Research & Development
Atossa Therapeutics' (Z)-endoxifen receives US FDA Orphan Drug Designation to treat Duchenne muscular dystrophy
19 January 2026 -

Clinical-stage biopharmaceutical company Atossa Therapeutics Inc (Nasdaq:ATOS) announced on Friday that it has received Orphan Drug Designation from the US Food and Drug Administration (FDA) Office of Orphan Products Development (OOPD) for (Z)-endoxifen for the treatment of Duchenne muscular dystrophy (DMD).

Atossa said that it plans to continue engaging with FDA as it advances development efforts, and will provide updates as appropriate.

(Z)-Endoxifen is a potent Selective Estrogen Receptor Modulator/Degrader (SERM/SERD) with demonstrated activity across multiple mechanisms of interest. Atossa is evaluating its potential applications in oncology and rare diseases. According to the company, its proprietary oral formulation has shown a favourable safety profile and pharmacology distinct from tamoxifen, including ER-targeted effects and PKC inhibition. Atossa's (Z)-Endoxifen is not currently approved for any indication.

Orphan Drug Designation is granted by the FDA to therapies intended to treat rare diseases or conditions. The designation is designed to encourage drug development by offering certain potential incentives, such as regulatory support and, if the product ultimately receives marketing approval for the designated indication, eligibility for a period of market exclusivity.

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