Litigation Details for Duchesnay Inc. v. Mylan Pharmaceuticals Inc. (D. Del. 2015)

Duchesnay Inc. v. Mylan Pharmaceuticals Inc. (D. Del. 2015)

Docket		Date Filed	2015-05-13
Court	District Court, D. Delaware	Date Terminated	2016-07-15
Cause	35:271 Patent Infringement	Assigned To	Sue Lewis Robinson
Jury Demand	None	Referred To
Patents	6,340,695; 7,560,122
Link to Docket	External link to docket

Details for Duchesnay Inc. v. Mylan Pharmaceuticals Inc. (D. Del. 2015)

Date Filed	Document No.	Description	Snippet	Link To Document
2015-05-13				External link to document
2015-05-13	4		the Commissioner of Patents and Trademarks for Patent/Trademark Number(s) 6,340,695 B1;. (dmp, ) (Entered…2015 15 July 2016 1:15-cv-00385 830 Patent None District Court, D. Delaware	External link to document
2015-05-13	9		the Commissioner of Patents and Trademarks for Patent/Trademark Number(s) 7,560,122; . (Matterer, Mary)…2015 15 July 2016 1:15-cv-00385 830 Patent None District Court, D. Delaware	External link to document

Duchesnay Inc. v. Mylan Pharmaceuticals Inc. Litigation Summary and Patent Analysis, 1:15-cv-00385

Last updated: August 5, 2026

Duchesnay Inc. v. Mylan Pharmaceuticals Inc., No. 1:15-cv-00385, was a Hatch-Waxman patent dispute in the U.S. District Court for the District of Delaware involving Mylan’s abbreviated new drug application for generic doxylamine succinate and pyridoxine hydrochloride delayed-release tablets, the generic equivalent of Duchesnay’s Diclegis product. The case centered on U.S. Patent No. 6,340,695, a method-of-use patent covering treatment of nausea and vomiting in pregnancy.

The dispute ended without a reported merits judgment invalidating or upholding the asserted patent. The public docket reflects termination of the action following a settlement-related dismissal. The docket does not disclose the commercial terms, launch date, or licensing provisions of the agreement.

What drug and patent were involved in Duchesnay v. Mylan?

The case involved Diclegis, a prescription delayed-release combination of doxylamine succinate and pyridoxine hydrochloride.

Item	Detail
Branded product	Diclegis
Active ingredients	Doxylamine succinate and pyridoxine hydrochloride
Dosage form	Delayed-release oral tablet
Strength	10 mg doxylamine succinate / 10 mg pyridoxine hydrochloride
NDA holder	Duchesnay Inc.
Regulatory pathway	Mylan ANDA under Hatch-Waxman
Asserted patent	U.S. Patent No. 6,340,695
Patent title	“Methods of treating nausea and vomiting”
Court	U.S. District Court for the District of Delaware
Civil action	No. 1:15-cv-00385
Filing period	2015
Case disposition	Dismissed pursuant to settlement-related proceedings

Diclegis received FDA approval in April 2013 under NDA 021876. The product label describes treatment of nausea and vomiting associated with pregnancy in women who do not respond adequately to conservative management. The labeled regimen begins with two tablets at bedtime and may increase to four tablets daily depending on symptoms. [1]

What patent protected Diclegis in the Mylan litigation?

The principal patent at issue was U.S. Patent No. 6,340,695.

The ’695 patent is a method-of-use patent rather than a conventional composition-of-matter patent. Its claims concern the administration of doxylamine and pyridoxine for treating nausea and vomiting, including pregnancy-related symptoms. The patent did not create basic molecular exclusivity for either active ingredient. Both compounds had long histories of medical use before the Diclegis approval.

The asserted patent therefore protected the approved therapeutic use and dosing concept rather than ownership of doxylamine, pyridoxine, or their underlying chemical structures.

What formulation patents were asserted?

