"Pharma bro" Martin Shkreli — widely reviled for astronomically jacking up prescription medication for HIV and cancer sufferers — continued to annoy as he remained silent at a US congressional hearing on pill pricing. But he smirked, rolled his eyes, and complained about the proceedings on Twitter.

Shkreli, the former CEO of Turning Pharmaceuticals — who has been dubbed the "most hated man in America" — invoked his constitutional Fifth Amendment right against self-incrimination and refused to answer any questions from the House Committee on Oversight and Government Reform. But he was highly expressive through the proceedings. He smiled and looked away when the panel's ranking Democrat tried to appeal to his sense of morality, NBC noted.

"Drug company executives are lining their pockets at the expense of some of the most vulnerable families in our nation," said Maryland Democratic Congressman Elijah Cummings. "It's not funny, Mr. Shkreli. People are dying and they're getting sicker and sicker."

Shkreli, 32, continued to smirk and play with his pencil, remaining silent. At times he looked like he was close to laughter. Not long later, he called the politicians "imbeciles" — on his Twitter account.

Shkreli has amassed an army of enemies for jacking up Turing's life-saving drug Daraprim by more than 5,000% from $13.50 (£9.28) to $750 (£515). The pill is used to treat toxoplasmosis, a parasitic disease that afflicts people with weakened immune systems, such as those with AIDS and pregnant women.

One congressman asked the mega-wealthy boy executive about his purchase of a one-of-a-kind Wu-Tang Clan album for $2 million. He tried to goad Shkreli into responding, noting Shkreli wasn't shy about sharing information on Twitter.

"This is a great opportunity if you want to educate the members of Congress about drug pricing, or what you call the fictitious case against you," said Trey Gowdy, the Republican congressman from South Carolina. "We can even talk about the purchase of the — what is it — Wu-Tang Clan, is that the name of the album? The name of the group?"

Shkreli again invoked his right to not answer questions.

Shkreli was busted in December 2015 on charges of securities fraud. He is accused of repeatedly losing money for investors in a separate operation and lying to them about it, illegally taking assets from another pharmaceutical company that he founded to pay off debtors in what Brooklyn prosecutors have branded a Ponzi scheme.