US Patent 10,166,242: Claim Scope, Validity Risks, Orange Book Position, and Generic Entry Exposure

US Patent 10,166,242 protects a pharmacokinetic treatment protocol for Cushing’s syndrome using mifepristone. Its independent claim requires prolonged treatment, serum-level testing, a mifepristone concentration above 1,631 ng/mL, and dose adjustment to reach that threshold. The patent does not broadly claim mifepristone for Cushing’s syndrome, the Korlym product, or every dose-adjustment regimen. Its commercial value depends on whether the claimed concentration-guided protocol is used in clinical practice and whether the patent is listed against the relevant FDA-approved drug product.

The core claim is narrower than the approved Korlym dosing framework but potentially reaches a physician-directed titration strategy involving repeated blood-level testing and dose escalation. The principal validity risks are obviousness, written description, enablement, claim-construction disputes concerning “serum” and “blood” levels, and proof that an accused treatment actually targets the claimed concentration.

What does US Patent 10,166,242 claim?

The patent’s independent claim 1 requires all of the following:

Limitation	Required scope
Disease	Patient suffers from Cushing’s syndrome
Drug	Mifepristone
Treatment duration	At least seven daily doses over at least seven days
Monitoring	Testing serum levels to determine whether mifepristone exceeds 1,631 ng/mL
Dose adjustment	Adjusting the daily dose to achieve blood levels greater than 1,631 ng/mL
Exclusion	Patient is not already suffering from a condition indicated for treatment with mifepristone

The claim is a method-of-treatment claim. It requires an act of treatment, a pharmacokinetic measurement, and an adjustment based on that measurement. A product containing mifepristone does not infringe merely because it can produce concentrations above 1,631 ng/mL.

The phrase “greater than 1,631 ng/mL” is a strict numerical limitation. A measured concentration of exactly 1,631 ng/mL would not satisfy the literal language. The claim also requires dose adjustment to achieve the threshold, not merely a dose that happens to produce the threshold.

How do claims 2 through 9 narrow the patent?

Claim	Added limitation	Practical effect
2	Seven or more doses administered orally	Excludes nonoral administration
3	Daily dose of at least 300 mg	Covers the lower end of the approved Korlym starting-dose range
4	Daily dose of at least 600 mg	Covers intermediate dosing
5	Daily dose of at least 900 mg	Covers higher-dose titration
6	Daily dose of at least 1,200 mg	Covers the upper end of the FDA-labeled dose range
7	At least 28 daily doses over at least 28 days	Requires a longer treatment period
8	Testing with a plasma-sampling collection device suitable for detecting mifepristone	Adds a device-based sampling limitation
9	Dose adjustment includes increasing the daily dose	Narrows the adjustment step to upward titration

Claims 3 through 6 are nested dose limitations. A regimen of 1,200 mg per day would generally fall within claims requiring at least 300 mg, 600 mg, 900 mg, and 1,200 mg, assuming the other limitations are satisfied.

Claim 7 is narrower than claim 1 because it requires at least 28 days of treatment. Claim 9 is also narrower because it specifically requires increasing the daily dose rather than adjusting it in either direction.

What patient population does US 10,166,242 cover?

The patent targets patients with Cushing’s syndrome who are being treated with mifepristone under a concentration-guided protocol. The exclusionary proviso removes patients already suffering from a condition for which mifepristone was indicated.

The approved US indication for Korlym is control of hyperglycemia secondary to hypercortisolism in adults with endogenous Cushing’s syndrome who have type 2 diabetes mellitus or glucose intolerance and have failed surgery or are not candidates for surgery. The FDA-approved indication therefore overlaps materially with the patent’s disease population, although the patent’s patient proviso and pharmacokinetic requirements limit the overlap. (U.S. Food and Drug Administration, 2024a)

The claim does not require:

A particular Cushing’s syndrome etiology;
A particular cortisol or ACTH level;
A specific CYP3A4 medication;
A particular body weight;
Diabetes or glucose intolerance;
Surgical failure;
A particular formulation or tablet strength; or
A particular clinical endpoint beyond improved efficacy.

The absence of a diabetes or glucose-intolerance limitation may make the patent broader than the FDA-approved Korlym indication in one respect. The blood-level and dose-adjustment requirements make it narrower in another.

How does the patent compare with FDA-approved Korlym dosing?

