The main goal of this study is to find the right dose of investigational compound INS1202 and to check how safe and tolerable it is when given as a single injection into the spinal fluid. We are looking at how the investigational compound INS1202 works in the body. This clinical study is for people aged 18 to 79 who have ALS, a disease affecting nerve cells, and either have a specific genetic change called SOD1 mutation or do not have any known genetic changes related to ALS.