Shares of Aspen Insurance Holdings Ltd. surged 3.4% in premarket trade Tuesday, after the insurance company announced overnight an agreement to be acquired by private-equity company Apollo Global Management LLC in a cash deal valued at about $2.6 billion. Under terms of the deal, Apollo will pay $42.75 for each Aspen share outstanding, which is 6.6% above Monday's closing price of $40.10. The deal is expected to close in the first half of 2019. Apollo's stock was still inactive in premarket trade.