Biogen and Guess slide while Darden and Micron rise

Stocks that moved substantially or traded heavily on Thursday:

Biogen Inc., down $93.71 to $226.88

The biotechnology company is ending development of a potential Alzheimer's disease drug after concluding it will be ineffective.

Guess Inc., down $2.76 to $19.31

The clothing retailer's fourth-quarter profit fell short of Wall Street expectations and it issued a weak forecast for the year.

G-III Apparel Group Ltd., up $3.91 to $39.07

The owner of Calvin Klein and other fashion brands gave investors a better-than-expected profit forecast.

Williams-Sonoma Inc., up $2.37 to $59.22

The seller of cookware and home furnishings beat Wall Street's profit and revenue forecasts for the fourth quarter.

Darden Restaurants Inc., up $7.46 to $116.11

The operator of Olive Garden restaurants beat Wall Street's fourth-quarter profit and revenue forecasts.

Raven Industries Ltd., down $3.43 to $35.16

The industrial products maker's fourth-quarter profit fell far short of analysts' expectations.

Micron Technologies Inc., up $3.86 to $43.99

The chipmaker beat Wall Street's profit and revenue forecasts and issued a solid outlook for memory chip sales.

Conagra Brands Inc., up $2.92 to $25.82

The packaged food company beat third-quarter profit forecasts thanks to higher prices for some of its products.