Nektar is also developing NKTR-181, a long-acting mu-opioid analgesic for the treatment of chronic pain conditions, such as osteoarthritis and low back pain. The company has completed Phase 1 clinical development of NKTR-181 demonstrating sustained and dose-dependent analgesic responses with NKTR-181, a dramatically slower rate of entry into the CNS and an excellent tolerability profile. Nektar plans to advance NKTR-181 into Phase 2 clinical development in chronic pain patients in mid-2012.About NKTR-192 NKTR-192 is Nektar Therapeutics' drug candidate for the treatment of moderate to severe acute pain. NKTR-192 is a novel mu-opioid analgesic created using Nektar's advanced polymer conjugation technology to slow drug entry into the central nervous system (CNS). By dramatically slowing the rate of drug entry into the CNS, NKTR-192 is intended to maintain opioid-like efficacy without the abuse potential and other CNS side effects associated with rapid-acting opioids. In preclinical testing, NKTR-192 demonstrates a rapid onset of analgesia and relatively short half-life, without exhibiting sedative or abuse potential at analgesic doses. About Opioids and Pain Management Approximately 140 million prescriptions are written annually in the U.S. for acute and sub-chronic pain indications, such as muscle injuries, post-operative pain, and kidney stones.(1,2) Although prescription opioids are considered the most effective treatment for moderate-to-severe pain, their abuse has been identified by the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control as a significant public health issue. The abuse properties of opioid drugs are believed to be related to their rapid rate of entry into the brain.(3) Rapid-acting opioids enter the brain quickly, frequently causing a euphoric effect, or drug-related "high" which results in high potential for substance abuse, addiction and diversion. In addition to the potential to be abused, opioids can also cause drowsiness, impacting a patient's ability to function normally. The pharmaceutical industry has invested heavily in the development of new formulations of these drugs in order to combat the abuse and diversion of these painkillers. However, these reformulations have been primarily focused on physical means of deterrence, and abusers have found ways to overcome these formulation barriers.