NEW YORK (MarketWatch) -- American Express's stock AXP, -1.16% is on track to open at a four-month low, after the charge card company said the loss of its exclusivity deal with Costco Wholesale COST, -0.86% will hurt profit and sales this year and next. The stock, a component of the Dow Jones Industrial Average, slumped dropped $6.11, or 7.1%, in premarket trade, to trade below $80 for the first time since Oct. 15. That decline would shave off 39 points from the Dow. "While we expect the negative impact on earnings and revenue growth in 2015 and 2016, we remain confident in our ability to achieve our 12% to 15% EPS growth target over the moderate to long-term," said Chief Executive Kenneth Chenault in a conference call, according to a FactSet transcript.