A federal lawsuit is accusing three of the biggest drug manufacturers of insulin of conspiring together to raise their prices, but the pharmaceutical companies deny the allegations.

The lawsuit, filed on in January in a federal court in Massachusetts, said Sanofi SA, Novo Nordisk and Eli Lilly & Co simultaneously hiked the price of the drug.

Investment research firm SSR Health analyzed list prices for insulin from the three companies and found that the prices increased between 99 and 120 percent from 2012 to 2016, CBS News reported.

In addition, they also found that the prices of two prime insulin drugs increased lockstep 12 times between 2008 and 2014.

A federal lawsuit is accusing three of the biggest drug manufacturers of insulin (file above) of conspiring together to raise their prices, but the pharmaceutical companies deny the allegations

The lawsuit, filed on in January in a federal court in Massachusetts, said Sanofi SA, Novo Nordisk and Eli Lilly & Co simultaneously hiked the price of the drug (file above)

The lawsuit’s twelve named plaintiffs, residents of Georgia, Florida, California and Massachusetts who have diabetes, claim Sanofi, Novo Nordisk and Lilly raised their public benchmark price for insulin products while maintaining a lower ‘true’ price they charged large pharmacy benefit managers like Express Scripts, CVS Health and OptumRX.

The pharmacy benefit managers act as intermediaries with health insurers and keep a percentage of the price difference, according to the lawsuit.

The plaintiffs claim the alleged price-fixing scheme caused them to overpay for insulin.

According to the lawsuit, some skipped meals or underdosed their insulin because they could not afford treatment otherwise.

Others intentionally experienced severe diabetic complications to obtain insulin samples from emergency rooms, the complaint said.

Senator Bernie Sanders (above last week) asked federal antitrust regulators to investigate possible insulin price collusion by Sanofi, Lilly, Novo Nordisk and Merck & Co Inc. All three companies deny the allegations

Uninsured patients and those on high-deductible plans are particularly affected by rising insulin prices, plaintiffs said.

The lawsuit, which seeks class action status, alleged violations of the federal racketeering statute, which allows for triple damages, as well as consumer protection laws in virtually every state.

In November, Vermont Independent Senator Bernie Sanders and Democratic Rep. Elijah Cummings of Maryland asked federal antitrust regulators to investigate possible insulin price collusion by Sanofi, Lilly, Novo Nordisk and Merck & Co Inc.

‘Just coincidentally it happens that the three major suppliers of insulin seem to be raising their prices at the same exact time, at the same level,’ Sanders told CBS News.

‘So I think you have to be very naïve not to believe there is collusion.’

Ashleigh Koss, a spokeswoman for Sanofi said: ‘We strongly believe these allegations have no merit, and will defend against these claims.’

Eli Lilly spokesman Greg Kueterman declined to comment on the lawsuit but said the company complied with all applicable laws and adhered to the highest ethical standards.

Ken Inchausti, a spokesman for Novo Nordisk, said the company disagreed with the complaint’s characterization of the pharmaceutical supply chain and noted its commitment to patients’ access to medicine.

Lilly said in December it would provide some patients with up to 40 percent discounts on insulin products via its partnership with Express Scripts Holding Co.

Six million people across the United States use insulin to treat diabetes, as more than 29 million live with the incurable disease.