US Patent 10,561,659: Scope, Claims, Expiration, and Deuruxolitinib Patent Landscape

US Patent No. 10,561,659 protects specific dosing regimens and pharmaceutical compositions of deuruxolitinib, also known as CTP-543, for treating hair-loss disorders, particularly alopecia areata. The patent is directed to deuterium-enriched ruxolitinib analogs administered at clinically relevant daily doses. Its principal commercial relevance is Leqselvi, Sun Pharmaceutical Industries’ oral treatment for severe alopecia areata.

The patent does not broadly claim every use of a JAK inhibitor in alopecia areata. Its enforceable scope depends on four technical elements: the claimed deuterated compound, minimum deuterium incorporation, specified dose, and treatment or composition context.

What drug does US Patent 10,561,659 protect?

The patent protects deuruxolitinib, a deuterated analog of ruxolitinib.

Deuruxolitinib is a selective Janus kinase inhibitor developed by Concert Pharmaceuticals under the code CTP-543. Deuterium atoms replace specified hydrogen atoms in the ruxolitinib structure. The claims require at least 95% deuterium incorporation at each expressly designated deuterium position, with dependent claims requiring at least 97% incorporation.

The relevant product is:

Item	Description
Active ingredient	Deuruxolitinib
Development code	CTP-543
Brand	Leqselvi
Sponsor at development	Concert Pharmaceuticals
Current commercial owner	Sun Pharmaceutical Industries
Therapeutic area	Severe alopecia areata
Dosage form	Oral tablet
FDA pathway	NDA approval
FDA approval date	July 25, 2024
Principal approved strength	8 mg and 12 mg tablets
Recommended regimen	8 mg twice daily; increase to 12 mg twice daily based on response

The structural formula is essential to the claim analysis. In the supplied claim text, the formula is omitted and replaced by a placeholder. The patent number and claim language identify the compound as the CTP-543/deuruxolitinib program, but the precise substitution pattern must be read from the issued patent drawings and specification.

What are the main claim categories in US Patent 10,561,659?

The claims divide into method-of-treatment claims and pharmaceutical-composition claims.

Method-of-treatment claims

Claim 1 is the principal independent claim. It covers:

Treating a hair-loss disorder;
In a mammalian subject;
By administering 16 mg/day or 24 mg/day;
Of the specified deuterated compound or a pharmaceutically acceptable salt;
With at least 95% deuterium incorporation at every designated position.

The claim is broad as to the hair-loss disorder. It is not limited to alopecia areata. Claim 2 narrows the disorder to alopecia areata.

Claims 9 and 11 separately protect twice-daily regimens:

Claim	Free-compound dose	Frequency	Disease limitation
1	16 mg/day or 24 mg/day	Not limited in independent claim	Any hair-loss disorder
9	8 mg	Twice daily	Any hair-loss disorder
11	12 mg	Twice daily	Any hair-loss disorder
14	8 mg or 12 mg	Twice daily	Any hair-loss disorder

Claims 3, 4, 5, and 6 add oral administration, tablet formulation, once-daily administration, and twice-daily administration. Claims 15, 18, and 21 add alopecia areata, human subjects, or both.

Pharmaceutical-composition claims

Claim 8 covers a composition containing:

A pharmaceutically acceptable carrier or diluent;
8 mg or 12 mg of the specified deuterated compound or salt;
At least 95% deuterium incorporation at each designated position.

This claim is commercially important because it reaches the drug product itself, not only the act of prescribing or administering the drug.

Isotope-purity limitations

Claims 7, 13, 17, and 20 address isotope composition. The claims distinguish the specifically labeled deuterium atoms from all other atoms in the molecule:

Designated positions must contain at least 95% deuterium under the base claims.
Certain dependent claims raise the threshold to at least 97%.
Non-designated atoms may remain at natural isotopic abundance.

These limitations create a product-identification issue. A generic or follow-on product would need to establish the isotopic composition of its active ingredient through analytical testing. A product with the same substitution pattern but lower deuterium incorporation may fall outside the literal claim, although it could raise infringement issues under the doctrine of equivalents depending on the circumstances.

How do the claimed doses correspond to Leqselvi tablets?

The patent claims both free-compound equivalent doses and phosphate-salt quantities.

Claimed active-compound amount	Claimed phosphate-salt amount	Administration
8 mg	10.5 mg	Twice daily
12 mg	15.8 mg	Twice daily
16 mg/day	Equivalent daily exposure	Once or twice daily depending on dependent claim
24 mg/day	Equivalent daily exposure	Once or twice daily depending on dependent claim

Claims 10 and 12 specify that 8 mg and 12 mg of Compound (I), respectively, correspond to 10.5 mg and 15.8 mg of the phosphate salt administered twice daily.

