shares of merck  co inc mrk shed 366 to 7901 thursday on what proved to be an allaround grim trading session for the stock market with the sp 500 index spx falling 244 to 447744 and dow jones industrial average djia falling 145 to 3511116 the stocks fall snapped a fiveday winning streak merck  co inc closed 1239 short of its 52week high 9140 which the company achieved on november 4th the stock underperformed when compared to some of its competitors thursday as johnson  johnson jnj fell 001 to 17276 roche holding ag part cert rhhvf fell 210 to 38100 and pfizer inc pfe fell 089 to 5338 trading volume 192 m eclipsed its 50day average volume of 141 m editors note this story was autogenerated by automated insights an automation technology provider using data from dow jones and factset see our market data terms of use