NEW YORK: U.S. President-elect Donald Trump on Wednesday said pharmaceutical companies are "getting away with murder" in what they charge the government for medicines, and promised that would change, sending drugs stocks sharply lower.

The benchmark S&P 500 index slipped into negative territory after his remarks at a news conference spooked investors. The Ishares Nasdaq Biotech ETF dropped 4 percent at its session low and was on track for its largest daily percentage drop since late June.

"When the president-elect says we're going to negotiate drug pricing, you have to take that seriously, but at the same this is a complicated issue because there's not going to be clarity on drug pricing reform anytime soon," said Brad Loncar, manager of the Loncar Cancer Immunotherapy ETF. "When somebody that high profile says something that negative, people do not want to invest in it."

Trump has blasted other industries for charging the government too much, particularly defense companies, but has made only a few public statements about drug pricing since being elected. He briefly mentioned Lockheed Martin Corp and Ford & Co , and United Technologies Corp during the Wednesday news conference and promised a border tax for companies producing products for U.S. consumers outside the United States.

After his promise to bring down drug spending, the ARCA pharmaceutical index fell 2 percent as Pfizer Inc gave up 2.6 percent and Johnson & Johnson fell 1 percent. Biotech Gilead Sciences Inc fell 2.3 percent. 

The drug industry has been on edge for two years about the potential for more government pressure on pricing after sharp increases in the costs of some life-saving drugs drew scrutiny in the press and among lawmakers. The government is investigating Medicaid and Medicare overspending on Mylan NV's allergy treatment EpiPen, for instance.

David Katz, chief investment officer at Matrix Asset Advisors in New York, said negative comments on drug pricing trigger selling both from algorithms and investors who suffered from share drops when Democrat Hillary Clinton campaigned against healthcare cost increases.

Options traders' expectation for near-term volatility in shares of Health Care Select Sector SPDR Fund jumped to a one-month high.