US Patent 11,491,137: Atrasentan for IgA Nephropathy Patent Scope and Competitive Landscape

US Patent No. 11,491,137 protects methods of treating biopsy- or biomarker-confirmed IgA nephropathy with atrasentan. The strongest commercial embodiment is a daily atrasentan dose of about 0.75 mg in patients with persistent proteinuria and reduced or preserved renal function within defined eGFR ranges. The patent is a method-of-use patent, not a composition, formulation, manufacturing, or product-by-process patent.

The claims can create a meaningful barrier to an atrasentan generic used for IgA nephropathy, but they do not block every use of atrasentan. Infringement generally requires practice of the claimed IgA nephropathy treatment method, including the specified diagnosis and, for dependent claims, dose, salt form, proteinuria, or eGFR limitations.

What does US Patent 11,491,137 protect?

The independent claim protects:

Administration of atrasentan or a pharmaceutically acceptable salt.
To a subject previously diagnosed with IgA nephropathy.
For improving kidney function.
Where the diagnosis includes at least one of:
- Kidney biopsy;
- Detection of anti-glycan antibodies;
- Detection of IgA immune-complex deposition in the kidney; or
- A combination of those diagnostic approaches.

The patent does not require a particular formulation, tablet design, dosing frequency, duration of therapy, background standard of care, or renal endpoint in claim 1.

Claim group	Principal limitation	Commercial significance
Claim 1	Atrasentan for improving kidney function in diagnosed IgA nephropathy	Broadest enforceable treatment concept
Claims 2-5	Dose narrowed to 0.20-1.5 mg, ultimately about 0.75 mg	Covers likely clinical dose selection
Claims 6-10	Free base, hydrochloride, or mandelate salt	Extends protection across chemical forms
Claims 11-14	Persistent proteinuria, generally at least 0.5 g/day for three months	Targets higher-risk IgA nephropathy patients
Claims 15-17	Average eGFR of 20-90, 30-90, or 20-60 mL/min/1.73 m²	Covers clinically relevant renal-function populations
Claims 18-24	Proteinuria plus dose and salt/free-base limitations	Layered protection around the likely pivotal-trial population
Claims 25-30	eGFR plus dose and salt limitations	Alternative renal-function limitation set

How broad are the independent and dependent claims?

Claim 1 is broad in dose and product presentation but narrow in disease context. It does not specify:

A minimum proteinuria level;
An eGFR threshold;
A 0.75 mg dose;
A salt form;
A particular route of administration;
A treatment duration;
A requirement that the patient be receiving an ACE inhibitor, ARB, SGLT2 inhibitor, or other background therapy.

The disease-diagnosis limitation is central. A patient must have been previously diagnosed with IgA nephropathy, and the claim identifies biopsy, anti-glycan antibody detection, or IgA immune-complex deposition as diagnostic routes.

The dependent claims create multiple fallback positions. If a court limits claim 1 based on prior art or written-description arguments, claims directed to 0.75 mg, persistent proteinuria, and defined eGFR ranges may remain commercially important.

What dose is most directly protected?

The most commercially relevant dose is about 0.75 mg of atrasentan. Claims 5 and 21 expressly recite that dose. The broader nested ranges are:

Claim	Dose range
Claims 2 and 18	About 0.20-1.5 mg
Claims 3 and 19	About 0.25-1.25 mg
Claims 4 and 20	About 0.40-0.85 mg
Claims 5 and 21	About 0.75 mg

The use of "about" introduces claim-construction questions concerning acceptable manufacturing, dosing, and measurement variation. A generic product labeled at a nominal dose other than 0.75 mg could still implicate broader range claims if the administered amount falls within those ranges.

What patient populations are covered?

The patent covers several overlapping IgA nephropathy populations.

Proteinuria-defined population

Claims 11-14 require average urinary protein excretion before treatment for at least approximately three months. The ranges include:

At least about 0.5 g/day;
About 0.3-2.0 g/day;
About 0.5-1.5 g/day;
About 0.75-1.5 g/day.

