Large U.S. drugstore chain Walgreen Co. (NYSE: WAG) announced Thursday it would be renewing its contract with Express Scripts Holding Co. (NASDAQ: ESRX), to provide customers of that pharmaceutical claims manager with prescription drugs at Walgreens retail stores. The deal, which goes into effect Sept. 15, will reinstate a cooperative system between the two companies that ended Dec. 31 of last year.

The market cheered the news. Shares of Walgreen Co. jumped as much as 17 percent in premarket trading and recently went for $34.37, up $3.40, or 10.98 percent from the previous day's close. Shares of Express Scripts Holding Co., rose 2.20 percent to $58.96, on automated NASDAQ trading.