Peer-reviewed preclinical study published in npj Breast Cancer identifies new chemical entities with activity in ESR1-mutant models

Findings suggest potential for combination with abemaciclib

SEATTLE, July 28, 2026 /PRNewswire/ -- Atossa Therapeutics, Inc. (NASDAQ:ATOS) ("Atossa" or the "Company"), a clinical-stage biopharmaceutical company developing novel therapies in oncology and other areas of significant unmet clinical need, today announced the publication of a peer-reviewed preclinical study in npj Breast Cancer evaluating five novel chemical entities structurally related to (Z)-endoxifen. The study titled, "Novel (Z)-endoxifen-related new chemical entities exhibit potent anti-cancer activity in ERα+ breast cancer," reported anti-estrogenic and anti-cancer activity across multiple estrogen receptor-positive breast cancer models, including models harboring clinically relevant activating mutations in ESR1.