Assessment of Efficacy and Safety in Relieving Opioid-induced Constipation in Patients With Cancer-related Pain

The purpose of this study is to compare the effect of NKTR-118 with placebo in the treatment of opioid-induced constipation (OIC) in patients with cancer-related pain, including those patients that have inadequate response to laxative therapy (LIR). The study consists of 2 parts; A initial 4-week treatment period (part A) and then a 12 week extension with active treatment (part B).