Embodiments described herein relate to compositions, methods and uses for alpha-1 antitrypsin (AAT) or derivatives or analogs or peptides or mutants thereof for treating a subject exposed to radiation. In certain embodiments, AAT or derivatives thereof or analogs thereof can be used to modulate adverse effects of radiation therapy on subjects undergoing treatment for cancer. In other embodiments, compositions disclosed herein can be used for treating a subject having been exposed to non-therapeutic or accidental radiation. Some embodiments reported herein concern compositions and methods for enhancing radiotherapy. Certain embodiments relate to methods and compositions for preventing or reducing radiation exposure-induced cellular damage in a subject.