Last updated: August 2, 2026
United Therapeutics Corporation lost its Federal Circuit challenge to the invalidation of U.S. Patent No. 10,716,793, a patent covering inhaled treprostinil treatment for pulmonary hypertension. In United Therapeutics Corp. v. Liquidia Technologies, Inc., No. 23-1805, the Federal Circuit affirmed the Patent Trial and Appeal Board’s determination that the challenged claims were unpatentable as obvious. The decision removed the ’793 patent as a barrier to Liquidia’s development of Yutrepia, an inhaled treprostinil product competing with United Therapeutics’ Tyvaso franchise. [1]
What did the Federal Circuit decide in United Therapeutics v. Liquidia, 23-1805?
The Federal Circuit affirmed the PTAB’s final written decision invalidating claims 1 through 8 of U.S. Patent No. 10,716,793.
The case arose from a post-grant review filed by Liquidia against the ’793 patent. Liquidia argued that the claimed inhaled treprostinil treatment regimen was obvious in view of prior-art publications and the existing clinical and commercial knowledge surrounding treprostinil.
The Federal Circuit rejected United Therapeutics’ arguments that the PTAB:
- Applied an incorrect claim construction;
- Failed to give sufficient weight to the patent’s written description;
- Improperly combined the cited prior art;
- Discounted objective indicia of nonobviousness; and
- Used hindsight to reconstruct the claimed invention.
The court held that substantial evidence supported the PTAB’s factual findings and that the Board correctly applied the obviousness framework under 35 U.S.C. § 103. [1]
Case identification
| Item |
Details |
| Case |
United Therapeutics Corp. v. Liquidia Technologies, Inc. |
| Federal Circuit docket |
No. 23-1805 |
| Court |
U.S. Court of Appeals for the Federal Circuit |
| Patent at issue |
U.S. Patent No. 10,716,793 |
| Patent owner |
United Therapeutics Corporation |
| Petitioner |
Liquidia Technologies, Inc. |
| Proceeding below |
PTAB post-grant review |
| Federal Circuit outcome |
Affirmed PTAB invalidity determination |
| Challenged claims |
Claims 1-8 |
| Technology |
Inhaled treprostinil treatment for pulmonary hypertension |
| Principal commercial products |
United’s Tyvaso franchise and Liquidia’s Yutrepia program |
What patent did United Therapeutics assert against Liquidia?
U.S. Patent No. 10,716,793 is directed to methods of treating pulmonary hypertension with inhaled treprostinil. Treprostinil is a prostacyclin analogue used to treat pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease.
The patent is relevant to United Therapeutics’ inhaled treprostinil products because it addresses administration by inhalation and therapeutic dosing. The patent was issued in 2020 and assigned to United Therapeutics Corporation. [2]
The challenged claims covered a treatment method involving administration of treprostinil, or a pharmaceutically acceptable salt, to a patient with pulmonary hypertension. The claimed treatment parameters included inhalation-based delivery and defined dosage conditions.
The dispute did not concern whether treprostinil itself was known. Treprostinil had been disclosed and commercialized before the ’793 patent. The central issue was whether the claimed inhaled administration regimen represented a patentable advance over the prior art.
Why did the PTAB find the ’793 patent obvious?
The PTAB concluded that a skilled person would have had reason to use inhaled treprostinil in the claimed manner based on the prior-art record. The Board found a motivation to combine relevant disclosures and determined that the claimed result was within the expected scope of the prior art.
The PTAB’s analysis relied on evidence concerning:
- Prior clinical work involving treprostinil;
- Inhaled prostacyclin therapy;
- Known pulmonary hypertension treatment protocols;
- Treprostinil dosing and pharmacology;
- Nebulized or inhaled pulmonary vasodilator delivery; and
- The expected benefits of administering treprostinil directly to the lungs.
United Therapeutics argued that the prior art did not provide a sufficient reason to select the claimed dose and administration parameters. It also relied on alleged unexpected results and commercial success.
The PTAB found those arguments insufficient. The Board determined that the evidence did not overcome the prima facie showing of obviousness.
How did the Federal Circuit analyze obviousness?
The Federal Circuit applied the conventional four-part obviousness framework:
- The scope and content of the prior art;
- Differences between the prior art and the challenged claims;
- The level of ordinary skill in the art; and
- Objective evidence of nonobviousness.
