Abstract: Disclosed herein are methods and compositions for determining and improving the likelihood of response and/or determining and decreasing the likelihood of toxicity to a cellular therapy using metabolomics. Embodiments of the disclosure include methods for measuring certain metabolites in biological samples of an individual for determining whether the individual has a responder or non-responder phenotype to the cellular therapy or to a toxicity of the cellular therapy. Embodiments also include compositions for increasing the response to a cellular therapy or decreasing toxicities associated with a cellular therapy. Embodiments also show that plasma metabolomics correlate with efficacy and toxicities associated with CAR-T therapy towards a cancer. The present disclosure relates to compositions and methods for predicting a subject's response to a CAR T-cell therapy, by analyzing the plasma metabolomics of the subject.