Biotech companies might be in the business of healing people, but the industry’s stock market performance last week probably left shareholders feeling sick.

Pharmaceutical companies accounted for five of the 10 biggest losers on the LABJ Stock Index for the week ended Sept. 23, led by Westwood breast cancer drug developer Puma Biotechnology Inc., which dropped nearly 14 percent to close at $88.27.

The specialty drug industry was hit hard after a Sep. 21 tweet from Democratic presidential frontrunner Hillary Clinton in which she promised to take on the issue of price-gouging.

The issue surfaced after New York’s Turing Pharmaceuticals raised the price of its drug, which treats parasitic infections, to $750 a tablet from $13.50 in one day. The New York Times also reported that the practice has become increasingly common, which coupled with Clinton’s tweet prompted a wave of negative coverage.

Other local firms feeling the pain of a more than 10 percent weekly drop include Woodland Hills’ Lion Biotechnologies Inc.; Xencor Inc. of Monrovia; Pasadena’s Arrowhead Research Corp.; and Ritter Pharmaceuticals Inc., which is headquartered in Century City.

Turing subsequently bowed to pressure and agreed to lower its drug’s price, but the biotech selloff continued.

“It always pops up in political context and it will again,” said David Nierengarten, an analyst at Wedbush Securities Inc. in San Francisco.

Nierengarten said the political environment has affected the sector in the past and suggested that, as before, there would be a rebound from the recent dip.

“The markets have recovered. I think we’ll see that again.”

Since Clinton’s tweet, the Nasdaq Biotechnology Index, which is used to track the sector, fell more than 250 points to close at 3,488 on Sept. 23. The index is still up by roughly 12 percent since the beginning of the year.

Puma, however, is facing other issues.

The company’s drug, neratinib, has not yet received approval from the Food and Drug Administration. It is also working to convince the medical community that neratinib should be administered to patients since it causes severe diarrhea in about 40 percent of patients, based on clinical data.

However, a Sept. 18 memo from JPMorgan Chase & Co. analyst Cory Kasimov should give Puma Chief executive Alan Auerbach reason to be cautiously optimistic.

After polling 33 physicians, J.P. Morgan analysts said reactions were more positive than negative, causing the firm to maintain its “overweight” rating on Puma’s stock.

“Impressions did come back more favorably than we anticipated suggesting that there would be a role for neratinib,” reads the note.