The U.S. Senate Finance Committee sent a letter on July 11 to Gilead Sciences, informing the drugmaker that the federal government will be investigating and requesting documents on the pricing of Sovaldi (sofosbuvir), the company’s newest, breakthrough treatment for the hepatitis C virus (HCV), WebMD reports.

Sovaldi, which currently works far better and faster than older hep C treatments, has been widely criticized internationally for its $1,000 per-pill price tag, which can add up to about $84,000 per patient for a standard 12-week course of treatment. Treatment advocates argue that the price is far too high and could ultimately limit efforts to end the epidemic. Gilead argues that the drug’s novelty and efficacy make the price worth it when considering the long-term costs of untreated liver disease.

In the new letter, senators expressed the most concern over Sovaldi’s impending cost to the nation’s Medicare and Medicaid programs. The congressional committee argues that if pricing is not adjusted lower, the new drug could cost the federal government nearly $2 billion in extra spending per year, just to treat 25,000 people. It is estimated that 3.2 million Americans are living with hepatitis C.

The letter also argues that Gilead is already starting to offer the drug in other countries for a fraction of the price. For example, a new deal was recently reached with Egypt that will offer Sovaldi for just $300 a treatment, just 1 percent of the projected U.S. cost.

To read the full letter, click here.