Mitotoxic effects of the melanin-concentrating hormone receptor 1 (MCHr1) antagonist AZD1979 are influenced by mitochondrial DNA variation in HepG2 cybrids

AZD1979 is a melanin-concentrating hormone receptor 1 (MCHr1) antagonist, which was developed for obesity treatment, but clinical development was halted due to unanticipated liver toxicity. Mitochondrial DNA (mtDNA) variation influences hepatic energy metabolism and may underlie individual susceptibility to drug-induced mitotoxicity. Transmitochondrial cybrids offer a model to assess the impact of mtDNA variation on drug response against a constant nuclear background. This study assessed the mitotoxic potential of AZD1979 in HepG2 wild-type (WT) cells and HepG2 transmitochondrial cybrids representing distinct mtDNA haplogroups from the H and J haplogroup lineages. A 2-hour acute metabolic switch assay was performed in HepG2 WT cells and transmitochondrial cybrids to identify mitochondrial toxicity, with confirmatory Seahorse extracellular flux analysis. AZD1979 was identified as a potent mitotoxicant in HepG2 WT cells, inducing mitochondrial dysfunction prior to cell death. AZD1979 caused reductions in basal respiration, ATP-linked respiration, and spare respiratory capacity, and inhibited complex I-driven respiration. Cybrids displayed haplogroup-specific differences in susceptibility. Haplogroup J2b1g showed the highest sensitivity, while J1c1e, despite lacking spare respiratory capacity, was less susceptible. These findings highlight the role of mtDNA in shaping individual responses to mitochondrial toxicants and that transmitochondrial cybrid models could support early assessment of mitochondrial liability.