Dec 19 (Reuters) - Amicus Therapeutics said itsexperimental drug to treat a rare, inherited disorder failed tomeet the main goal of a late-stage study, sending its sharesdown 50 percent in extended trade on Wednesday. The company is developing migalastat HCl in partnership withBritish drugmaker GlaxoSmithKline plc to treat Fabrydisease, a genetic condition in which a type of fat getsdeposited in human tissue, particularly in the kidneys. The disease is caused by the body's inability to produce theenzyme that helps breaks down the fat. The six-month study found that 13 out of the 32 patients whowere put on migalastat HCl reported a reduction of 50 percent ormore in the fat deposits in their kidneys, compared to 9 of the32 in the group that was given a placebo. "This difference did not achieve statistical significanceaccording to the pre-specified primary endpoint analysis," thecompany said. Amicus said it expects to report results from 12 months oftreatment in the first half of 2013, after which it plans tomeet with the FDA to discuss a U.S. "approval pathway." Fabry disease affects about 5,000 to 10,000 people worldwideand is believed to cause pain, kidney failure and increased riskof heart attack and stroke, according to the company. Amicus shares closed at $5.77 on Wednesday on the Nasdaq,but fell as low as $2.80 after the bell. (Reporting by Prateek Kumar and Zeba Siddiqui; Editing bySreejiraj Eluvangal)