RM-0256

RM-0256 is a novel antibody-drug conjugate developed by Rakuten Medical. It consists of a proprietary anti-PD-L1 monoclonal antibody conjugated to IRDye®700DX (IR700), a light-activatable dye. The drug is designed for photoimmunotherapy, where the conjugate accumulates specifically on PD-L1-expressing cells—both tumor cells and immunosuppressive cells within the tumor microenvironment. Upon activation with near-infrared light, IR700 induces necrosis of these targeted cells. RM-0256 exerts its effects through three complementary mechanisms: 1) Direct depletion (necrosis) of PD-L1-expressing tumor cells via photoactivation, 2) Depletion of PD-L1-expressing immunosuppressive cells (such as tumor-associated macrophages and myeloid-derived suppressor cells), 3) Systemic immune checkpoint blockade by inhibiting the interaction between PD-L1 and PD-1, thereby enhancing anti-tumor immune responses. Preclinical studies have shown that RM-0256 can suppress tumor growth more effectively than anti-PD-L1 antibody alone in both sensitive and resistant mouse models, with favorable tolerability in GLP toxicity studies in non-human primates[3][4][5][6].