Hardeman's case was considered a bellwether trial to help determine the range of damages and define settlement options for the more than 760 other federal cases pending in the same court before U.S. District Judge Vince Chhabria.

In the first trial phase of Hardeman's case, the jury deliberated for more than four days before finding Roundup responsible for the man's cancer. Bayer on Wednesday said that was an indication that jurors were "very likely divided over the scientific evidence."

The company said its appeal would focus on legal rulings by Chhabria, who allowed some of Hardeman's scientific experts to testify despite calling plaintiffs' expert opinions "shaky" in a 2018 ruling.

But legal experts have noted that the 9th U.S. Circuit Court of Appeals, which oversees the San Francisco federal court, has generally been permissive in allowing expert testimony.

Monsanto's Roundup was the first to contain glyphosate, the world's most widely used weed killer. But it is no longer patent-protected and many other versions are available. Bayer does not provide sales figures for the product.

The U.S. Environmental Protection Agency, the European Chemicals Agency and other regulators have found that glyphosate is not likely carcinogenic to humans. The World Health Organization's cancer arm in 2015 reached a different conclusion, classifying glyphosate as "probably carcinogenic to humans."

In the first U.S. Roundup trial, another California man was awarded $289 million in August after a state court jury found Roundup caused his cancer. That award was later reduced to $78 million and is on appeal.

Hardeman's case featured a significant difference from that trial after Chhabria decided to split cases before him into two phases: one to decide causation on purely scientific grounds, the other to determine Bayer's potential liability and damages only if the jury first ruled that the weed killer was a substantial factor in causing cancer.

That decision had been seen as beneficial to Bayer. Legal experts said the jury's verdict in the first phase of the Hardeman case was a significant setback, narrowing the company's legal options going forward.

Chhabria has scheduled another bellwether trial for May and a third trial is likely to also take place this year. All three will be split into causation and liability phases.

Bayer is also scheduled to face another Roundup trial in California state court beginning on March 28 and at least two trials in Missouri state court in the fall. (Reporting by Alexandria Sage in San Francisco; Writing by Tina Bellon in New York Editing by Bill Berkrot and Lisa Shumaker)