ERRalpha antagonist-1 (ERR+/- antagonist-1) is a high-affinity, selective antagonist of the estrogen-related receptor alpha (ERRalpha). It effectively prevents the interaction of ERRalpha with both Proliferator-activated Receptor gamma Coactivator-1alpha (PGC-1alpha) and PGC-1beta, displaying IC50 values of 170 nM and 180 nM, respectively. Notably, ERRalpha antagonist-1 does not interfere with the interactions involving ERRbeta or ERRgamma and the PGC-1alpha and PGC-1beta coactivators. Furthermore, it does not affect the interaction between either ERalpha or ERbeta and PGC-1alpha or SRC-1.