---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-25-037634"
form_type: "8-K"
ticker: "ATOS"
cik: "0001488039"
company_name: "ATOSSA THERAPEUTICS, INC."
filed_at: "2025-03-12T23:59:59+00:00"
generated_at: "2026-05-24T22:16:34.381127+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# Atossa to pursue metastatic breast cancer indication; (Z)-endoxifen more than doubled PFS vs tamoxifen (7.2 vs 2.4 mo)

## Summary
- Strategic decision to pursue metastatic breast cancer indication for (Z)-endoxifen, citing potentially faster regulatory path.
- Median PFS more than doubled to 7.2 months vs 2.4 months for tamoxifen in CDK4/6i-naïve patients.
- Also engaging FDA on additional indications: breast cancer prevention and neoadjuvant therapy.
- Early data show Ki-67 ≤10% response rate above 85% across doses in neoadjuvant setting.

## SEC filing metadata
- accession: 0000950170-25-037634
- form_type: 8-K
- ticker: ATOS
- cik: 0001488039
- company_name: ATOSSA THERAPEUTICS, INC.
- filed_at: 2025-03-12T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1488039/000095017025037634/0000950170-25-037634-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1488039/000095017025037634/atos-20250311.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-25-037634
- JSON: https://secwatch.observer/filing/0000950170-25-037634.json
- Plain text: https://secwatch.observer/filing/0000950170-25-037634.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.