US Patent 10,947,183: Fenfluramine Manufacturing Claims, Patent Scope and Competitive Landscape

US Patent 10,947,183 protects defined fenfluramine manufacturing routes and impurity profiles rather than fenfluramine as a molecule. The core claim requires four operations: hydrolysis of a 3-trifluoromethyl phenylacetonitrile, crystallization-based removal of regioisomer impurities, ketone formation with acetic anhydride, and reductive amination with ethylamine and a borohydride reagent. The patent also claims fenfluramine compositions containing controlled amounts of 2- and 4-fenfluramine regioisomers.

The estate is strongest against manufacturers using the claimed synthetic sequence or producing an API with the claimed process-linked impurity profile. It is weaker against an independent route that avoids the specified intermediates, purification steps, reagents and impurity limitations.

What does US Patent 10,947,183 cover?

The patent covers two principal categories:

Fenfluramine API defined by the process used to manufacture it.
Fenfluramine compositions defined by the presence of trifluoromethyl-phenyl regioisomers.

The independent process claims require the following sequence:

Required element	Claim requirement
Starting material	2-(3-(trifluoromethyl)phenyl)acetonitrile composition
Hydrolysis	Conversion to 2-(3-(trifluoromethyl)phenyl)acetic acid
First purification	Crystallization to reduce total trifluoromethyl-phenyl regioisomers below 0.2 wt%
Ketone formation	Reaction with acetic anhydride and a catalyst
Intermediate	1-(3-(trifluoromethyl)phenyl)propan-2-one
Reductive amination	Ethylamine plus a borohydride reducing agent
Product	Fenfluramine API containing at least one regioisomer impurity
Core impurity limit	Less than 0.2 wt% 4-fenfluramine or its salt in claim 1

The claims are unusual because they combine process limitations with final-product characteristics. A product-by-process claim may be infringed where the accused product is made by the claimed process, but the enforceability and scope depend on claim construction, prosecution history and controlling case law.

How strong is the independent claim?

Claim 1 is the principal enforcement claim for the manufacturing process. It requires every listed operation. A competing process that omits one required limitation generally has a direct-infringement defense, subject to the doctrine of equivalents.

Claim 28 is similar to claim 1 but changes the final limitation to less than 1.0 wt% reduced alcohol side product. Claim 29 adds crystallization of fenfluramine or a fenfluramine salt from a crude composition. Claim 30 adds conversion to a pharmaceutically acceptable salt and crystallization of that salt.

The claim structure creates several enforcement paths:

Claim group	Commercial target	Relative breadth
1, 28-30, 33	Full manufacturing sequence	Moderate, because all four reaction stages are required
2	Nitrile made from trifluoromethylbenzene	Narrower
3	Bisulfite purification of the ketone	Narrow
5	1-methylimidazole and acetic anhydride conditions	Narrow
6	70% aqueous ethylamine and triacetoxyborohydride in methanol	Narrow
8, 29, 30	Downstream free-base or salt crystallization	Narrow to moderate
9	Chiral separation	Narrow
25-27	Fenfluramine compositions containing regioisomers	Composition-focused

A process developer can seek design-around protection by changing the starting material, using a different route to the ketone, replacing the reductive amination chemistry, or avoiding the specified crystallization step. The composition claims may still create risk if the resulting API contains the claimed regioisomer profile.

What impurity profile does the patent require?

The patent treats regioisomers as controlled process impurities. The relevant compounds are 2-fenfluramine and 4-fenfluramine, together with corresponding trifluoromethyl-phenyl regioisomers in upstream intermediates.

