The Internal Revenue Service has filed a tax lien for $4,628,928.55 against Martin Shkreli, the former CEO of Turing Pharmaceuticals who hiked the price of a lifesaving medication produced by the company by 5,000 percent.

The IRS prepared the tax lien against Shkreli on December 18, a day after the FBI arrested him for securities fraud charges related to his management of a hedge fund, and filed the tax lien last month. The tax lien against Shkreli comes from unpaid 2014 taxes of $4,625,496.70 and unpaid 2013 taxes of $3,431.85, according to Gawker.

In the unrelated securities fraud case, Shkreli is accused of using money from a pharmaceutical company that he founded, Retrophin, to pay off investors in his hedge fund. Retrophin filed suit against him last August for $65 million. His other drug company, Turing, replaced him as CEO last December following his arrest.

Shkreli gained notoriety last summer after he defended his decision to increase the price of Turing’s HIV medication Daraprim from $13.50 to $750 for each pill, opening him to accusations of price gouging.

He has continued to stoke controversy for paying $2 million for the only copy of a Wu-Tang Clan album, “Once Upon a Time in Shaolin,” and then argued in a series of back-and-forth YouTube videos with Wu-Tang Clan rapper Ghostface Killah. He has gained the nickname of "Pharma Bro." Last week, Shkreli offered rapper Kanye West $10 million for his new album, “The Life of Pablo,” on Twitter.

Earlier this month, Shkreli refused to testify before Congress about drug prices, repeatedly invoking his Fifth Amendment privilege against self-incrimination during the House Oversight and Government Reform Committee hearing. Lawmakers repeatedly criticized him for refusing to answer questions and smirking during the hearing before they dismissed him. “It’s not funny, Mr. Shkreli,” said Rep. Elijah Cummings, D-Md., the ranking member on the committee. “People are dying and they’re getting sicker and sicker.”

Soon after leaving the hearing, Shkreli called the lawmakers “imbeciles” on Twitter. “Hard to accept that these imbeciles represent the people in our government,” he wrote.