The court gave deference to the PTAB’s factual findings, including findings concerning what the prior art disclosed, what a skilled person would have understood, and whether the prior art supplied a reason to combine references. The ultimate legal conclusion of obviousness was reviewed de novo, but the underlying findings were reviewed for substantial evidence. [1]
The Federal Circuit held that the PTAB’s reasoning was supported by the record. It did not identify a legal error in the Board’s treatment of the prior art or secondary considerations.
The decision is significant because it confirms that a dosing or administration regimen involving a known active ingredient can be invalidated when the prior art provides a reason to select the claimed route and dosing parameters and the claimed results are reasonably predictable.
What was the litigation timeline?
| Date |
Event |
| 2020 |
U.S. Patent No. 10,716,793 issued to United Therapeutics |
| 2021 |
Liquidia initiated a post-grant review challenging the ’793 patent |
| 2023 |
PTAB issued a final written decision finding claims 1-8 unpatentable |
| 2023 |
United Therapeutics appealed to the Federal Circuit |
| 2024 |
Federal Circuit affirmed the PTAB in No. 23-1805 |
| Post-decision |
The ’793 patent could no longer operate as an enforceable barrier against Liquidia’s corresponding product program |
The Federal Circuit’s judgment ended the appellate challenge to the PTAB decision. The decision did not invalidate every United Therapeutics patent relating to treprostinil. It addressed the ’793 patent and the claims challenged in that proceeding.
What is the relationship between the 23-1805 appeal and the Delaware litigation?
The Federal Circuit appeal was a patent-validity appeal from a PTAB post-grant review. It should be distinguished from United Therapeutics’ separate infringement litigation against Liquidia in the U.S. District Court for the District of Delaware.
United Therapeutics pursued district-court claims concerning Liquidia’s proposed Yutrepia product under the Hatch-Waxman Act. Those proceedings involved patent infringement allegations based on Liquidia’s abbreviated or hybrid drug application and included patents other than, or in addition to, the ’793 patent.
The two proceedings had different legal functions:
| Proceeding |
Primary issue |
Result or commercial effect |
| PTAB post-grant review |
Whether claims 1-8 of the ’793 patent were patentable |
Claims invalidated as obvious |
| Federal Circuit No. 23-1805 |
Whether the PTAB correctly invalidated the claims |
PTAB affirmed |
| Delaware Hatch-Waxman litigation |
Whether Liquidia’s proposed product infringed enforceable United patents |
Separate analysis involving other patent rights and regulatory timing |
Invalidation of the ’793 patent weakened United Therapeutics’ position, but it did not automatically dispose of every patent claim or every litigation issue in Delaware.
What FDA and Orange Book issues affected Liquidia’s Yutrepia?
Liquidia developed Yutrepia as an inhaled treprostinil product for pulmonary hypertension. United Therapeutics marketed Tyvaso inhalation solution and Tyvaso DPI, both based on treprostinil delivery through inhalation.
For a small-molecule drug, the principal regulatory pathway is an ANDA or, depending on the product and reference-product relationship, a 505(b)(2) application. The applicant’s certification against Orange Book-listed patents can trigger Hatch-Waxman litigation and a potential 30-month stay under the statutory framework.
The ’793 litigation formed part of a larger patent dispute concerning whether United Therapeutics’ listed patents could delay approval or commercial launch of Liquidia’s product. FDA approval, patent certification, court orders and settlement terms must be analyzed separately. A patent invalidity judgment does not itself grant FDA approval, and FDA approval does not eliminate an enforceable patent.
Tyvaso and Yutrepia are small-molecule products. Biosimilar law under the Biologics Price Competition and Innovation Act does not apply. The relevant competitive threat is generic or follow-on inhaled treprostinil competition, not biosimilar substitution.
What patent protections remain for Tyvaso and inhaled treprostinil?
United Therapeutics’ patent estate has included multiple patent families covering treprostinil products and delivery systems. The relevant categories include:
Active ingredient and chemical patents
Earlier patents covering treprostinil chemistry, salts, intermediates or pharmaceutical compositions may expire before later formulation and method patents. These patents are less likely to provide long-term protection if the active ingredient is already established as a generic drug substance.
Formulation patents
Formulation claims can cover:
- Treprostinil inhalation solutions;
- Dry-powder formulations;
- Pharmaceutical salts;
- Excipient combinations;
- Particle-size distributions;
- Concentration ranges; and
- Stability characteristics.
Formulation patents can impose meaningful launch risk if a proposed product uses the claimed composition, even when the active ingredient is old.
