Atossa Therapeutics, Inc. is a clinical-stage biopharmaceutical company. It is engaged in developing medicines in areas of significant unmet medical need in oncology with a focus on using (Z)-endoxifen to prevent and treat breast cancer. Its lead drug candidate under development is oral (Z)-endoxifen, which it is developing for both the prevention and treatment of breast cancer. (Z)-endoxifen is the potent Selective Estrogen Receptor Modulator for estrogen receptor inhibition and causes estrogen receptor degradation. In addition to its potent anti-estrogen effects, (Z)-endoxifen has been shown to target PKCB1, a known oncogenic protein, at clinically attainable blood concentrations. It is developing a form of (Z)-endoxifen which is administered orally for the potential treatment of breast cancer and reduction of breast density. It has completed four Phase I clinical studies and two Phase II clinical studies with its proprietary (Z)-endoxifen (including oral and topical formulations).