Shares of Adolor Corp. lost more than half their value in early trading Tuesday as the drug maker and GlaxoSmithKline said two out of three clinical studies for their intestinal obstruction treatment Entereg did not meet their primary endpoints, according to the Associated Press. Adolor shares fell $12.95, or 52 percent, to $12.02 in early trading on the Nasdaq, on very heavy volume of 5.5 million shares, compared with average volume of about 400,000 shares. Shares have traded between $9.12 and $27.80 over the past 52 weeks. Entereg is a treatment to relieve constipation in people who must take opiates for cancer and other chronic pain. In one study that enrolled 518 patients, the companies said 72 percent of patients taking Entereg had three or more bowel movements per week, compared with 48 percent of those given a placebo. Results for this study were statistically significant. However, in an another study that followed 485 patients, results were not statistically significant with 63 percent of patients taking Entereg reaching the primary endpoint, compared 56 percent of patients taking placebo. Patients given Entereg in a third study had an average increase of up to 2.1 bowel movements per week, compared with 1.6 in patients given placebo. These results were also not statistically significant. American depositary shares of GlaxoSmithKline were down 70 cents, at $56.06 on the New York Stock Exchange.