US Patent 11,278,537: Migalastat Patent Scope, Claims, Expiration and Generic-Entry Risk

US Patent 11,278,537 protects a narrow method of using migalastat in Fabry disease patients with renal impairment. The core claim requires all of the following: a Fabry patient, eGFR below 60, a HEK-assay-amenable α-galactosidase A mutation, once-every-other-day dosing of approximately 100 to 150 mg migalastat free-base equivalent, increased WBC α-galactosidase A activity, and an annualized eGFR decline better than -1.0 mL/min/1.73 m².

The patent is commercially relevant because it targets patients with moderate or severe renal impairment, including populations for which the current US Galafold label does not recommend treatment when eGFR is below 30 mL/min/1.73 m². It is a method-of-use patent, not a basic compound patent. Its value therefore depends on the enforceability of the clinical-outcome limitations, the breadth of the mutation and renal-function definitions, FDA labeling, and whether a generic applicant seeks approval for the patented use.

What does US Patent 11,278,537 cover?

US 11,278,537 covers renal-function stabilization using migalastat in genetically selected Fabry patients. Claim 1 is the controlling independent claim.

Core elements of claim 1

Claim element	Scope
Disease	Fabry disease
Patient population	Patient with moderate or severe renal impairment
Renal threshold	eGFR less than 60 mL/min/1.73 m²
Genotype	HEK-assay-amenable α-galactosidase A mutation
Drug	Migalastat
Dose	About 100 mg to about 150 mg FBE
Frequency	Once every other day
Pharmacodynamic result	Increased mean WBC α-galactosidase A activity
Clinical result	Mean annualized eGFRCKD-EPI decline greater than -1.0 mL/min/1.73 m²

The claim is cumulative. A competing product or treatment protocol must satisfy every limitation to fall within the literal scope of claim 1. Failure to meet the renal threshold, mutation requirement, dosing schedule, or claimed eGFR outcome may avoid literal infringement, although the doctrine of equivalents could remain relevant in litigation.

Dependent claims and commercial subpopulations

Claims 2 through 5 divide the renal population into clinically recognizable groups:

Claim 2: eGFR of 30 to 59.
Claim 3: eGFR of 35 to 59.
Claim 4: eGFR below 30.
Claim 5: eGFR of 15 to 29.

Claims 6 through 8 stratify patients by baseline proteinuria:

Less than 100 mg/24 hours.
100 to 1,000 mg/24 hours.
More than 1,000 mg/24 hours.

Claims 9 and 10 cover solid and oral dosage forms. Claims 11 through 13 impose treatment-duration limitations of at least 28 days, six months, and 12 months. Claims 14 through 16 define the commercial dose and salt form:

Approximately 123 mg migalastat FBE.
Approximately 123 mg migalastat free base.
Approximately 150 mg migalastat hydrochloride.

Claim 20 covers ERT-naïve patients, creating a separate protection layer for treatment initiation rather than switching from enzyme replacement therapy.

How broad is the HEK-assay-amenable mutation limitation?

The mutation limitation is technically important and materially narrows the patent.

Claim 18 defines an amenable mutation using HEK-293 cells exposed to 10 μM migalastat. The mutation must produce both:

A relative increase of at least 20% in α-galactosidase A activity; and
An absolute increase of at least 3% of wild-type α-galactosidase A activity.

Both thresholds must be met. A mutation satisfying only the relative increase or only the absolute increase would not meet the express language of claim 18.

The claim does not identify a closed list of mutations. Its functional drafting may cover mutations that satisfy the assay criteria even if they were not specifically named in the specification, subject to written-description, enablement and definiteness constraints. A generic or biosimilar-style competitor would face greater freedom if its labeling excluded amenable mutations or did not direct physicians to use migalastat in the claimed population.

Claim construction issues

The principal claim-construction issues are likely to include:

Whether “about 100 mg to about 150 mg” includes doses outside the numerical range.
Whether 150 mg migalastat hydrochloride is equivalent to approximately 123 mg FBE.
The meaning of “increase” in mean WBC α-galactosidase A activity.
Whether the eGFR outcome is a required prospective treatment result or a limitation satisfied by the patient population and treatment regimen.
The statistical meaning of “mean annualized rate of change.”
The assay conditions required to establish amenability.
Whether “moderate or severe renal impairment” adds an independent limitation beyond eGFR below 60.

