Preclinical studies with IRX‐2 and thymosin α1 in combination therapy

Thymosin alpha1 (Talpha1) is a 28 amino acid biologically active protein with pleiotropic immune enhancing activity. IRX-2 is a primary cell-derived biologic containing multiple cytokines that enhance dendritic cell maturation, promote T-cell growth and differentiation, and inhibit tumor-mediated apoptosis of T cells. IRX-2 is being developed as an immunotherapeutic agent as a novel T-cell adjuvant platform for vaccines as well. Based on their biological activities, thymosin alpha1 and IRX-2 were predicted to exhibit synergistic effects when evaluated in animal and human studies. In animal studies, the combination of IRX-2 and Talpha1 (IRX-3) increased T-cell numbers compared to either alone during recovery from hydrocortisone mediated reduction. IRX-3 further enhanced reduction in tumor burden following chemotherapy compared to IRX-2. Based on these studies, IRX-3 is predicted to be especially important in a setting where reversal of immune suppression due to the presence of tumor, irradiation, and/or chemotherapy is likely to be an important factor in cytokine activity.