Public outrage boiled over this fall after news that Turing increased by more than 5,000 percent the price of Daraprim, a drug used to treat a life-threatening infection, jacking it up from $13.50 to $750 per pill.
Daraprim, a 62-year-old drug whose patent expired decades ago, is the only approved treatment for a rare parasitic infection called toxoplasmosis that mainly strikes pregnant women, cancer patients and AIDS patients.
The Senate panel, which began the investigation last month, is examining the price increases for prescription drugs that are no longer protected by patents, and their impact on patients who need the medications.
Valeant, a Canadian company based in Quebec, already had been under investigation by several members of Congress for its business strategy, and Turing and Valeant have received subpoenas from U.S. federal prosecutors seeking information about drug pricing and other policies.
The company said in a statement it makes "significant investments" to improve access to its treatments and in research and development for promising drugs to treat rare diseases.
The powerful pharmaceutical lobby has repeatedly fended off proposals that would cut into profits, from setting up price controls to allowing Medicare to negotiate discounts on drugs it buys for beneficiaries.