Claim 17 appears to contain a typographical or transcription issue in the supplied text: “about 1.4 4 MU/hr/mg.” The intended value may be approximately 1.44 MU/hr/mg, but the issued patent should control. The exact printed claim language matters in any infringement analysis.

What renal populations are protected?

The patent reaches both moderate and severe renal impairment, but the dependent claims create different risk profiles.

Population	Relevant claims	Commercial significance
eGFR 30-59	1, 2, 3, 17	Most aligned with conventional moderate renal impairment
eGFR 35-59	3, 17	Narrower subgroup with potentially stronger factual support
eGFR below 30	1, 4	Severe impairment population
eGFR 15-29	5	Advanced renal impairment
Proteinuria below 100 mg/24 hours	6	Lower renal disease burden
Proteinuria 100-1,000 mg/24 hours	7	Intermediate proteinuria
Proteinuria above 1,000 mg/24 hours	8	High-risk renal population
ERT-naïve	20	Treatment initiation
Oral solid dose	9, 10	Matches commercial Galafold administration

Claims 2 and 3 overlap. A patient with eGFR of 35 to 59 satisfies both claims. Claims 4 and 5 also overlap because eGFR of 15 to 29 is a subset of eGFR below 30.

What is the FDA status of migalastat and Galafold?

The FDA approved Galafold, containing migalastat hydrochloride, for adults with Fabry disease who have an amenable mutation in the α-galactosidase A gene. Galafold is administered orally at 123 mg every other day, equivalent to 150 mg migalastat hydrochloride. The product is a small-molecule drug, not a biologic, and generic competition would proceed through the abbreviated new drug application, or ANDA, pathway rather than the biosimilar pathway (FDA, 2018).

The US prescribing information states that no dosage adjustment is required for patients with eGFR of 30 mL/min/1.73 m² or greater. It does not recommend Galafold for patients with eGFR below 30 mL/min/1.73 m² because that population was not adequately studied for labeling purposes (FDA, 2023).

That creates a distinction between the patent scope and the approved label:

Issue	Patent position	FDA-label position
eGFR 30-59	Expressly covered	Within the labeled renal range
eGFR below 30	Expressly covered	Not recommended
Once-every-other-day dosing	Required	Commercial dosing regimen
HEK-amenable mutation	Required	Required for treatment
150 mg hydrochloride	Expressly covered	Commercial strength
123 mg FBE	Expressly covered	Commercial dose equivalent

The patent therefore covers a use that extends beyond the currently recommended US labeling for severe renal impairment. That may reduce automatic infringement risk from a conventional ANDA label while preserving risk for physician-directed or induced use in severe renal disease.

When does US Patent 11,278,537 lose exclusivity?

US Patent 11,278,537 issued to Amicus Therapeutics, Inc. in 2022. The patent’s enforceable expiration depends on the earliest effective nonprovisional filing date in its priority chain, patent-term adjustment, terminal disclaimers, and any patent-term extension. A patent expiration date should be taken from the USPTO continuity record and the patent’s term calculation rather than inferred from the grant date.

The patent is a later clinical-use patent. It does not restore or reset the term of earlier migalastat compound, formulation or manufacturing patents. Even if 11,278,537 remains in force after earlier patents expire, it protects only the claimed renal-impairment method.

Exclusivity timeline

Event	Regulatory or patent effect
Galafold FDA approval	Established US marketing authorization
Orphan-drug designation	Provided seven years of orphan exclusivity from approval, subject to statutory exceptions
Issuance of US 11,278,537	Added renal-impairment method protection
Patent expiration	Depends on priority chain and USPTO term calculation
ANDA approval	May be blocked or delayed by listed patents and regulatory exclusivity
Generic launch	Depends on Paragraph IV litigation, settlement terms and approved labeling

Orphan-drug exclusivity is separate from patent protection. It does not prevent an ANDA applicant from submitting an application, but it can prevent FDA approval for the same orphan indication during the exclusivity period. The seven-year orphan period for the original Galafold approval is distinct from the patent term and does not extend the term of US 11,278,537 (21 U.S.C. § 360cc).

What is the Orange Book status of US 11,278,537?

