BONN (Reuters) - Bayer shareholders vented their anger over its stock price slump on Friday as litigation risks mount from the German drugmaker’s $63 billion takeover of seed maker Monsanto.

Several large investors said they will not support aspirin investor Bayer’s management in a key vote scheduled for the end of its annual general meeting.

Bayer’s management, led by chief executive Werner Baumann, could see an embarrassing plunge in approval ratings, down from 97 percent at last year’s AGM, which was held shortly before the Monsanto takeover closed in June.

A vote to ratify the board’s actions features prominently at every German AGM. Although it has no bearing on management’s liability, it is seen as a key gauge of shareholder sentiment.

“Due to the continued negative development at Bayer, high legal risks and a massive share price slump, we refuse to ratify the management board and supervisory board’s actions during the business year,” Janne Werning, representing Germany’s Union Investment, a top-20 shareholder, said in prepared remarks.

About 30 billion euros ($34 billion) have been wiped off Bayer’s market value since August, when a U.S. jury found the pesticide and drugs group liable because Monsanto had not warned of alleged cancer risks linked to its weedkiller Roundup.

Bayer suffered a similar defeat last month and more than 13,000 plaintiffs are claiming damages.

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Bayer is appealing or plans to appeal the verdicts.

Deutsche Bank’s asset managing arm DWS said shareholders should have been consulted before the takeover, which was agreed in 2016 and closed in June last year.

“You are pointing out that the lawsuits have not been lost yet. We and our customers, however, have already lost something - money and trust,” Nicolas Huber, head of corporate governance at DWS, said in prepared remarks for the AGM.

He said DWS would abstain from the shareholder vote of confidence in the executive and non-executive boards.

Two people familiar with the situation told Reuters this week that Bayer’s largest shareholder, BlackRock, plans to either abstain from or vote against ratifying the management board’s actions.

Asset management firm Deka, among Bayer’s largest German investors, has also said it would cast a no vote.

Baumann said Bayer’s true value was not reflected in the current share price.

“There’s no way to make this look good. The lawsuits and the first verdicts weigh heavily on our company and it’s a concern for many people,” he said, adding it was the right decision to buy Monsanto and that Bayer was vigorously defending itself.

This month, shareholder advisory firms Institutional Shareholder Services (ISS) and Glass Lewis recommended investors not to give the executive board their seal of approval.