Shares of Amicus Therapeutics (NASDAQ:FOLD) opened 40% lower than yesterday's close on results from a phase 3 study. Amicus and partner GlaxoSmithKline (NYSE:GSK) disclosed after the market close Wednesday that migalastat HCl failed to meet its primary endpoint of the late-stage study in treating Fabry disease. GlaxoSmithKline opened slightly higher this morning. 

The study involved 67 patients with Fabry disease, a genetic disorder impacting only 5,000 to 10,000 people worldwide. Thirty-two of those patients had baseline biopsies that could be evaluated. Of those patients, 13 taking migalastat experienced 50% or greater reduction in fat deposits in their kidneys. However, nine of the patients taking placebo experienced a similar reduction -- a statistically insignificant difference.

Although the news clobbered Amicus' stock, the company remains committed to moving forward with migalastat at this point. CEO John Crowley stated that further results from the six-month study would be announced in February with 12-month results coming in the first half of 2013. He maintained that migalastat still "may become an important treatment option as an oral monotherapy drug for both men and women with Fabry disease who have amenable mutations." Crowley said that Amicus intends to meet with the Food and Drug Administration after those results are analyzed about potential approval.

Glaxo is also attempting to spin the bad news as positively as it can. Marc Dunoyer, Glaxo's global head of rare diseases, said that his company remained committed to advancing migalastat. He also noted that another phase 3 study for migalastat is in progress. Enrollment for the second study, also targeting Fabry disease, was completed this month. Results from this study are expected in 2014.

Many investors appear to have been blindsided by the disappointing results. As of yesterday's close, Amicus shares were up more than 60% year-to-date. The stock has been on an upward trajectory since mid-November.

Migalastat is Amicus' only late-stage drug. The company currently has one other drug, duvoglustat HCl, in a phase 2 study. Its fortunes ride for good or bad on migalastat. All other drugs in Amicus' pipeline are still in pre-clinical stages.

Despite the setback, the continued public commitment from GlaxoSmithKline could help Amicus hold steady through completion of the studies for migalastat. In addition to partnering on development of the drug, Glaxo holds a 20% stake in Amicus.