US Patent 8,575,146: Midostaurin Mastocytosis Claims, Expiration, and Generic Risk
US Patent 8,575,146 is a Novartis method-of-treatment patent covering use of midostaurin, also known as PKC412, in mastocytosis patients whose KIT tyrosine kinase receptor has the D816V mutation. The patent does not broadly claim midostaurin, the compound’s chemical composition, or every use of the drug. Its central protection is narrower: administering midostaurin to a defined mastocytosis population, with dependent claims addressing imatinib resistance, dose, schedule, route, and dosage form.
The patent is listed in the FDA Orange Book for Rydapt and has an Orange Book expiration date of June 29, 2026. Rydapt received FDA approval in 2017 for aggressive systemic mastocytosis, systemic mastocytosis with associated hematological neoplasm, and newly diagnosed FLT3-mutated acute myeloid leukemia.[1,2]
What drug does Formula VII represent in US Patent 8,575,146?
Formula VII is midostaurin, the active ingredient in Rydapt.
| Attribute |
Details |
| Generic name |
Midostaurin |
| Development code |
PKC412 |
| Brand |
Rydapt |
| Sponsor |
Novartis Pharmaceuticals |
| Drug class |
Multikinase inhibitor |
| Relevant targets |
KIT, FLT3, PDGFR, VEGFR and other kinases |
| FDA dosage form |
25-mg oral capsules |
| Relevant mastocytosis target |
KIT D816V |
| FDA approval |
April 28, 2017 |
| Patent at issue |
US 8,575,146 |
| Orange Book expiration |
June 29, 2026 |
Midostaurin is a small molecule rather than a biologic. Biosimilar regulation is therefore not relevant. Any competitive product would ordinarily proceed through an abbreviated new drug application, or ANDA, rather than a biosimilar application.
What are the independent claims of US Patent 8,575,146?
The patent has two principal independent method claims.
Claim 1: KIT D816V mastocytosis
Claim 1 requires all of the following:
- A human patient.
- Mastocytosis.
- A KIT tyrosine kinase receptor carrying the D816V mutation.
- Administration of a therapeutically effective amount of midostaurin or a pharmaceutically acceptable salt.
This is a patient-selection claim. It does not cover treatment of every mastocytosis patient. The KIT D816V limitation is central and materially narrows the claim.
The claim also requires administration. Mere manufacture, sale, or possession of midostaurin would not ordinarily satisfy the conduct element of direct method infringement. Liability would depend on the facts, including inducement, labeling, marketing, and the relationship between the product’s approved uses and the claimed treatment population.
Claim 11: Imatinib-resistant mastocytosis
Claim 11 adds a second clinical limitation. The patient must have:
- mastocytosis;
- resistance to imatinib; and
- KIT D816V mutation.
Claim 11 is narrower than claim 1 because every patient covered by claim 11 must satisfy the additional imatinib-resistance requirement. A product label directed only to imatinib-sensitive disease would not, on its face, satisfy that limitation.
How do the dependent claims narrow the patent scope?
The dependent claims specify dosing, administration frequency, treatment cycles, route, and formulation.
| Claim |
Limitation |
| 1 |
Mastocytosis, KIT D816V, midostaurin |
| 2 |
Intermittent schedule: administration for one to six weeks, followed by one to three weeks without treatment |
| 3 |
100 to 300 mg daily |
| 4 |
One, two, or three administrations daily, totaling 100 to 300 mg |
| 5 |
Three administrations daily, totaling 225 mg |
| 6 |
Oral administration |
| 7 |
Microemulsion, soft gel, or solid dispersion |
| 8 |
Up to 125 mg per day |
| 9 |
Oral administration under claim 4 |
| 10 |
Microemulsion under claim 9 |
| 11 |
Imatinib-resistant mastocytosis with KIT D816V |
| 12-19 |
Corresponding schedule, dose, route, and formulation limits for claim 11 |
Claims 8 and 3 appear to create overlapping but different dose ranges. Claim 8 covers administration of up to 125 mg per day, while claim 3 covers 100 to 300 mg per day. The overlap is 100 to 125 mg daily.
Claim 5 is particularly specific. It requires a total daily dose of 225 mg administered three times daily. The FDA-approved Rydapt regimen for advanced systemic mastocytosis is generally 100 mg twice daily, or 200 mg per day, rather than 225 mg daily.[2] That distinction matters because the approved label does not necessarily practice every dependent dosing claim.
What is the likely claim construction of “KIT D816V”?
“KIT D816V” refers to substitution of valine for aspartic acid at amino acid position 816 in the KIT receptor tyrosine kinase. The mutation is associated with constitutive KIT activation and is common in advanced systemic mastocytosis.
The claims require that the patient have a KIT receptor with the D816V mutation. A diagnostic test showing the mutation would be relevant to infringement analysis. The patent language does not appear to require a particular testing platform, assay, mutation burden, or tissue source.
