The present disclosure relates to methods and products for reducing side effects associated with immunotherapy using immune agonist antibodies. In certain embodiments, the present disclosure provides a method of reducing one or more side effects associated with immunotherapy using an immune agonist antibody alone, or in combination with an immune checkpoint inhibitor, in a subject suffering from a cancer, the method comprising modifying the gut microbiota in the subject and thereby reducing the one or more side effects associated with the immunotherapy in the subject.