Atossa Therapeutics, Inc.

We are a clinical-stage biopharmaceutical company focused on developing innovative medicines for significant unmet medical needs in oncology, specifically breast cancer and other breast conditions. Our primary drug candidate is oral (Z)-endoxifen, a selective estrogen receptor modulator (SERM)/selective estrogen receptor degrader (SERM/D), which is currently in Phase 2 clinical development. We are exploring various indications for (Z)-endoxifen based on its pharmacological profile, including its potential to reduce the risk of and treat breast cancer, as well as other therapeutic areas. We hold U.S. and international patents for our proprietary (Z)-endoxifen and have numerous applications pending in the U.S. and other major countries. We anticipate patent protection for (Z)-endoxifen through at least November 17, 2038. Our business strategy involves advancing our programs through clinical studies, potentially with partners, and opportunistically acquiring or developing new programs in areas of high unmet medical need. (Z)-endoxifen is the most active metabolite of Tamoxifen, demonstrating substantially greater potency as an estrogen receptor antagonist compared to Tamoxifen and other approved SERMs. Unlike Tamoxifen, (Z)-endoxifen does not require metabolic activation via CYP2D6 and other liver enzymes to reach therapeutic concentrations, meaning its activity is not affected by patient-specific metabolic variability. This small-molecule oral agent is designed to directly inhibit estrogen receptor signaling, induce estrogen receptor degradation, and promote apoptosis in estrogen receptor positive (ER+) breast cancer cells. Preclinical and clinical data indicate that (Z)-endoxifen may inhibit clinically relevant ESR1 mutations linked to aromatase inhibitor resistance and may also inhibit protein kinase C beta one (PKCβ1), leading to downregulation of the AKT signaling pathway. We are evaluating (Z)-endoxifen in multiple settings within the ER+/human epidermal growth factor receptor 2 negative (HER2-) breast cancer treatment continuum, including neoadjuvant, adjuvant, and breast density reduction indications. An ongoing neoadjuvant clinical study has shown early signs of anti-tumor activity for (Z)-endoxifen.