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Atossa Therapeutics Announces Plans to Pursue Metastatic Breast Cancer Indication for (Z)-Endoxifen and Continued Engagement with FDA on Additional Indications
SEATTLE, March 11, 2025 (GLOBE NEWSWIRE) -- Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), a clinical-stage biopharmaceutical company
About this update from Atossa Therapeutics, Inc.
[{"type":"text","content":"SEATTLE, March 11, 2025 (GLOBE NEWSWIRE) -- Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), a clinical-stage biopharmaceutical company dedicated to the prevention and treatment of breast cancer, today announced its strategic decision to pursue a metastatic breast cancer indication for (Z)-endoxifen. Atossa believes that pursuing a metastatic indication may offer a more efficient regulatory pathway to deliver (Z)-endoxifen to women in urgent need, and simultaneously plans to work with the FDA to advance additional indications, such as breast cancer prevention and neoadjuvant therapy, that often require larger and longer clinical trials. Addressing the High Unmet Need in Metastatic Breast Cancer Metastatic breast cancer remains a significant area of unmet medical need, with current treatment options often providing limited durability of response and substantial side effects. (Z)-endoxifen, a potent and well-tolerated selective estrogen receptor modulator (SERM), has shown encouraging signals in previous clinical trials, which we believe supports its potential to fill this critical gap in treatment. Promising Data from Phase 1 and Phase 2 Trials (Z)-endoxifen has shown encouraging results in early-stage trials, which we believe reinforces its potential as a transformative therapy for breast cancer. Key findings from early clinical programs include: Significantly improved progression-free survival (PFS) in CDK4/6i-naïve patients: (Z)-endoxifen more than doubled the median PFS compared to tamoxifen (7.2 vs. 2.4 months), highlighting its potency in an endocrine-sensitive population. Substantial activity observed even after tamoxifen progression: Patients in the crossover arm who progressed on tamoxifen and switched to (Z)-endoxifen experienced clinical benefit, including partial responses and prolonged stable disease exceeding 2-3 years in some cases. Favorable safety profile: Despite its higher potency, (Z)-endoxifen has not shown unexpected safety concerns beyond what is typically seen with tamoxifen and has been generally well-tolerated. Dr. Steven Quay, Chairman and Chief Executive Officer of Atossa Therapeutics, stated: “Our decision to advance (Z)-endoxifen into a metastatic breast cancer indication underscores our unwavering commitment to developing a best-in-class therapy for women facing this devastating...