Chugai Pharmaceutical shares jumped up to 6% on Monday, the biggest intraday gain since Feb 9.
Citigroup analyst Hidemaru Yamaguchi said Foundayo, licensed to Eli Lilly, recorded 1,390 prescriptions in its first two days.
Novo Nordisk’s Wegovy logged roughly 3,100 scripts in its first full week, indicating Foundayo’s early uptake may outpace the rival.