Updated from 9:14 a.m. EDTProgenics ( PGNX) and Wyeth ( WYE) said Wednesday that their experimental bowel drug, intravenous methylnaltrexone, failed a phase III study in patients undergoing surgery. The negative results are a significant setback for the drug, also known as MNTX, as the companies face competition from another, similar bowel drug being developed by Adolor ( ADLR) and GlaxoSmithKline ( GSK). Progenics shares closed Tuesday at $13.55. The stock was tumbling 57% to $5.76 in morning trading Wednesday. The failed phase III study investigated the use of MNTX as a treatment for post-operative ileus, a medical term for painful bloating and constipation following abdominal surgery. Progenics and Wyeth said MNTX, administered intravenously, did not reduce the time required for gastrointestinal function to return to normal, compared to a placebo. The drug also failed to help patients leave the hospital sooner. The companies are conducting a second phase III study with a similar design. Results are expected in the middle of the year. There are no drugs currently approved to treat POI. That, however, may change in May, when the Food and Drug Administration is expected to issue a decision on Entereg, a bowel drug administered as a pill that is being developed by Adolor and GlaxoSmithKline. In early February, the FDA pushed back the decision date on Entereg to take more time to review the drug's data, including a risk-management plan submitted by the companies to better inform doctors and patients of safety risks. (Full disclosure, I had been bullish on Progenics since the stock was $18 and bearish on Adolor because I thought MNTX was a superior drug. Clearly, Wednesday's negative study results from MNTX is a big knock to that call.) MNTX is a variation of naltrexone, a drug approved and used today to treat opioid and alcohol dependence. MNTX has been filed with the FDA for the treatment of patients with advanced medical illness. These are nursing home and hospice patients in the advanced stages of disease who require heavy doses of painkillers. An FDA approval decision was expected in February, but was pushed back until April so the agency could review more safety data. Know What You Own: Progenics operates in the pharmaceutical sector of the healthcare industry, and some of the other stocks in its field include Eli Lilly ( LLY), Novartis ( NVS) and Pfizer ( PFE). These stocks were recently trading at $50.23, $48.07 and $21.46, respectively.