– ERRα antagonist-1 (ERR+/- antagonist-1) is a high-affinity, selective antagonist of the estrogen-related receptor α (ERRα). It effectively prevents the interaction of ERRα with both Proliferator-activated Receptor γ Coactivator-1α (PGC-1α) and PGC-1β, displaying IC50 values of 170 nM and 180 nM, respectively. Notably, ERRα antagonist-1 does not interfere with the interactions involving ERRβ or ERRγ and the PGC-1α and PGC-1β coactivators. Furthermore, it does not affect the interaction between either ERα or ERβ and PGC-1α or SRC-1.