United States Patent 11,603,356: Avacopan Amorphous-Form Claims, Patent Scope and Generic Entry Risk

U.S. Patent No. 11,603,356 protects an amorphous solid form of avacopan, the active ingredient in Tavneos, together with selected analytical characteristics, manufacturing processes, pharmaceutical compositions, aqueous suspensions, injectable preparations, and therapeutic uses. The patent was assigned to ChemoCentryx, now part of Amgen, and has an expected patent-term expiration in April 2038, subject to any adjustment or extension recorded by the USPTO.

The strongest commercial claims are claims 1, 2, 18, and 22. They target the amorphous active pharmaceutical ingredient and oral formulations using that form. Claims 16 and 17 cover spray-drying and solvent-removal processes. Claims 21 and 37-43 provide method-of-use coverage for C5a receptor-mediated diseases, including ANCA-associated vasculitis, granulomatosis with polyangiitis, microscopic polyangiitis, C3 glomerulopathy, and hidradenitis suppurativa.

What drug does U.S. Patent 11,603,356 protect?

Compound 1 is avacopan, also known as CCX168. Avacopan is an orally administered selective C5a receptor antagonist. The FDA approved Tavneos on October 7, 2021, for adults with active antineutrophil cytoplasmic autoantibody-associated vasculitis, specifically granulomatosis with polyangiitis and microscopic polyangiitis, in combination with standard therapy [2].

Item	Data
Patent	U.S. 11,603,356
Patent subject	Amorphous avacopan and related compositions and processes
Original developer	ChemoCentryx, Inc.
Current commercial owner	Amgen Inc., following its acquisition of ChemoCentryx
Product	Tavneos
Active ingredient	Avacopan
FDA dosage form	10 mg oral capsule
FDA approval date	October 7, 2021
Primary approved use	ANCA-associated vasculitis
Patent family priority	April 13, 2017, based on the disclosed family record
Expected nominal expiration	April 13, 2038
Regulatory pathway	505(b)(1) new drug application
Biosimilar pathway	Not applicable

The patent does not protect the basic avacopan molecule in the abstract. Its central subject is a particular physical form of avacopan and products made with that form.

What are the main claim categories in U.S. Patent 11,603,356?

The 43 claims divide into five practical groups.

Claim group	Claims	Subject matter	Commercial relevance
Amorphous API	1-15	Amorphous avacopan defined by XRPD, DSC, TGA, DVS, SEM, and PLM properties	High
Manufacturing processes	16-17	Spray drying or solvent removal from a polar aprotic solution	High for process replication
Pharmaceutical products	18-20	Pharmaceutical compositions, aqueous suspensions, injectable or infusible solutions	Medium to high
Broad treatment method	21	Treatment of C5a receptor-mediated disease	Medium
Oral compositions and uses	22-43	Oral formulations containing the amorphous form and specified disease indications	High for generic capsules

Claims 22-36 largely replicate the analytical limitations in claims 1-15, but place them in the context of an oral pharmaceutical composition. Claims 37-43 link those compositions to particular diseases.

How broad is claim 1 for amorphous avacopan?

Claim 1 is the principal product claim. It covers:

An amorphous form of Compound 1.
An XRPD pattern having no distinct peaks.
A material substantially free of other forms of Compound 1.

The claim does not require a particular solvent, drying method, particle size, excipient, dosage strength, or disease indication. A manufacturer could therefore infringe claim 1 by producing or selling substantially pure amorphous avacopan even if it used a process different from the disclosed spray-drying procedure.

The term "amorphous" distinguishes the claimed material from crystalline polymorphs and solvates. The requirement that the XRPD pattern have "no distinct peaks" is intended to identify a noncrystalline solid. The phrase "substantially free of other forms" narrows the claim by requiring a predominantly amorphous product rather than a mixture containing meaningful crystalline material.

The principal validity and enforcement questions would concern:

Whether the accused material is truly amorphous.
Whether any crystalline phase is present above the relevant detection threshold.
Whether the XRPD pattern contains distinct peaks.
Whether the accused product is substantially free of other avacopan forms.
Whether the claim terms provide sufficient analytical boundaries under 35 U.S.C. §112.

Because amorphous solids can partially crystallize during storage, manufacture, milling, granulation, or formulation, the product’s physical state at the relevant point of manufacture or sale would be material to infringement analysis.

What analytical properties are protected by the dependent claims?

