Finally, we evaluated the efficacy of AB21 in combination with an agonist antibody against the immune stimulatory molecule 4-1BB in C57BL/6 mice bearing subcutaneous B16F10 tumors, a poorly immunogenic, highly aggressive mouse melanoma that is resistant to anti-PD-1 therapy but partially responsive to anti-4-1BB [36]. Here, TNFRSF9 is linked to melanoma.