The FDA has delivered another twist in United Therapeutics’ long-running effort to win approval for the dry powder version of pulmonary hypertension drug Tyvaso. After rejecting the drug last year, the FDA has delayed its decision on the resubmission to review data on the safety of an excipient.
In July, a law firm acting on behalf of an unnamed client asked the FDA to refuse to approve Tyvaso DPI in the absence of additional clinical data on its safety in patients with chronic lung diseases. The Citizen Petition raised concerns with the risk of acute bronchospasm linked to fumaryl diketopiperazine, a novel excipient only previously approved for use in Mannkind’s ill-fated inhaled insulin product Afrezza.
The FDA was still reviewing the petition when it hit United Therapeutics with a complete response letter in relation to an open inspection issue at a third-party facility. As part of its review, the FDA asked United Therapeutics to submit additional information on the pulmonary safety of Tyvaso DPI.
With the FDA classing United Therapeutics’ response as a major amendment, the agency has pushed back its review deadline until May 2022. United Therapeutics CEO Martine Rothblatt downplayed the impact of the delay on a quarterly results conference call with investors.
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“That three-month detour is not important compared to the product's blockbuster revenue potential and patent life well into the 2030s. Three-months delay to start on a billion-dollar revenue trajectory is no big deal,” Rothblatt said. “We have not experienced those bronchospasm side effects. We really don't believe that that's going to be an issue at all.”
United Therapeutics still expects to launch Tyvaso DPI in the summer. Inventory and a sales team are in place, positioning the company to move quickly if the FDA approves the product in May. The draft label prepared for the original, rejected submission lacked any contraindications or boxed warnings.