In the past few years, several biased ligands acting at the mu-opioid receptor were reported in the literature. These agonists are aimed at reducing pain while having fewer side effects than morphine, the gold standard of opioid analgesics. In this mini-review, we describe and discuss the recent advances in mu-biased ligands actually in preclinical and clinical development stages, including the latest U.S. Food and Drug Administration review of oliceridine, a biased mu-agonist for moderate to severe acute pain treatment developed by the company Trevena.