United States Patent 10,835,530: Levoketoconazole Claims, Expiration, Orange Book Status, and Generic Risk

U.S. Patent No. 10,835,530 protects methods of treating Cushing's syndrome with ketoconazole compositions containing specified concentrations of the 2S,4R ketoconazole enantiomer, also known as levoketoconazole. The patent does not claim ketoconazole as a chemical compound, a tablet formulation, or a manufacturing process. Its principal value is as a method-of-use patent directed to the stereochemically enriched active ingredient used in Recorlev.

The three claims establish escalating enantiomeric-purity thresholds:

Claim	Required 2S,4R ketoconazole content	Claim type
1	At least 90%	Method of treating Cushing's syndrome
2	At least 95%	Method of treating Cushing's syndrome
3	At least 99%	Method of treating Cushing's syndrome

The patent's reported expiration date is March 20, 2035, subject to any patent-term adjustment or extension reflected in official USPTO or FDA records.[1][2]

What does U.S. Patent 10,835,530 cover?

The patent covers a treatment method requiring four core elements:

A patient with Cushing's syndrome.
Administration of a composition containing a ketoconazole component.
The ketoconazole component contains at least the specified amount of the 2S,4R enantiomer.
The composition is administered for treatment of the patient's disease.

The claims are not limited to a particular tablet strength, dose, dosing frequency, treatment duration, excipient system, route of administration, or commercial product name. The central limitation is the stereochemical composition of the ketoconazole component.

What is the protected enantiomer?

Ketoconazole is a chiral compound. Levoketoconazole is the 2S,4R enantiomer. Conventional ketoconazole products generally contain a racemic mixture of ketoconazole stereoisomers, while levoketoconazole products use the selected 2S,4R form.

The claims measure the percentage of the ketoconazole component made up of the 2S,4R enantiomer. A composition containing 90% or more of that enantiomer falls within claim 1. A composition containing 95% or more falls within claim 2, and a composition containing 99% or more falls within claim 3, assuming the other claim elements are satisfied.

What is not required by the claims?

The issued claims do not expressly require:

Recorlev as the administered product;
a tablet or oral dosage form;
a specific daily dose;
a specific plasma concentration;
suppression of cortisol through a particular biochemical pathway;
a particular excipient;
a particular manufacturing process;
a particular patient age or sex;
prior failure of another Cushing's syndrome therapy.

This broad claim architecture gives the patent potential reach across multiple pharmaceutical presentations containing sufficiently pure 2S,4R ketoconazole.

How do the three claims differ?

The claims are nested purity claims. Claim 3 is narrower than claim 2, and claim 2 is narrower than claim 1.

Composition purity	Claim 1	Claim 2	Claim 3
89% 2S,4R	No	No	No
90%	Yes	No	No
94%	Yes	No	No
95%	Yes	Yes	No
98%	Yes	Yes	No
99%	Yes	Yes	Yes

The practical consequence is that a product containing 99% levoketoconazole would generally satisfy all three purity limitations, while a product containing 92% would satisfy only claim 1's purity limitation. A product below 90% would not satisfy any of the three claims based on the quoted limitations.

The claims do not create a purity safe harbor below 90% if a competing product uses a different claim theory or is covered by another patent. A lower-purity product could still face separate patent issues involving formulation, dosing, manufacturing, or another method of treatment.

What is the patent expiration date for U.S. Patent 10,835,530?

The patent is associated with a March 20, 2015 priority date and has a reported expiration date of March 20, 2035.[1] The relevant term can be affected by patent-term adjustment, patent-term extension, terminal disclaimers, or corrections in the official patent record.

Event	Date or status
Earliest reported priority date	March 20, 2015
U.S. patent grant	2020
Patent number	US 10,835,530
Reported expiration	March 20, 2035
Patent type	Method-of-use
Therapeutic area	Cushing's syndrome
Active ingredient	2S,4R ketoconazole, levoketoconazole

Patent expiration does not automatically establish the earliest lawful generic launch date. FDA regulatory exclusivity, other Orange Book patents, litigation outcomes, settlement terms, and product-specific approval requirements can affect market entry.

What is the Orange Book status of levoketoconazole and Recorlev?

