US Patent 11,712,459: Rezafungin Dosing Claims, Scope, Expiration, and Patent Landscape

US Patent No. 11,712,459 protects weekly intravenous dosing of CD101, the active pharmaceutical ingredient later developed as rezafungin acetate and marketed as Rezzayo. The patent claims two regimens for invasive candidiasis: 400 mg followed by 200 mg weekly, or 400 mg weekly. Both regimens require intravenous administration in an aqueous composition over 30 to 180 minutes. The claims also cover candidemia and permit a day-15 dose when cure or mycological eradication has not occurred.

The patent is commercially important because the 400-mg loading dose followed by 200-mg weekly dosing corresponds to the approved Rezzayo regimen for adult patients with candidemia and invasive candidiasis. The most material generic risk is therefore a Paragraph IV challenge directed to the dosing method, rather than a conventional small-molecule composition challenge.

What does US Patent 11,712,459 protect?

The patent claims a treatment method with tightly defined dose, timing, route, formulation, and infusion-duration limitations.

Claim element	Scope
Active ingredient	CD101, in salt or neutral form
Disease	Invasive candidiasis
Route	Intravenous administration
Formulation	Aqueous pharmaceutical composition
Infusion duration	30 to 180 minutes
Initial dose	400 mg on day 1
Second dose, regimen 1	200 mg on day 8
Second dose, regimen 2	400 mg on day 8
Optional third dose	200 mg or 400 mg on day 15, depending on regimen
Salt limitation	Dependent claim 3 specifies CD101 acetate
Disease limitation	Dependent claim 4 specifies candidemia

The independent claim is drafted in two alternatives:

A 400-mg dose on day 1 followed by 200 mg on day 8, with an optional 200-mg dose on day 15.
A 400-mg dose on day 1 followed by 400 mg on day 8, with an optional 400-mg dose on day 15.

The claim uses the closed transition "consists of." That language narrows the claimed treatment protocol to the listed administration steps. It does not ordinarily exclude conventional excipients, diluents, catheter materials, or routine medical care, but it creates a potential dispute over whether an additional antifungal or other therapeutic intervention falls outside the claimed method.

How does the patent map onto Rezzayo dosing?

Rezzayo is rezafungin for injection, a once-weekly echinocandin antifungal developed from CD101. The FDA-approved regimen for adults with candidemia and invasive candidiasis is a 400-mg loading dose on day 1 followed by 200 mg once weekly. The FDA prescribing information specifies intravenous infusion over approximately one hour, which falls within the patent's 30-to-180-minute limitation.[2]

Rezzayo label feature	Claim 1 alternative
400 mg on day 1	Required
200 mg on day 8	Required
Weekly administration	Required by day-8 timing
Intravenous route	Required
Aqueous formulation	Required
Infusion over approximately 1 hour	Within 30-to-180-minute range
Invasive candidiasis	Required
Candidemia	Covered by claim 4

The approved regimen appears to fall directly within claim 1(i). Claim 3 strengthens the commercial relevance by expressly covering CD101 acetate, the salt form associated with rezafungin acetate. Claim 4 separately captures the principal approved disease population of candidemia.

The 400-mg weekly alternative in claim 1(ii) is broader in dose exposure but less directly aligned with the standard labeled maintenance regimen. It may become relevant if a sponsor studies or markets a higher maintenance dose.

What are the individual claim scopes?

Claim 1: Core weekly dosing method

Claim 1 is the central commercial claim. It requires all of the following:

treatment of invasive candidiasis;
intravenous dosing;
CD101 in salt or neutral form;
an aqueous pharmaceutical composition;
administration over 30 to 180 minutes;
one of the two specified dose sequences; and
day-1, day-8, and optional day-15 timing.

The claim does not require that the patient have candidemia. Invasive candidiasis includes candidemia and other deep-seated Candida infections, subject to the ordinary clinical and regulatory meaning of the disease.

The use of "comprising" is absent from the method's principal transition. Because the claim says the method "consists of" the listed steps, infringement analysis may turn on whether a defendant's protocol includes additional therapeutic steps that materially alter the claimed regimen.

Claim 2: Conditional third dose

Claim 2 narrows claim 1 by requiring that the optional third dose be administered when:

mycological eradication has not been achieved;
clinical cure has not been achieved; or
the subject displays symptoms of a fungal infection on day 15.

