Testing the Addition of an Anti-cancer Drug, Abemaciclib, to the Usual Chemotherapy Treatment (Gemcitabine) for Soft Tissue Sarcoma

This phase I/II trial tests the side effects and best dose of abemaciclib when added to gemcitabine and compares the effectiveness of that treatment to the usual treatment of gemcitabine with docetaxel for the treatment of patients with soft tissue sarcoma that may have spread from where it first started to nearby tissue, lymph nodes, or distant parts of the body (advanced) or that has spread from where it first started (primary site) to other places in the body (metastatic) (phase 1) or patients with leiomyosarcoma or dedifferentiated liposarcoma (phase 2). Abemaciclib is in a class of medications called kinase inhibitors. It works by blocking the action of an abnormal protein that signals tumor cells to multiply. This helps slow or stop the spread of tumor cells. Gemcitabine is a chemotherapy drug that blocks the cells from making deoxyribonucleic acid and may kill tumor cells. Docetaxel is in a class of medications called taxanes. It stops cancer cells from growing and dividing and may kill them. Giving abemaciclib with gemcitabine may be safe and effective when compared to treatment with gemcitabine and docetaxel for patients with advanced or metastatic soft tissue sarcoma or leiomyosarcoma or dedifferentiated liposarcoma.