Nektar Therapeutics Inc., of San Francisco, reported single-dose Phase I interim data showing that NKTR-181 has an excellent safety and tolerability profile, with no dose-limiting tolerability issues observed to date. With slower entry into the central nervous system, the µ-opioid analgesic candidate has the potential to reduce the euphoria that underlies opioid abuse liability and dependence, as well as the side effects of respiratory depression and sedation.