Atossa Therapeutics Advances Breast Cancer Treatment with Promising (Z)-endoxifen Findings at ASCO 2026

Atossa Therapeutics (ATOS) announces significant advancements in breast cancer treatment with two abstracts accepted for presentation at the ASCO 2026 Annual Meeting. The focus is on the efficacy of (Z)-endoxifen in targeting estrogen receptor-positive (ER-positive) breast cancer, a common subtype that presents challenges in treatment due to endocrine resistance often linked to ESR1 mutations. CEO Dr. Steven C. Quay highlights the critical role of their preclinical studies, which demonstrate substantial inhibition of estrogen receptors across clinically relevant ESR1 mutations. This breakthrough presents (Z)-endoxifen as a potential alternative in the treatment landscape, addressing a pressing need for innovative therapies that can overcome the limitations posed by existing options.

Robust Findings on (Z)-endoxifen's Efficacy

In the detailed findings of the studies, Atossa reveals robust dose-dependent inhibition of the estrogen receptor in MCF-7 breast cancer cells. The results indicate that (Z)-endoxifen proves effective against several ESR1 mutations, positioning it as a promising contender against current therapies such as elacestrant, which has its own limitations. This data underscores the importance of continuous research and development in finding viable solutions for patients with resistant forms of breast cancer.

Ongoing EVANGELINE Phase 2 Trial

The company also shares insights from its ongoing EVANGELINE Phase 2 trial. This pivotal study evaluates the combination of (Z)-endoxifen and goserelin as a neoadjuvant treatment for premenopausal women suffering from ER+/HER2-negative breast cancer. The primary goal is to achieve a significant reduction in Ki-67, a marker of cancer proliferation, with a target of at least 65% of participants showing improvement after just four weeks. The trial has begun enrollment, which is a crucial milestone for Atossa’s clinical development and holds promise for enhancing treatment outcomes in a demographic often underrepresented in clinical trials.

Future Prospects for Breast Cancer Treatment

As Atossa Therapeutics moves forward with these initiatives, the company seeks to address the urgent need for effective treatments in breast cancer, focusing on various mutations and patient demographics. The culmination of these efforts not only aligns with their mission to innovate but also signifies a hopeful outlook for many patients navigating the complexities of cancer therapies.