Sirnaomics' (HKG:2257) Chairman Poon Hung Fai acquired 20,300 additional ordinary shares in the company, according to a Wednesday Hong Kong bourse filing.
Shares of the biotechnology company were down nearly 4% in Thursday afternoon trading.
The shares were purchased from the open market at an average price of HK$5 apiece on Wednesday.
Poon now holds nearly 17.7 million, or 16.12%, shares in the company.