Shares of the biopharmaceutical company KaloBios were down 50% in premarket trading on Thursday before being halted.

The move comes after a Bloomberg news story reported that the company's CEO, Martin Shkreli, was arrested in a securities-fraud investigation.

KaloBios has been developing a treatment for leukemia. In an interview with Bloomberg in November, Shkreli said the firm was in discussions to acquire three other drugs.

Shkreli initially made headlines this past fall after presidential candidate Hillary Clinton called out the pricing practices of his company Turing Pharmaceuticals, which raised the price of its drug Daraprim by 5,000%.

Shkreli quickly came to represent all that critics of the pharmaceutical industry reviled as he unapologetically defended himself and his pricing practices, often on Twitter and often employing references to hip-hop music.

On November 19, KaloBios named Shkreli CEO and chairman of the board. Trading for less than $1 a share just a month ago, the stock exploded to over $45 after news of the management change.

Shares closed at $23.59 on Wednesday. And in premarket trading following news of the arrest, they are closer to $11.80.

KaloBios (KBIO). Google Finance

"Prosecutors charged him with illegally taking stock from Retrophin Inc., a biotechnology firm he started in 2011, and using it pay off debts from unrelated business dealings," Bloomberg's Christie Smythe and Keri Geiger reported. "In the case that closely tracks that suit, federal prosecutors accused Shkreli of engaging in a complicated shell game after his defunct hedge fund, MSMB Capital Management, lost millions. He is alleged to have made secret payoffs and set up sham consulting arrangements."

Read the whole story at Bloomberg.com.