PEMBROCABOSARC: Combination of pembrolizumab and cabozantinib in patients with advanced sarcomas

TPS11586 Background: Despite optimal treatment, up to 40% of patients with sarcomas will develop locoregional and/or distant relapse and median survival in this setting is less than two years. There are very few options in the treatment of undifferentiated pleomorphic sarcomas whereas there is no specific treatment regimen established for recurrent osteosarcoma (OSS) and Ewing sarcoma (ES). Innovative strategies are therefore urgently needed in these settings. In preclinical studies, while immune checkpoint inhibitors were insufficient in controlling tumour growth, combining them with M2 macrophage or angiogenesis targeting resulted in superior tumour control (Mao et al, Clin Cancer Res 2016; Zhu et al, Cancer Res 2014). Combining both antiangiogenic and MET inhibition properties, cabozantinib has shown both preclinical and clinical activity, notably in osteosarcoma and Ewing sarcoma (Italiano et al. ESMO 2018). Interestingly, cabozantinib has also recently been shown to trigger an innate immune response in a preclinical model (Patnaik et al, Cancer Discov 2017). Altogether, these findings pave the way for studies assessing the impact of targeting angiogenesis, MET and immune response in soft-tissue and bone sarcomas. Methods: PEMBROCABOSARC (NCT05182164) is a multi-stratum, three single-arm phase 2, multicenter, open-label study investigating pembrolizumab combined with cabozantinib in patients with advanced selected sarcomas: undifferentiated pleomorphic sarcoma (stratum 1), osteosarcoma (stratum 2), Ewing sarcoma (stratum 3). Strata 1 and 2 will enroll ~32 patients and stratum 3 ~55 patients, respectively. Each stratum phase II will be conducted using a Simon's optimal two-stage design. Eligible and consented patients must be ECOG PS 0–1, have measurable and progressive disease according to RECIST 1.1 and have received less than 3 previous lines of systemic therapy for advanced disease and consent also to baseline and per treatment biopsies. Cabozantinib will be administered orally, once daily at a fixed dose of 40 mg, continuously. Pembrolizumab will be administered by intravenous infusion every 3 weeks on Day 1 of each cycle, at a fixed dose of 200 mg. Both treatments will start on Day 1 (of cycle 1). The primary endpoint is 6-months non progression rate as per RECIST 1.1. Secondary endpoints include adverse events (AEs)/serious AEs, best overall response, and progression-free survival. Pharmacodynamic and other biomarkers will be explored on blood and tumor tissue. The first patient received study drug on May, 31, 2022; 8 of planned 119 patients have been enrolled and 5 sites across France among the planned 10, are currently enrolling patients. Clinical trial information: NCT05182164 .