The phrase “human patient ha KIT” in the supplied claim text is a typographical error. The issued patent should control the analysis. The apparent intended language is that the human patient “has” a KIT tyrosine kinase receptor with a D816V mutation.
The phrase “7 to 4 times a week” in claims 2 and 12 is also facially irregular. It appears to be intended to describe administration from four to seven times weekly, or approximately 50% to 100% of days during the treatment period. The prosecution history and issued claim record would control whether the language is treated as an obvious typographical error or as an ambiguity affecting enforceability.
What patent rights does US 8,575,146 not cover?
US 8,575,146 does not appear, based on the supplied claims, to provide broad protection for:
- the midostaurin molecule itself;
- every chemical salt or polymorph as a composition claim;
- every cancer indication;
- FLT3-mutated acute myeloid leukemia;
- KIT-mutated cancers other than mastocytosis;
- treatment of mastocytosis without KIT D816V;
- treatment of mastocytosis without administration to a patient;
- manufacturing midostaurin;
- a generic capsule as a product claim independent of use;
- all oral formulations of midostaurin regardless of patient population.
The patent’s commercial relevance therefore depends heavily on the scope of an ANDA label and the prescribing behavior that follows that label.
When does US Patent 8,575,146 lose exclusivity?
The Orange Book expiration date is June 29, 2026.[1] That date is the principal US patent-loss date for the claims at issue.
| Exclusivity type |
Relevance to Rydapt |
| Patent term |
June 29, 2026 for US 8,575,146 |
| New chemical entity exclusivity |
Expired in 2022 |
| Orphan-drug exclusivity |
Seven-year periods applied to FDA-designated orphan indications |
| Pediatric exclusivity |
No conclusion should be drawn without the current FDA exclusivity record |
| Regulatory exclusivity after patent expiry |
Not expected to block a compliant ANDA indefinitely |
Rydapt’s FDA approval occurred in 2017. Its five-year new chemical entity exclusivity therefore expired in 2022. Orphan-drug exclusivity may restrict approval of the same drug for the same orphan indication during the applicable seven-year period, but it does not create a permanent product monopoly and is distinct from patent protection.[3]
The practical generic-entry date depends on the ANDA applicant’s Paragraph IV position, litigation, any settlement, and the exact Orange Book listing. The June 29, 2026 patent date is not automatically the same as the earliest possible launch date for every generic applicant.
What is the Orange Book status of Rydapt?
Rydapt is an FDA-approved prescription product with midostaurin as its active ingredient. US 8,575,146 is listed against Rydapt for method-of-use protection.[1]
The patent does not operate like a formulation patent that blocks every generic capsule. It is principally a use patent. An ANDA applicant may challenge the listing through a Paragraph IV certification or attempt to avoid the claimed methods through a Paragraph III certification and post-expiration launch.
An ANDA applicant could also evaluate a section viii statement, commonly called a skinny label, if the listed indication or method can be omitted without encouraging use covered by the patent. That strategy is difficult where the patented population overlaps substantially with the drug’s principal FDA-approved mastocytosis indication.
What Paragraph IV challenges and litigation affect Rydapt?
A Paragraph IV certification would assert that the listed patent is invalid, unenforceable, or not infringed. If the patent owner files an infringement action within 45 days of receiving notice, FDA approval of the ANDA is generally subject to a 30-month stay under the Hatch-Waxman framework, subject to statutory exceptions.[4]
The principal litigation issues for this patent would likely include:
- Whether an ANDA label induces treatment of KIT D816V mastocytosis.
- Whether the label covers imatinib-resistant mastocytosis.
- Whether the dosage instructions practice the claimed ranges.
- Whether the formulation limitation is present.
- Whether the claims are anticipated or obvious in view of prior midostaurin, KIT, or mastocytosis disclosures.
- Whether the irregular schedule language in claims 2 and 12 is indefinite or correctable.
- Whether the patent’s priority chain and written description support the claimed patient population.
No conclusion of invalidity follows from the narrowness of the claims. The claims may be narrower than a composition patent but can still create meaningful inducement risk when the label expressly identifies KIT D816V disease.
How strong is the patent estate for midostaurin?
The estate is mixed.
Strengths
- The patent targets the clinically important KIT D816V mastocytosis population.
- The independent claims are directed to a defined disease and molecular biomarker.
- Claim 11 adds imatinib resistance, creating a distinct treatment subset.
- FDA-approved mastocytosis labeling can provide evidence relevant to inducement.
- The patent remains listed through 2026.
Weaknesses
- The claims are method claims, not broad composition claims.
- Several dependent claims recite narrow or commercially nonstandard doses.
- The supplied schedule language contains apparent drafting defects.
- Midostaurin’s kinase activity and use in oncology were publicly disclosed before this patent family.
- A generic sponsor may design its label around narrower dependent claims while contesting the independent claims.
- Small-molecule generic entry is structurally easier than biosimilar entry because no biologic comparability program is required.
