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WASHINGTON — Martin Shkreli, reviled former chief executive officer at Turing Pharmaceuticals, has invoked the Fifth Amendment in refusing to produce documents subpoenaed by a Senate committee investigating drug-pricing practices, the panel's chairwoman said Wednesday.

Sen. Susan Collins, R-Maine, said on Twitter that the investigation by the Senate Special Committee on Aging could be hindered without Shkreli's cooperation.

“Absent a valid justification for the grounds for invoking the Fifth Amendment, Mr. Shkreli’s assertion could hinder our investigation.” — Sen. Susan Collins (@SenatorCollins) January 20, 2016

Word of Shkreli's refusal to cooperate with the Senate investigation came after it was reported that House lawmakers have issued a subpoena to compel Shkreli to appear at a congressional hearing next Tuesday.

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An aide to the House Committee on Oversight and Government Reform confirmed the news to the Associated Press. The committee is investigating several companies for exorbitant drug price increases.

Martin Shkreli, former CEO of Turing Pharmaceuticals, is brought out of 26 Federal Plaza by law enforcement officials after being arrested on securities fraud charges on Dec. 17, 2015, in New York City. Andrew Burton / Getty Images

Shkreli became notorious for hiking the price of Daraprim, the only approved drug for a rare and sometimes deadly parasitic infection, by 5,000 percent. Since then, Shkreli has been deluged with criticism from patients, politicians and the media, some calling him the "most hated man in America."

Last month, the 32-year-old former hedge fund manager was arrested in New York and charged with securities fraud and conspiracy. The charges stem from another pharmaceutical company he previously ran called Retrophin.

Ex-Pharma CEO Martin Shkreli Sacks His Legal Team in Fraud Case

On Tuesday, Shkreli's lawyers in the case filed court papers indicating that he wished to replace them and was in the process of hiring new counsel.