TAK-243 (MLN7243) is a first-in-class, selective ubiquitin activating enzyme, UAE (UBA1) inhibitor (IC50=1 nM), which blocks ubiquitin conjugation, disrupting monoubiquitin signaling as well as global protein ubiquitination. TAK-243 (MLN7243) induces endoplasmic reticulum (ER) stress, abrogates NF-κB pathway activation and promotes apoptosis.