FuseBio is developing a first in class functionally-selective IL-18, "F-18", that is resistant to IL-18BP, 1 million percent less active than the natural cytokine in circulation for safety, and retains nearly full activity when brought into close proximity of the immune cell of interest. This allows FuseBio to unleash the full power of F-18 onto tumors without any checks-and-balances while minimizing side effects that can occur from a non-targeted, fully active cytokine.