Cathay General Bancorp ( CATY) said Friday that it agreed to buy a 20% stake in Shanghai-based First Sino Bank for an estimated $52.2 million. As part of the agreement, Cathay Bank will have a right to name two members to First Sino Bank's board, it said. It will buy the shares from First Sino Bank's largest shareholder. The investment is subject to regulatory approval from the China Bank Regulatory Commission and Cathay Bank's regulators in the United States. The purchase price is subject to adjustment for dividends and will be fixed at closing after completion of First Sino Bank's audited financial statements for the year ended Dec. 31. For the year ended Dec. 31, 2004, First Sino Bank earned about $4.1 million and had assets of about $630 million. Cathay's shares closed Friday at $37.72, down 26 cents, or 0.7%.