Recorlev is the FDA-approved oral levoketoconazole product for endogenous hypercortisolemia in adults with Cushing's syndrome for whom surgery is not an option or has not been curative.[3] Xeris Pharmaceuticals commercializes Recorlev after acquiring Strongbridge Biopharma.[4]

U.S. Patent 10,835,530 has been identified as an Orange Book-listed patent associated with Recorlev. An Orange Book listing can require an ANDA applicant to make a patent certification under the Hatch-Waxman Act. For a patent that claims an approved method of use, a generic applicant may use a Paragraph IV certification or a section viii statement, depending on the scope of the proposed label and the relationship between the patent claims and the approved indication.[5]

What does a section viii carve-out mean?

A section viii statement allows an ANDA applicant to omit a patented method of use from the proposed label if the generic product can be marketed for a nonpatented use. That route is difficult where the listed patent covers the primary or only approved indication.

Because the claims of U.S. Patent 10,835,530 are directed specifically to treatment of Cushing's syndrome with high-purity 2S,4R ketoconazole, a generic levoketoconazole product seeking the same indication would face a direct method-of-use patent issue. A label carve-out would have to remove the patented Cushing's syndrome use, which would materially reduce the commercial value of the product.

When does Recorlev lose regulatory exclusivity?

Recorlev received FDA approval on December 15, 2021.[3] The product's regulatory exclusivity must be analyzed separately from patent protection.

Exclusivity category	Relevant date or issue
FDA approval	December 15, 2021
New chemical entity exclusivity	Potentially through December 15, 2026, if applicable
Orphan-drug exclusivity	Potentially through December 15, 2028, subject to the approved orphan indication and FDA records
U.S. Patent 10,835,530	Reported expiration March 20, 2035

The five-year new-chemical-entity period and seven-year orphan-drug period are regulatory barriers, not patent rights. Orphan exclusivity generally prevents FDA approval of the same drug for the same disease or condition, subject to statutory exceptions. It does not prevent all competing products, all off-label uses, or all products containing a related active ingredient.[6]

The commercial significance of U.S. Patent 10,835,530 is therefore concentrated after the regulatory exclusivity periods end. The patent may remain an important barrier through 2035 even if FDA regulatory exclusivity expires earlier.

How strong is the patent estate for levoketoconazole?

U.S. Patent 10,835,530 is strong against a competitor that:

uses the 2S,4R enantiomer;
reaches at least 90% enantiomeric content;
seeks to treat Cushing's syndrome;
includes that use in its label or otherwise induces the patented use.

Its principal weaknesses are claim-type limitations. It does not independently protect:

the levoketoconazole molecule as a composition of matter;
every use of levoketoconazole;
treatment of diseases other than Cushing's syndrome;
a specific tablet formulation;
a particular manufacturing or purification process;
a product with less than 90% 2S,4R ketoconazole.

The patent is therefore commercially meaningful but targeted. It is most effective when paired with formulation, dosage, process, or additional method-of-use patents.

Patent-strength assessment

Factor	Assessment
Claim breadth	Moderate; broad across dosage forms but limited to Cushing's syndrome and purity
Chemical scope	Narrow; only the 2S,4R ketoconazole enantiomer at specified concentrations
Formulation protection	None apparent from the quoted claims
Method-of-use protection	Direct and commercially relevant
Design-around potential	Moderate, depending on product composition, indication, and label
Generic litigation risk	High for a same-indication levoketoconazole ANDA
Biosimilar relevance	None; levoketoconazole is a small molecule, not a biologic
Manufacturing barrier	Not established by the quoted claims
Geographic reach	U.S. only

What formulation patents protect Recorlev?

The three quoted claims do not contain formulation limitations. They cover administering a qualifying composition, regardless of whether the composition is a tablet, capsule, suspension, or another dosage form.

A complete Recorlev patent analysis must distinguish this patent from any separate patents directed to:

tablet composition;
excipient selection;
dissolution or bioavailability;
crystalline or polymorphic forms;
salt forms;
particle size;
enantiomeric purification;
manufacturing processes;
dose escalation;
treatment monitoring;
combination therapy.

A formulation patent can create a separate infringement risk even if a competitor avoids U.S. Patent 10,835,530. Conversely, avoiding a formulation patent would not avoid the method-of-use claims if the competing product still contains at least 90% 2S,4R ketoconazole and is labeled for Cushing's syndrome.

What Paragraph IV challenges could affect levoketoconazole?