This claim is directed to treatment continuation or rescue dosing. The disjunctive "and/or" creates multiple paths to infringement. A day-15 dose may satisfy the claim if any specified clinical condition is present, although the meaning of "displays symptoms of a fungal infection" could be litigated if the patient has equivocal or nonspecific symptoms.

Claim 3: CD101 acetate

Claim 3 limits the CD101 salt to CD101 acetate. This is the most product-specific dependent claim because rezafungin is administered as the acetate salt.

A generic or follow-on manufacturer using a different CD101 salt could avoid literal infringement of claim 3, but it could remain exposed under claim 1 if the alternative salt is otherwise covered. The neutral form is also expressly included in claim 1.

Claim 4: Candidemia

Claim 4 narrows invasive candidiasis to candidemia. This claim is commercially significant because candidemia is the principal approved treatment population for Rezzayo. A product used only for non-bloodstream invasive candidiasis may avoid claim 4 while remaining within claim 1.

When does US Patent 11,712,459 expire?

The patent's term is expected to be governed by the earliest effective nonprovisional filing or priority date, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and any statutory corrections. Public patent records identify a priority framework associated with the CD101 development program and an expected nominal expiration in the mid-2030s.

For practical market analysis, the key distinction is:

Exclusivity category	Relevance
Patent exclusivity	Potentially extends into approximately 2035, subject to the official term calculation
New chemical entity exclusivity	FDA exclusivity for five years from approval, subject to applicable exceptions
Orphan-drug exclusivity	Seven years for the qualifying orphan indication, if applicable
Qualified Infectious Disease Product exclusivity	Five-year extension to certain FDA exclusivity periods, if awarded
Pediatric exclusivity	Six additional months if granted after completion of an FDA pediatric requirement

The exact enforceable patent end date must be taken from the USPTO patent record and any FDA Orange Book listing. Patent-term adjustment can move the expiration date beyond the basic term. A patent-term extension under 35 U.S.C. § 156 would require a qualifying regulatory review period and an approved application for extension.[3]

What is the Orange Book status of US Patent 11,712,459?

The relevant FDA regulatory question is whether US 11,712,459 is listed in the Orange Book for the rezafungin product approved under NDA 214367. Orange Book listing determines whether an ANDA applicant must address the patent through a Paragraph IV certification or may defer approval until the listed patent expires.

A listed method-of-use patent can be particularly important where:

the patent claims the approved disease;
the approved label contains the claimed regimen; and
the applicant seeks approval for the same use.

If the patent is listed with a use code covering candidemia or invasive candidiasis, a generic applicant may use a section viii statement to carve out the patented indication only if the remaining label can be lawfully marketed without encouraging the patented use. A complete label carve-out may be difficult where the protected dosing regimen is the principal or only approved regimen.

The FDA Orange Book, rather than the patent document alone, controls the regulatory listing status. Patent listing and enforceability are separate issues. An Orange Book-listed patent may still be challenged for invalidity, noninfringement, improper listing, or unenforceability.

When does Rezzayo lose regulatory exclusivity?

Rezzayo received FDA approval in 2023 for adult patients with candidemia and invasive candidiasis.[2] The relevant regulatory protections can overlap:

five-year new chemical entity exclusivity, unless an earlier Paragraph IV filing is permitted under the statute;
seven-year orphan-drug exclusivity for a qualifying orphan indication;
a possible five-year QIDP extension, if the product received that designation and the extension applies to the relevant exclusivity period; and
possible pediatric exclusivity.

Regulatory exclusivity does not prevent all clinical development or off-label use. It primarily affects FDA approval of competing applications. Patent protection can continue after regulatory exclusivity expires.

The first commercially realistic generic entry date will be the later of:

the end of applicable FDA exclusivity;
the effective date of a successful Paragraph IV challenge or settlement license;
patent expiration;
expiration of any patent-term extension; or
a court-authorized launch date.

What Paragraph IV challenges could target the patent?

A generic applicant seeking approval for an injectable rezafungin product could challenge the patent through a Paragraph IV certification. Likely theories would include:

Anticipation

The challenger would search earlier CD101 or echinocandin references for the precise combination of:

400 mg on day 1;
200 mg on day 8;
optional day-15 dosing;
intravenous aqueous administration; and
infusion over 30 to 180 minutes.

A reference that discloses only weekly echinocandin therapy, without the claimed dose sequence or infusion duration, may not anticipate the full claim.

