United sues FDA to try to block rival’s drug application

In an unusual move, United Therapeutics has filed a lawsuit against the FDA which claims the regulator is sidestepping established norms in allowing rival Liquidia to file for approval of a competitor to its Tyvaso product.

The suit claims that the FDA “mistakenly permitted Liquidia…to skirt longstanding FDA rules, precedents, and procedures on how pending drug approval applications are handled by the agency.”

The complaint revolves around the attempt by Liquidia to add pulmonary hypertension associated with interstitial lung disease (PH-ILD) to the label of Yutrepia, a dry powder inhaler (DPI) formulation of prostacyclin analogue treprostinil, as an amendment to the product’s earlier new drug application (NDA) for pulmonary arterial hypertension (PAH).

United’s Tyvaso – also based on treprostinil and available in DPI and nebuliser formulations – has been approved to treat PH-ILD since 2021 and has also been cleared since 2009 to treat PAH. The DPI version is the company’s top-selling product with sales of $731 million last year, almost a third of total revenues, so there is a lot at stake for United.

Yutrepia received a tentative approval from the FDA in 2021 for PAH but has been unable to launch due to a patent infringement lawsuit filed by United. Under the long-established Hatch-Waxman Act, that triggers a stay on full approval by the FDA for 30 months or until the litigation is resolved.

United’s position is that by allowing Liquidia to file for PH-ILD as an amendment rather than a new NDA last July, Liquidia has been able to dodge the 30-month stay process for the second indication that would kick in with pending patent litigation.

The FDA had been due to deliver its verdict on PAH last month but delayed that to deal with the amendment and has not issued a new deadline.

In allowing the amendment route, the FDA has ignored “the proper review and approval of new drug applications in a fair, equitable manner consistent with the FDA’s prior practices with which industry has complied for decades,” according to the complaint.

United claims that before 2021, every clinical trial of drugs approved for the treatment of PAH that were studied for the treatment of PH-ILD failed, and some approved therapies worsened symptoms.

Tyvaso was the first approved therapy for PH-ILD, showing efficacy in the INCREASE clinical trial which United ran at “considerable expense,” and Liquidia is now piggy-backing on that effort, according to the company.

“We are simply asking that the FDA apply its own rules and precedents consistently to honour the Hatch-Waxman balance struck by Congress between innovators and imitators,” said United’s head of global regulatory affairs Dean Bunce.

“Liquidia can rely on United Therapeutics’ innovation to speed its path to market, but the cost of that shortcut is that Liquidia must address the infringement claim against it before rushing to market,” he added.