Vertex Pharmaceuticals Inc. said that the underwriters of itsinitial public offering, Kidder, Peabody & Co. Inc., Cowen & Co.and BT Securities Corp., have exercised an option to purchasean additional 200,000 shares of stock at $9 per share to coveroverallotments. Stock of the Cambridge, Mass.-based drugdesign company (NASDAQ:VRTX) closed at $9.38, up 13 cents,on Wednesday.