The strongest commercial barrier is claim 1, not claims 5, 8, 10, 17, or 19. The strongest litigation defense is likely to focus on whether the proposed label requires or encourages treatment of KIT D816V mastocytosis, rather than on the narrower 225-mg or microemulsion limitations.
What formulation patents protect Rydapt?
The supplied claims do not claim a formulation in isolation. Claims 7, 10, 16, and 19 protect administration of midostaurin in a microemulsion, soft gel, or solid dispersion only when the other method limitations are met.
That distinction limits the formulation risk. A generic product using a conventional oral dosage form could avoid those dependent claims, but it would still need to assess claims 1 and 11. A formulation patent would be more powerful if it covered the capsule composition regardless of indication. US 8,575,146, based on the claims provided, does not have that structure.
Are biosimilars or generic drugs the main competitive risk?
Generic drugs are the relevant competitive threat. Midostaurin is a small molecule and Rydapt is an oral capsule. A competitor would likely pursue an ANDA supported by bioequivalence data.
Biosimilar risk is not applicable because Rydapt is not a biologic reference product. The main launch scenarios are:
| Scenario |
Commercial effect |
| No successful challenge before June 2026 |
Novartis retains effective market protection until patent expiry |
| Paragraph IV challenge with litigation |
Entry depends on validity, infringement, settlement, and court timing |
| Skinny-label strategy |
Possible partial competition if patented uses can be omitted |
| Post-expiry ANDA entry |
Standard generic price and share erosion |
| Formulation or manufacturing workaround |
May reduce dependent-claim exposure but not necessarily claim 1 risk |
What licensing and settlement issues affect the landscape?
The supplied patent claims do not establish a license, covenant not to sue, or settlement. No licensing right can be inferred from FDA approval, Orange Book listing, or the existence of the patent.
A commercial settlement would be material if it granted an authorized generic, permitted an agreed entry date, or imposed restrictions on a Paragraph IV applicant. Settlement terms would need to be reviewed in the relevant court docket and FTC settlement disclosures. The patent itself does not disclose a generic-entry agreement.
What is the revenue exposure from US patent expiry?
Rydapt revenue is exposed to generic erosion after method-of-use protection expires, but the magnitude depends on the percentage of sales attributable to mastocytosis versus FLT3-mutated AML, the number of generic entrants, and whether the generic label includes or omits patented uses.
The patent is more commercially important for mastocytosis than for AML because the claims provided are directed to mastocytosis. A generic could therefore seek to compete first in nonclaimed or differently labeled indications while limiting exposure to the mastocytosis claims.
Key Takeaways
- US 8,575,146 covers midostaurin treatment of mastocytosis in patients with KIT D816V.
- Claim 11 is narrower because it also requires imatinib resistance.
- The patent is a method-of-use patent, not a broad midostaurin composition patent.
- Dependent claims cover dose, frequency, oral administration, and selected formulations.
- The FDA Orange Book expiration date is June 29, 2026.
- Rydapt is a small-molecule drug, so generic rather than biosimilar competition is expected.
- The principal Paragraph IV issue is whether a proposed ANDA label induces treatment of KIT D816V mastocytosis.
- The narrowest dose and formulation claims may be avoidable, but avoiding those claims does not automatically avoid claim 1.
- The apparent errors in claims 2 and 12 make the prosecution history and issued patent record important to enforceability analysis.
- No license or settlement can be inferred from the patent or FDA listing alone.
FAQs About US Patent 8,575,146
Does US 8,575,146 cover all uses of Rydapt?
No. It covers specified methods of treating mastocytosis, particularly KIT D816V disease. It does not, on the supplied claims, cover every use of midostaurin or every Rydapt indication.
Does the patent cover FLT3-mutated acute myeloid leukemia?
Not based on the claims provided. The claims require mastocytosis and KIT D816V. AML protection would require separate claims or another patent.
Can a generic launch before June 29, 2026?
Potentially, if the applicant establishes invalidity or noninfringement, reaches a settlement, uses a legally effective label carve-out, or obtains another lawful basis for entry. Patent expiry alone supports entry only on the applicable statutory and regulatory timeline.
Is a microemulsion required for Rydapt infringement?
No. Microemulsion is a limitation in dependent claims 10 and 19. The independent claims do not require that formulation.
Does imatinib resistance apply to every patent claim?
No. It applies to independent claim 11 and its dependents. Claim 1 and its dependents require mastocytosis and KIT D816V but do not expressly require imatinib resistance.
References
- U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
- U.S. Food and Drug Administration. (2017). Rydapt (midostaurin) prescribing information. FDA.
- U.S. Food and Drug Administration. (2023). Regulatory exclusivity and orphan-drug designation provisions. FDA.
- U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act, 21 U.S.C. § 355(j).
- United States Patent and Trademark Office. (2013). U.S. Patent No. 8,575,146: Methods of treating mastocytosis. U.S. Department of Commerce.
