The biomolecular basis for the HsClpP-dependent cytotoxicity of imipridones is proposed to be rooted in OXPHOS impairment associated with specific respiratory chain subunits.First, identification and profiling of HsClpP-interacting proteins by BioID revealed that treating cells with ONC201 significantly reduced the level of expression of subunits ofComplex I, Complex II, and Complex IV, resulting in a decrease in both basal oxygen consumption rate (OCR) and spare reserve capacity (i.e., difference between basal andmaximal OCR), while mitochondrial ROS production was increased.Furthermore, structural damage to both the mitochondrial cristae and the matrix was observed in drugtreatedcells.The imipridone-induced mitochondrial stress may also activate the integrated stress response (ISR) and subsequent cellular events, as evidenced by drug-treated cellsshowing an increased level of expression of the ISR-activating ATF4 (activating transcription factor 4) and CHOP and the downregulation of TFAM and TUFM (elongation factor Tu,mitochondrial), thereby inhibiting de novo mitochondrial protein biosynthesis.