Claims 2-15 add identity and quality controls. They do not create unrelated inventions. They narrow claim 1 by specifying additional characteristics.

Claims	Analytical limitation	Scope implication
2	XRPD substantially according to Figure 2	Fingerprint-based amorphous-form limitation
3-4	Glass transition temperature of about 108°C or DSC profile of Figure 4	Thermal identity and stability limitation
5-6	Approximately 0.015% TGA weight loss to about 235°C or Figure 5 profile	Low-solvent or low-moisture characterization
7-10	DVS weight gain and no hysteresis, including Figure 6	Hygroscopicity and moisture-uptake limitations
11-13	Predominantly spherical particles, generally 2-50 micrometers, or Figures 8A-8D	Particle morphology and size
14-15	Lack of birefringence or PLM profiles in Figures 9A-9C	Optical confirmation of noncrystallinity

These claims provide fallback positions if claim 1 is challenged. A generic manufacturer may avoid a dependent claim by producing an amorphous form with different particle morphology or different moisture behavior, but that does not necessarily avoid claim 1.

The claims also create evidentiary complexity. XRPD, DSC, TGA, DVS, SEM, and PLM measurements are method-sensitive. Results can vary with sample preparation, instrument configuration, heating rate, humidity equilibration, particle aggregation, and storage history. The figures may be more useful as reference fingerprints than as absolute numerical boundaries.

What manufacturing processes are covered?

What does claim 16 cover?

Claim 16 requires:

Dissolving avacopan in a polar aprotic solvent.
Spray drying the resulting solution.
Producing the claimed amorphous form.

The claim is directed to a process that generates the amorphous product through rapid solvent removal. Polar aprotic solvents can include solvents such as acetone, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, acetonitrile, or related solvents, depending on the specification’s definitions and examples.

A process using a different solvent class, such as a protic solvent, may avoid the literal solvent limitation. It could still infringe the product claims if the resulting material is the claimed amorphous avacopan.

What does claim 17 cover?

Claim 17 covers a broader solvent-processing route:

Dissolving avacopan in a polar aprotic solvent.
Using a concentration of no more than 0.3 g/mL.
Optionally filtering the solution.
Removing solvent from the solution or filtrate.

Unlike claim 16, claim 17 does not require spray drying. Solvent removal may occur through evaporation, precipitation-related processing, vacuum drying, or another disclosed technique, depending on the specification and claim construction.

The concentration ceiling is a meaningful limitation. A process using a concentration above 0.3 g/mL could avoid literal infringement of claim 17, although the resulting solid could still fall within claims 1-15 or 18-43.

What formulations are protected?

Claim 18 covers a pharmaceutical composition containing the amorphous form and at least one pharmaceutically acceptable excipient. This is broad enough to cover oral solid dosage forms, including capsules and potentially tablets, powders, granules, or other oral preparations.

Claim 19 covers an aqueous suspension containing the amorphous form and an excipient. The claim could be relevant to liquid formulations, extemporaneous preparations, or alternative dosage forms.

Claim 20 covers an injectable or infusible solution containing Compound 1 and at least one wetting agent or solvent, where the solution is prepared using the amorphous form. This is a preparation-source limitation. The final solution may no longer contain the original solid-state form, creating potential proof issues.

Claims 22-36 are particularly important for oral generic products. They require an oral composition prepared using amorphous avacopan characterized by the same physical attributes recited in claim 1 and its dependent claims.

A generic capsule that uses crystalline avacopan would have a stronger noninfringement position against the formulation claims, but it could face separate patents covering the avacopan molecule, compositions, dosage regimens, or approved uses.

What therapeutic uses are covered?

Claim 21 broadly covers administering the amorphous form to treat a disease involving pathological activation of C5a receptors.

Claims 37-43 narrow that protection to oral pharmaceutical compositions and named diseases:

ANCA-associated vasculitis.
Granulomatosis with polyangiitis.
Microscopic polyangiitis.
C3 glomerulopathy.
Hidradenitis suppurativa.

Claim 38 also lists rheumatoid arthritis, systemic lupus erythematosus, lupus nephritis, IgA nephropathy, Crohn’s disease, psoriasis, multiple sclerosis, asthma, pemphigus, pemphigoid, scleroderma, myasthenia gravis, transplant rejection, and other immune-mediated conditions.