Korlym is mifepristone, a small-molecule glucocorticoid and progesterone receptor antagonist. The FDA label provides a 300 mg once-daily starting dose, with increases of 300 mg as clinically required, up to 1,200 mg once daily or 20 mg/kg per day, whichever is lower. (U.S. Food and Drug Administration, 2024a)

Issue	FDA-approved Korlym use	US 10,166,242
Starting dose	300 mg daily	Claim 3 covers at least 300 mg
Escalation	Increase by 300 mg as needed	Claim 9 covers increasing the daily dose
Maximum labeled dose	1,200 mg daily or 20 mg/kg daily	Claim 6 covers at least 1,200 mg
Blood-level target	No general labeled target of greater than 1,631 ng/mL	Central limitation
Routine therapeutic drug monitoring	Not the central labeled dosing requirement	Required by claim 1
Treatment duration	Chronic treatment as clinically appropriate	At least seven days; claim 7 requires at least 28 days
Indication	Hyperglycemia secondary to endogenous Cushing’s syndrome	Cushing’s syndrome generally, subject to the proviso

The critical distinction is that ordinary Korlym dose escalation is not automatically the patented method. An infringement case would likely turn on whether the prescriber or treatment protocol includes testing and adjustment directed to a blood concentration above 1,631 ng/mL.

What patent term and expiration issues apply?

US Patent 10,166,242 was issued on January 1, 2019. The patent is associated with Corcept Therapeutics and concerns methods for treating Cushing’s syndrome with mifepristone. The relevant statutory term is generally 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, terminal disclaimers, and any applicable regulatory extension. (U.S. Patent and Trademark Office, 2024)

Public patent-family records associate the application with a 2013 priority period. On that basis, the nominal expiration is expected to fall in late 2034, before any patent-term adjustment or other term-specific modification. The controlling date is the USPTO patent-term calculation, not the grant date.

Milestone	Date or period
Earliest public priority period	2013
US patent application filing	2017
Patent grant	January 1, 2019
Expected nominal term end	Approximately late 2034
Possible adjustment	PTA, terminal disclaimer, or other USPTO-recorded modification

The patent therefore has a potentially longer life than older Korlym patents directed to the composition, treatment, or use of mifepristone. Its commercial importance increases if earlier patents expire before the concentration-guided method claim.

What is the Orange Book status of US 10,166,242?

The FDA Orange Book lists patents submitted by an NDA holder for an approved drug when the patents meet FDA listing requirements. Method-of-use patents may be listed when they claim an approved use or an approved method of using the drug. (U.S. Food and Drug Administration, 2024b)

The patent’s ability to delay an ANDA launch depends on three separate questions:

Whether Corcept submitted US 10,166,242 for listing against Korlym;
Whether FDA accepted the patent for Orange Book listing; and
Whether an ANDA applicant made a Paragraph IV certification against it.

The patent claims a concentration-guided method rather than the mifepristone molecule itself. That distinction can produce a narrower listing and enforcement position. A listed method-of-use patent may support a statutory stay if an ANDA applicant certifies that the patent is invalid, unenforceable, or not infringed and the NDA holder timely files suit. The patent does not independently block approval of an ANDA if the applicant uses a proper section viii statement and omits the patented method from its labeling, assuming the FDA accepts the carve-out.

The Orange Book must therefore be evaluated together with the approved labeling. If blood-level testing to exceed 1,631 ng/mL is absent from the Korlym label, a generic applicant may argue that the claimed method is not an approved use suitable for listing or can be carved out of the proposed label.

What Paragraph IV challenges and litigation risks exist?

A Paragraph IV challenge would likely attack both infringement and validity.

Infringement theories

A generic applicant could reduce method-infringement risk by:

Omitting any instruction to measure mifepristone serum levels;
Omitting the 1,631 ng/mL target;
Omitting instructions to increase the dose based on mifepristone levels;
Relying on symptom-based or cortisol-based dose adjustment;
Carving out any labeled language that expressly describes the patented protocol.

The risk would be higher if the generic label, physician materials, medication guide, or risk-management materials instructed clinicians to measure mifepristone concentrations and escalate dosing above the claimed threshold.

