The Massachusetts attorney general's office is investigating whether the makers of a breakthrough treatment for hepatitis C are violating state law by pricing the drug too high.

Attorney General Maura Healey on Wednesday released a letter sent to the chief executive of California-based Gilead Sciences Inc. In it, Healey said her office was examining whether the pricing constituted an unfair trade practice.

Sovaldi was the company's first hepatitis C drug. It was priced at $1,000 per pill in the U.S., or $84,000 for a course of treatment. It has since introduced Harvoni, a more expensive, next-generation pill.

Healey urged Gilead to adjust its pricing to make the treatments more accessible.

Messages left with Gilead weren't immediately answered. The company has said the drugs were responsibly and thoughtfully priced.

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