Obviousness

Obviousness is the more substantial potential challenge. The challenger could combine:

prior clinical or preclinical CD101 dosing data;
known echinocandin weekly pharmacokinetics;
conventional intravenous infusion practice; and
treatment-duration guidance for invasive candidiasis.

The patent holder would likely argue that the particular loading and maintenance doses, weekly interval, infusion window, and day-15 decision rule produced an unexpected clinical or pharmacokinetic result.

Written description and enablement

The claims cover CD101 in salt or neutral form, two dose schedules, optional third dosing, and a broad 30-to-180-minute infusion period. A challenger could argue that the specification does not adequately support the full breadth of those alternatives or enable every salt and every infusion duration without undue experimentation.

The risk is higher for the broad neutral-form language if the clinical development program primarily used CD101 acetate.

Indefiniteness

Potential disputes could concern:

"mycological eradication";
"clinical cure";
"displays symptoms of a fungal infection";
the relationship between "optional" day-15 dosing and claim 2; and
the scope of "consists of" in a clinical treatment method.

These terms have clinical context, which may reduce indefiniteness risk, but their application to individual patients could be contested.

How strong is the patent estate?

US 11,712,459 has strong product-label relevance because claim 1 tracks the approved weekly regimen. Its commercial strength is greater than its breadth. The patent does not broadly claim all uses of rezafungin, all echinocandin compositions, or all treatment of Candida infections.

Strength factor	Assessment
Alignment with approved regimen	High
Coverage of candidemia	High through claim 4
Coverage of rezafungin acetate	High through claim 3
Coverage of alternative salts	Moderate to high under claim 1
Breadth across diseases	Limited to invasive candidiasis
Breadth across administration routes	Limited to intravenous use
Breadth across formulations	Limited to aqueous compositions
Vulnerability to dosing prior art	Material
Vulnerability to obviousness arguments	Material
Design-around potential	Moderate

The patent is strongest against a generic that copies the approved product, label, weekly schedule, and infusion process. It is weaker against a competitor using a different dose schedule, different route, nonaqueous formulation, different clinical indication, or a materially different infusion protocol.

What formulation and manufacturing barriers remain?

Claim 1 requires an aqueous pharmaceutical composition but does not claim a particular excipient system, pH, container, lyophilization process, reconstitution method, or impurity profile. A competitor may therefore avoid this patent through a different formulation while remaining subject to other composition, formulation, process, or solid-state patents.

For an injectable echinocandin, practical barriers may include:

control of degradation products;
solubility and concentration management;
sterile manufacturing;
lyophilization and reconstitution;
particulate and container-closure controls;
impurity specifications;
salt formation;
analytical methods; and
comparability of the finished injectable product.

These barriers can delay generic entry even when the dosing patent is invalidated or avoided. They do not, by themselves, establish infringement of US 11,712,459.

Which companies are likely to challenge the patent?

The most likely challengers are manufacturers with sterile injectable capacity and experience in antifungal products. A conventional oral generic company is less likely to be an immediate competitor because rezafungin is an intravenous product requiring complex manufacturing and FDA approval of an injectable dosage form.

A Paragraph IV challenger would face several commercial constraints:

limited market size relative to major hospital anti-infectives;
costly sterile manufacturing;
clinical and pharmacokinetic bridging requirements;
possible Orange Book patent litigation;
limited ability to omit the approved candidemia indication;
potential exposure to multiple patents in the broader rezafungin estate; and
the risk that a court preserves the approved weekly regimen patent.

No specific company can be identified as a confirmed challenger from the supplied patent and claim information alone.

What generic launch scenarios exist?

Scenario 1: At-risk launch after Paragraph IV challenge

A generic applicant could launch before patent expiration after sending a Paragraph IV notice and prevailing in litigation, obtaining dismissal, or accepting the risk of damages and injunction.

Scenario 2: Label carve-out

The applicant could remove patented uses from the proposed label. This strategy is difficult if the remaining label still instructs the claimed 400-mg loading and 200-mg weekly maintenance regimen for invasive candidiasis.

Scenario 3: Noninfringing dosing regimen

A competitor could pursue a different dosing schedule, dose amount, infusion duration, or formulation. This approach would require clinical support and would not necessarily obtain approval for the same indication.

Scenario 4: Settlement with delayed entry

A settlement could provide an agreed entry date before patent expiry, subject to antitrust scrutiny and FDA approval mechanics. The commercial value of the settlement would depend on the remaining patent term, regulatory exclusivity, manufacturing readiness, and the number of potential entrants.

What patent litigation affects US 11,712,459?

