S4 Capital shares jumped after the U.K. advertising company founded and led by industry titan Martin Sorrell said it was in talks with One Equity Partners’ MSQ about a potential tie-up.

Shares in S4 Capital climbed as much as 17% in European early morning trade Monday, before giving up some of the gains. The news lifted the stock from an all-time low hit Friday that gave the company a market value of 132 million pounds ($177.6 million), according to FactSet. At its peak in September 2021, S4 Capital was valued at more than 4.5 billion pounds.