(Bloomberg) -- Activist investor Jeff Ubben has bought a stake in Bayer AG, the German drugs and agriculture company whose shares have slumped since its Monsanto takeover.

Ubben’s Inclusive Capital Partners directly owns 8.18 million Bayer shares, equivalent to a 0.83% interest, the San Francisco-based firm said in a filing Monday. The stock is worth about €414 million ($442 million) based on Friday’s closing price. 

Bayer Chief Executive Officer Werner Baumann has been under pressure from shareholders since the company’s 2018 deal for crop science giant Monsanto. The record German takeover became a legal headache, with Bayer setting aside an estimated $16 billion to cover lawsuits that claim controversial weedkiller Roundup causes cancer.

Amid the Monsanto litigation, Bayer’s share price has fallen by about half from its level before the deal. Some investors have called for the company — which has three big divisions devoted to pharmaceuticals, crop science and consumer health — to split up into different entities. Baumann has insisted the company’s current configuration is the right one.

Shares of Bayer jumped as much as 4.2% in Monday trading, the biggest intraday gain in nearly two months. They were up 3.6% at 1:54 p.m. in Frankfurt, giving the company a market value of €51.5 billion.  

Ubben left the hedge fund he founded, ValueAct Capital Management, in 2020 and started Inclusive Capital. The firm, which focuses on social and environmental investing, has previously taken positions in electric-truck company Nikola Corp., power generator AES Corp. and bioenergy firm Enviva Inc., according to data compiled by Bloomberg. 

Exxon Mobil Corp. appointed Ubben to its board in 2021 following investor criticism of the oil giant for its environmental record and poor capital allocation. He’s also bought a stake in Fertiglobe Plc, the Middle Eastern fertilizer venture backed by Abu Dhabi National Oil Co. and OCI NV, and serves as an independent director. 

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