These limitations align the patent with patients who have persistent proteinuria, a major risk marker for IgA nephropathy progression and a common enrollment criterion in renal clinical trials.

eGFR-defined population

Claims 15-17 cover patients with average eGFR values over at least approximately three months of:

About 20-90 mL/min/1.73 m²;
About 30-90 mL/min/1.73 m²;
About 20-60 mL/min/1.73 m².

The claims therefore reach both moderate chronic kidney disease and patients with relatively preserved kidney function. They do not cover every IgA nephropathy patient because subjects outside the stated eGFR ranges may fall outside the narrower claims, although claim 1 has no eGFR limitation.

What formulations and salt forms are protected?

US 11,491,137 does not claim a specific tablet, capsule, excipient system, release profile, particle size, coating, or fixed-dose combination.

It covers the active ingredient as:

Atrasentan free base;
Atrasentan hydrochloride;
Atrasentan mandelate;
Other pharmaceutically acceptable salts under the broader claims.

Claims 7-9 specifically identify hydrochloride and mandelate forms. Claim 8 is directed to atrasentan hydrochloride, while claim 9 is directed to atrasentan mandelate. Claim 10 covers the free base.

This structure gives the patent chemical-form coverage but does not establish that a particular commercial tablet formulation is protected by this patent. Separate formulation or solid-state patents would be required to block non-infringing use of the active ingredient based on tablet architecture or manufacturing characteristics.

When does US Patent 11,491,137 lose exclusivity?

The patent issued on November 8, 2022. Its base patent term should run approximately 20 years from the earliest effective nonprovisional or international filing date under 35 U.S.C. §154. Based on the patent family’s reported priority framework, the expected base term is in the 2037 period, subject to:

Patent-term adjustment;
Any terminal disclaimer;
Patent-term extension;
Post-grant modification;
Continuation or divisional family rights.

The grant date does not determine expiration. The controlling date is the USPTO patent-term record for the specific patent and its priority chain. No conclusion that the patent expires in 2042 should be drawn merely from its November 2022 issuance.

Exclusivity timeline

Event	Date or status
Patent grant	November 8, 2022
Patent type	Method of medical treatment
Expected base term	Approximately 2037, subject to USPTO term calculations
FDA approval-linked exclusivity	None established by the patent itself
Orange Book status	No Orange Book listing identified for atrasentan as an FDA-approved product
Generic approval pathway	Not available without an approved reference-listed drug
Biosimilar pathway	Not applicable because atrasentan is a small molecule

What is the Orange Book status of atrasentan?

Atrasentan is not an FDA-approved commercial drug as of the cited public regulatory record. The FDA Orange Book lists approved drug products and patent information submitted for those products. Without an approved atrasentan reference-listed drug, US 11,491,137 is not functioning as an Orange Book-listed patent for an approved product.

That distinction matters. The absence of an Orange Book listing means:

No standard ANDA applicant can make a conventional Paragraph IV certification against this patent as an Orange Book-listed patent;
A generic applicant cannot rely on an ANDA until an approved reference product and applicable regulatory pathway exist;
The patent remains potentially enforceable against commercial conduct that practices the claimed method;
Patent litigation risk may arise through a declaratory judgment action, a competing approval strategy, or later Orange Book listing after FDA approval.

The regulatory position can change if atrasentan receives FDA approval and the sponsor submits the patent for listing.

Are Paragraph IV challenges available?

A Paragraph IV challenge is not currently the principal risk mechanism for this patent because it depends on an approved reference-listed drug and an Orange Book-listed patent. If atrasentan is later approved and US 11,491,137 is listed, an ANDA applicant could potentially challenge it by asserting that:

The claims are invalid;
The claims are unenforceable;
The proposed generic product will not infringe;
The listed patent is not properly listable.