The principal thresholds are:

Claim limitation	Threshold
Total trifluoromethyl-phenyl regioisomers in purified acid	Less than 0.2 wt%
4-trifluoromethyl-phenyl regioisomer in acid	Less than 0.1 wt%
2-trifluoromethyl-phenyl regioisomer in acid	Less than 0.1 wt%
4-fenfluramine in claim 1 product	Less than 0.2 wt%
Regioisomer content in claim 4	At least 0.01 wt%
Regioisomer content in claim 7	At least 0.01 wt% of 2- and 4-fenfluramine
Regioisomer content in claims 14-24	At least 0.2 wt% to at least 10 wt%
Reduced alcohol side product in claim 28	Less than 1.0 wt%
Reduced alcohol side product in claim 30	Less than 0.1 wt%

Claims 14 through 24 create nested concentration ranges. A product containing at least 10 wt% of the specified regioisomer also falls within the lower threshold claims, assuming all other limitations are met. These claims are not independent compositions; they depend on claim 1 and therefore retain claim 1's process requirements.

What is the scope of claims 25 through 27?

Claims 25 through 27 are composition claims and are structurally broader than the process claims.

They require:

Fenfluramine;
At least one trifluoromethyl-phenyl regioisomer of fenfluramine; and
A specified amount of that regioisomer.

The thresholds are:

Claim	Regioisomer limitation
25	Less than 0.2 wt% in total
26	Greater than zero and less than 0.2 wt%
27	0.01 wt% in total

Claims 25 through 27 do not expressly require the four-step manufacturing route recited in claim 1. That distinction matters. If valid and properly construed, these claims could reach an API made by a different process if the product has the claimed composition.

The practical weakness is analytical proof. An accused product would need to be tested using a validated method capable of reliably distinguishing and quantifying the relevant regioisomers at concentrations near 0.01 wt%. Batch sampling, analytical variability, salt-to-free-base conversion and the meaning of "in total" may become material in litigation.

Which dependent claims create the most meaningful commercial restrictions?

Claims 3, 5, 6, 8, 9, 29, 30 and 33 are the most operationally relevant.

Ketone purification

Claim 3 requires purification of the ketone intermediate through a ketone bisulfite adduct. A manufacturer using ordinary distillation, extraction, chromatography or another crystallization system may avoid this limitation, provided the broader independent claim is not otherwise satisfied.

Acylation conditions

Claim 5 requires approximately 0.5 equivalents of 1-methylimidazole and approximately five or more equivalents of acetic anhydride. The use of different catalysts or materially different stoichiometry may support a design-around position.

Reductive amination conditions

Claim 6 requires 70 wt% ethylamine in water, at least approximately 2.25 equivalents of triacetoxyborohydride, and methanol solvent. It is narrower than claim 1, which broadly recites ethylamine and a borohydride reducing agent.

Chiral separation

Claim 9 covers a route that resolves racemic fenfluramine to produce a non-racemic composition with a predominant stereoisomer. The claim does not itself establish a particular chiral resolving agent or separation technology.

Salt formation and crystallization

Claims 30 and 33 cover downstream formation and crystallization of a pharmaceutically acceptable fenfluramine salt, including fenfluramine hydrochloride through claim 31. These claims can increase risk for manufacturers that use the claimed synthesis and then reproduce the claimed salt-purity profile.

When does US Patent 10,947,183 lose exclusivity?

The patent issued on March 16, 2021. The patent term cannot be determined solely from the grant date. For a US utility patent, the ordinary term is generally 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers and the complete priority chain (35 U.S.C. § 154).

The relevant exclusivity analysis is therefore:

Exclusivity component	Assessment
Patent grant	March 16, 2021
Ordinary statutory term	20 years from the applicable earliest nonprovisional filing date
Patent-term adjustment	Must be checked in the USPTO patent record
Patent-term extension	Requires a separate regulatory and patent-record determination
Terminal disclaimer	Must be checked against related applications
Regulatory exclusivity	Separate from this patent
Orange Book effect	Depends on FDA listing and the patent's listed claim category

The grant date alone does not establish the expiration date. A reliable expiration analysis must use the patent's front-page priority data and USPTO term information.

What is the FDA and Orange Book status of fenfluramine?

