) today announced that the first subjects were dosed in a new Phase 1 clinical study to evaluate NKTR-181, the company's next-generation opioid analgesic candidate. NKTR-181 is being developed to effectively treat pain while addressing the abuse liability and serious CNS side effects associated with currently available opioid therapies. The single-dose Phase 1 study is assessing the pharmacokinetics, pharmacology, safety and efficacy of NKTR-181 in up to 75 healthy subjects. The primary objective of the Phase 1 trial is to establish the effective analgesic dose range of NKTR-181 associated with minimal CNS side effects. The study is being conducted in the U.S. and Nektar expects to complete the study in the second half of 2011.