Abstract OT2-11-02: Ameera-1 Arm 4: Phase 1/2 study of amcenestrant (SAR439859), an oral selective estrogen receptor (ER) degrader (SERD), with everolimus in postmenopausal women with ER+/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer

Abstract

Abstract Background Amcenestrant (SAR439859) is an optimized oral SERD with potent dual activity that antagonizes and degrades the ER, resulting in inhibition of the ER signaling pathway. Amcenestrant, as monotherapy or in combination with palbociclib, has shown antitumor activity and a favorable safety profile in postmenopausal women with heavily pretreated ER+/HER2- advanced breast cancer. Published data support the addition of targeted therapy to endocrine therapy for patients with ER+/HER2- advanced breast cancer. The objective of Arm 4 of the AMEERA-1 study is to evaluate safety and antitumor activity of amcenestrant in combination with the mammalian target of rapamycin (mTOR) inhibitor everolimus for patients with ER+/HER2- advanced breast cancer. Methods AMEERA-1 (NCT03284957) is an open-label, non-comparative, dose escalation and dose expansion Phase 1/2 study of amcenestrant as monotherapy, then in combination with other anti-cancer targeted therapies. Arm 4 investigates dose escalation (Part H) and dose expansion (Part I), of amcenestrant in combination with everolimus. Postmenopausal women with ER+/HER2- advanced breast cancer, ECOG performance status 0-1, and ≥ 6 months prior endocrine therapy are eligible. In Arm 4 (Parts H and I), ≤ 1 prior line of a single endocrine therapy for advanced disease is allowed. Patients must have progressed on a non-steroidal aromatase inhibitor plus cyclin-dependent kinase 4/6 inhibitor as first-line therapy for advanced disease. Prior treatment with fulvestrant or any other SERD is not allowed. Part H allows ≤ 1 prior chemotherapy for advanced disease; no prior chemotherapy for advanced disease is allowed in Part I. Exclusion criteria in Arm 4 include prior drugs targeting the phosphoinositide 3-kinase axis; history of or concurrent pneumonitis; history of severe cutaneous reactions; type 1 diabetes; uncontrolled type 2 diabetes; uncontrolled hypercholesterolemia, hypertriglyceridemia, and hyperglycemia; any uncontrolled infection; uncontrolled stomatitis, angioedema due to angiotensin-converting enzyme inhibitors, and impaired wounds. Part H evaluates the selected amcenestrant dose for combination therapy plus everolimus 10 mg once daily (QD) (the approved standard dose) or everolimus 5 mg QD, taken in 28-day cycles. Additional amcenestrant doses may be explored based on safety and pharmacokinetics (PK). The objective of Part H is to determine the recommended dose (RD) of everolimus in combination with the selected amcenestrant dose for combination therapy, based on preliminary safety, PK, and antitumor activity data. The primary endpoint in Part H is the incidence of treatment-related dose-limiting toxicities (DLTs) at Cycle 1. Approximately up to 12 DLT-evaluable patients will be needed to establish the RD of everolimus in combination with amcenestrant in Part H. In Part I, approximately 12 patients will be treated at the RD of everolimus for combination therapy with amcenestrant, the primary endpoint being safety and tolerability. Secondary endpoints include PK and antitumor activity. Funding: Sanofi. Citation Format: Mario Campone, Patrick Neven, Katarina Petrakova, Sofia Braga, Marina Celanovic, Patrick Cohen, Alice Gosselin, Sylvaine Cartot-Cotton, Vasiliki Pelekanou, Valentina Boni. Ameera-1 Arm 4: Phase 1/2 study of amcenestrant (SAR439859), an oral selective estrogen receptor (ER) degrader (SERD), with everolimus in postmenopausal women with ER+/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-11-02.