Atossa Therapeutics Receives Positive FDA Feedback for (Z)-endoxifen Trial

Atossa Therapeutics received positive feedback from the FDA on its proposed dose optimization trial for (Z)-endoxifen in metastatic breast cancer. The FDA affirmed key elements of Atossa's clinical development plan, negating the need for a virtual meeting, and paving the way for a potential IND submission in Q4 2025.

Atossa Therapeutics, Inc. (NASDAQ: ATOS) has received positive feedback from the U.S. Food and Drug Administration (FDA) regarding its proposed dose optimization trial for (Z)-endoxifen in treating estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer. The FDA's constructive responses affirmed key elements of Atossa's clinical development plan, negating the need for a pre-Investigational New Drug (IND) meeting and paving the way for a potential IND submission in the fourth quarter of 2025 [1].

The FDA's feedback includes approval of Atossa's dose optimization strategy, support for combination studies with standard-of-care therapies, confirmation of adequate nonclinical data, and agreement on cardiac safety assessments [2]. Notably, the FDA deemed the existing nonclinical safety data package sufficient to proceed without additional toxicity studies, which represents a significant time and cost advantage for the company [2].

The positive feedback aligns with the FDA's Project Optimus initiative, which emphasizes data-driven dose exploration to maximize benefits while minimizing toxicity [2]. Atossa plans to submit an IND in Q4 2025 and will soon announce specific details about the target patient population and trial design [2].

The development of (Z)-endoxifen, an active metabolite of tamoxifen, holds promise for treating ER+/HER2- metastatic breast cancer, which represents approximately 70% of all breast cancer cases [2]. The compound directly binds to estrogen receptors and has shown activity in tumors resistant to other endocrine therapies [3].

Atossa's progress reflects strong strategic momentum, aligning well with FDA expectations and regulatory standards. The company is committed to advancing its clinical research programs to improve patient outcomes and create sustainable value for shareholders [3].

References:
[1] https://www.marketscreener.com/news/atossa-therapeutics-announces-positive-fda-feedback-advances-toward-ind-for-z-endoxifen-clinical-ce7c5fd9de8cfe20
[2] https://www.stocktitan.net/news/ATOS/atossa-therapeutics-announces-positive-fda-feedback-advances-toward-pdh6ocu9e3nc.html
[3] https://www.morningstar.com/news/pr-newswire/20250729sf39600/atossa-therapeutics-announces-positive-fda-feedback-advances-toward-ind-for-z-endoxifen-clinical-program-in-erher2-metastatic-breast-cancer