Validity theories

The principal obviousness argument would combine:

Prior mifepristone treatment for Cushing’s syndrome;
Known 300 mg to 1,200 mg dose escalation;
Known pharmacokinetic variability;
Therapeutic drug monitoring concepts;
Routine blood-level testing; and
A motivation to identify a concentration associated with efficacy.

The patent holder would respond that the 1,631 ng/mL threshold was not an arbitrary target and that the claimed result reflects a clinically meaningful exposure-efficacy relationship. The strength of that response depends on the specification’s data, statistical support, patient population, assay methodology, and evidence that crossing the threshold improves efficacy rather than merely correlates with dose or disease severity.

Written description and enablement

The claims cover all Cushing’s syndrome patients who reach the concentration threshold, across multiple doses and treatment durations. A validity challenge could argue that the specification does not demonstrate the claimed benefit across the full breadth of that population.

Enablement questions include:

Whether clinicians can reliably achieve concentrations above 1,631 ng/mL;
Whether the concentration is reproducible across patients;
Whether serum and plasma assays produce comparable results;
Whether dose escalation creates clinically significant safety risks;
Whether the threshold applies across CYP3A4 inhibitor use and other drug interactions; and
Whether the claimed improved efficacy is predictable from the disclosed data.

The FDA label warns about drug interactions, adrenal insufficiency, endometrial effects, hypokalemia, QT-related considerations, and pregnancy-related risks. These safety issues create a possible tension between pushing concentrations above a defined threshold and the labeled risk-management framework. (U.S. Food and Drug Administration, 2024a)

How strong is the patent estate around Korlym and mifepristone?

The patent estate is layered rather than dependent on a single patent category.

Estate category	Protection objective	Relevance to US 10,166,242
Active ingredient and composition	Mifepristone molecule or pharmaceutical compositions	Separate from the pharmacokinetic method
Cushing’s syndrome treatment	Use of mifepristone in a defined disease population	Overlaps with the disease context
Dose regimen	300 mg to 1,200 mg dosing and titration	Claims 3 through 6 overlap with labeled doses
Pharmacokinetic targeting	Achieving a concentration above 1,631 ng/mL	Core protection of US 10,166,242
Formulation	Tablets, excipients, release characteristics, or administration formats	Not expressly claimed in the supplied claims
Monitoring device	Plasma sampling collection device	Narrow protection under claim 8
Method of use	Clinical use in defined patients	Core infringement pathway for claims 1 and 9
Manufacturing	API synthesis, impurity control, and finished-dose manufacturing	Not covered by the supplied claims

The strongest commercial feature of US 10,166,242 is its potential extension beyond basic composition or indication patents. Its weakness is that the claimed method may be avoidable through labeling, clinical practice, or a noninfringing dosing algorithm.

The patent does not create biosimilar exposure because mifepristone is a small molecule. The relevant competitive pathway is an ANDA for a generic version of Korlym, not a biosimilar application under the Public Health Service Act.

What formulation and manufacturing barriers remain?

The supplied claims do not cover a particular tablet formulation, excipient system, dissolution profile, polymorph, salt, manufacturing process, or impurity specification. A competitor could therefore challenge the product estate through an alternative formulation or manufacturing route without directly implicating these claims.

Claims 1 through 7 are formulation-neutral. They can potentially read on any oral mifepristone product if the clinical protocol satisfies the treatment-duration, concentration, and dose-adjustment requirements.

Claim 8 is different. It requires a plasma-sampling collection device suitable for detecting mifepristone. That claim may be difficult to enforce unless the accused treatment protocol specifically identifies or supplies such a device. A generic manufacturer could avoid direct product infringement while still facing induced-infringement arguments if its labeling promotes the claimed testing method.

Which companies are most likely to challenge the patent?

The most credible challengers are manufacturers that submit ANDAs for generic mifepristone tablets or obtain rights to market a generic Korlym equivalent. The likely challenge structure is:

Paragraph IV certification against any listed method-of-use patent;
A noninfringement position based on labeling carve-outs;
Invalidity arguments based on obviousness and inadequate disclosure;
A proposed launch after the relevant listed patents expire or after litigation resolution.

The supplied patent claims alone do not establish that a particular company has filed a Paragraph IV certification, initiated litigation, or entered a settlement. Those events must be tied to an FDA Orange Book record and federal docket.

What generic launch scenarios exist?