The claim set alone does not establish a pending district-court action, ANDA litigation, settlement, or Federal Circuit decision involving US 11,712,459. A litigation search must distinguish between:

cases naming the patent;
cases involving related CD101 or rezafungin patents;
declaratory-judgment actions;
FDA Orange Book disputes;
patent-owner enforcement actions; and
administrative proceedings before the Patent Trial and Appeal Board.

The absence of a litigation event in the supplied materials should not be treated as a determination that no action exists.

How does US 11,712,459 compare with broader rezafungin protection?

US 11,712,459 is a regimen patent. It should be analyzed alongside, rather than substituted for, potential patents covering:

the rezafungin chemical entity;
CD101 salts;
compositions for intravenous delivery;
lyophilized formulations;
preparation and purification processes;
crystalline or solid-state forms;
methods for treating specific fungal infections;
prophylaxis;
combination therapy; and
dosage regimens other than those claimed here.

The focal patent has high label relevance but a narrower technical perimeter than a composition-of-matter patent. If the basic compound patent has expired or is absent, this dosing patent may still delay a directly substitutable generic, but its enforceability will depend heavily on the strength of dose-selection prior art and the availability of a credible label or clinical design-around.

Key Takeaways

US 11,712,459 is directed to weekly intravenous CD101 dosing for invasive candidiasis.
Claim 1 covers 400 mg on day 1 followed by either 200 mg or 400 mg on day 8, with an optional day-15 dose.
The approved Rezzayo regimen appears to fall within claim 1(i).
Claim 3 specifically covers CD101 acetate, the salt associated with rezafungin acetate.
Claim 4 specifically covers candidemia.
The 30-to-180-minute infusion limitation is broad enough to include the approximately one-hour infusion described in the FDA labeling.
The main invalidity risks are obviousness, anticipation based on earlier CD101 dosing data, written description, and enablement.
The main design-around options are a different regimen, route, formulation, indication, or infusion duration.
Patent expiration, Orange Book listing, FDA exclusivity, and any litigation outcome must be analyzed separately.
The patent is commercially strong against a copycat product using the approved weekly regimen but is not a broad monopoly over all rezafungin products or all antifungal treatment.

Frequently Asked Questions

Does US 11,712,459 cover all rezafungin products?

No. It covers specified intravenous treatment regimens for invasive candidiasis. A product using a different dose schedule, route, formulation, or indication may fall outside the claims.

Does claim 4 cover all candidemia treatments?

No. Claim 4 covers candidemia only when all limitations of claim 1 are also met, including the CD101 dose sequence, intravenous route, aqueous composition, and infusion duration.

Can a generic avoid the patent by using rezafungin acetate over a 20-minute infusion?

Potentially, if the product and approved labeling genuinely require an infusion shorter than 30 minutes. The commercial and regulatory feasibility of that design would require separate analysis.

Does a third dose automatically infringe claim 2?

No. Claim 2 requires the claim 1 regimen and a day-15 third dose administered under the specified clinical conditions, such as failure to achieve mycological eradication or clinical cure.

Is a Paragraph IV certification enough to permit generic launch?

No. A Paragraph IV certification can trigger patent litigation and a statutory approval stay. Launch timing depends on litigation, settlement, court orders, FDA exclusivity, patent-term calculations, and any applicable injunction.

Sources

United States Patent and Trademark Office. (2023). U.S. Patent No. 11,712,459, methods of treating fungal infections.
U.S. Food and Drug Administration. (2023). Rezzayo (rezafungin for injection) prescribing information.
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. (2017). Guidance for industry: Regulatory exclusivity extensions and qualified infectious disease products.
35 U.S.C. §§ 156, 271(e), 282.
21 U.S.C. §§ 355(j), 360cc.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Mundipharma	REZZAYO	rezafungin acetate	POWDER;INTRAVENOUS	217417-001	Mar 22, 2023		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y			TREATMENT OF CANDIDEMIA AND INVASIVE CANDIDIASIS WITH REZAFUNGIN BY INTRAVENOUS ADMINISTRATION	⤷ 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
Canada	3017485	⤷ Start Trial
China	109154603	⤷ Start Trial
European Patent Office	3430400	⤷ Start Trial
European Patent Office	4268896	⤷ Start Trial
Spain	2955711	⤷ Start Trial
Japan	2019511496	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,712,459

Which drugs does patent 11,712,459 protect, and when does it expire?

Summary for Patent: 11,712,459