HONG KONG – Undeterred by the underperformance of peers on the Hong Kong Stock Exchange, Suzhou's Cstone Pharmaceuticals Co. Ltd. filed for an IPO on Monday, becoming the 16th biotech company to seek a listing in Hong Kong under the new rules. Proceeds will be used to advance its core asset, CS-1001, aiming to be one of the first PD-L1 antibodies approved in China.