Development of a novel lactate dehydrogenase A inhibitor with potent antitumor activity and immune activation.

Lactate accumulation in the tumor microenvironment was shown to be closely related to tumor growth and immune escape, and suppression of lactate production by inhibiting lactate dehydrogenase A (LDHA) has been pursued as a potential novel antitumor strategy. However, only a few potent LDHA inhibitors have been developed and most of them did not show potent antitumor effects in vivo. To this end, we designed new LDHA inhibitors and obtained a novel potent LDHA inhibitor, ML-05. ML-05 inhibited cellular lactate production and tumor cell proliferation, which was associated with inhibition of ATP production and induction of reactive oxygen species and G phase arrest. In a mouse B16F10 melanoma model, intratumoral injection of ML-05 significantly reduced lactate production, inhibited tumor growth, and released antitumor immune response of T cell subsets (Th1 and GMZB CD8 T cells) in the tumor microenvironment. Moreover, ML-05 treatment combined with programmed cell death-1 Ab or stimulator of interferon genes protein (STING) could sensitize the antitumor activity in B16F10 melanoma model. Collectively, we developed a novel potent LDHA inhibitor, ML-05, that elicited profound antitumor activity when injected locally, and was associated with the activation of antitumor immunity. In addition, ML-05 could sensitize immunotherapies, which suggests great translational value.