ATOS Stock Jumps 8% Today – An FDA Designation Draws Investor Cheer For Atossa Therapeutics

• The RPD designation is given to therapies targeting serious or life-threatening conditions that primarily affect children.
• (Z)-endoxifen already has an RPD designation for the treatment of Duchenne muscular dystrophy.
• Atossa is currently evaluating the potential applications of (Z)-endoxifen in oncology and rare diseases

Atossa Therapeutics (ATOS) was on investors’ radar on Monday, with the stock gaining more than 8%, after the U.S. Food and Drug Administration granted Rare Pediatric Disease designation to its drug for the treatment of McCune-Albright Syndrome in females.

The RPD designation is given to therapies targeting serious or life-threatening conditions that primarily affect children. If approved through a New Drug Application (NDA) or a Biologics License Application (BLA), drugs with RPD designation may qualify for a Priority Review Voucher (PRV), which provides an expedited review process.

“McCune-Albright Syndrome (MAS) is a rare and serious pediatric disorder with significant unmet medical need, particularly in young girls affected by hormone dysregulation and early puberty. We believe (Z)-endoxifen has the potential to address key disease drivers and improve outcomes for these patients, while also creating potential non-dilutive value through the Rare Pediatric Disease program,” said CEO Steven Quay.

MAS is a rare disorder that can cause early puberty, abnormal bone growth, and endocrine issues in young patients.

Treatment Of DMD

(Z)-endoxifen already has an RPD designation. In December 2025, the FDA granted RPD designation to the drug for the treatment of Duchenne muscular dystrophy (DMD), a severe, genetic muscle disorder that primarily affects young boys. Atossa added that over the past 18 to 24 months, publicly reported PRV sales have ranged between about $100 million and $205 million.

Atossa is evaluating the potential applications of (Z)-endoxifen in oncology and rare diseases, though it has not yet been approved for any indication.

How Did Retail Traders React?

Retail sentiment for ATOS on Stocktwits turned ‘neutral’ from ‘bearish’ a day earlier.

Given the importance of the news, one user expressed disappointment that the stock could not climb to $10. It is currently trading around $5.7.

The stock has declined more than 40% so far this year.

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