A pricey pill made by Gilead Sciences Inc. caused Medicaid spending on hepatitis C treatments to soar last year, even as most states restricted access to the drug, leaving many low-income patients untreated.

State Medicaid programs spent $1.33 billion on hepatitis C therapies through the third quarter of last year, or nearly as much as the states spent in the previous three years combined, a Wall Street Journal analysis of federal data shows.

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