Phase I-II, randomized, open-label, multicenter, international clinical trial Patients with advanced soft-tissue sarcoma (undifferentiated pleomorphic sarcoma, leiomyosarcoma, alveolar soft-part sarcoma) and osteosarcoma will receive selinexor in combination with gemcitabine.~In the Phase I part safety and toxicity of the combination will be assessed using a 3+3 design. The recommended dose for the Phase II will be determined.~In the Phase II part there will be 4 different cohorts:~Cohort 1: Undifferentiated pleomorphic sarcoma (UPS) Cohort 2: Leiomyosarcoma (LMS) Cohort 3: Alveolar soft-part sarcoma (ASPS) Cohort 4: Osteosarcoma Patients will be randomized for phase II part only (except in cohort 3) in an open-label way to receive selinexor in combination with gemcitabine versus gemcitabine alone
Phase I-II, randomized, open-label, multicenter, international clinical trial Patients with advanced soft-tissue sarcoma (undifferentiated pleomorphic sarcoma, leiomyosarcoma, alveolar soft-part sarcoma) and osteosarcoma will receive selinexor in combination with gemcitabine.