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.

Deliberations are ongoing and Tsuruha could still decide against a deal, said the people, who asked not to be identified as the information is private. A representative for Tsuruha didn’t immediately respond to requests for comment.

Tsuruha is the second-largest drug store chain in Japan in terms of market share, according to Euromonitor International. Tracing its roots to 1929, the company has almost 2,600 stores with another 18 overseas, its latest investor presentation shows. It aims to grow its network to 2,750 stores with revenue hitting ¥1.06 trillion by May 2025, according to its medium-term management plan.

Oasis Management, which owns a 12.8% stake in Tsuruha, earlier this year said the drug store chain is in "disproportionate control” in the hands of the delegates from the three founding families, harming the Japanese firm’s ability in evaluating consolidation opportunities. The Hong Kong-based investor asked shareholders to vote for its proposals on corporate governance reforms and support the five directors it nominated, replacing the incumbents.

In August, shareholders approved all the directors nominated by Tsuruha and rejected the five external candidates backed by Oasis.

Tsuruha rejected Oasis’s claims and said the board has a track record of implementing mergers and acquisitions that strengthens the firm’s profitability. The company continues to promote strategic M&A, it said.