A method-of-use patent may be addressed through a label that omits the patented indication, subject to the scope of the approved labeling, induced-infringement principles, and the Hatch-Waxman skinny-label framework. A label that expressly promotes atrasentan for IgA nephropathy would present a materially stronger infringement case than a label limited to an unrelated indication.

What patent litigation affects atrasentan?

No major public US infringement action involving US 11,491,137 is established in the information provided. The principal future litigation scenarios are:

A sponsor sues an ANDA applicant after a Paragraph IV notice.
A generic seeks a declaratory judgment before approval.
A competing sponsor challenges validity or enforceability after regulatory filing.
The patent owner asserts induced infringement based on an IgA nephropathy label, promotional materials, payer submissions, or treatment protocols.
A later entrant challenges written description, enablement, obviousness, anticipation, or claim construction.

The most likely validity pressure points are the pre-existing use of endothelin receptor antagonists in renal disease, prior clinical investigation of atrasentan, obviousness of dose selection, and whether the specification adequately supports the full diagnostic, proteinuria, eGFR, salt, and dose combinations.

How strong is the patent estate?

US 11,491,137 has moderate-to-strong commercial value as a clinical-use patent if the approved product label tracks the claimed population and dose. Its strengths are:

Direct coverage of IgA nephropathy;
Coverage of the likely 0.75 mg dose;
Alternative proteinuria and eGFR limitations;
Coverage of free base and specified salts;
Multiple dependent-claim fallback positions.

Its limitations are:

No composition or formulation claims in the supplied claims;
No manufacturing claim;
No exclusive protection for atrasentan in all renal diseases;
Potential design-around through an unclaimed indication or dosing regimen;
Reliance on proof that the accused conduct satisfies the diagnosis and treatment limitations;
Exposure to obviousness arguments based on prior renal-disease use of atrasentan or related endothelin antagonists.

The estate is stronger against an identical IgA nephropathy label than against an off-label or disease-specific label that omits the patented indication.

How does this patent compare with generic and biosimilar risk?

Atrasentan is a small molecule, so biosimilar risk is not relevant. The relevant competitive threat is a generic or another small-molecule endothelin receptor antagonist.

Risk category	Relevance
Biosimilar substitution	None
Traditional generic substitution	High after approval and loss of enforceable barriers
Skinny-label generic	Potentially material if IgA nephropathy is omitted
Alternative endothelin antagonist	Commercial substitution risk, but not direct infringement of this patent solely from using another molecule
Formulation workaround	Feasible in principle because the supplied claims do not require a particular formulation
Dose workaround	Potentially feasible outside the claimed ranges, subject to claim 1 and clinical efficacy
Salt-form workaround	Limited because the broad claims include free base and pharmaceutically acceptable salts

What licensing and commercial issues matter?

Atrasentan development rights have been associated with Chinook Therapeutics, which Novartis acquired in 2023. Novartis has advanced atrasentan development in IgA nephropathy, including the ALIGN program. The patent’s commercial value therefore depends on whether atrasentan receives approval, the approved label, and the extent to which the label overlaps the claimed dose and patient populations.

No product revenue can be attributed to atrasentan under an FDA-approved IgA nephropathy indication before approval. Revenue exposure is prospective rather than current. If approved, the patent could protect the primary indication through the late 2030s, but other patents, regulatory exclusivity, clinical differentiation, and payer restrictions will determine the practical launch barrier.

What generic launch scenarios exist?

Scenario 1: No approval before patent expiry

The patent creates no immediate generic launch pathway because an ANDA cannot substitute for an unapproved reference product. Commercial entry would require approval of atrasentan or a different regulatory route.

Scenario 2: Approval with the IgA nephropathy indication

A generic applicant would face the strongest risk if its labeling includes:

IgA nephropathy;
Atrasentan around 0.75 mg;
Patients with persistent proteinuria;
Patients within the claimed eGFR ranges.

This scenario is most likely to produce a Paragraph IV dispute if the patent is listed.