The salt conversion is significant. A generic manufacturer could not necessarily avoid infringement by labeling the product according to the mass of the phosphate salt rather than the mass of the active moiety. Claims 10 and 12 expressly address that distinction.

What is the scope of the independent claims?

Claim 1: broad treatment claim

Claim 1 covers a relatively broad therapeutic field because “hair loss disorder” is not limited to alopecia areata. Potentially relevant disorders include alopecia areata and other disorders involving hair loss, subject to the compound, dose, and isotope limitations.

The claim is narrower in its dosing requirement. A regimen outside 16 mg/day or 24 mg/day is not literally covered by claim 1, although claims 9, 11, and 14 separately capture 8 mg twice daily and 12 mg twice daily.

Claim 8: composition claim

Claim 8 is directed to a pharmaceutical composition containing 8 mg or 12 mg of the deuterated compound. It does not require a particular disease indication or administration frequency. Its scope can therefore reach a tablet manufactured for treatment of alopecia areata even before administration occurs.

The claim requires a carrier or diluent. A pure active pharmaceutical ingredient, absent a carrier or diluent, would not satisfy the composition claim as written.

Claims 9 and 11: regimen-specific claims

Claims 9 and 11 are commercially aligned with the approved Leqselvi regimen. They require twice-daily administration of 8 mg or 12 mg, respectively.

These claims are more defensible against a product-specific generic challenge than claim 1 if the approved label and proposed generic labeling contain the same twice-daily doses. Their scope is narrower, but the overlap with the commercial label is direct.

What patent expiration date applies to US 10,561,659?

The patent family is associated with a June 2015 priority date. The ordinary United States patent term is therefore expected to extend into June 2035, subject to the patent’s recorded term adjustment, terminal-disclaimer status, and the official USPTO calculation.

Milestone	Date or period
Earliest reported priority	June 2015
Patent issue	February 18, 2020
Expected nominal expiration	Approximately June 2035
FDA approval of Leqselvi	July 25, 2024
Patent term extension	No extension should be assumed without an FDA or USPTO record confirming it

The relevant commercial question is not only the nominal expiration date. Orange Book listing status, patent-term adjustment, patent-term extension, and any later-issued continuation patents can affect generic-entry timing.

What is the FDA and Orange Book status of Leqselvi?

The FDA approved Leqselvi for adults with severe alopecia areata on July 25, 2024. The approved dosage is 8 mg orally twice daily, with an increase to 12 mg twice daily for patients with inadequate response after an appropriate treatment period. The product is supplied as oral tablets. [1]

US Patent 10,561,659 is part of the CTP-543/deuruxolitinib patent estate and is commercially relevant to Orange Book protection for Leqselvi. Orange Book analysis should distinguish:

Patents listed against the approved drug product;
Patents covering the active ingredient;
Method-of-use patents;
Formulation or dosage-form patents;
Continuations with later issue dates but the same underlying priority;
FDA-recognized pediatric exclusivity or other regulatory exclusivity.

The patent itself is not an FDA exclusivity period. Patent protection and regulatory exclusivity operate independently.

Regulatory exclusivity

Leqselvi’s regulatory protection depends on the FDA classification of deuruxolitinib and the statutory exclusivity awarded with the NDA. Because deuruxolitinib is a deuterated analog of ruxolitinib, the relevant regulatory analysis includes whether FDA treated it as a new active moiety or as a product relying in part on previously approved information.

A five-year new-chemical-entity period, if awarded, would block submission of a standard ANDA for the applicable period, subject to statutory exceptions. A three-year exclusivity period would protect the specific clinical investigations supporting approval but would not necessarily block all ANDA submissions. The FDA’s Orange Book and approval records control this issue. [1, 2]

Which patents cover the wider deuruxolitinib patent estate?

US 10,561,659 should be analyzed as one member of a broader patent family rather than as an isolated asset.

The estate is expected to include claims directed to:

The deuterated active ingredient;
Pharmaceutical compositions;
Specific dose ranges;
Twice-daily and once-daily administration;
Treatment of alopecia areata;
Other hair-loss disorders;
Salt forms;
Deuterium incorporation levels;
Follow-on formulations and therapeutic uses.

Concert Pharmaceuticals developed CTP-543 through a series of patent filings directed to deuterated ruxolitinib compounds and their use in alopecia areata. Sun acquired Concert and its CTP-543 rights in 2023. [3]

Later-issued continuation patents can have substantial practical value even where they share the same priority date. A continuation may issue with different claim language and can preserve a separate litigation position after one patent is narrowed or invalidated.

