IACS-010759, a potent inhibitor of glycolysis-deficient hypoxic tumor cells, inhibits mitochondrial respiratory complex I through a unique mechanism

Abstract

The small molecule IACS-010759 has been reported to potently inhibit the proliferation of glycolysis-deficient hypoxic tumor cells by interfering with the functions of mitochondrial NADH-ubiquinone oxidoreductase (complex I) without exhibiting cytotoxicity at tolerated doses in normal cells. Considering the significant cytotoxicity of conventional quinone-site inhibitors of complex I, such as piericidin and acetogenin families, we hypothesized that the mechanism of action of IACS-010759 on complex I differs from that of other known quinone-site inhibitors. To test this possibility, here we investigated IACS-010759's mechanism in bovine heart submitochondrial particles. We found that IACS-010759, like known quinone-site inhibitors, suppresses chemical modification by the tosyl reagent AL1 of Asp160 in the 49-kDa subunit, located deep in the interior of a previously proposed quinone-access channel. However, contrary to the other inhibitors, IACS-010759 direction-dependently inhibited forward and reverse electron transfer and did not suppress binding of the quinazoline-type inhibitor [125I]AzQ to the N terminus of the 49-kDa subunit. Photoaffinity labeling experiments revealed that the photoreactive derivative [125I]IACS-010759-PD1 binds to the middle of the membrane subunit ND1 and that inhibitors that bind to the 49-kDa or PSST subunit cannot suppress the binding. We conclude that IACS-010759's binding location in complex I differs from that of any other known inhibitor of the enzyme. Our findings, along with those from previous study, reveal that the mechanisms of action of complex I inhibitors with widely different chemical properties are more diverse than can be accounted for by the quinone-access channel model proposed by structural biology studies.

Targeting Mitochondrial Metabolism in Clear Cell Carcinoma of the Ovaries

“…As shown in Figure 4B, all nine inhibitors induced a dose-dependent decrease in the clonogenicity of ES-2 cells. However, only IACS-010759 (Tsuji et al, 2020) and dapagliflozin (Nasiri et al, 2019) displayed selectivity for ES-2 cells where ARID1A has been knocked down. Of these two, IACS-010759 showed a much higher potency.…”

“…IACS-010759 is a clinical-grade small-molecule inhibitor of the Complex I of the electron transport chain (Molina et al, 2018). IACS-010759 has been shown to selectively kill tumor cells that depend on OXPHOS both, in vitro and in preclinical models of human cancers with no cytotoxicity at tolerated doses in normal cells (Bajpai et al, 2020; Fischer et al, 2019; Lissanu Deribe et al, 2018; Molina et al, 2018; Panina et al, 2020; Sun et al, 2019; Teh et al, 2020; Tsuji et al, 2020; Vashisht Gopal et al, 2019; Zhang et al, 2019).…”

Targeting multiple signaling pathways: the new approach to acute myeloid leukemia therapy

“…Photoaffinity labeling experiments have shown that IACS-010759 binds to membrane subunit ND1 of complex I. 213 Another study also suggested that the complex I-binding site of IACS-010759 is at the ND1 subunit as H292 cell clones containing a Leu55Phe mutation in the ND1 subunit showed lower susceptibility to IACS-010759. This suggests that Leu55, which is located at the proposed ubiquinone access channel, is likely involved in the mechanism of inhibition.…”

“… 212 IACS-010759 was derived from BAY 87–2243, which is an agent that specifically suppressed HIF-1 target gene expression through inhibition of complex I. 213 Like other complex I and ETC inhibitors studied, BAY 87–2243 was cytotoxic to normal cells, limiting its use in clinical application. BAY 87-2243 failed phase I clinical trials due to dose-limiting toxicities, highlighting the barrier to application of these inhibitors as therapies.…”

“… 214 Though IACS-010759 is similar in structure to BAY 87-2243, its mechanism of complex I inhibition differs from that of other quinone-site inhibitors in its class in that it has been suggested to indirectly affect quinone redox reactions by inducing structural changes to the quinone-binding pocket. 213 It has been proposed that this may contribute to the reduced toxicity observed in in vivo models, and there is hope that this alternative mechanism of action will contribute to an improved safety profile in ongoing clinical studies.…”