Delivery-device patents
United Therapeutics and its commercial partners have pursued intellectual property relating to inhalation devices and delivery systems. Device patents may cover aerosol generation, cartridge design, dose metering, airflow, powder dispersion and reusable hardware.
A device patent may be avoided through a redesigned delivery system, but the commercial substitute must still satisfy performance, usability and regulatory requirements.
Method-of-use patents
Method patents can cover:
- Treatment of pulmonary arterial hypertension;
- Treatment of pulmonary hypertension associated with interstitial lung disease;
- Dose escalation;
- Frequency of administration;
- Treatment of specific patient populations; and
- Use of inhaled treprostinil in defined disease settings.
These patents can create litigation exposure even when a generic applicant does not copy a formulation or device claim. Their practical value depends on claim scope, labeling, inducement evidence and the availability of a lawful carve-out.
When does United Therapeutics lose exclusivity for Tyvaso?
There is no single exclusivity date for the Tyvaso franchise. Exclusivity depends on the specific product, patent, regulatory approval and listed Orange Book rights.
The ’793 patent lost enforceability against the challenged claims when the Federal Circuit affirmed the PTAB’s invalidity determination. That result removed one patent barrier but did not establish a universal Tyvaso patent-expiration date.
United’s commercial exposure depends on four separate dates:
- FDA regulatory exclusivity expiration;
- Orange Book patent expiration;
- The enforceability of formulation and method-of-use patents; and
- Any settlement, license or launch agreement with Liquidia.
Patent-term calculations also depend on patent-term adjustment, terminal disclaimers, priority claims and any applicable patent-term extension. A simple 20-year calculation from the filing date is not sufficient for a definitive launch date.
Which company challenged United Therapeutics’ patent estate?
Liquidia Technologies was the principal challenger in the ’793 post-grant review and the associated Yutrepia patent controversy.
Liquidia’s strategy combined:
- PTAB validity challenges;
- FDA regulatory development of Yutrepia;
- Hatch-Waxman patent certifications;
- District-court litigation; and
- Commercial preparation for a competing inhaled treprostinil product.
The strategy targeted the commercial concentration of United Therapeutics’ pulmonary hypertension portfolio. United’s response relied on its patent estate, infringement litigation and regulatory exclusivity.
How strong is the patent estate after the 23-1805 decision?
The estate is weaker than before the Federal Circuit ruling, but the decision does not establish that all United Therapeutics treprostinil patents are invalid.
Strengthening factors
- Multiple patent families may cover different aspects of the product.
- Formulation and device claims can be difficult to design around.
- Method-of-use patents may remain relevant to labeled indications.
- Regulatory approval and physician prescribing behavior can delay practical substitution.
- United has commercial and clinical data supporting the Tyvaso franchise.
Weakening factors
- Treprostinil is an established active ingredient.
- Inhaled prostacyclin therapy was known before the ’793 patent.
- Dose and administration claims may face obviousness challenges.
- Liquidia demonstrated an effective PTAB challenge strategy.
- A competing inhaled product can create price and formulary pressure even if some patents remain enforceable.
The ’793 decision is adverse precedent for broad treatment-regimen claims where the active ingredient, disease indication and inhaled delivery route were already known.
What generic launch risks existed after the Federal Circuit ruling?
Liquidia’s launch risk shifted from validity of the ’793 patent to the remaining patent and regulatory barriers.
Low-risk scenario
Liquidia obtains FDA approval, defeats or resolves the remaining patent claims, and launches Yutrepia without a material launch restriction.
Intermediate-risk scenario
Liquidia receives FDA approval but must delay launch, limit its label or negotiate a license because one or more formulation, device or method patents remain enforceable.
High-risk scenario
A court enters an injunction or finds infringement of a surviving patent with claims that cover Liquidia’s product. Approval would not necessarily permit immediate commercial marketing.
The Federal Circuit ruling materially improved Liquidia’s position because it eliminated the ’793 patent as an enforceable claim set. It did not eliminate the need to evaluate the rest of the Orange Book and litigation record.
What was the commercial impact on Tyvaso and Yutrepia?
United Therapeutics’ pulmonary hypertension business is heavily exposed to treprostinil products. Tyvaso has been a major revenue contributor, with sales growth supported by the inhaled product’s use in pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease.
A competing inhaled treprostinil product could affect United through:
- Lower net pricing;
- Payer-driven substitution;
- Reduced new-patient starts;
- Rebate pressure;
- Distributor and specialty-pharmacy negotiations;
- Slower growth of Tyvaso DPI; and
- Reduced franchise valuation.
