The purpose of this study is to determine if AC-1204 is safe and tolerated in subjects with ALS. The reason why the investigator wants to use AC-1204 in patients with ALS is to determine if, by taking AC-1204, the body will make substances called ketone bodies. Further, if AC-1204 is well tolerated, the investigators want to change the amount the participant takes, to determine if the amount of ketone bodies in the blood increase in accordance with increases in the amount of AC-1204 the participant takes. The investigators want to do this study because when the investigators gave AC-1204 to mice with ALS, findings suggest the disease course is altered for the better and that the cause of this change is due to the presence of ketones in the blood. If AC-1204 can be proven to be safe and able to cause ketones to increase in the blood, the investigators will likely do subsequent studies to determine if the presence of ketone bodies will slow or stop the progression of the disease. However, this study is not designed to determine if AC-1204 will stop or slow the progression of ALS. It is designed to only determine if patients with ALS can tolerate AC-1204, if ketone bodies are produced and if the amount of ketone bodies produced increases with increasing dose.