Scenario	Commercial result
Patent not listed	No automatic 30-month stay based on this patent
Listed patent with Paragraph IV and timely suit	FDA approval may be subject to a statutory stay
Label carve-out accepted	Generic may launch without instructions for the patented method
Patent invalidated	Generic can launch subject to other patents and exclusivities
Patent held valid and infringed	Launch may be delayed until expiration or settlement date
Generic avoids concentration monitoring	Direct method infringement risk decreases
Physician practice independently adopts monitoring	Induced-infringement and divided-infringement issues become central

The greatest launch risk is not the existence of a 1,200 mg dose. It is the extent to which the branded label or clinical practice directs physicians to measure mifepristone concentrations and increase dosing above 1,631 ng/mL.

What is the geographic coverage of the patent?

US Patent 10,166,242 has territorial effect only in the United States. Foreign counterparts, if granted, require separate analysis for:

European Patent Convention states;
Canada;
Japan;
Australia;
China;
South Korea; and
Other markets where mifepristone is commercially supplied for Cushing’s syndrome.

A US patent does not block generic or branded activity outside the United States. Foreign claim scope may differ because patent offices apply different standards to medical-treatment claims, dosage regimens, diagnostic steps, and pharmacokinetic correlations.

Key Takeaways

US 10,166,242 is a method patent, not a basic mifepristone composition patent.
Claim 1 requires at least seven daily doses, serum testing, a concentration greater than 1,631 ng/mL, and dose adjustment to reach that concentration.
Claims 3 through 6 cover daily doses of at least 300 mg, 600 mg, 900 mg, and 1,200 mg.
Claim 7 extends the minimum treatment period to 28 days.
Claim 9 specifically requires increasing the daily dose.
The patent’s expected nominal term reaches approximately late 2034, subject to the official USPTO term calculation.
Korlym’s FDA-labeled dose range overlaps materially with the dependent claims, but the FDA label does not make ordinary dose escalation equivalent to the patented concentration-guided method.
The principal generic defenses are label carve-out, noninfringement, obviousness, written description, and enablement.
No biosimilar pathway applies. Generic competition would proceed through the ANDA framework.
Commercial protection depends heavily on Orange Book listing, the approved label, Paragraph IV activity, and whether physicians actually perform the claimed concentration-guided titration.

FAQs About US Patent 10,166,242

Does US 10,166,242 prevent all generic mifepristone sales?

No. It covers a specific treatment method. A generic could potentially launch with labeling that omits the claimed concentration-monitoring and dose-adjustment protocol, subject to other Korlym patents, regulatory requirements, and infringement theories.

Is 1,631 ng/mL a mifepristone dose?

No. It is a blood-concentration threshold. The claims distinguish the daily dose, measured in milligrams, from the mifepristone level, measured in nanograms per milliliter.

Can a patient receiving 1,200 mg infringe the patent?

Possibly, but dose alone is insufficient. The patient must also satisfy the disease, treatment-duration, testing, concentration, and dose-adjustment limitations.

Does claim 8 cover every blood test for mifepristone?

No. Claim 8 requires a plasma-sampling collection device suitable for detecting mifepristone. The device limitation narrows the claim beyond ordinary clinical blood testing.

Does the patent cover mifepristone treatment for pregnancy termination?

The supplied claims are directed to Cushing’s syndrome and contain an exclusion for a patient already suffering from a condition indicated for treatment with mifepristone. They do not claim pregnancy termination as a use.

References

Corcept Therapeutics, Inc. (2019). U.S. Patent No. 10,166,242, Methods for treating Cushing’s syndrome. U.S. Patent and Trademark Office.
U.S. Food and Drug Administration. (2024a). Korlym (mifepristone) tablets: Prescribing information. FDA.
U.S. Food and Drug Administration. (2024b). Approved drug products with therapeutic equivalence evaluations, Orange Book. FDA.
U.S. Patent and Trademark Office. (2024). Patent term adjustment and patent term calculation guidance. USPTO.
Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355.
Leahy-Smith America Invents Act, 35 U.S.C. §§ 271(e), 282.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Corcept Therap	KORLYM	mifepristone	TABLET;ORAL	202107-001	Feb 17, 2012	AB	RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				TREATING CUSHING'S SYNDROME	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Details for Patent: 10,166,242

Which drugs does patent 10,166,242 protect, and when does it expire?

Summary for Patent: 10,166,242