Nearly two months after hiking the price of a life-saving drug by 5,000 percent overnight, Turing Pharmaceuticals is being investigated by the U.S. Senate.

The Senate’s Special Committee on Aging is targeting Turing and three other drugmakers, Valeant Pharmaceuticals, Retrophin Inc. and Rodelis Therapeutics, for dramatic increases in certain prescription drugs.

In a letter to Turing CEO Martin Shkreli, the committee requested a face-to-face meeting with Shkreli, the former hedge fund manager turned drug company head. Shkreli has come under fire for acquiring the rights to Daraprim, a drug commonly used by HIV patients and pregnant women to treat toxoplasmosis, a potentially deadly parasitic infection, then hiking its price overnight from $13.50 per pill to $750 per pill.

The letter asks for the identity of “the Turing employee responsible for setting the price of Daraprim.”

Turing Pharmaceuticals released this statement regarding the investigation:

“[W]e look forward to having an open and honest dialogue about drug pricing. We’re proud of our patient assistance program which limits out-of-pocket costs for nearly all patients to $10 per prescription, with most receiving Daraprim for $1 or less. More than 60 percent of our revenues are going straight into research and development of new and improved therapies for a variety of indications.”

Meanwhile, Shkreli has dismissed the Senate committee investigation has nothing more than a poorly conducted attempt to gain political capital.

“The senators have their facts wrong,” Shkreli told CNBC. “They’re trying to make a tempest out of a teacup, and a mountain out of a molehill.”

Amid a public outcry over the massive Daraprim price hike, Shkreli agreed to make a modest decrease in the price of the drug by the end of the year, CNBC reports. There’s no word yet on just how much the decrease will be.

“I haven’t decided it to be 10 [percent] or 5 or 20 percent or anything yet, but it’ll be modest,” Shkreli said.

Escalating drug prices have been in the spotlight recently. With some drug price costs skyrocketing upward of 400 to 1,200 percent, people are taking notice.

“We need to get to the bottom of why we’re seeing huge spikes in drug prices that seemingly have no relationship to research and development costs,” said Sen. Claire McCaskill of Missouri, the ranking Democrat on the committee spearheading the drug price probe.

McCaskill added that some of the increases appear to be “little more than price gouging.”

The committee has a tentative hearing date of Dec. 9.

Have you noticed any significant price hikes in your prescription drugs? Share your experiences below or on our Facebook page.