Abstract: Provided herein are methods for determining if a subject is at risk for developing a toxicity, e.g., neurotoxicity, following administration of a therapy, such as an immunotherapy or cell therapy, e.g., a chimeric antigen receptor (CAR) T cell therapy based on the expression, in a sample obtained from the subject, of one or more genes or gene products that are associated with and/or correlate to a risk of developing toxicity following administration of the therapy. In some aspects, the sample is a sample obtained from the subject prior to receiving the therapy. Also provided are methods for treating a subject having a disease or condition, such as acute lymphoblastic leukemia (ALL), according to a particular treatment regimen, in some cases involving administration of the immunotherapy or cell therapy, based on assessment of risk of developing a toxicity following administration of the therapy. Also provided herein are reagents and kits for performing the methods.