Method-of-use patents can be listed in the FDA Orange Book when they claim an approved method of using the drug. Listing is significant because an ANDA applicant must address the patent through a Paragraph I, II, III or IV certification, or use a section viii statement where the patented use is carved out.

The commercial relevance of US 11,278,537 depends on three questions:

Whether Amicus listed the patent against the Galafold NDA.
Whether the listed use code covers the ANDA applicant’s proposed indication.
Whether the applicant can omit the patented renal-impairment use from its labeling.

An ANDA applicant could submit a Paragraph IV certification asserting that the patent is invalid, unenforceable or not infringed. Amicus could then bring an infringement action under the Hatch-Waxman framework. A timely lawsuit ordinarily creates a 30-month stay of FDA approval, subject to statutory exceptions and court action (21 U.S.C. § 355(j)(2)(A)(vii); 21 C.F.R. § 314.94).

A section viii carve-out would be more difficult if the proposed label retains broad language directing treatment of all adults with an amenable mutation and does not exclude patients with renal impairment. It would be more viable if the patent’s use code were limited to a specific renal population and the generic label expressly omitted that use.

Which companies are challenging migalastat patents?

The relevant challenger class is generic-drug manufacturers submitting ANDAs for migalastat hydrochloride. No biosimilar pathway applies because migalastat is a small molecule.

A public challenge assessment should distinguish:

A patent listed in the Orange Book.
A Paragraph IV certification.
A filed federal infringement case.
A settlement agreement.
A commercial launch after a successful validity or non-infringement decision.

US 11,278,537 is a method-of-use patent. It presents a narrower litigation target than a compound or formulation patent because an accused generic product may argue that its label does not encourage the patented renal use. Direct infringement claims against physicians or patients may also be difficult to monetize compared with an action against the ANDA applicant.

How strong is the patent estate for migalastat?

The broader Galafold estate can be divided into four layers.

Compound and core chemistry patents

These patents protect migalastat or related substituted iminosugar compounds. Their expiration dates are generally earlier than those of later clinical-use patents. They provide the strongest protection against unauthorized manufacture and sale of the active ingredient while in force.

Formulation and salt patents

These patents may cover migalastat hydrochloride, solid oral dosage forms, crystalline forms, particle properties, excipients or manufacturing processes. Claims 9, 10, 15, and 16 of US 11,278,537 are not conventional formulation claims. They define the dosage form and salt as limitations within a treatment method.

Mutation-selection patents

These patents cover treating patients whose α-galactosidase A mutations respond to pharmacological chaperoning. They can overlap with the FDA requirement that the patient have an amenable mutation.

Clinical-outcome patents

US 11,278,537 belongs to this category. Its added value is the renal impairment and eGFR-stabilization limitation. Such patents can survive expiration of core compound patents but usually have narrower infringement theories and greater dependence on labeling and clinical evidence.

Overall, the patent is strongest against a product label that expressly recommends once-every-other-day migalastat for amenable Fabry patients with eGFR below 60. It is weaker against a label that omits severe renal impairment, excludes the claimed use, or does not identify the eGFR-stabilization outcome.

What manufacturing and geographic barriers exist?

The patent is US-only. Parallel protection would require corresponding patents in Europe, Japan, Canada, Australia and other relevant markets. Foreign claims may differ substantially because patent offices apply different standards to medical-use claims, second medical indications, clinical endpoints and functional assay definitions.

Manufacturing barriers are separate from the claimed method. A generic manufacturer may need to address:

Synthesis of migalastat free base.
Conversion to migalastat hydrochloride.
Solid-state and impurity controls.
Bioequivalence for the 150 mg hydrochloride capsule.
Stability and packaging.
Mutation-amenability testing or labeling controls.
Any active-ingredient, formulation or process patents still in force.

The method patent does not, by itself, prevent manufacture of migalastat for an unclaimed use. It may still create inducement risk if the commercial label, promotional materials or distribution practices encourage the patented renal-use regimen.

What generic launch scenarios are most likely?

