Abstract OT3-06-06: A phase I/II study of preoperative letrozole, everolimus, and TRC105 in women with newly diagnosed local or locally advanced potentially resectable hormone-Receptor positive and Her2 negative breast cancer

Hypothesis: Pharmacologic inhibition of angiogenesis and mTOR pathway blockade will enhance the efficacy of aromatase inhibitors in the neoadjuvant setting in women with hormone receptor-positive and Her2-negative (HR+/Her2-) breast cancer. Background: In non-metastatic HR+/Her2- breast cancer, downstaging to stage I or 0 in the neoadjuvant setting has been associated with favorable prognosis. With chemotherapy yielding similar benefits with endocrine therapy, aromatase inhibitors have become the agents of choice in postmenopausal women. The elucidation of pathways that are operational in luminal breast cancer and compromise the efficacy of hormonal therapy along with preclinical and clinical evidence of successful combinations of endocrine therapy with targeted agents set the stage for more rational, effective, and equally well tolerated regimens. Proangiogenic signaling has been strongly associated with accelerated hormone-independent growth and resistance to endocrine therapies. Breast cancer cells with upregulated PI3K/AKT/mTOR pathway are resistant to hormonal therapy and this resistance has been restored by everolimus. Inhibiting mTOR, a downstream signaling node where multiple pathways converge has the potential to abrogate primary and escape signaling cascades that mediate resistance to endocrine therapies. Study Design: Phase I dose escalation: follows a 3+3 design. During the phase I, the Maximum Tolerated Dose (MTD) and Recommended Phase 2 Dose (RP2D) will be determined. Letrozole will be kept the same for all cohorts (2.5 mg PO qd). Everolimus will be escalated from 5 mg (cohort 1) to 10 mg PO qd (cohort 2). TRC105 will be 15 mg/kg q2 weeks (cohorts 1 and 2). Premenopausal women at the time of enrollment will receive goserelin 3.6 mg SC q4 weeks to achieve ovarian suppression. Duration of treatment is 24 weeks. Phase II dose expansion: will be initiated once the MTD and RP2D have been determined. Phase II follows a Gehan9s two-stage design: 10 patients will enroll first, and if no patient has achieved downstaging, the study will close since it is unlikely (p=0.1) that 0/10 responses would occur if true response rate were >20%. If at least one patient has downstaging, 10 additional patients will enroll (total, 20). Primary Objectives Phase I: Determine the tolerability and feasibility of letrozole, everolimus, and TRC105 in women with newly diagnosed stage 2 and 3 HR+/Her2- breast cancer. Phase II: in the same patient population determine the efficacy, pharmacokinetic, and pharmacodynamic parameters of the combination. Correlative Studies: Immunohistochemistry for pAKT and PTEN, CD105, CD31/CD34, NG2, MCAM/CD146 on diagnostic tissue, research biopsy, and final surgical specimen. Surgical specimens that meet criteria for next-generation sequencing will undergo ribosome profiling Key Eligibility Criteria: Recent diagnosis of HR+Her2- breast cancer Stage 2 and 3 breast cancer Any histological grade No prior treatment specific for breast cancer Pre- and perimenopausal women are eligible if ovarian suppression is achieved with goserelin. Current Status: Cohort 1 of the Phase 1 complete. Cohort 2 of Phase 1 actively enrolling. Citation Format: Vaklavas C, Lamaster KV, Stringer EM, Falkson CI, Li Y, Forero A. A phase I/II study of preoperative letrozole, everolimus, and TRC105 in women with newly diagnosed local or locally advanced potentially resectable hormone-Receptor positive and Her2 negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-06-06.