United States Patent 10,071,977: Tasimelteon Purification Claims, Patent Scope and Generic Risk

US Patent No. 10,071,977 is a Vanda Pharmaceuticals patent directed to manufacturing and quality-control processes for highly purified tasimelteon, the active ingredient in Hetlioz. Its commercial importance is narrower than a composition-of-matter patent but potentially relevant to tasimelteon API suppliers, contract manufacturers and generic applicants that use the claimed impurity-control workflow.

The patent does not claim tasimelteon as a molecule. It claims specified manufacturing sequences, impurity testing, crystallization, purification decisions, particle-size processing and, in claims 23 and 24, tasimelteon batches or purified tasimelteon defined by impurity limits.

What does US Patent 10,071,977 claim?

The patent has four principal claim groups:

Claim group	Claims	Subject matter	Primary risk
Propionylation and crystallization process	1-17	Conversion of a defined cyclopropyl amine intermediate to tasimelteon, crystallization and impurity testing	Process infringement
GMP batch release process	18-21	Testing impurities 1-7 and deciding whether to continue processing, purify or discard	Quality-control workflow infringement
Crystalline tasimelteon processing	22	Testing impurity limits, milling and recrystallization	Process infringement
Product and batch limitations	23-24	Tasimelteon batch or purified tasimelteon meeting defined impurity thresholds	Product-by-process or composition-related infringement

The central technical concept is controlled production of tasimelteon with limits on seven specified impurities. The patent ties commercial release to analytical results rather than relying solely on the synthetic reaction.

What is the scope of independent claim 1?

Claim 1 requires all of the following:

Propionylating the specified chiral amine or a salt of that amine.
Producing tasimelteon.
Crystallizing the tasimelteon.
Assaying the crystallized material for Impurity 5, Impurity 6, or both.
Either collecting the batch if it passes preset specifications, or further purifying or discarding it if it fails.

The claim is broader than a single reaction recipe. Claim 2 expressly covers multiple propionylating agents, including:

Propionyl halides.
Propionyl anhydride.
Propionyl esters.
Propionyl amides.
Propionyl imidazolides.
Propionic acid used with a dehydrating agent or the resulting product.

Claim 1 therefore reaches a process even where a manufacturer avoids propionyl chloride, TBME or aqueous sodium hydroxide. Those conditions appear in narrower dependent claims.

Which technical steps are narrowed by the dependent claims?

The dependent claims add progressively specific operating conditions.

Claims	Limitation
3	Organic solvent during propionylation
4	Propionyl chloride, organic solvent and aqueous base
5	TBME and NaOH
6	Intermediate 5, the amine hydrochloride, plus testing before crystallization
7	Aqueous-base wash and disposal of the aqueous layer
8-9	Distillation, with ethanol, pot temperature up to about 58°C and pressure below about 100 mmHg
10-11	Crystallization in a C1-C4 alkanol, warming to about 35-40°C and cooling to about 13-17°C
12	Optional seeding
13	HPLC assay
14	Impurity 5 and/or Impurity 6 at no more than 0.15% area/area
15	Recrystallization as the further-purification step
16-17	Particle-size reduction and formulation with excipients

A generic manufacturer that uses the same high-level workflow may face claim 1 even if it avoids the TBME/NaOH conditions in claim 5. Conversely, a manufacturer that uses a different coupling chemistry, skips the claimed crystallization or does not make the required impurity-based disposition decision may have a design-around position.

How do claims 18 through 22 expand the patent?

Claims 18 and 22 create alternative infringement theories that are less dependent on the exact synthesis route.

Claims 18-21: GMP batch testing

Claim 18 applies to a batch of tasimelteon synthesized under GMP conditions. It requires:

Testing for one or more of Impurities 1-7.
Continuing processing if preset specifications are met.
Further purification or batch disposal if specifications are not met.

Claim 19 sets the threshold for each selected impurity at no more than 0.15 weight percent.

Claim 20 adds:

At least 95.0% purity by area.

Claim 21 adds:

No other single impurity above 0.10 area percent.

These claims could reach a manufacturer that uses a different upstream synthesis but adopts substantially the same batch-release controls. The phrase "one or more" makes the claim potentially broad, because the manufacturer need not test every listed impurity if it tests only one or more of them and follows the claimed disposition process.

Claim 22: crystalline batch plus milling or recrystallization

Claim 22 requires:

Synthesizing crystalline tasimelteon.
Testing for one or more of Impurities 1-7.
Meeting limits of no more than 0.15 weight percent for the selected impurities.
Having no more than 0.10 weight percent of any single unidentified impurity.
Milling the material to meet particle-size specifications, or recrystallizing and retesting if it fails.