The publicly identified Mylan case was principally associated with the ’695 method patent. The case record does not show a reported trial involving a separate Diclegis formulation patent.

That distinction matters. Mylan’s product targeted a delayed-release dosage form, but the core litigation risk arose from the patent listed for the approved method of use. A generic manufacturer can face infringement exposure even when the active ingredients are old if the ANDA product is accompanied by a Paragraph IV certification against a listed method-of-use patent.

The patent estate was therefore narrower than an estate based on:

• A new chemical entity patent;
• A composition-of-matter patent;
• A broad formulation patent;
• A manufacturing-process patent; or
• Multiple issued patents covering different dosage forms.

Why did Duchesnay sue Mylan?

Duchesnay sued after receiving Mylan’s Paragraph IV notice concerning its ANDA for generic doxylamine succinate and pyridoxine hydrochloride delayed-release tablets.

A Paragraph IV certification asserts that a listed patent is invalid, unenforceable, or will not be infringed by the proposed generic product. Under the Hatch-Waxman Act, the filing of a patent-infringement action within 45 days of receiving a Paragraph IV notice generally triggers a 30-month stay of FDA approval, subject to statutory exceptions. [2]

Duchesnay’s suit sought to prevent FDA approval or commercial launch of Mylan’s product before expiration of the ’695 patent. The case was a standard branded-drug response to an ANDA challenge.

What were Mylan’s likely Paragraph IV defenses?

The docket and related patent record identify the litigation as an ANDA dispute over the ’695 patent. Mylan’s statutory defenses would have been expected to include invalidity, noninfringement, and unenforceability.

Invalidity

The principal invalidity theories available in this type of case were likely obviousness and lack of adequate written description or enablement, depending on the asserted claims and the contents of Mylan’s certification.

The obviousness issue would have focused on whether a skilled person, using prior art concerning doxylamine, pyridoxine, pregnancy-related nausea, and delayed-release dosing, would have had a reason to arrive at the claimed treatment method with a reasonable expectation of success.

The underlying technology had a difficult patent profile because:

• Doxylamine and pyridoxine were known compounds;
• The ingredients had historical use for pregnancy-related nausea;
• The commercial product relied on a delayed-release regimen;
• The claims were directed to a therapeutic method rather than a new molecular entity; and
• The patent’s commercial value depended heavily on FDA-listed use protection.

Noninfringement

Mylan could have argued that its ANDA product would not infringe the asserted method claims, including by relying on labeling limitations or a proposed label that omitted the patented use.

For a method-of-use patent, the generic label is often central. If the proposed label instructs use for the patented indication, induced-infringement risk increases. If the label excludes the patented use and the product has substantial noninfringing uses, the generic applicant may have stronger arguments under the ANDA framework.

The final public disposition did not produce a reported claim-construction or trial decision resolving those issues.

When did the Diclegis patent expire?

The Orange Book-listed expiration date for U.S. Patent No. 6,340,695 was June 30, 2020. [3]

Milestone	Date
’695 patent filing basis	1999
’695 patent issued	January 22, 2002
Diclegis FDA approval	April 8, 2013
Duchesnay v. Mylan filed	2015
Listed ’695 patent expiration	June 30, 2020

The effective commercial exclusion period was shorter than the full patent term because Diclegis entered the market in 2013, approximately seven years before the listed patent expiration date.

The record does not establish that the litigation produced a statutory pediatric exclusivity extension. The relevant Orange Book analysis is the patent expiration date and any separate FDA exclusivity listed for the NDA.

What was the litigation status and final outcome?

The case did not generate a reported merits opinion establishing that the ’695 patent was valid, invalid, infringed, or not infringed.

The public docket indicates that the action was terminated through a settlement-related dismissal. As a result:

• No public trial verdict resolved the patent’s validity;
• No reported Federal Circuit decision issued from this case;
• The court did not publish a final damages award;
• The settlement terms were not made public in the docket;
• The generic launch date was not established by a reported judicial order; and
• The parties’ allocation of launch rights was not disclosed.

