Oct. 27, 2009 (PR Newswire) --

SAN DIEGO, Oct. 27 /PRNewswire-FirstCall/ -- Data from a phase II study demonstrated that oral NKTR-118 improved lower gastrointestinal dysfunction by increasing the frequency of bowel movements in patients with opioid-induced constipation, while simultaneously preserving opioid-mediated analgesia. NKTR-118, an oral peripherally-acting opioid antagonist, is an investigational product candidate in clinical development for the treatment of opioid-induced constipation.

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In the phase II double blind, randomized, placebo-controlled study of 208 patients with opioid-induced constipation, NKTR-118 achieved the primary endpoint of change from baseline in spontaneous bowel movements (SBMs). Patients receiving either 25 mg or 50 mg of oral NKTR-118 once daily had a significantly greater change from baseline in SBMs during the first week of treatment than patients receiving placebo. The mean change from baseline in SBMs per week for patients receiving 25 mg NKTR-118 was 3.6 versus 1.9 in the placebo group (p= 0.002). Patients receiving 50 mg NKTR-118 had a mean change from baseline in SBMs per week of 4.4 versus 1.9 in the placebo group (p=0.0001). The increase from baseline in SBMs versus placebo averaged over the four-week treatment period was significant for both the 25 mg (p=0.002) and 50 mg (p<0.0001) dose groups. Results for the 5 mg dose of NKTR-118 were not significant.

The study also showed that there was a statistically significant difference in median time to first SBM for patients in the 25 mg and 50 mg dose cohorts as compared to placebo. Median time to first SBM for patients in the 25 mg dose cohort was 6.6 hours as compared to placebo which was 48.6 hours (p=0.001), and for patients in the 50 mg dose cohort, median time to first SBM was 2.9 hours as compared to placebo, which was 44.9 hours (p<0.002). Results for the 5 mg dose of NKTR-118 were not significant.

"Patients who take opioids are at risk of experiencing the painful and potentially serious side effect of opioid-induced constipation (OIC) -- which can require patients to seek remedies only available in a hospital or in-office setting," said Dr. Lynn Webster, Medical Director of Lifetree Clinical Research and lead clinical investigator of the phase II trial.