What generic entry risks exist for deuruxolitinib?

A generic applicant would face several potential infringement paths.

Dose and label overlap

A proposed generic label that includes 8 mg twice daily or 12 mg twice daily would directly overlap claims 9 and 11. A label covering 16 mg/day or 24 mg/day could overlap claim 1.

Under the Hatch-Waxman framework, a generic applicant could file a Paragraph IV certification against listed patents. The applicant would argue that the patent is invalid, unenforceable, or not infringed. The patent owner could then bring an infringement action within 45 days, triggering a statutory stay of FDA approval for up to 30 months, subject to statutory qualifications. [4]

Composition overlap

A product containing the claimed deuterated compound at 8 mg or 12 mg with a carrier or diluent could implicate claim 8 even if the generic applicant disputes the method claims.

Isotopic purity

A product with the same deuterium substitution pattern and at least 95% incorporation would present a strong literal-infringement risk. A product below the claimed threshold could attempt design-around protection, but the result would depend on whether the product retains the claimed molecular identity and whether the patent owner asserts equivalents.

Salt-form exposure

Claims 10 and 12 reduce the value of a salt-based design-around. A generic product using the phosphate salt at 10.5 mg or 15.8 mg twice daily would fall within the expressly recited embodiments if the other claim limitations are satisfied.

How strong is the patent estate?

The patent has meaningful commercial strength because its core regimen claims align with the approved product.

Strength factor	Assessment
Product alignment	High; claims 8 mg and 12 mg twice daily
Disease alignment	High for alopecia areata through dependent claims
Formulation coverage	Moderate to high; composition and tablet claims
Isotope limitation	Strong product-identification barrier, but creates purity-based design-around questions
Broad disease coverage	Moderate; claim 1 covers hair-loss disorders beyond alopecia areata
Generic label vulnerability	High if the proposed label copies the approved dosing regimen
Validity risk	Includes ordinary written-description, enablement, anticipation, obviousness, and double-patenting issues
Continuation support	Material; later family members may preserve additional claim scope

The central validity issue is obviousness. A challenger could argue that deuterating ruxolitinib and testing it for alopecia areata would have been obvious based on prior art concerning ruxolitinib, deuterated analogs, JAK inhibition, and hair-growth disorders. The patent owner would rely on the specific substitution pattern, pharmacokinetic properties, clinical dose selection, deuterium purity, and treatment results.

The strength of the claims also depends on whether the specification supports the full breadth of “hair loss disorder” and the full dose range. The alopecia areata claims and commercially tested doses generally present a stronger written-description and enablement posture than an unrestricted claim covering every mammalian hair-loss disorder.

Have companies filed Paragraph IV challenges or started litigation?

The supplied information does not identify a Paragraph IV notice, ANDA litigation complaint, settlement, or license involving US 10,561,659.

No litigation conclusion should be inferred merely from the patent’s inclusion in the Leqselvi estate. A complete Hatch-Waxman assessment requires reviewing:

FDA Orange Book listings;
Paragraph IV notices;
Federal district court complaints;
Delaware and New Jersey docket activity;
Court orders addressing the 30-month stay;
Patent-term adjustments;
Any confidential or public settlement terms.

As a business matter, the most likely initial challenge would target the dose and composition claims because they map directly onto the approved product. A generic applicant could combine invalidity arguments with a non-infringement position based on isotopic purity, salt identity, labeling, or a proposed dosage limitation.

What licensing and ownership transactions affect the patent?

Concert Pharmaceuticals was the original developer and patent owner for CTP-543. Sun Pharmaceutical Industries agreed to acquire Concert in 2023 for approximately $576 million in cash, plus contingent value rights reported in transaction materials. The acquisition transferred Concert’s CTP-543 program and associated intellectual property to Sun. [3]

The transaction changed the enforcement and commercialization profile of the patent estate. Sun controls both Leqselvi commercialization and the underlying CTP-543 patent portfolio, reducing the separation between licensee and patent owner that often exists in pharmaceutical transactions.

How does US 10,561,659 compare with competing alopecia areata patents?

The closest competitive patent estates involve other JAK inhibitors, particularly baricitinib and ritlecitinib.

