Former Turing Pharmaceuticals Chief Executive Officer Martin Shkreli invoked his Fifth Amendment right against self-incrimination and declined to answer questions on Thursday from U.S. lawmakers interested in why the company raised the price of a lifesaving medicine by 5,000 per cent.

Shkreli, 32, sparked outrage last year among patients, medical societies and Democratic presidential front-runner Hillary Clinton after Turing raised the price of 62-year-old Daraprim to $750 a pill from $13.50.

The medicine, used to treat a parasitic infection, once sold for $1 a pill. At a hearing of the U.S. House Committee on Oversight and Government Reform, Shkreli sat at a table with arms crossed and repeatedly declined to answer questions about the effects of the price hike on patients.

"I intend to follow the advice of my counsel, not yours," Shkreli told Rep. Trey Gowdy, a South Carolina Republican. The Fifth Amendment of the U.S. Constitution says no person shall be compelled in any criminal case "to be a witness against himself."

Shkreli was arrested in December and charged with running his investment funds and companies almost like a Ponzi scheme. He has pleaded not guilty, stepped down from Turing and was fired from KaloBios Pharmaceuticals Inc.