United Therapeutics’ effort to renew a dismissed patent on its ageing pulmonary arterial hypertension medication Tyvaso (treprostinil) was denied two months ago by a federal appeals court. This removed one obstacle for the FDA to grant approval for a competing therapy from Liquidia Corporation of North Carolina.

United is now taking a new approach in its fight against its prospective rival: it is suing the FDA, casting doubt on the agency’s diligence in approving Yutrepia, Liquidia’s heart medication.

United asserts in a complaint submitted that the FDA provided Liquidia with the opportunity to circumvent “rules, precedents, and procedures” by adding an addendum to its pending application for a new drug application (NDA) in September of the previous year. In the revision, a second indication, pulmonary hypertension linked to interstitial lung disease (PH-ILD), is proposed to be added. United maintains that this indication should only be granted approval through the use of a separate NDA.

The FDA appears to have concerns over its method as well. The regulatory body postponed its decision on whether or not to approve Yutrepia, which had a target decision date of January 24. The case was filed four weeks after the postponement.

The next day, Liquidia issued a press statement in which it explained that the FDA is “confirming the process for adding the PH-ILD indication as an amendment to the NDA.” The company also mentioned that the FDA did not require any further clinical data and made no announcement on a new decision date.

In 2020, Liquidia filed its request for approval of Yutrepia. One year later, the FDA gave its provisional blessing to the drug, indicating that it was both effective and safe.

As per Chief Business Officer Jason Adair, Liquidia did not have any comment other than to say that it was examining the news and the case before making any further statements.

United also announced its annual earnings and fourth-quarter results. The company disclosed that it had achieved an all-time high revenue of $2.33 billion for 2023, which represented a 20% increase from 2022. This was mostly attributable to the growing sales of Tyvaso. The revenue generated by the medication for the year reached $1.23 billion, representing a 41% increase from 2022. The new dry-powdered formulation of the therapy that United developed contributed $731 million to the total income.

The original nebulized form of Tyvaso saw a 30% drop in sales to $512 billion in the previous year; in May 2022, an alternative called Tyvaso DPI was authorized. In April 2021, United included the PH-ILD indication for Tyvaso.

United has entered into agreements that would enable generics manufacturers to start selling nebulized Tyvaso imitations beginning in January 2026, as revealed in an annual filing with the Securities and Exchange Commission that was made public on Wednesday.

United’s legal action against the FDA has captured the attention of the Public Innovation Project (PIP), an advocacy outfit that has referred to the litigation as a “sham.”

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