FRANKFURT (Reuters) - Shares in German chemicals company Bayer BAYGn.DE rose 1.8% in early trade on Tuesday after a U.S. judge slashed a damages award Bayer owes a California man who blamed its Roundup weed killer for his cancer.

Broker Lang & Schwarz said premarket trades had seen the stock up 4.2%. The stock had fallen 6.5% so far this month.

The judge said evidence against the former Monsanto Co, which Bayer bought last year, supported punitive damages over the glyphosate ingredient contained in Roundup but reduced damages to $20 million from $75 million.

A Frankfurt-based trader said that in his view early Tuesday gains were not sustainable.

“Next Glyphosate trials will start in August,” he said. “Bayer will only see an ongoing recovery when it enters mediation talks to settle the 13,400 claims.”

Germany's DAX .GDAXI was 0.06% up.