A forceful tweet from Sen. Bernie Sanders (I-Vt.) is being credited for causing shares of a drug company to fall on Friday. Sanders linked to a report about Ariad Pharmaceuticals, which raised the price of a leukemia drug four times this year, and within hours the company's shares dropped 15 percent.

"Drug corporations' greed is unbelievable," Sanders wrote. "Ariad has raised the price of a leukemia drug to almost $199,000 a year."

Sanders sent the tweet during a visit to California for an event on a drug pricing initiative the state will be voting on in November. During the primaries, the then-Democratic presidential candidate made pharmaceutical industry reform and drug pricing issues central focuses of his campaign. He has a habit of calling out the industry on social media.

This time, the effect seemed to be felt immediately. Ariad experienced "the biggest intraday decline in more than a year" and lost "as much as $387 million on Friday afternoon" after the tweet was posted, Bloomberg reported.

What was the report Sanders linked to about?

Bigstock/Daniel fung - bigstockphoto.com

Last week, Stat News reported on Ariad's chronic myeloid leukemia treatment drug, Iclusig. It found that the drug company raised the price four times this year alone — a 27 percent increase, taken altogether — increasing the cost of a year's worth of the life-saving medication to about $199,000.

Ariad told Stat that it's "pricing [is] based on a range of factors, including efforts to make sure that pricing appropriately reflects the benefit the therapy delivers to patients and to the healthcare system." But to Sanders, it represented yet another attempt by a drug company to profit off patients by gradually raising the cost.

Sanders has argued that the pharmaceutical industry lacks the proper regulation needed to avoid unfair price hikes of life-saving drugs such as Iclusig. He's proposed plans to allow patients and pharmacists to purchase drugs from Canada, where prices for some of the same drugs available in America are cheaper; he wants increased discounts for medications for senior citizens; and he's advocated for better pricing transparency and tougher penalties against drug companies are convicted of fraud.

ATTN: reached out to Ariad for a comment, but a representative was not immediately available.