terminal disclaimers;
- Patent-term adjustment;
- Any licensing or collaboration agreement affecting enforcement; and
- Whether SpringWorks or another rights holder owns the relevant patent rights.
What revenue exposure does this patent create?
The highest exposure is concentrated in patients who meet all of the following conditions:
- NF1 diagnosis;
- Inoperable PN;
- Body surface area of at least 1.5 m²;
- Treatment with 4 mg twice daily; and
- Use of the three-weeks-on, one-week-off schedule.
The patent has less direct reach over smaller pediatric patients receiving body-surface-area-adjusted doses below 4 mg twice daily. It also has limited direct reach over off-label use, alternative dosing, competing MEK inhibitors and formulations that do not practice the claimed method.
Commercial exposure depends on the proportion of the treated population with BSA at least 1.5 m², the share receiving the maximum dose, the duration of therapy and the availability of Koselugo or other MEK-inhibitor alternatives.
Key Takeaways
- US Patent 12,661,330 is a method-of-treatment patent for a defined high-dose mirdametinib regimen in NF1-associated inoperable PN.
- Claim 1 requires a patient at least 2 years old, BSA of at least 1.5 m², and 4 mg orally twice daily.
- Claim 13 protects the clinically important three-weeks-on, one-week-off schedule.
- Claims 17 through 19 cover detailed dose reductions and topical clindamycin treatment for acneiform adverse events.
- Claims 21 and 22 cover response-guided treatment selection based on MRI-defined tumor reduction and a response rate of at least 70%.
- The patent does not, by itself, establish composition, formulation or manufacturing protection.
- Gomekli received FDA approval in February 2025, and orphan-drug exclusivity would ordinarily extend for seven years from approval.
- Orange Book listing and the patent’s exact expiration date require confirmation from the current FDA and USPTO records.
- Generic entry could proceed through Paragraph IV litigation, a label carve-out, settlement, authorized launch or delayed entry after regulatory exclusivity.
- Koselugo, not only future mirdametinib generics, is the principal commercial alternative in NF1-associated inoperable PN.
FAQs
Is US Patent 12,661,330 a composition-of-matter patent?
No. The supplied claims are method-of-treatment claims. They cover administering mirdametinib under specified clinical conditions and do not claim the molecular structure, tablet composition or manufacturing process.
Does a 2 mg twice-daily mirdametinib regimen infringe claim 1?
Not literally, because claim 1 requires 4 mg twice daily. A separate patent could still cover the lower dose, and induced-infringement analysis could depend on the full product label and related claims.
Does the patent cover all patients with NF1 and plexiform neurofibromas?
No. The core claim requires inoperable PN, age at least 2 years, BSA of at least 1.5 m² and 4 mg twice-daily oral dosing.
Can a generic mirdametinib applicant omit this patent from its label?
Potentially, if the patented method can be validly carved out while preserving a lawful and commercially viable noninfringing label. The feasibility depends on the FDA-approved uses, listed patent claims and the proposed labeling.
Is mirdametinib interchangeable with selumetinib for patent purposes?
No. Mirdametinib and selumetinib are different active ingredients with separate patents, regulatory approvals, labels and infringement analyses. Clinical competition does not create patent interchangeability.
References
- U.S. Food and Drug Administration. (2025). Gomekli (mirdametinib) prescribing information.
- U.S. Food and Drug Administration. (2025). Drugs@FDA: Gomekli, NDA 219430.
- Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355(j).
- U.S. Food and Drug Administration. (2025). Orphan drug designation and exclusivity database.
- U.S. Food and Drug Administration. (2020). Koselugo (selumetinib) prescribing information.
- Federal Trade Commission. (2023). Agreements filed with the Federal Trade Commission under the Medicare Prescription Drug, Improvement, and Modernization Act.
- U.S. Patent and Trademark Office. (2025). United States Patent No. 12,661,330.