Fenfluramine hydrochloride is marketed as Fintepla for seizures associated with Dravet syndrome and Lennox-Gastaut syndrome. The FDA approved Fintepla under NDA 212102. The product is subject to controlled-substance and risk-management requirements, including the Fintepla Risk Evaluation and Mitigation Strategy (FDA, 2024).

Patent 10,947,183 should not be assumed to block an ANDA solely because it concerns fenfluramine API manufacturing. Orange Book relevance depends on whether the patent is listed for the approved drug and whether its claims qualify under FDA listing rules. A process patent may have limited practical value in an ANDA dispute if it is not listed or if the listed claims do not cover the proposed generic product or method of manufacture.

An ANDA applicant could face separate issues involving:

Drug-substance manufacturing;
Fenfluramine hydrochloride composition;
Finished oral solution;
Approved seizure indications;
Method-of-use patents;
Pediatric-use or formulation claims;
REMS implementation.

Patent 10,947,183 is not, based on the supplied claims, a formulation patent for the Fintepla oral solution. It does not claim a particular container, concentration, excipient system, dosage regimen or administration device.

What generic entry risks exist?

Generic entry risk depends on the applicant's source and manufacturing route.

Scenario 1: Same or substantially identical route

Risk is high if the applicant:

Starts with the claimed 3-trifluoromethyl phenylacetonitrile;
Hydrolyzes it to the claimed acid;
Uses crystallization to meet the claimed impurity limit;
Forms the claimed ketone with acetic anhydride;
Uses ethylamine and a borohydride reducing agent; and
Produces the claimed regioisomer profile.

The risk increases if the applicant uses the specific conditions in claims 3, 5 or 6.

Scenario 2: Alternative synthesis

Risk is lower if the applicant avoids the claimed starting material or does not perform the claimed acid crystallization, ketone formation or reductive amination sequence. Claims 25 through 27 remain relevant if the finished API contains the claimed regioisomer concentration.

Scenario 3: Different impurity profile

A product with no detectable or materially different regioisomer content may avoid claims 25 through 27, but this does not independently resolve process-claim exposure. Analytical methods and detection limits would be central.

Scenario 4: Different salt or finished dosage form

Changing from fenfluramine hydrochloride to another salt does not necessarily avoid claims directed to the API or generic fenfluramine composition. It may avoid a salt-specific dependent claim if the claim requires hydrochloride or a particular salt-purity profile.

Which companies are challenging fenfluramine exclusivity?

The supplied record does not establish any filed Paragraph IV certification, ANDA filer, patent litigation, settlement agreement or licensing transaction involving Patent 10,947,183. No company-specific challenge can be attributed to this patent on the claim information alone.

The relevant competitive groups are:

Group	Commercial position
Zogenix, now part of UCB	Originator and commercial rights holder associated with Fintepla
UCB	Current commercial owner of the Fintepla franchise
Generic manufacturers	Potential ANDA applicants, subject to patent, regulatory and supply-chain analysis
API manufacturers	Potential process-licensees or alternative-route suppliers
Contract manufacturers	Potentially exposed through manufacturing records and supply agreements

A manufacturer can face infringement exposure without marketing a finished product if it performs the patented API process in the United States. Conversely, foreign manufacture raises territorial and importation issues under 35 U.S.C. §§ 271(a), 271(g) and related provisions.

How does this patent compare with formulation and method-of-use protection?

Patent 10,947,183 is primarily a process and API-quality patent.

Protection type	Present in supplied claims?	Commercial effect
New chemical entity	No	Does not claim fenfluramine as a new molecule
API manufacturing process	Yes	Can restrict specified synthesis routes
API impurity profile	Yes	Can reach products with defined regioisomer levels
Salt form	Yes, through dependent claims	Adds downstream coverage
Oral formulation	No apparent claim	Does not claim excipients or dosage form
Method of treatment	No apparent claim	Does not claim Dravet or Lennox-Gastaut treatment
Dosage regimen	No	No regimen exclusivity in supplied claims
Device or packaging	No	No device-specific protection

The patent is therefore best viewed as one layer in a broader fenfluramine exclusivity strategy. It may complement, but does not replace, formulation, method-of-use, regulatory and supply-chain protections.

