Atossa Therapeutics Provides Five-Year (Z)-Endoxifen Treatment Update on FDA-Approved "Expanded Access" Program for a U.S. Breast Cancer Patient

SEATTLE, March 19, 2024 (GLOBE NEWSWIRE) -- Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), today announced that the pre-menopausal, Estrogen Receptor positive (ER+) / Human Epidermal Growth Factor Receptor 2 negative (HER2-), breast cancer patient who received neoadjuvant and adjuvant (Z)-endoxifen therapy under an FDA-approved "expanded access" program has completed five years of treatment. As of the date of this press release, the patient remains cancer-free and has reported no significant safety or tolerability issues over the course of her treatment. Atossa is a clinical stage biopharmaceutical company developing innovative medicines in areas of significant unmet medical need in oncology with a focus on breast cancer.

"We believe this patient, and her successful treatment journey, is representative of the opportunity (Z)-endoxifen has to change the treatment paradigm for the approximately 250,000 women diagnosed with estrogen receptor positive breast cancer each year in the U.S.,” said Steven Quay, M.D., Ph.D., Atossa’s President and Chief Executive Officer. "The current standard of care is sub-optimal as it often requires ovarian suppression in premenopausal women and aromatase inhibitors in postmenopausal women, both of which are associated with potential short-term and long-term side effects that diminish adherence. Over five years of adjuvant treatment, her daily (Z)-endoxifen treatment has been well tolerated, and there were no vasomotor symptoms commonly associated with standard of care adjuvant pharmaceuticals. She remains cancer-free today and we are grateful to have been able to help her with a difficult treatment problem.”

Patient / Treatment Background

Diagnosis. In late 2018, a 51-year-old premenopausal woman was diagnosed with a moderately differentiated invasive ductal breast carcinoma with the most frequently reported subtype: ER+, PR+, and HER2-. The initial diagnostic biopsy demonstrated that 90% of the tumor cells were ER+ and 20% expressed Ki-67, a tumor proliferation antigen. Pharmacogenomics analysis showed a CYP2D6 genotype of CYP2D6*4/*4, a nonfunctioning variant, suggesting tamoxifen would be a poor treatment option.

Other than breast cancer, the patient had no comorbidities and took no medications. Her family history was strong for osteoporosis, a contraindication for aromatase inhibitor treatment.

Neoadjuvant treatment. Neoadjuvant treatment is given in the window of time between the diagnosis and the primary treatment, which in the case of locally advanced breast cancer is surgery. The intent of neoadjuvant therapy is to slow the growth of the cancer or even shrink the cancer prior to surgery. The goal of this treatment is to help increase the effectiveness of surgery, and it has also been shown to reduce the likelihood that the cancer returns.