Atossa Therapeutics Announces Shift Towards Metastatic Breast Cancer Indication For (Z)-Endoxifen, Aiming For Efficient Regulatory Pathway; Plans FDA Collaboration For Additional Indications

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.

 

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.