Shares of SS&C Technologies Holdings Inc. SSNC, -3.99% sank 2.7% in premarket trade Tuesday, after the portfolio management software company said it commenced a $1.25 billion public stock offering, which implies a more than 10% increase in the shares outstanding. The company said it plans to use the proceeds to financing its pending acquisition of DST Systems Inc. DST, +0.09% for more than $5 billion, announced in January. Based on Monday's closing price of $51.84, the offering would imply the sale of 24.1 million shares, which represents about 11.7% of the shares outstanding. SS&C said it was also granting the underwriters of the offering options to buy an additional $187.5 million worth of common stock. The stock had soared 26.3% over the past three months through Monday, while the S&P 500 SPX, +0.60% has lost 4.8%.