Patients will be accrued to either of the gemcitabine/dasatinib arms in alternating sequential order. In the case where there is an open slot on a particular arm but not the alternative, the enrolled patient will be assigned to that open slot. For example, at the start of the trial, patient #1 will be treated on the gemcitabine with dasatinib twice daily dosing arm, patient #2 on the gemcitabine with dasatinib once daily dosing arm, patient #3 on the gemcitabine with dasatinib twice daily dosing arm, and so on. However, if, due to cohort expansion there is a slot available on one treatment arm but not the other, the patient will be accrued to the open slot.