Atossa Therapeutics Inc (NASDAQ:ATOS) unveiled encouraging safety and efficacy findings from its Phase 2 EVANGELINE clinical trial evaluating (Z)-endoxifen as a neoadjuvant therapy for breast cancer.
Data presented at the American Association for Cancer Research (AACR) Annual Meeting showed that six out of seven individuals displayed Ki-67 levels below 10%, indicating favorable responses to treatment.
The data originates from the 40mg pharmacokinetic run-in cohort of the study for pre-menopausal women diagnosed with Grade 1 or 2 Estrogen Receptor positive (ER+)/Human Epidermal Growth Factor Receptor 2 negative (HER2-) breast cancer.
Seven participants were enrolled and treated daily for 28 days.
Of the six patients treated for a total of 24 weeks, magnetic resonance imaging central review showcased positive outcomes, with all patients witnessing a reduction in target lesion size. Notably, one patient achieved complete response, another achieved partial response, and four experienced stable disease, as per Response Evaluation Criteria In Solid Tumors criteria.
On average, there was a 32% reduction in target lesion size at 12 weeks, increasing to 37% at 24 weeks, with all patients observing at least a 15% decrease in target lesions by the 24-week mark.
One participant, while experiencing a reduction in Ki-67 levels, discontinued treatment as her levels remained above the threshold.
Ki-67 levels among the 40mg cohort patients were significantly reduced, plummeting from an average of 14.5% at screening to 1.2% at 24 weeks – a notable reduction of 92% at 24 weeks, indicating a significant slowdown in tumor growth.
Steven Quay, Atossa’s CEO, called the results “extremely encouraging” as it shows that (Z)-endoxifen can not only stop ER+ breast cancer from growing, but it can also shrink or eliminate the tumor.
“The depth of response at 40mg may even improve in the next phase of the study where we are now treating women with 80mg of (Z)-endoxifen daily,” Quay said.
“We expect this dose to deliver the optimal steady-state plasma concentrations required to fully target PKCβ1 inhibition and further enhance (Z)-endoxifen’s antitumor efficacy.”
Atossa's proprietary oral formulation of (Z)-endoxifen, which is currently under development, aims to bypass liver metabolism to achieve therapeutic concentrations and has shown promising results in Phase 1 studies and small Phase 2 trials.
The drug is also undergoing evaluation in four Phase 2 trials, including the EVANGELINE study, providing hope for an effective treatment option for ER+/HER2- breast cancer patients.
Shares of Atossa gained 5.1% on Tuesday in New York.