Bad-boy pharmaceutical company executive Martin Shkreli says fraud allegations against him are "baseless and without merit."

Public anxiety over rising drug prices has prompted a U.S. Senate committee to launch an investigation into Turing Pharmaceuticals, Canada's Valeant Pharmaceuticals, and two other drugmakers.

The political scrutiny of Valeant Pharmaceuticals is heating up as the U.S. Senate formally launched a probe Wednesday into skyrocketing prices for three of the company's prescription drugs.