Soft tissue sarcoma (STS) is a relatively rare and histologically diverse neoplasm of mesenchymal origin, occurring with an incidence of about 1% of all adult cancers, and includes >70 histologic subtypes. Treatment options for metastatic/relapsed STS are limited to anthracycline-based chemotherapy (eg, doxorubicin), administered alone or in combination with alkylating agents (eg, dacarbazine). However, drug resistance and toxicities often limit beneﬁts of chemotherapy used to treat metastatic sarcomas. Aberrant signaling of the mammalian target of rapamycin (mTOR) pathway is common in sarcomas and other malignancies, and mTOR inhibitors have shown antitumor activity in sarcomas. 
Phase 1/2 studies are currently investigating in the safety and efficacy of ABI-009 in combination with nivolumab in patients with advanced undifferentiated pleomorphic sarcoma, liposarcoma, chondrosarcoma, osteosarcoma and Ewing’s sarcoma (NCT03190174) and in combination with pazopanib in patients with advanced nonadipocytic soft-tissue sarcomas (NCT03660930).