AmEx Said to Boost Rates for More Than 1 Million Customers

American Express Co., the lender that lost one of its biggest retailer partnerships and suffered a defeat in an antitrust lawsuit this month, is raising interest rates on a swath of credit cards for the first time in more than five years.

AmEx told more than a million customers this month that their annual rates will climb an average of 2.5 percentage points, following a review last year, said people briefed on the move. The firm sent letters saying it’s making adjustments after finding their rates were below those for rival cards held by borrowers “with similar credit profiles,” according to a copy obtained by Bloomberg News.