#USA #Chicago #Atossa Therapeutics #Z-Endoxifen #EVANGELINE Trial

Atossa Therapeutics at ASCO 2026

Atossa Therapeutics Inc. recently announced that two significant abstracts will be presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting scheduled for May 29 to June 2, 2026, in Chicago, IL. These presentations focus on their lead investigational drug, (Z)-endoxifen, which is currently being developed as a treatment for estrogen receptor-positive (ER+) breast cancer, particularly in patients with ESR1 mutations that lead to endocrine resistance.

Insights into (Z)-endoxifen and ESR1 Mutations

Dr. Steven C. Quay, President and CEO of Atossa, emphasized the promising potential of (Z)-endoxifen, indicating that recent preclinical results exhibit strong estrogen receptor (ER) inhibition across clinically relevant ESR1 mutations. This capability is particularly notable, as ESR1 mutations are linked to significant challenges in treating ER+ breast cancers due to their often-resistant nature against standard endocrine therapies, which limits available treatment options.

Key Findings from Preclinical Studies

The first abstract presented at ASCO highlights how (Z)-endoxifen achieved robust inhibition of ER signaling in various ESR1-mutant models at concentrations typically found in clinical settings. Noteworthy data from the studies include:

• - Robust Dose-Dependent Inhibition: (Z)-endoxifen showcased statistically significant inhibition of ER activity, reducing it to percentages ranging from 16% to 26% in control models (p < 0.001).
• - Consistent Effect Across Mutations: The drug exhibited uniform ER inhibition across key mutations, such as Y537N, Y537S, and D538G (p < 0.01).
• - Comparison with Other SERDs: When compared to other oral Selective Estrogen Receptor Degraders (SERDs) like elacestrant and imlunestrant, (Z)-endoxifen displayed enhanced efficacy, particularly in models with the D538G mutation that is typically notorious for its resistance to treatment.

EVANGELINE Phase 2 Trial Overview

The second abstract concerns the ongoing EVANGELINE Phase 2 trial, which focuses on the use of (Z)-endoxifen combined with goserelin as a neoadjuvant therapy for premenopausal women diagnosed with ER+/HER2-negative breast cancer. The trial, identified as NCT05607004, uses a multicenter, open-label design, and aims to measure the drug's effectiveness in reducing tumor proliferation markers such as Ki-67.

Trial Objectives and Design

The goals of the EVANGELINE trial are multifaceted:

• - Primary Objective: To evaluate the percentage of women with baseline Ki-67 levels exceeding 10% who manage to achieve levels of 10% or less after a treatment period of four weeks.
• - Design: Using a Simon two-stage design, the trial intends to initially enroll 20 patients, with an additional 25 expected if the results from the first stage show promise.
• - Secondary Objectives: Besides assessing safety and tolerability, the trial aims to analyze residual cancer burdens and evaluate the PEPI score, complemented by a look at specific tumor and plasma biomarkers.

Dr. Quay iterated the importance of the EVANGELINE trial in delineating (Z)-endoxifen’s neoadjuvant potential, reinforcing its capability to meet the pressing needs of patients facing limited therapeutic options for advanced ER+ breast cancer.

Conclusion

As (Z)-endoxifen progresses through clinical trials, Atossa Therapeutics continues to focus on innovative solutions for breast cancer treatment, seeking to bridge the gap in care for patients with ESR1 mutations through effective and targeted therapies. The anticipation surrounding their presentations at ASCO 2026 underscores the ongoing commitment to develop treatment avenues to combat an area of critical unmet need in oncology.

For more details, visit Atossa Therapeutics’ official website here.