Product	Active ingredient	Manufacturer	Approved indication	Main patent-risk distinction
Leqselvi	Deuruxolitinib	Sun Pharma	Severe alopecia areata in adults	Deuterated molecule, dose, composition, and method claims
Olumiant	Baricitinib	Eli Lilly	Severe alopecia areata in adults	Conventional small-molecule JAK inhibitor estate
Litfulo	Ritlecitinib	Pfizer	Severe alopecia areata in patients 12 and older	JAK3/TEC-family inhibitor with separate composition and method patents

Leqselvi’s patent differentiation is the deuterated ruxolitinib structure and its defined isotopic purity. Olumiant and Litfulo do not practice the CTP-543 structure and do not create literal infringement risk under US 10,561,659.

The competitive threat is commercial rather than direct patent overlap. Prescribers may switch among approved oral JAK inhibitors based on age eligibility, efficacy, safety warnings, payer access, and dosing.

What revenue exposure is tied to US 10,561,659?

US 10,561,659 protects dosing and composition features that correspond closely to Leqselvi’s commercial product. Its economic exposure therefore tracks the US market for severe alopecia areata rather than the full JAK-inhibitor market.

Leqselvi launched after its July 2024 approval. Public company reporting should be used to measure quarterly sales, launch trajectory, payer coverage, and management forecasts. The patent’s practical value is highest during the period before generic or authorized-generic competition can enter with the approved dosing regimen.

Key Takeaways

US Patent 10,561,659 protects deuterium-enriched deuruxolitinib, or CTP-543, for hair-loss disorders.
The strongest commercial claims cover 8 mg twice daily and 12 mg twice daily.
Claim 8 is a composition claim covering 8 mg or 12 mg with a pharmaceutical carrier or diluent.
Claims 10 and 12 expressly address phosphate-salt quantities of 10.5 mg and 15.8 mg twice daily.
The patent requires at least 95% deuterium incorporation at designated positions, with dependent claims reaching 97%.
The patent has an expected nominal expiration around June 2035, subject to the official patent-term record.
Leqselvi was FDA-approved on July 25, 2024, for severe alopecia areata in adults.
Sun Pharma acquired Concert Pharmaceuticals and the CTP-543 patent estate in 2023.
A generic label copying the approved 8 mg or 12 mg twice-daily regimen would face direct exposure to the method claims.
The principal legal issues are obviousness, written description, enablement, isotope purity, salt-form coverage, and the scope of any continuation patents.

FAQs About US Patent 10,561,659 and Leqselvi

Does US Patent 10,561,659 cover ruxolitinib?

No. The claims are directed to a specified deuterated compound, not ordinary ruxolitinib. A product containing non-deuterated ruxolitinib would not literally satisfy the claimed Compound (I) limitation.

Does the patent cover alopecia areata treatment only?

No. Claim 1 and several related claims refer broadly to a hair-loss disorder in a mammalian subject. Separate dependent claims narrow the disorder to alopecia areata.

Can a generic avoid the patent by using a different tablet strength?

Changing tablet strength alone may not avoid infringement. The relevant questions include the total administered dose, dosing frequency, salt form, isotopic substitution pattern, and deuterium incorporation.

Does a 12 mg tablet necessarily equal 12 mg of free deuruxolitinib?

No. The patent distinguishes active-compound amounts from phosphate-salt amounts. Claim 12 recites 15.8 mg of the phosphate salt as the twice-daily amount corresponding to 12 mg of Compound (I).

Are biosimilars relevant to Leqselvi?

No. Leqselvi is a chemically synthesized small molecule, not a biologic. The relevant competitors are ANDA generics or, depending on the regulatory pathway, other small-molecule applicants. Biosimilar approval procedures do not apply.

References

U.S. Food and Drug Administration. (2024). Leqselvi (deuruxolitinib) prescribing information and approval materials. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
Sun Pharmaceutical Industries Limited. (2023). Sun Pharma completes acquisition of Concert Pharmaceuticals. Company transaction announcement.
U.S. Food and Drug Administration. (n.d.). Hatch-Waxman Amendments and abbreviated new drug applications. FDA.
United States Patent and Trademark Office. (2020). U.S. Patent No. 10,561,659, Deuterated compounds for the treatment of hair loss disorders. USPTO.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Sun Pharm Inds Inc	LEQSELVI	deuruxolitinib phosphate	TABLET;ORAL	217900-001	Jul 25, 2024		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				TREATMENT OF ADULT PATIENTS WITH ALOPECIA AREATA	⤷ 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
Australia	2017261286	⤷ Start Trial
Australia	2023201112	⤷ Start Trial
Australia	2025213576	⤷ Start Trial
Brazil	112018072339	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 10,561,659

Which drugs does patent 10,561,659 protect, and when does it expire?

Summary for Patent: 10,561,659