"We can't just withhold life-saving cancer drugs from Russian patients. There is international consensus that medicines are exempt from sanctions," Schwan told Swiss newspaper TagesAnzeiger, adding that prices being fixed in Russian roubles meant the pharmaceutical giant was currently losing money on Russian sales.

The statement echoed other pharmaceutical giants, who have said they will supply essential medicines in Russia but halt some other activities in response to Russia's invasion of Ukraine.

Roche has 800 sales staff in Russia, he said.

Speaking about his upcoming exit from the board of big bank Credit Suisse, Schwan said he had already considered resigning a year ago but it had become opportune after a twin set of scandals hammered the bank last March.

The bank was now in "good hands" under new Chairman Axel Lehmann, the outgoing vice-chair said.

Asked whether larger Swiss rival UBS or a foreign bank might take over Credit Suisse since its share price had been battered, Schwan said he hoped the bank would remain independent.

"It would be a huge loss for Switzerland if there were only one major Swiss bank. That's why it's important that CS stabilises its business, rebuilds trust and seizes its opportunities," he said.

He said he would be willing to take on another board role in the future.

"In principle, I think it is feasible to sit on the board of a bank alongside my job as CEO at Roche," he said.

"The fact that I'm stepping down now doesn't mean that I don't think it's important for an active CEO to take on such a task. We need banks, they are like the oil in the gears. And for some things we need specifically Swiss banks."

(Reporting by Brenna Hughes Neghaiwi; Editing by Stephen Coates)