The U.S. Food and Drug Administration has granted orphan drug status to SM04646, San Diego-based Samumed‘s treatment for idiopathic pulmonary fibrosis.

SM04646, which is delivered in a mist, could be approved as a stand-alone therapy. Or it could win authorization as a combo treatment with Esbriet (pirfenidone) or Ofev (nintedanib).

“The FDA’s decision to grant an orphan drug designation to SM04646 for IPF is another important milestone in the development of SM04646,” Yusuf Yazici, Samumed’s chief medical officer, said in a press release.

“IPF is a chronic, progressive, fibrotic [tissue-scarring] disorder that causes deteriorating lung function and severe dyspnea [shortness of breath] in patients and ultimately ends in fatality,” Yazici said. “Early trials demonstrate the therapeutic potential of SM04646 to help address the unmet medical need of individuals with IPF.”

An orphan drug designation is granted to treatments for rare diseases — those that affect fewer than 200,000 people in the United States. The maker must also show that the therapy is likely to be effective against the disease it is designed to treat.

The FDA decision follows Samumed’s announcement this month that a Phase 1 clinical trial in healthy people in Australia (ACTRN12615001349538) showed that a nebulized inhalation solution of SM04646 was safe.

Participants also tolerated SM04646 well, with no reports of serious adverse events or dose-limiting toxicity.

A presentation at the American Thoracic Society‘s annual meeting in Washington in May 2017 indicated that SM04646 countered tissue scarring better than Esbriet and Ofev in laboratory cultures of normal human lung cells and cells with IPF.

Samumed’s next challenge will be to change physicians’ and patients’ perceptions. A recently published comparison study showed that Esbriet and Ofev, the first two approved therapies for IPF, are still the most prescribed.

Studies have also shown that other drugs, such as Promedior‘s PRM-151, outperform Esbriet and Ofev. Physicians say Esbriet and Ofev’s reliability is why they keep prescribing them.

IPF is the most common scarring-related lung disease that pulmonologists see. There is no cure for it, and treatments remain limited.