An ANDA applicant seeking approval for the Cushing's syndrome indication could challenge U.S. Patent 10,835,530 through a Paragraph IV certification. The likely legal theories would include:

Invalidity

Potential invalidity arguments could address anticipation, obviousness, written description, enablement, indefiniteness, or claim construction. The central technical questions would include whether the prior art disclosed or suggested:

use of the 2S,4R enantiomer for Cushing's syndrome;
the claimed 90%, 95%, or 99% purity thresholds;
clinical advantages associated with the selected enantiomer;
treatment of the claimed patient population.

Noninfringement

A challenger could argue that its product or label does not satisfy one or more claim elements. The most direct arguments would involve:

less than 90% 2S,4R content;
absence of a Cushing's syndrome indication;
a label that excludes the patented use;
a product that does not contain the claimed ketoconazole component.

Induced infringement

Even if the generic manufacturer does not directly administer the product to patients, a product label that instructs physicians and patients to use the product for Cushing's syndrome could support an induced-infringement theory. Label language, promotional materials, regulatory submissions, and post-approval conduct would be relevant.

Under Hatch-Waxman, a patent-owner lawsuit filed within 45 days after receiving a Paragraph IV notice can trigger a statutory stay of FDA approval, generally for up to 30 months, subject to court action and statutory exceptions.[5]

Which companies are challenging Recorlev patents?

No specific Paragraph IV challenger, patent settlement, or final infringement judgment is established by the patent claims supplied in the request. Publicly reported commercial activity has centered on Xeris Pharmaceuticals and its Recorlev product, following Strongbridge's development and commercialization work.[4]

A definitive challenger analysis requires review of current ANDA litigation dockets, FDA Paragraph IV notices where available, district-court complaints, PTAB proceedings, and Xeris SEC disclosures. The quoted patent claims alone do not identify a challenger or settlement.

What patent litigation affects levoketoconazole?

The principal litigation risk is a Hatch-Waxman action involving a generic applicant seeking approval for levoketoconazole treatment of Cushing's syndrome. The expected dispute would focus on:

Whether the patent claims are valid.
Whether the proposed label induces the patented use.
Whether the ANDA product contains at least 90% 2S,4R ketoconazole.
Whether other Orange Book patents create independent barriers.
Whether any settlement permits an agreed launch date before March 2035.

A settlement could establish an authorized-generic arrangement, a license, a delayed entry date, or a permitted launch tied to a court ruling. No settlement terms should be inferred from the patent grant or Orange Book listing alone.

Are there biosimilar risks for levoketoconazole?

There is no biosimilar pathway risk because levoketoconazole is a chemically synthesized small molecule. Competition would proceed through the ANDA pathway, not through a biologics license application or biosimilar application under the Public Health Service Act.[5]

The relevant competitors are therefore:

generic levoketoconazole manufacturers;
potential alternative ketoconazole products;
other steroidogenesis inhibitors;
surgery and radiation for appropriate Cushing's syndrome patients;
competing pharmacologic therapies such as osilodrostat, metyrapone, pasireotide, and mifepristone.

These alternatives do not necessarily infringe U.S. Patent 10,835,530 because the patent requires the specified 2S,4R ketoconazole composition.

How does the patent compare with competing Cushing's syndrome therapies?

Product	Active ingredient	FDA pathway	Relationship to US 10,835,530
Recorlev	Levoketoconazole	NDA	Directly aligned with claimed method
Nizoral and generic ketoconazole	Racemic ketoconazole	Older drug products	May not meet the 90% 2S,4R threshold
Isturisa	Osilodrostat	NDA	Different active ingredient; no direct claim overlap
Signifor	Pasireotide	NDA	Different active ingredient
Korlym	Mifepristone	NDA	Different mechanism and active ingredient
Metyrapone products	Metyrapone	Drug product pathway varies by jurisdiction	No direct chemical overlap

The patent gives Recorlev a differentiated position against generic levoketoconazole, while leaving non-ketoconazole steroidogenesis inhibitors outside its chemical scope.

What generic launch scenarios exist?

Launch after patent expiration

The clearest pathway is launch after the reported March 20, 2035 patent expiration, assuming no additional unexpired patents or regulatory barriers block approval.

Launch after a successful Paragraph IV challenge

A generic applicant could launch earlier if a court holds the patent invalid or not infringed, or if the patent owner does not obtain effective preliminary relief.

Launch under a negotiated settlement

A settlement could permit entry before patent expiration on an agreed date. The date and conditions would depend on the settlement and antitrust review.

Label carve-out

A generic might seek approval without the patented Cushing's syndrome use. This route would have limited value if Cushing's syndrome is the principal commercial indication for levoketoconazole.

