Shares of Affirm Holdings Inc. AFRM, -6.17% were up more than 3% in premarket trading Thursday after the company announced that it would launch a buy-now-pay-later option on Amazon.com Inc.’s AMZN, -1.54% site in Canada. The company already has a relationship with Amazon in the U.S. Affirm noted in a Thursday press release that eligible Canadian Amazon shoppers will be able to split purchases into monthly installments on purchases of $50 or more. Shares of Affirm have lost 79% so far this year as the S&P 500 SPX, -0.60% has declined 20%.