A dismissal following settlement is commercially important but does not provide the same patent-strength signal as a judgment after claim construction and trial. The settlement preserved uncertainty over the validity and enforceability of the ’695 patent while allowing the parties to manage regulatory and launch timing privately.

Did the case involve a Paragraph IV challenge?

Yes. The case arose from Mylan’s ANDA filing and Paragraph IV challenge to Duchesnay’s listed patent protection for Diclegis.

The Paragraph IV framework gave Duchesnay the right to bring an infringement action before FDA approval of Mylan’s ANDA. The lawsuit likely imposed the statutory approval stay associated with the patent challenge. Because the case ended through settlement, the public docket does not establish whether Mylan obtained:

• A licensed early-entry date;
• A launch date tied to patent expiration;
• A launch date tied to another commercial event;
• A royalty-bearing license;
• A supply arrangement; or
• Any restriction on marketing, promotion, or indication.

What is the Orange Book status of Diclegis?

The relevant Orange Book protection was the listing of U.S. Patent No. 6,340,695 against Diclegis. FDA Orange Book listings identify patents that the NDA holder represents as covering the approved drug or an approved method of using the drug. [3]

The listing was significant because it enabled Duchesnay to invoke the Hatch-Waxman litigation mechanism against an ANDA applicant. It did not mean that the ’695 patent covered the chemical structures of doxylamine or pyridoxine.

Diclegis also received three years of new clinical investigation exclusivity associated with its 2013 approval. That exclusivity period was separate from the patent and would not by itself have prevented a later ANDA filing after the applicable exclusivity period ended. [1, 4]

How strong was Duchesnay’s Diclegis patent estate?

The estate was commercially useful but technically concentrated.

Strengths

The ’695 patent had several practical advantages:

1. It was listed in the Orange Book.
2. It covered the approved pregnancy-related treatment method.
3. An ANDA applicant was required to confront the patent through a certification.
4. The patent had several years of remaining term when the 2015 case was filed.
5. The approved label could create induced-infringement arguments if it directed use within the claimed indication.

Weaknesses

The estate also had structural limitations:

1. The patent was not a new chemical entity patent.
2. The active ingredients were known before Diclegis.
3. The claims were vulnerable to prior-art and obviousness arguments.
4. A single principal patent created concentration risk.
5. Method-of-use protection can be affected by label design and substantial noninfringing uses.
6. The patent expired in 2020, limiting long-term defensive value.

On balance, the estate had meaningful near-term blocking value in 2015 but less durability than a mult patent portfolio covering composition, formulation, method of use, and manufacturing.

Did biosimilar risk apply to Diclegis?

No. Diclegis is a small-molecule drug, not a biologic. Mylan’s product was subject to the ANDA pathway, not the FDA biosimilar pathway under the Public Health Service Act.

The relevant competitive threats were:

• ANDA-based generic entry;
• Authorized-generic competition;
• Label carve-outs;
• Paragraph IV settlements;
• Formulation substitution; and
• Post-expiration price competition.

Biosimilar approval, interchangeable biosimilar status, and the Biologics Price Competition and Innovation Act were not relevant to this case.

Did Duchesnay disclose a licensing deal with Mylan?

The public docket does not disclose the economic terms of the settlement or a separate license agreement. No public court order in the case establishes a royalty, authorized-generic arrangement, supply transaction, or specific Mylan launch date.

The absence of disclosed terms limits the ability to calculate the settlement’s value from the docket alone. The case can be analyzed as a resolved Hatch-Waxman dispute, but not as a publicly quantified launch-rights transaction.

What generic launch risks existed after the settlement?

Mylan’s principal launch risks were tied to the scope and remaining term of the ’695 patent, the settlement’s confidential restrictions, and FDA approval of the ANDA.

