There was a time not that long ago when Merck & Co. Inc.’s Keytruda (pembrolizumab), with its multiple cancer indications, was seen as the heir apparent to Humira’s title of the biggest blockbuster drug. Not anymore. That title now belongs to Novo Nordisk A/S’ semaglutide, approved as Ozempic in 2017 to treat diabetes and as Wegovy in 2021 to help with weight loss.