• The FDA designation expands Atossa’s investigational therapy into rare pediatric neuromuscular disease.
• The program could become eligible for a Priority Review Voucher upon future approval.
• Preclinical data remains encouraging, with the therapy not limited to exon-specific targeting.

Shares of Atossa Therapeutics (ATOS) rose 10% on Thursday after the company said the U.S. Food and Drug Administration (FDA) granted Rare Pediatric Disease designation to its investigational therapy (Z)-Endoxifen for Duchenne Muscular Dystrophy.

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Potential For Priority Review Voucher

The company said the designation expands the program into rare pediatric neuromuscular disease and may qualify Atossa for a Priority Review Voucher (PRV) upon future approval. 

The Rare Pediatric Disease designation is reserved for serious or life-threatening conditions affecting individuals from birth to 18 years old. Atossa noted that FDA authority to award new vouchers may lapse unless renewed, with pending U.S. legislation seeking to extend the program through 2029.

Janet Rea, Senior Vice President of Research and Development, said emerging preclinical data is encouraging and noted that (Z)-Endoxifen does not target specific genetic errors, potentially allowing broader applicability.

Last Week’s FDA Interaction

Last week, Atossa completed a Type C meeting with the FDA to review regulatory strategy for advancing (Z)-Endoxifen across metastatic disease, neoadjuvant treatment and breast cancer risk-reduction settings. The FDA provided feedback on expedited regulatory pathways, clinical development design and endpoint strategy that the company said could support a streamlined registrational approach.

CEO Steven Quay said the meeting allowed the company to incorporate FDA input into development planning and could shorten its regulatory timeline. Rea said the clinical program is now supported by data from nearly 800 participants enrolled across multiple trials.

Drug Targets Key Cancer Pathways

(Z)-Endoxifen is a medicine designed to block and break down estrogen receptors, including in tumors that no longer respond to other hormone treatments. It also acts on another cancer-related pathway called protein kinase C beta 1.

Atossa is developing an oral version of the drug that passes through the stomach without being changed. This prevents some of the active form from turning into an inactive form and helps keep the drug working as intended.

Clinical studies in nearly 800 adults, including both healthy volunteers and people with breast cancer, have shown the drug to be well tolerated at doses up to 360 mg per day, with no maximum tolerated dose identified.

How Did Stocktwits Users React?

On Stocktwits, retail sentiment for Atossa was ‘extremely bullish’ amid ‘extremely high’ message volume.

One bullish user said compliance might still be achievable given Atossa’s current position, though they noted it would depend on the stock staying above $1 or on fresh fund inflows.

Another user said they were “100% confident we get fda fast track for p3 [phase 3].” 

Atossa’s stock has declined 3.7% so far in 2025.

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