The major biotech ETF fell to its lows of the day after Democratic presidential hopeful Hillary Clinton said Monday she would take on "price gouging" in the pharmaceutical industry.
A Sunday New York Times article told of a specialty drug that went from $13.50 to $750 per tablet overnight. Responding on Twitter to this piece, Clinton said Monday she will propose a fix to the situation on Tuesday.
The iShares Nasdaq Biotechnology ETF (IBB) was trading down more than 4 percent by early afternoon, taking a visible leg down around the time of the 10:56 a.m. ET tweet by the presidential candidate.
Biotech stocks are among the hottest group of stocks even as the bull market wanes. The ETF is up 27 percent over the last 12 months, compared with a 2 percent decline for the S&P 500 over the same period.
Investors in the biotech sector often feel as though they are immune from the market lows, according Bradd Kern, managing director at Armored Wolf, which is short IBB. Instead, he said, all the hot money in the sector makes it prone to sharp downward turns when confidence is shaken.
"I do think there will be more days like today," Kern said.
Shares of Retrophin, started by Martin Shkreli, traded down more than 11 percent following Clinton's tweet. Shkreli is also the founder and Turing Pharmaceuticals, which was the subject of the Times article.
Shkreli told CNBC's "Power Lunch" that he stands by the increased price of Daraprim, the specialty drug at the center of the aforementioned New York Times article.
Read More Clinton calls drug price hike 'outrageous,' vows plan
"At this price Daraprim is still actually on the low end of what orphan drugs cost and we're certainly not the first company to raise drug prices," he said.
"We paid a very, very large amount to buy an unprofitable medicine. We can't continue to lose money on the drug at that price so we took it to a price where we can make a comfortable profit but not any kind of ridiculous profit," Shkreli added. "Turing is a very small company. It's a new company and we're not a profitable company, so for us to try and exist and maintain a profit is pretty reasonable."
Still, the pharmaceutical sector may need reforms, Steve Case, chairman and CEO of investment firm Revolution told CNBC.
"A lot of development now is moving offshore that we're at risk of losing our lead in terms of innovation in this space in the United States," he said. "If we can figure out a way to lower the cost of development and expedite the process of getting these things from the labs into the marketplace, I think that will result in better products, better services for more people, better drugs at lower costs."
Correction: An earlier version misstated the time of Clinton's tweet
—CNBC's Evelyn Cheng contributed to this report.