The treatment claims are narrower in practical scope than a claim covering avacopan itself. Their commercial value is highest where the approved product is prescribed for a listed indication and the generic label includes that indication. A generic applicant may seek a skinny label that omits patented uses, but regulatory labeling, prescribing behavior, promotional conduct, and induced-infringement issues would remain relevant under 35 U.S.C. §271(b).

What is the Orange Book status of U.S. Patent 11,603,356?

U.S. Patent 11,603,356 is associated with the Tavneos patent estate and is relevant to Hatch-Waxman generic-entry analysis. The FDA Orange Book identifies patents submitted by the NDA holder or patent owner for an approved drug. Orange Book listing does not determine validity or infringement; it triggers statutory notice and regulatory consequences for an abbreviated new drug application.

The patent appears directed to a drug substance form and formulation rather than only a method of treatment. That distinction matters because product and formulation patents generally create greater generic-entry exposure than use patents that can be omitted from a label.

The relevant regulatory outcomes are:

Generic strategy	Risk under Patent 11,603,356
Use amorphous avacopan	High risk under claims 1 and 18
Use the same spray-drying process	High risk under claim 16
Use a polar aprotic solvent at or below 0.3 g/mL	High risk under claim 17
Use crystalline avacopan	Lower risk under this patent, subject to other patents
Use a different amorphous form	Potentially lower risk, but analytical comparison is required
File a Paragraph IV certification	Likely route for an invalidity or noninfringement challenge
Omit patented indication only	May not avoid product-form or composition claims

A Paragraph IV certification would assert that the patent is invalid, unenforceable, or will not be infringed by the proposed generic. If the NDA holder files a timely infringement action, FDA approval may be stayed for up to 30 months under 21 U.S.C. §355(j)(5)(B)(iii), subject to statutory exceptions.

When does avacopan lose exclusivity?

Tavneos received FDA approval in 2021. The product’s regulatory exclusivity and patent exclusivity are separate.

Exclusivity type	General position
New chemical entity exclusivity	Five years from approval, subject to Paragraph IV timing rules
Orphan-drug exclusivity	Depends on the approved indication and orphan designation
Patent term	Nominally through April 2038 for the relevant patent family
Generic approval before patent expiry	Possible after successful patent challenge, settlement, license, or statutory certification outcome
Biosimilar exclusivity	Not applicable because avacopan is a small molecule

The effective generic-entry date cannot be determined solely from the patent expiration date. It may be affected by pediatric exclusivity, patent-term adjustment, patent-term extension, litigation stays, settlement agreements, authorized generic arrangements, or other listed patents in the Tavneos estate.

How strong is the patent estate?

Patent 11,603,356 has meaningful commercial strength because its independent product claim is not limited to a particular indication or dosage form. A manufacturer that uses the patented amorphous API may face infringement exposure before formulation or labeling is considered.

Its principal weaknesses are technical and claim-construction related:

Amorphous materials can be difficult to define with precise boundaries.
"No distinct peaks" may depend on XRPD sensitivity and measurement conditions.
"Substantially free" may require a disputed quantitative threshold.
Figure-based claims can create reproducibility and claim-construction disputes.
Product-by-process distinctions may limit process claims if the same product can be made by another route.
The disclosed analytical values may support anticipation or obviousness arguments if similar amorphous forms were known.
The process claims are narrower than the product claims and can be designed around.

The estate is stronger as a barrier to use of the same amorphous avacopan form than as a barrier to every possible avacopan formulation.

Which companies are challenging avacopan patents?

The supplied claims and the cited FDA materials do not establish a named Paragraph IV challenger, infringement complaint, or settlement agreement involving U.S. Patent 11,603,356. FDA approval records and Orange Book listings identify regulatory status but do not provide a complete litigation history.

No biosimilar challenge is expected because Tavneos contains a chemically synthesized small-molecule active ingredient. The relevant competitive threat is an ANDA applicant seeking approval for generic avacopan, potentially using a different solid form or a certification challenging the listed patents.

How does this patent compare with competing C5a therapies?

Avacopan is a selective C5a receptor antagonist. Other complement products generally act at different points in the pathway.

Product or class	Target	Modality	Relevance to Patent 11,603,356
Avacopan/Tavneos	C5a receptor	Small molecule, oral	Directly covered
C5 inhibitors such as eculizumab or ravulizumab	C5	Monoclonal antibody	No direct product overlap
C5a antibodies	C5a ligand	Biologic	Different target and patent estate
Other oral complement inhibitors	Varies	Small molecule	Potential clinical competition but no automatic patent overlap

The patent does not prevent development of a different C5a receptor antagonist, a C5a ligand inhibitor, or a C5 inhibitor. It does create a barrier to commercializing the protected amorphous avacopan form.

