Tsuruha Holdings is exploring a sale that could value the Japanese pharmacy chain at about $4 billion (about ¥602.6 billion) or even more, people familiar with the matter said, after winning a proxy fight with activist investor Oasis Management over a reshuffle of the board.

The company is working with an adviser on the potential transaction and has reached out to some private equity firms to gauge their interest, the people said. Tsuruha is looking to collect nonbinding bids from potential investors as soon as next week, the people said.

Shares of Tsuruha jumped by a record 26% following the report. The stock was up 19.63% at the close of the market in Tokyo on Wednesday, giving the Sapporo-based firm a market value of around $4.2 billion.