Additional Study Information: This study is for subjects with either cancer of the head and neck, lung cancer or colorectal cancer. The aim of this research study is to identify the best dose of an experimental drug called MEDI1873 and to see if it is safe and tolerable in subjects with advanced solid tumor types. The study will occur in two parts: Part 1 (dose escalation) and Part 2 (dose confirmation). Part 1 of this study will evaluate up to 7 planned dose levels of MEDI1873 in research subjects/participants with selected tumor types. Each subject will only receive one of the assigned dose levels. In Part 2, subjects with either cancer of the head and neck, lung cancer or colorectal cancer will receive one of the MEDI1873 dose levels selected from Part 1 of the study. You are being asked to participate only in Part 1 (dose escalation) of this study. Approximately 66 people will take part at up to 20 sites (research centers or hospitals) in the United States. More people may be enrolled into the study if more information is needed to find the best dose level or dosing interval for MEDI1873.