What generic launch scenarios exist?

Scenario 1: Same amorphous form

A generic manufacturer reproduces the amorphous form and uses a similar oral formulation. This presents the highest infringement risk under claims 1, 18, and 22.

Scenario 2: Different amorphous form

A manufacturer develops a separate amorphous form with different XRPD, DSC, DVS, or particle characteristics. The design-around position depends on whether claim 1 is interpreted broadly enough to cover all substantially pure amorphous avacopan.

Scenario 3: Crystalline form

A crystalline avacopan product may avoid the central amorphous-form claims. It would still require review against other patents covering avacopan, compositions, polymorphs, manufacturing methods, and approved uses.

Scenario 4: Skinny-label launch

A generic applicant omits patented indications. This may reduce method-of-use exposure but does not avoid claims directed to the active form or pharmaceutical composition.

Scenario 5: Paragraph IV litigation

The applicant challenges validity, enforceability, or infringement. The likely technical issues include amorphous-form enablement, obviousness, anticipation, indefiniteness, and whether the proposed product meets the analytical limitations.

Key Takeaways

U.S. Patent 11,603,356 is a solid-state and formulation patent for amorphous avacopan.
Claim 1 is the central product claim and does not depend on a specific manufacturing process.
Claims 16 and 17 cover spray drying and solvent-removal processes using polar aprotic solvents.
Claims 18 and 22 are the main formulation barriers for an oral generic capsule.
Claims 21 and 37-43 provide use coverage for C5a-mediated diseases, including ANCA-associated vasculitis.
The nominal expiration date is April 2038, subject to USPTO term adjustment or extension.
A biosimilar pathway is irrelevant; the competitive pathway is an ANDA.
The strongest generic design-around is a crystalline or demonstrably different amorphous form, but other Tavneos patents must also be cleared.
The claims supplied do not establish a specific Paragraph IV litigation or settlement involving this patent.

FAQs

Is U.S. Patent 11,603,356 a composition-of-matter patent?

It is a solid-state composition patent covering amorphous avacopan. It is not the foundational patent for the avacopan molecular structure.

Does the patent cover all amorphous avacopan?

Claim 1 is drafted broadly enough to create substantial risk for substantially pure amorphous avacopan. The ultimate scope depends on construction of "no distinct peaks," "amorphous," and "substantially free."

Can a generic manufacturer use crystalline avacopan?

Potentially, but crystalline avacopan must be evaluated against other patents in the Tavneos estate. Avoiding this patent alone does not establish freedom to operate.

Does spray drying automatically infringe the patent?

No. Spray drying infringes claim 16 only if the process uses the required polar aprotic solvent and produces the claimed amorphous form. The resulting product may independently infringe claim 1.

Is Tavneos eligible for a biosimilar challenge?

No. Avacopan is a small-molecule drug. The relevant regulatory route for a competing product is an ANDA, not a biologics license application or biosimilar application.

References

United States Patent and Trademark Office. (2023). U.S. Patent No. 11,603,356: Amorphous forms of C5a receptor antagonists. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2021). Tavneos (avacopan) prescribing information. FDA.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, 44th ed.: Orange Book. FDA.
U.S. Food and Drug Administration. (2021). FDA approves first oral treatment for patients with certain types of vasculitis. FDA.
United States Code, Title 35, §§102, 103, 112, 271, and 282.
United States Code, Title 21, §355.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Chemocentryx	TAVNEOS	avacopan	CAPSULE;ORAL	214487-001	Oct 7, 2021		RX	Yes	Yes	11,603,356	⤷ Start Trial	Y	Y		AN ADJUNCTIVE TREATMENT OF ADULT PATIENTS WITH TAVNEOS (AVACOPAN) WITH SEVERE ACTIVE ANCA-ASSOCIATED VASCULITIS (GPA AND MPA) IN COMBINATION WITH STANDARD THERAPY INCLUDING GLUCOCORTICOIDS	⤷ 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	2020378397	⤷ Start Trial
Brazil	112022007489	⤷ Start Trial
Canada	3155542	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,603,356

Which drugs does patent 11,603,356 protect, and when does it expire?

Summary for Patent: 11,603,356