Atossa Therapeutics is a clinical-stage biopharmaceutical company developing a single drug candidate, oral (Z)-endoxifen, primarily for breast cancer. (Z)-endoxifen is the active metabolite of tamoxifen — one of the most widely used breast cancer drugs — but unlike tamoxifen, it doesn't require metabolic conversion via the CYP2D6 enzyme, which Atossa argues makes it more potent and consistent across patients. Atossa is running multiple clinical programs across breast cancer indications: metastatic ER+/HER2- breast cancer (its stated near-term priority), neoadjuvant breast cancer (the I-SPY 2 trial), mammographic breast density reduction, DCIS, and a neoadjuvant study comparing (Z)-endoxifen to exemestane. Beyond breast cancer, Atossa is exploring (Z)-endoxifen in rare diseases including Duchenne Muscular Dystrophy and McCune-Albright Syndrome, where the FDA has granted Orphan Drug and Rare Pediatric Disease designations — potentially making Atossa eligible for a Priority Review Voucher, which could be sold to another pharmaceutical company for significant cash. Atossa has no products approved and no revenue. The company relies entirely on cash reserves and periodic equity raises to fund operations, and has disclosed going concern doubt. Atossa uses third-party CROs and CMOs for all research and manufacturing, keeping fixed costs low but creating dependency on external partners. If approved, Atossa would sell (Z)-endoxifen as a prescription drug targeting the large ER+ breast cancer market.