This claim is directed to a manufacturing sequence after tasimelteon has already been synthesized. It may be more relevant to API finishing operations than to the initial chemical synthesis.

What impurity limits are central to US 10,071,977?

The principal numerical thresholds are:

Limitation	Threshold
Listed Impurities 1-7 in claims 19 and 22	NMT 0.15 wt% each
Impurity 5 and Impurity 6 in claim 14	NMT 0.15 area/area
Total tasimelteon purity in claim 20	NLT 95.0% by area
Other single impurity in claim 21	NMT 0.10 area%
Unidentified single impurity in claim 22	NMT 0.10 wt%
Product purity in claim 23	At least 98.0 area%
Listed impurities in claim 23	NMT 0.15 wt% each
Listed impurities in claim 24	No concentration greater than about 0.15%

The mixed use of weight percent, area percent and area/area is significant. Analytical method, reference standards, response factors and calculation conventions may affect whether a batch falls within the claims. HPLC data alone may not resolve the issue if the patent’s specification or prosecution history gives special meaning to assay methodology.

What are the listed tasimelteon impurities?

The patent identifies seven impurities associated with tasimelteon manufacture:

Impurity	General structural origin
Impurity 1	Isobutyramide-related analog
Impurity 2	Pentanamide-related analog
Impurity 3	Bis-cyclopropylmethyl urea
Impurity 4	Benzofuran oxidation or dehydrogenation analog
Impurity 5	Dimeric bis-propionamide impurity
Impurity 6	Complex carbonate or phenolic degradation-related impurity
Impurity 7	Oxidized 3-oxo-dihydrobenzofuran analog

Impurities 5 and 6 receive special treatment in claim 1. Claims 18, 22, 23 and 24 cover broader panels containing Impurities 1-7.

The impurity list creates an important evidentiary issue. A manufacturer may produce pharmaceutical-grade tasimelteon without detecting the listed impurities at material levels, but the patent focuses on the act of testing and the resulting release decision. The absence of an impurity does not necessarily avoid the process claim if the required assay and disposition steps are performed.

Are claims 23 and 24 product claims or process claims?

Claims 23 and 24 are drafted as product-oriented claims, but their enforceability may depend on how a court characterizes the limitations.

Claim 23 covers:

A batch for use in preparing a human pharmaceutical composition.
Tasimelteon purity of at least 98.0 area percent.
No more than 0.15 weight percent of one or more selected impurities.

Claim 24 covers purified tasimelteon that does not contain the seven listed impurities above approximately 0.15%.

These claims may provide a stronger enforcement theory against a product imported or sold in the United States than claims limited to an upstream process. They also may face greater validity scrutiny because purity-defined product claims can raise issues involving:

Anticipation by previously disclosed pharmaceutical-grade tasimelteon.
Obviousness of purifying a known drug to conventional impurity specifications.
Written description and enablement.
Indefiniteness caused by "about," assay methodology or unspecified analytical conditions.
Whether the claimed impurity profile is a true product limitation or merely a process result.

A product claim does not automatically cover every tasimelteon batch meeting the same analytical profile if the claim construction requires a particular manufacturing history. The prosecution record would be important in resolving that issue.

When does US Patent 10,071,977 lose exclusivity?

US Patent 10,071,977 was granted on September 11, 2018. Its expected base patent term is tied to the earliest effective nonprovisional filing date in its priority chain. Public patent records identify a 2014 priority period for the claimed tasimelteon purification technology, placing the nominal expiration around March 2034, subject to patent-term adjustment and any applicable patent-term extension. The precise expiration date should be taken from the USPTO patent record rather than inferred solely from the grant date (USPTO, 2018).

The patent’s practical exclusivity can end earlier if:

The patent expires for failure to pay a maintenance fee.
A court invalidates or narrows the asserted claims.
The patent is disclaimed.
A generic manufacturer proves noninfringement.
A license or settlement authorizes commercial entry.

The patent is not a new chemical entity patent. FDA exclusivity for Hetlioz therefore does not arise from this patent. Hetlioz received FDA approval in 2014; regulatory exclusivity periods and patent rights are separate legal mechanisms (FDA, 2014).

What is the Orange Book status of US 10,071,977?

The patent’s Orange Book significance is likely narrower than its litigation significance.

FDA Orange Book listings generally concern patents claiming the approved drug substance, drug product, formulation or an approved method of use. Pure manufacturing-process patents ordinarily are not listed as ANDA certification patents under 21 C.F.R. § 314.53. US 10,071,977 is dominated by process claims, although claims 23 and 24 contain product or batch limitations.

