Atossa Therapeutics Inc. (NASDAQ: ATOS) announced the publication of results from its KARISMA Endoxifen trial in the Journal of the National Cancer Institute. The randomized, double-blind, placebo-controlled Phase 2 study evaluated the drug endoxifen in 240 healthy premenopausal women and found it reduced mammographic breast density, a risk factor for breast cancer.

The study, conducted at Karolinska Institutet in Stockholm, Sweden, tested placebo, 1 mg, and 2 mg doses of endoxifen administered daily for six months. Both dose levels produced statistically significant reductions in mammographic breast density compared with placebo. The 1 mg dose reduced density by 19.3% versus placebo, while the 2 mg dose reduced it by 26.5%.

The 1 mg dose showed a tolerability profile similar to placebo. Discontinuations due to adverse events considered related to the study drug occurred in 4 placebo participants and 5 participants receiving 1 mg endoxifen, compared with 11 participants receiving 2 mg endoxifen. Adverse events were generally vasomotor in nature.

"These data are an important step toward redefining breast cancer prevention," said Steven Quay, President and Chief Executive Officer of Atossa Therapeutics. "Tamoxifen is approved by the U.S. Food and Drug Administration for breast cancer risk reduction, but its use has been limited by tolerability, variable metabolism, and patient acceptance."

The study enrolled women aged 40 to 55 years participating in Sweden's national mammography screening program. Participants were randomized 1:1:1 to receive the treatments for six months. The study is registered at ClinicalTrials.gov under identifier NCT05068388.

The authors noted that future studies are needed to determine whether endoxifen reduces incidences of breast cancer in women at increased risk. Atossa is a clinical-stage biopharmaceutical company developing medicines in oncology and other areas.