Abstract PS15-08: Final Overall Survival (OS) analysis of the SAKK 21/12 trial. CR1447 in HR+/HER2- metastatic breast cancer and androgen receptor positive triple negative breast cancer

Abstract

Abstract Introduction: CR1447 (4-Hydroxytestosteron) is a compound with aromatase inhibitor and anti-androgen receptor activity and is applied transdermally. We assessed its activity and safety in metastatic breast cancer (mBC). The primary endpoint (disease control rate at week 24) was reported in 2019. We now present the final overall survival (OS) analysis of the trial. Methods In cohort A (ER+/HER2-negative metastatic disease), one prior treatment line was allowed and 29 patients (ITT 21 patients) were included. In cohort B (triple negative mBC), eight patients were included. The trial was closed in 2018 due to futility (cohort A) and slow accrual (cohort B). Results At data cut-off on 11.04.2023 92% of all patients had died. Median OS for cohort A was 35.4 months (95% CI: 24.6-49.1) in the ITT population and 19.4 months (95% CI: 2.3-36.8) in the non-ITT population (patients with more than one line of endocrine therapy). In cohort B, median OS was 10.8 months (95% CI: 3.3-28.6). Treatment was well tolerated with no new safety signals and the majority of treatment-related adverse events (TRAE) were Grade 1 and 2. The most common TRAEs were dry skin (43%), rash (16%), fatigue (16%) and nausea (16%). Discussion Despite the trial being negative in terms of the primary endpoint, cohort A (ITT) had a median OS of 35.4 months. There were no new safety signals. Mutational analysis of AR/ER is ongoing to determine benefit of this treatment in specific subgroups. CR1447 might be a candidate drug to combine with other agents (CDK4/6 inhibitors or other targeted therapies). Citation Format: Marcus Vetter, Holer Lisa, Karin Rothgiesser, Wolfgang Schönfeld, Salome Riniker, Roger von Moos, Andreas Torjan, Elena Kralidis, Manuela Rabaglio, Mathias K. Fehr, Andreas Müller, Beat Thürlimann. Final Overall Survival (OS) analysis of the SAKK 21/12 trial. CR1447 in HR+/HER2- metastatic breast cancer and androgen receptor positive triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS15-08.