The key consequences are:

If the patent is not listed in the Orange Book, an ANDA applicant ordinarily would not need to submit a Paragraph IV certification specifically against it.
The patent holder could still assert non-Orange-Book process claims under 35 U.S.C. §§ 271(a), 271(b), 271(c) or 271(g), depending on the conduct.
A Paragraph IV challenge to other listed Hetlioz patents would not necessarily resolve infringement of US 10,071,977.
A process patent can remain commercially relevant even without delaying FDA approval.

The FDA-approved product is Hetlioz capsules containing tasimelteon. The approved label identifies Vanda Pharmaceuticals as the sponsor and describes tasimelteon as a melatonin MT1 and MT2 receptor agonist used for Non-24-Hour Sleep-Wake Disorder (FDA, 2020).

What generic entry risks exist for tasimelteon?

The primary risk is API manufacturing overlap rather than formulation overlap.

High-risk conduct

A generic or API manufacturer would face heightened risk if it:

Starts from the specified chiral amine or Intermediate 5.
Uses propionyl chloride or an equivalent propionylating reagent.
Crystallizes tasimelteon.
Tests for Impurity 5 or Impurity 6.
Releases, recrystallizes or discards the batch according to preset specifications.
Uses the claimed impurity thresholds.
Mills the crystalline API to meet particle-size specifications.

Lower-risk design-around approaches

Potentially lower-risk approaches include:

Using a different protected or unprotected intermediate.
Using a different sequence in which propionylation is not the claimed conversion step.
Avoiding the claimed crystallization sequence.
Using in-process controls that do not make the claimed impurity-based release decision.
Applying a different purification operation and analytical strategy.
Producing a material that does not satisfy the product limitations in claims 23 or 24.

These approaches do not eliminate risk. A process may infringe under the doctrine of equivalents, and independently developed manufacturing instructions may still fall within claims 18 or 22.

How strong is the patent estate for tasimelteon?

The '977 patent is best characterized as a medium-strength secondary patent with meaningful manufacturing leverage.

Factor	Assessment
Chemical scope	Moderate; claim 1 covers broad propionylation alternatives
Process specificity	Mixed; claims 4-11 are narrow and operationally defined
Analytical limitations	Potentially strong for proving batch characteristics, but dependent on assay validity
Product claims	Potentially valuable but exposed to anticipation, obviousness and claim-construction defenses
Orange Book leverage	Likely limited if only process claims are listed or eligible for listing
Detectability	Moderate to high for product claims; lower for internal process steps
Design-around potential	Moderate
Litigation value	Higher against API manufacturers than against finished-dose formulators
Biosimilar relevance	None in the conventional sense because tasimelteon is a small molecule

Because tasimelteon is a small-molecule drug, biosimilar procedures under the Biologics Price Competition and Innovation Act do not apply. Competition would proceed through an ANDA or, in some cases, a 505(b)(2) application rather than a biosimilar application.

Which companies are challenging Hetlioz exclusivity?

Generic competition must be evaluated through FDA application records, Orange Book patent listings, ANDA litigation dockets and public company disclosures. The supplied patent claims do not identify an opposing manufacturer, Paragraph IV notice, settlement or license.

No conclusion about a specific challenger, settlement date or authorized generic arrangement should be drawn from US 10,071,977 alone. The patent itself does not establish that a Paragraph IV certification has been filed or that litigation is pending.

What patent litigation affects tasimelteon?

For a litigation assessment, the relevant distinction is between:

Orange Book-listed patents covering the approved product or method of use.
Non-listed manufacturing patents such as US 10,071,977.
Patent claims covering the tasimelteon molecule or earlier synthetic intermediates.
Regulatory exclusivity under the Federal Food, Drug, and Cosmetic Act.

A suit involving a listed Hetlioz patent could trigger the 30-month stay mechanism under 21 U.S.C. § 355(j)(5)(B)(iii). Assertion of the '977 patent alone would not necessarily create that statutory stay if the patent is not properly listed for the ANDA product.

The most important litigation evidence would include the patent’s prosecution history, any terminal disclaimer, maintenance-fee record, Orange Book listing history, ANDA notice letters and district-court complaints. Patent Center and FDA Orange Book records are the controlling sources for those questions (USPTO, n.d.; FDA, n.d.).

Does US 10,071,977 block formulation or finished-dose manufacture?

The patent does not expressly claim:

A particular capsule shell.
A specific excipient system.
A controlled-release formulation.
A tablet coating.
A pharmacokinetic profile.
A method of treating Non-24-Hour Sleep-Wake Disorder.

