The main purpose of this investigational research study is to determine how safe and tolerable the study drug volasertib is in combination with liposomal vincristine (Marqibo; an FDA-approved drug) in patients with relapsed/refractory acute lymphoblastic leukemia. While VSLI demonstrated an overall response rate of 35% in Acute Lymphoblastic Leukemia (ALL) patients that had failed to respond to or relapsed after chemotherapy, combining it with other agents may increase clinical benefit.