Does the patent create manufacturing or geographic barriers?

The patent is limited to the United States. Corresponding foreign patent rights must be assessed separately by jurisdiction. The claims do not require a specific manufacturing process, purification step, crystalline form, or facility. They therefore do not independently block manufacture of levoketoconazole for non-U.S. markets or for uses outside the claimed method.

A manufacturer could still face separate process or composition patents in the United States, Europe, Japan, Canada, and other markets. Patent-family continuity and national-stage prosecution should be reviewed independently from the issued U.S. claims.

What licensing deals affect U.S. Patent 10,835,530?

Strongbridge developed levoketoconazole and Recorlev, and Xeris acquired Strongbridge in 2021.[4] That transaction changed the commercial ownership and operating control of the Recorlev business. The acquisition is not, by itself, a license to generic manufacturers.

No specific third-party license or generic settlement can be established from the quoted patent claims. Any license analysis should distinguish assignments within the originator group from arm's-length licenses that permit third-party commercial entry.

Key Takeaways

U.S. Patent 10,835,530 is a method-of-use patent for treating Cushing's syndrome with compositions containing at least 90%, 95%, or 99% of the 2S,4R ketoconazole enantiomer.
The patent does not claim the ketoconazole molecule, a specific tablet, an excipient system, or a manufacturing process.
The claims are nested. A product containing at least 99% 2S,4R ketoconazole would generally satisfy all three purity limitations.
The reported patent expiration date is March 20, 2035.
The patent is commercially relevant to Recorlev, the FDA-approved levoketoconazole product marketed by Xeris.
A same-indication levoketoconazole ANDA would face a material Paragraph IV and induced-infringement risk.
A section viii label carve-out could avoid the patented indication but would limit the commercial value of a generic levoketoconazole product.
There is no biosimilar pathway because levoketoconazole is a small molecule.
The patent leaves non-ketoconazole Cushing's syndrome therapies outside its direct chemical scope.
Formulation, process, dosage, and additional method-of-use patents must be analyzed separately.

FAQs

What does 2S,4R mean in levoketoconazole patent claims?

It identifies the absolute stereochemical configuration of the ketoconazole enantiomer used in levoketoconazole. The patent measures the proportion of that specific enantiomer in the ketoconazole component.

Can a generic manufacturer avoid the patent by using racemic ketoconazole?

Potentially, if the product contains less than 90% of the 2S,4R enantiomer and does not infringe another patent. A racemic product may fall outside these claims, but it may not qualify as an equivalent generic to Recorlev for FDA approval purposes.

Does U.S. Patent 10,835,530 cover off-label use?

The claim language covers administering the qualifying composition to treat Cushing's syndrome. Off-label use can still create infringement exposure where the manufacturer induces the patented use through labeling, promotion, or other conduct.

Can a generic launch before 2035 without invalidating the patent?

Yes, possible routes include a successful Paragraph IV challenge, a settlement license, a court finding of noninfringement, or a label that omits the patented use. Other Orange Book patents could still affect launch timing.

Is levoketoconazole protected by a composition-of-matter patent?

The three claims supplied are method claims, not composition-of-matter claims. They protect the treatment method using specified enantiomeric purity, while separate patents would be required to establish composition, formulation, or manufacturing protection.

References

United States Patent and Trademark Office. (2020). U.S. Patent No. 10,835,530: Methods of treating Cushing's syndrome using a ketoconazole enantiomer.
United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term expiration records.
U.S. Food and Drug Administration. (2021). Recorlev (levoketoconazole) prescribing information.
Xeris Pharmaceuticals, Inc. (2021). Acquisition of Strongbridge Biopharma plc and Recorlev commercialization materials.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
U.S. Food and Drug Administration. (2023). Orphan drug designation and exclusivity provisions.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Strongbridge	RECORLEV	levoketoconazole	TABLET;ORAL	214133-001	Dec 30, 2021		RX	Yes	Yes	10,835,530	⤷ Start Trial				TREATMENT OF ENDOGENOUS HYPERCORTISOLEMIA IN PATIENTS WITH CUSHING’S SYNDROME FOR WHOM SURGERY IS NOT AN OPTION OR HAS NOT BEEN CURATIVE	⤷ 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

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	E528005	⤷ Start Trial
Australia	2006204334	⤷ Start Trial
Canada	2594433	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 10,835,530