Atossa Therapeutics provides five-year (Z)-endoxifen update

Atossa Therapeutics announced on Tuesday that the pre-menopausal, Estrogen Receptor positive, or ER+ / Human Epidermal Growth Factor Receptor 2 negative, breast cancer patient who received neoadjuvant and adjuvant-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. 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 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. The FDA authorized a single-patient study under its Expanded Access or compassionate use program for this woman to receive 4 mg/day oral (Z)-endoxifen for 20 days before surgery. Following surgery, her physician recommended adjuvant therapy but, like many women, she was not a candidate for tamoxifen due to her low liver enzyme activity. She also did not want to take drugs to suppress her ovarian function and go into early menopause, which meant aromatase inhibitors were not an option. Given the strong and rapid response to (Z)-endoxifen, it was recommended that she continue taking (Z)-endoxifen. This led to an additional compassionate use authorization by the FDA to allow this patient to continue taking 4 mg/day (Z)-endoxifen in the adjuvant setting. She has now completed five years of daily (Z)-endoxifen. As of the date of this press release, she has not had a recurrence of breast cancer or a new cancer in the contralateral breast, as assessed by clinical examination and mammography. Additionally, the treatment has been well tolerated, and there were no vasomotor symptoms commonly associated with tamoxifen. Under the FDA Expanded Access IND program, the use of Atossa’s proprietary (Z)-endoxifen is restricted to this patient only.