This is a prospective, open-label, single arm, phase 1 clinical trial. A single cohort of patients with relapsed or refractory Ewing sarcoma or osteosarcoma will be enrolled and treated in a 3+3 design with a combination of cabozantinib, topotecan and cyclophosphamide.~The research study procedures include screening for eligibility and study treatment including medical tests and follow up visits.~The names of the drugs are:~Cabozantinib~Topotecan~Cyclophosphamide~The names of the non-investigational supportive care drugs are:~Filgrastim, pegfilgrastim, or a related growth factor.~It is expected that up to 16 people will take part in this research study.~This research study is a Phase I clinical trial, which tests the safety of an investigational drug combination and also tries to define the appropriate doses of the drugs to use for further studies. Investigational means that the drug combination is being studied.~The FDA (the U.S. Food and Drug Administration) has approved all medications included in this trial as a treatment for multiple types of cancers.~The combination of topotecan and cyclophosphamide has been used for treatment of this population. Cabozantinib has been used alone for treatment of Ewing sarcoma and osteosarcoma and shown to have an effect in some patients. This is the first time that cabozantinib will be studied in combination with topotecan and cyclophosphamide.
This research study is a clinical trial of a new combination of drugs as a possible treatment for relapsed/refractory Ewing sarcoma and/or osteosarcoma.~The names of the drugs are:~Cabozantinib~Topotecan~Cyclophosphamide~The names of the non-investigational supportive care drugs are:~Filgrastim, pegfilgrastim, or a related growth factor.