The size of the impact depends on Yutrepia’s label, device usability, dosing convenience, reimbursement status, manufacturing capacity and launch timing. Patent invalidity alone does not determine market share.
What settlement agreements or licenses affected the dispute?
The Federal Circuit’s No. 23-1805 decision resolved the appeal concerning the ’793 patent. It did not itself create a license or settlement agreement.
Any separate settlement between United Therapeutics and Liquidia would need to be evaluated based on its operative terms, including:
- Permitted launch date;
- Product scope;
- Geographic territory;
- Royalty obligations;
- Patent releases;
- Authorized-label restrictions;
- Manufacturing rights; and
- Treatment of future patent claims.
A settlement can preserve commercial delay even after a patent is invalidated if the parties agree to a later launch or other market restriction.
What does the case mean for pharmaceutical patent strategy?
The case demonstrates the vulnerability of late-filed method patents built around an established active ingredient and known route of administration.
For branded companies, stronger protection usually requires claims that are technically distinct and supported by reproducible data, such as:
- Defined formulation properties;
- Device-specific performance;
- Narrow patient populations;
- Demonstrated pharmacokinetic advantages;
- Unexpected clinical outcomes; or
- Manufacturing constraints that are difficult to replicate.
For generic and follow-on applicants, the decision supports early use of PTAB proceedings against weakly supported formulation and treatment claims. A successful post-grant review can remove patent barriers before the applicant reaches commercial launch.
Key Takeaways
- The Federal Circuit affirmed invalidity of claims 1-8 of United Therapeutics’ ’793 patent.
- The patent covered inhaled treprostinil treatment for pulmonary hypertension.
- Liquidia was the successful post-grant review challenger.
- The decision removed the ’793 patent as a barrier to Liquidia’s Yutrepia program.
- The case did not invalidate every United Therapeutics patent covering Tyvaso or treprostinil.
- Tyvaso exclusivity depends on separate Orange Book patents, regulatory exclusivity, litigation outcomes and any settlement terms.
- Yutrepia is a small-molecule follow-on product, so biosimilar law does not apply.
- Remaining risks center on formulation, device, method-of-use and manufacturing patents.
- The ruling weakens broad dosing-regimen claims involving known treprostinil therapy.
- Commercial impact depends on FDA approval, reimbursement, product performance and the timing of any lawful launch.
FAQs
Does the Federal Circuit decision make Liquidia’s Yutrepia automatically available for sale?
No. The decision invalidated the challenged claims of the ’793 patent. Liquidia still required FDA approval and had to address other enforceable patents, regulatory conditions and any applicable court orders.
Was Tyvaso itself found invalid?
No. The decision concerned U.S. Patent No. 10,716,793. It did not invalidate Tyvaso, its FDA approval or every patent associated with the Tyvaso franchise.
Is Yutrepia a generic version of Tyvaso?
Yutrepia is a competing inhaled treprostinil product. Its regulatory pathway and legal relationship to Tyvaso depend on the application type, reference product and FDA determinations. It is not a biosimilar.
Can United Therapeutics sue Liquidia again after losing the ’793 appeal?
Yes. Patent owners can assert separate patents that cover a different formulation, device, manufacturing process or method of use. A final judgment concerning the ’793 patent does not eliminate unrelated patent claims.
What is the main patent weakness identified by the case?
The principal weakness was the use of broad treatment claims involving a known active ingredient, known pulmonary hypertension therapy and known inhaled administration concepts without sufficient evidence of a nonobvious technical advance.
References
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United States Court of Appeals for the Federal Circuit. (2024). United Therapeutics Corporation v. Liquidia Technologies, Inc., No. 23-1805. Federal Circuit opinions. https://cafc.uscourts.gov/opinions-orders/
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United States Patent and Trademark Office. (2020). U.S. Patent No. 10,716,793, Methods of treating pulmonary hypertension. Google Patents. https://patents.google.com/patent/US10716793B2/en
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U.S. Food and Drug Administration. (2024). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/
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U.S. Food and Drug Administration. (2024). Approved drug products and regulatory information for pulmonary hypertension therapies. https://www.fda.gov/drugs
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United States Patent and Trademark Office. (2024). Patent Trial and Appeal Board decisions and post-grant review proceedings. https://ptacts.uspto.gov/ptacts/public-informations/petitions/ biclent.cgi?application=G202100069