Claim 17 reaches a pharmaceutical composition only after the claimed crystal particle-size process is completed and the crystals are admixed with one or more excipients. It is therefore an intermediate-manufacturing claim with a formulation endpoint, not a broad formulation patent.

A finished-dose manufacturer using third-party API may avoid direct infringement of upstream process claims if it does not perform the claimed process. Exposure could remain through induced infringement, contributory infringement or importation theories if the manufacturer knowingly participates in or imports API made by the patented process.

Are there licensing deals tied to this patent?

The claims supplied do not identify a licensee or collaboration partner. Public disclosure of a tasimelteon supply, licensing or settlement agreement would need to be matched specifically to US 10,071,977. A general Hetlioz commercialization agreement would not establish a license under this patent.

Key Takeaways

US 10,071,977 protects tasimelteon manufacturing quality controls, not the tasimelteon molecule itself.
Claim 1 is the central process claim and covers broad propionylation alternatives followed by crystallization and impurity testing.
Claims 18 and 22 can reach downstream GMP batch-release and API-finishing workflows even where the upstream synthesis differs.
Claims 23 and 24 create potentially important purity-defined product claims but may face stronger validity and claim-construction challenges.
The key thresholds are 0.15% for specified impurities, 98.0 area% purity in claim 23 and 0.10% limits for certain unidentified impurities.
The patent’s nominal term is expected to extend to approximately 2034, subject to USPTO term calculations.
Orange Book leverage is likely limited because the patent is primarily process-focused.
The patent presents greater risk to API manufacturers and contract manufacturers than to formulators that purchase compliant tasimelteon API.
Tasimelteon is a small molecule. Biosimilar risk does not apply.
Generic entry analysis requires separate review of Orange Book-listed Hetlioz patents, FDA exclusivity, ANDA certifications and any litigation involving Vanda or generic applicants.

FAQs About US Patent 10,071,977 and Tasimelteon

Does US 10,071,977 cover all pharmaceutical-grade tasimelteon?

No. It covers specified manufacturing and analytical processes and certain purity-defined tasimelteon batches. It does not broadly claim every method of making tasimelteon or every pharmaceutical-grade batch.

Can a manufacturer avoid the patent by using a propionylating reagent other than propionyl chloride?

Not necessarily. Claim 2 covers several propionylating reagent classes, including propionyl anhydride, esters, amides, imidazolides and propionic acid with a dehydrating agent.

Is a Paragraph IV certification required against US 10,071,977?

Only if the patent is properly listed in the Orange Book for the relevant approved product and creates a certification obligation. A non-listed process patent generally does not independently require a Paragraph IV certification.

Does the patent cover tasimelteon capsules sold to patients?

The broad claims do not directly claim the capsule product. Claim 17 reaches a pharmaceutical composition prepared from crystals processed under the claimed particle-size limitation, while claims 23 and 24 concern the API’s purity characteristics.

What is the principal design-around opportunity?

The clearest design-around opportunities involve changing the synthetic intermediate, avoiding the claimed propionylation sequence, using a different crystallization and purification workflow, and implementing impurity controls that do not satisfy the claimed batch-release steps.

References

Food and Drug Administration. (2014). Hetlioz (tasimelteon) prescribing information. U.S. Department of Health and Human Services.

Food and Drug Administration. (2020). Hetlioz (tasimelteon) prescribing information. U.S. Department of Health and Human Services.

Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.

U.S. Patent and Trademark Office. (2018). U.S. Patent No. 10,071,977, processes for preparing highly purified tasimelteon. U.S. Department of Commerce.

U.S. Patent and Trademark Office. (n.d.). Patent Center. U.S. Department of Commerce.

U.S. Code. (2024). 35 U.S.C. §§ 271, 154.

U.S. Code. (2024). 21 U.S.C. § 355.

U.S. Food and Drug Administration. (2024). 21 C.F.R. § 314.53, submission of patent information.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Vanda Pharms Inc	HETLIOZ	tasimelteon	CAPSULE;ORAL	205677-001	Jan 31, 2014	AB	RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y	Y			⤷ Start Trial
Vanda Pharms Inc	HETLIOZ LQ	tasimelteon	SUSPENSION;ORAL	214517-001	Dec 1, 2020		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y	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
European Patent Office	3105212	⤷ Start Trial
European Patent Office	3470405	⤷ Start Trial
European Patent Office	4223747	⤷ Start Trial
Japan	2017506642	⤷ Start Trial
Japan	2020079248	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 10,071,977

Which drugs does patent 10,071,977 protect, and when does it expire?

Summary for Patent: 10,071,977