Shares of HDFC Bank, India’s largest private lender, tanked as much as 8.4% to their day's low of Rs 772 on the BSE on Thursday following a leadership change at the top. The bank’s part-time Chairman and independent director Atanu Chakraborty has stepped down, and Keki Mistry, former CEO of HDFC, has been appointed interim part-time chairman with approval from the Reserve Bank of India.