Shares of health-care companies fell as a victory for Hillary Clinton the U.S. presidential election looked increasingly likely. Fissures showed in the Republican party as House Speaker Paul Ryan said that he would no longer campaign for Donald Trump, effectively conceding that the controversial candidate was heading for defeat.

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Mrs. Clinton has pledged reviews on price increases proposed by drug companies, potentially cutting off one of the biggest sources of profit growth in recent years. One of the companies at the center of the controversy over price rises, Mylan, agreed to settle allegations it overcharged the government for its EpiPen emergency allergy treatment, causing its shares to surge.

Shares of gene-sequencing company Illumina fell sharply after it cut third-quarter revenue projections and forecast growth shy of Wall Street targets.

St. Jude Medical warned that hundreds of thousands of implanted defibrillators could quickly lose power and stop functioning because of faulty batteries.