Scenario 3: Approval with a narrow non-infringing label

A generic could attempt to omit IgA nephropathy or exclude the claimed patient population. The commercial value of that strategy depends on whether the omitted indication drives most prescribing and whether physicians, payers, or distributors encourage use for the patented indication.

Scenario 4: Patent invalidation or non-infringement ruling

A successful challenge could remove the principal use-of-treatment barrier while leaving any separate formulation, manufacturing, or regulatory exclusivity intact.

Key Takeaways

US 11,491,137 is a method-of-use patent for atrasentan treatment of diagnosed IgA nephropathy.
Claim 1 is broad in dose and formulation but requires the IgA nephropathy diagnosis and kidney-function improvement objective.
The most commercially important dependent claim is the approximately 0.75 mg regimen.
The patent separately targets patients with persistent proteinuria and defined eGFR ranges.
The patent covers free base, hydrochloride, mandelate, and broader pharmaceutically acceptable salt embodiments.
It does not, based on the supplied claims, protect a specific tablet formulation or manufacturing process.
Atrasentan is a small molecule, so biosimilar competition does not apply.
No current Orange Book or Paragraph IV framework is established for an FDA-approved atrasentan product.
The expected base patent term is in the 2037 period, subject to the USPTO’s final patent-term calculation.
The estate is strongest against a generic label expressly approved or promoted for IgA nephropathy at the claimed dose.
Commercial exposure is prospective and depends on FDA approval, label scope, and the outcome of any later patent challenge.

FAQs

Can a generic sell atrasentan for another kidney disease before this patent expires?

Potentially. The supplied claims are limited to IgA nephropathy and do not cover every renal indication. Liability would depend on the approved label, promotional conduct, and whether the treatment practice satisfies the claim limitations.

Does administering atrasentan hydrochloride automatically infringe the patent?

No. The salt form alone is insufficient. The patient must also have the claimed IgA nephropathy diagnosis, and the treatment must satisfy the relevant dose, proteinuria, eGFR, and other limitations of the asserted claim.

Is a 0.75 mg atrasentan tablet protected by a formulation patent?

Not by the supplied claims. The claims protect administration of approximately 0.75 mg in specified disease settings. A separate formulation patent would be required to protect tablet composition or release characteristics.

Can an applicant avoid the patent by using atrasentan mandelate instead of hydrochloride?

Not necessarily. Claims 7 and 9 expressly cover atrasentan mandelate, while broader claims cover pharmaceutically acceptable salts. Switching salt forms is unlikely to avoid every claim.

Does US Patent 11,491,137 protect treatment of all IgA nephropathy patients?

No. Claim 1 is broad within the disease indication, but the dependent claims require particular dose, proteinuria, eGFR, or salt limitations. Patients outside those limitations may still fall within claim 1, but not necessarily within the narrower claims.

References

Novartis AG. (2023). Novartis completes acquisition of Chinook Therapeutics.
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2023). Purple Book: Database of licensed biological products.
U.S. Patent and Trademark Office. (2022). U.S. Patent No. 11,491,137: Methods of treating IgA nephropathy with atrasentan.
ClinicalTrials.gov. (2024). ALIGN: A study of atrasentan in patients with IgA nephropathy. NCT04573478.
35 U.S.C. §154. Patent term.
21 U.S.C. §355. New drug applications and abbreviated applications.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Novartis	VANRAFIA	atrasentan hydrochloride	TABLET;ORAL	219208-001	Apr 2, 2025		RX	Yes	Yes	11,491,137	⤷ Start Trial				TREATMENT OF PRIMARY IMMUNOGLOBULIN A NEPHROPATHY (IGAN)	⤷ 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	2020404984	⤷ Start Trial
Brazil	112022012075	⤷ Start Trial
Canada	3161516	⤷ Start Trial
China	113272013	⤷ Start Trial
China	116173014	⤷ Start Trial
China	116327758	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,491,137

Which drugs does patent 11,491,137 protect, and when does it expire?

Summary for Patent: 11,491,137