The practical scenarios were:

Launch scenario	Commercial effect
Entry before patent expiration under settlement	Accelerated generic erosion of Diclegis sales
Entry at or after June 30, 2020	Patent-based blocking risk largely ends
Label carve-out	Potentially narrower market and reduced infringement exposure
Delayed launch after FDA approval	Patent litigation resolved but commercial timing deferred
Multiple generic entrants after expiry	Rapid price erosion and share fragmentation

Because Diclegis addressed a defined pregnancy-related indication and had a relatively simple active-ingredient profile, post-expiration competition was likely to focus on price, pharmacy substitution, manufacturing reliability, and label equivalence rather than molecular differentiation.

How did Duchesnay v. Mylan compare with broader branded-generic litigation?

The case was narrower than disputes involving blockbuster drugs protected by several patents with staggered expiration dates.

Issue	Duchesnay v. Mylan	Multi-patent branded drug case
Core protection	Primarily method of use	Composition, formulation, use, process
Molecule exclusivity	None for old active ingredients	Often present
FDA pathway	ANDA	ANDA
Biosimilar relevance	None	None for small molecules
Patent concentration	High	Lower
Settlement leverage	Based on one principal listed patent	Based on layered patent barriers
Long-term blocking power	Limited by 2020 expiration	Potentially extended by later patents

Duchesnay’s leverage came from regulatory listing and the remaining patent term, not from broad control over the active ingredients.

What patent litigation affects Diclegis generic entry?

The principal identified case was Duchesnay Inc. v. Mylan Pharmaceuticals Inc., No. 1:15-cv-00385. The case established the litigation vehicle for Mylan’s Paragraph IV challenge but did not produce a published ruling that resolved the ’695 patent’s merits.

Other generic applicants could have faced the same listed patent and separate litigation, depending on their ANDA filing dates and certifications. A settlement with one applicant would not automatically resolve disputes involving other ANDA filers.

Key Takeaways

• Duchesnay sued Mylan in the District of Delaware over an ANDA for generic Diclegis.
• The dispute centered on U.S. Patent No. 6,340,695.
• The patent protected a method of treating pregnancy-related nausea and vomiting, not the underlying active ingredients.
• The listed patent expiration date was June 30, 2020.
• The case ended through settlement-related dismissal without a reported merits judgment.
• Public filings do not disclose the settlement economics or a specific Mylan launch date.
• Diclegis faced generic, not biosimilar, competition.
• Duchesnay’s patent estate had meaningful short-term Orange Book leverage but was concentrated in a single principal method-of-use patent.

FAQs About Duchesnay Inc. v. Mylan Pharmaceuticals

Was Diclegis protected by a composition-of-matter patent?

No. The principal patent associated with the case was a method-of-use patent covering treatment with doxylamine and pyridoxine.

What was Mylan’s product?

Mylan sought approval for generic doxylamine succinate and pyridoxine hydrochloride delayed-release tablets, corresponding to Diclegis.

Did Duchesnay win the case?

The public docket does not show a merits victory. The action was dismissed in connection with a settlement.

Did the settlement authorize Mylan to launch before 2020?

The public record does not disclose the settlement’s launch terms.

Is Diclegis subject to biosimilar competition?

No. Diclegis is a small-molecule drug regulated through the ANDA generic-drug pathway.

References

1. U.S. Food and Drug Administration. (2013). Diclegis prescribing information and NDA 021876 approval materials. FDA.

2. U.S. Congress. (2012). The Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355(j).

3. U.S. Food and Drug Administration. (2020). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.

4. U.S. Food and Drug Administration. (2024). Drugs@FDA: Diclegis, NDA 021876. FDA.

5. U.S. District Court for the District of Delaware. (2015-2016). Duchesnay Inc. v. Mylan Pharmaceuticals Inc., No. 1:15-cv-00385-RGA, docket materials. PACER.

6. United States Patent and Trademark Office. (2002). U.S. Patent No. 6,340,695, Methods of treating nausea and vomiting. USPTO.