How strong is the patent estate?

The patent has meaningful but route-dependent value.

Strengths

Claims the full synthetic sequence from a defined aromatic nitrile.
Uses upstream impurity control to connect raw-material quality with final API quality.
Includes both process-linked API claims and composition claims.
Covers downstream crystallization and salt formation in dependent claims.
Includes multiple impurity thresholds, creating fallback positions.

Weaknesses

The independent process claims require numerous cumulative steps.
Several dependent claims are narrow and condition-specific.
Product-by-process interpretation may complicate enforcement.
Composition claims depend on trace-level analytical proof.
The supplied claims do not cover formulations, dosing, indications or delivery systems.
A genuinely different synthetic route may avoid the principal process claims.

Key Takeaways

US Patent 10,947,183 protects fenfluramine manufacturing and impurity-controlled compositions, not fenfluramine as a molecule.
Claim 1 requires hydrolysis, crystallization, acylation and borohydride reductive amination in a defined sequence.
Claims 25 through 27 are the broadest apparent composition claims because they do not recite the full manufacturing sequence.
Claims 3, 5 and 6 target specific purification and reaction conditions.
Claims 29, 30 and 33 extend coverage into crude-material crystallization, salt formation and finished API purity.
Generic risk is highest for an applicant using the claimed route and producing the claimed regioisomer profile.
The grant date is March 16, 2021. The expiration date requires the complete priority, patent-term-adjustment and terminal-disclaimer record.
The supplied material does not establish any Paragraph IV challenge, litigation, settlement or license involving this patent.
The claims do not appear to cover Fintepla formulation, dosing, indication or delivery-device technology.

FAQs

Does US 10,947,183 claim fenfluramine itself?

No. The claims focus on fenfluramine made by specified processes and compositions containing controlled amounts of regioisomer impurities.

Can a generic manufacturer avoid the patent by using a different starting material?

Potentially. A different route may avoid the process claims, but the composition claims can remain relevant if the resulting API contains the claimed regioisomer concentrations.

Does making fenfluramine hydrochloride create infringement risk?

It can. Claims 31, 32 and the salt-focused portions of claims 30 and 33 create risk where the manufacturer also satisfies the incorporated process and purity limitations.

Is US 10,947,183 a Fintepla formulation patent?

The supplied claims do not identify a formulation patent. They concern fenfluramine API manufacture, impurities, crystallization and salt conversion.

What evidence would be most important in a patent dispute?

The critical evidence would include batch records, raw-material specifications, reaction conditions, purification records, certificates of analysis, impurity methods, chromatograms, manufacturing location and API-to-finished-product supply documentation.

References

Food and Drug Administration. (2024). Fintepla (fenfluramine) prescribing information. U.S. Department of Health and Human Services.

U.S. Congress. (2012). 35 U.S.C. § 154: Contents and term of patent; provisional rights.

U.S. Congress. (2012). 35 U.S.C. §§ 271(a), 271(g): Infringement of patent.

U.S. Patent No. 10,947,183. (2021). Fenfluramine active pharmaceutical ingredient and compositions. United States Patent and Trademark Office.

U.S. Patent and Trademark Office. (2024). Manual of Patent Examining Procedure, Chapter 2700: Patent term.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Ucb Inc	FINTEPLA	fenfluramine hydrochloride	SOLUTION;ORAL	212102-001	Jun 25, 2020		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial			Y		⤷ 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	2016379346	⤷ Start Trial
Australia	2021201339	⤷ Start Trial
Australia	2021202576	⤷ Start Trial
Brazil	112018011777	⤷ Start Trial
Canada	3007286	⤷ Start Trial
China	108883399	⤷ Start Trial
China	113499330	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 10,947,183

Which drugs does patent 10,947,183 protect, and when does it expire?

Summary for Patent: 10,947,183