** Drug developer's shares down 2 pct at $108.97premarket
** Says its prostate cancer therapy Xtandi was not as safeas AstraZeneca Plc's treatment Casodex in a mid-stagestudy
** Says 31 pct patients given Xtandi had serious adversereactions compared with 23.3 pct patients who were given Casodex
** Says Xtandi increased the time patients survived withoutprogression of the disease to 15.7 months, compared to 5.8months among Casodex patients
** Up to Wednesday's close, the stock more than doubledsince Xtandi was approved on Aug. 31 2012