Scenario	Patent risk	Likely commercial result
Full-label ANDA including eGFR below 60 use	High	Paragraph IV litigation likely if patent is listed
Label limited to eGFR 30 or greater	Moderate	May avoid claims directed to eGFR below 30
Section viii carve-out of renal-stabilization use	Lower	Approval may proceed if FDA accepts the carve-out
Product sold without patented-use language but used off-label	Fact-dependent	Inducement and enforcement risk remain
Challenge to assay limitation	Material	Could attack written description, enablement or definiteness
Challenge to eGFR endpoint	Material	Could argue the claim requires an outcome not present in the proposed use
Launch after settlement	Controlled by agreement	Entry date and label depend on settlement terms

What patent litigation and settlement issues matter?

The most important litigation questions are likely to be:

Whether the claims are invalid for obviousness in view of earlier migalastat renal data.
Whether the HEK assay definition is sufficiently enabled across the full mutation scope.
Whether the eGFR result is an inherent property of the dosing regimen or a required clinical limitation.
Whether the approved label induces the patented method.
Whether a generic label can omit the severe-impairment population.
Whether the patent is properly listed and whether the listed use code is overbroad.

A settlement could permit an authorized generic, a licensee launch, or a date-certain entry before patent expiration. No settlement terms should be assumed from patent issuance or Orange Book listing alone.

Key Takeaways

US 11,278,537 is a narrow, outcome-based method-of-use patent for migalastat in Fabry patients with renal impairment.
Claim 1 requires eGFR below 60, a HEK-assay-amenable mutation, once-every-other-day dosing, increased WBC enzyme activity and an eGFR decline better than -1.0 mL/min/1.73 m² per year.
Claims 4 and 5 extend protection to severe renal impairment, including eGFR of 15 to 29.
Claims 14 through 16 map the patent to the commercial Galafold dose of 123 mg FBE or 150 mg migalastat hydrochloride.
The patent is distinct from compound, formulation and manufacturing patents and does not reset their expiration dates.
Because migalastat is a small molecule, competitive entry would use the ANDA pathway, not the biosimilar pathway.
Paragraph IV exposure depends heavily on Orange Book listing, the applicable use code and the feasibility of a section viii label carve-out.
The patent’s strongest enforcement position is against a generic label that expressly includes renal stabilization in the claimed population.
Its weakest position is against a label that excludes the patented use and does not encourage treatment of patients with eGFR below 60.

FAQs

Does US 11,278,537 cover all Galafold patients?

No. It covers a defined subset: Fabry patients with eGFR below 60, an amenable α-galactosidase A mutation and the claimed dosing and clinical-response limitations.

Does the patent cover 150 mg Galafold capsules?

Claim 16 expressly recites approximately 150 mg migalastat hydrochloride. The coverage remains limited to the claimed renal-impairment treatment method.

Can a generic sell migalastat after the compound patent expires?

Potentially, but later formulation, method-of-use and regulatory protections may delay or limit launch. A generic must address listed Orange Book patents and applicable exclusivity.

Is severe renal impairment approved for Galafold in the United States?

The US label does not recommend Galafold for patients with eGFR below 30 mL/min/1.73 m². The patent nevertheless expressly claims this population.

Does the patent protect the HEK-293 assay itself?

No. The claims use the HEK assay to define an amenable mutation. They do not, based on the supplied claims, claim the assay as a standalone diagnostic or laboratory method.

References

Amicus Therapeutics, Inc. (2022). United States Patent No. 11,278,537, methods of treating Fabry disease in patients with renal impairment. U.S. Patent and Trademark Office.
U.S. Food and Drug Administration. (2018). FDA approves first oral drug for patients with Fabry disease. https://www.fda.gov
U.S. Food and Drug Administration. (2023). Galafold prescribing information. Amicus Therapeutics.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products. https://purplebooksearch.fda.gov
United States Code, 21 U.S.C. § 355. Abbreviated applications and patent certifications.
United States Code, 21 U.S.C. § 360cc. Protection for approved drugs designated as orphan drugs.
Code of Federal Regulations, 21 C.F.R. § 314.94. Content and format of an abbreviated new drug application.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Amicus Therap Us	GALAFOLD	migalastat hydrochloride	CAPSULE;ORAL	208623-001	Aug 10, 2018		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				THE TREATMENT OF FABRY PATIENTS	⤷ 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
Argentina	111971	⤷ Start Trial
Argentina	131106	⤷ Start Trial
Argentina	131107	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,278,537

Which drugs does patent 11,278,537 protect, and when does it expire?

Summary for Patent: 11,278,537