Martin Shkreli, the 32-year-old former CEO of Turing Pharmaceuticals who made negative headlines last year after jacking up the price of the toxmoplasmosis drug Daraprim (pyrimethamine) from $13.50 to $750 a pill immediately after acquiring marketing rights, has refused to testify before a US Congressional committee.

The oversight committee of the House of Representatives is investigating Turing’s drug price hikes.

Shkreli invoked the Fifth Amendment to the US constitution, the right to remain silent. Instead of answering questions, the executive also facing charges of fraud in a US federal court in New York made headlines again by hurling insults at the assembled members of the committee.

At the hearing, the lawmakers released excerpts from a reported 250,000 documents said to show that Shkreli sought to make $1 billion in profit from selling the 62-year-old drug at the higher price.

The committee’s highest-ranking Democratic member, Maryland congressman Elijah Cummings, said that since acquiring Daraprim in August 2015 Turing took in $98 million in revenue.

This was despite the fact that the drug – available only on the US market – was out of reach for most people with compromised immune systems, such as HIV sufferers and pregnant women.

In December 2015, Express Scripts Holding, the biggest pharmacy benefits manager in the US, said it planned to list Imprimis Pharmaceuticals’ cheaper alternative to Daraprim for $1 per pill.

The US Federal Bureau of Investigation, FBI, is currently investigating Shrekli’s wider financial dealings. The 32-year-old stands accused of running a Ponzi scheme at drugmaker Retrophin and at a hedge fund, MSMB Capital Management, both of which he headed.

Retrophin meanwhile has agreed to pay $3 million to settle a class action lawsuit that accuses it of failing to disclose its former CEO’s actions. The suit was filed in 2014, the same year that Shkreli was fired from the company.

The proposed settlement would also resolve the related claims against Shkreli in his role as CEO. While in the position he is accused of siphoning off $11 million in assets to pay off defrauded investors from the failed hedge fund. The company’s current management has disputed the charges.

A federal judge in Manhattan has given preliminary approval to the settlement and will hold a hearing on June 10 to decide whether to give the final green light.