Business Insider reported exclusively last week that generic drug companies' lawyers allegedly coordinated to send " 'polite f-u' letters" in response to lawmakers' inquiries about the spiking prices of their products.

Senator Bernie Sanders of Vermont and Representative Elijah Cummings of Maryland just sent the Justice Department a letter urging action against generic drug manufacturers.

"In my view, their 'polite f-u' letters designed to obstruct our investigation were clearly illegal," Sanders said in a statement

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Years ago, when the prices of generic drugs like an antibiotic and an asthma medication jumped more than more than 8,000% and 4,000%, respectively, Senator Bernie Sanders of Vermont and Representative Elijah Cummings of Maryland began investigating.

They sent letters in fall of 2014 to 14 generic drugmakers, asking about the spiking prices.

But among the generic drugmakers, "the consensus at this point is that the responses will be 'polite f-u' letters," a lawyer for one allegedly reported in an email,

That's according to an unredacted antitrust complaint being brought by 44 states against generic drugmakers like Mylan, Teva and others that Business Insider reported on exclusively last week.

The unredacted version of an antitrust complaint being brought against 20 drugmakers cites this email from a lawyer for a generic drug company. 44-state unredacted complaint

You can read the full story here, and see the unredacted complaint here.

Sanders and Cummings just wrote to the Justice Department following up about the lawsuit and urging action against generic drug companies.

"In my view, their 'polite f-u' letters designed to obstruct our investigation were clearly illegal," Sanders said in a statement. "The Department of Justice must hold these bad actors accountable to the fullest extent of the law."

Generic drugmakers allegedly worked together to hike prices

The new letter from Sanders and Cummings refers back to allegations that drugmakers including Teva, the world's largest generic drugmaker, worked together to hike the prices of many of their drugs. Teva didn't immediately respond to a request for comment on the lawmakers' letter.

This claim has been the focus of lawsuits from state attorneys general and an ongoing criminal investigation by the Department of Justice.

These have all brought new scrutiny to generic drugs, which are inexpensive versions of brand name medicines that become available once their patents have expired.

Generics make up the vast majority of prescriptions dispensed in the US, and have been touted as a free-market solution to the US's high healthcare costs. But the lawsuits allege that drugmakers worked together to bring prices up, instead, hurting patients and taxpayers.

The Justice Department brought charges against two generic drug executives in late 2016, alleging that they had fixed drug prices and manipulated the market for the drugs, but "has not announced any charges against additional generic manufacturers or executives" since, the lawmakers said in the Thursday letter.

That drug company, Heritage, did admit to price fixing for a diabetes medication and agreed to pay a $225,000 criminal penalty and an additional $7 million in a separate civil resolution, the Department of Justice announced late last month.

But the $225,000 penalty is "wholly insufficient to deter future criminal conduct by Heritage or other generic manufacturers," Sanders and Cummings said in the new letter.

Pointing to the 44-state lawsuit that was recently filed against the generic drugmakers (and is separate from the Department of Justice investigation), the lawmakers urged the Justice Department to investigate and take enforcement actions, if justified.

They also pointed to evidence in the lawsuit suggesting that drugmakers misled the Congressional inquiry, and asked for an investigation into whether Teva and others had violated the law by doing so.

Sanders and Cummings also asked for a briefing by next Friday about any actions the department is taking.

"In response to our document and information requests, these companies gave excuses for raising prices — such as the costs of regulatory compliance, drug shortages, and user fees — that were at best, grossly misleading, and at worst, false statements to Congress," they said.