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May 13, 2015, 4:06 AM UTC / Updated May 13, 2015, 5:20 AM UTC

Pricey cancer drugs, expensive new cures for hepatitis and made-to-order drugs have driven U.S. prescription costs to new highs for some Americans, according to a report issued Wednesday.

It finds that more than half a million Americans each took home $50,000 or more worth of prescription drugs last year.

And the number of super-high spenders prescribed $100,000 or more worth of medications nearly tripled from 47,000 to 139,000, pharmacy benefits manager Express Scripts says.

These are often very sick people, the report found. “Among patients whose drug costs reached at least $100,000, more than one-third were treated for at least 10 conditions and more than 60 percent were taking at least 10 different prescription medications,” the report reads.

“Among patients whose drug costs reached at least $100,000, more than one-third were treated for at least 10 conditions."

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For those spending $100,000 or more a year, specialty, made-to-order drugs known as compounded therapies, as well as drugs for hepatitis C and to treat cancer accounted for two-thirds of the costs, Express Scripts found.

The hepatitis C drugs include Gilead Science’s Sovaldi, which can cure the liver-destroying virus. Gilead charges $84,000 for the three-month drug course, and argues that it costs less than treating patients for a lifetime of liver disease.

Express Scripts, which has actively fought drug companies over their pricing, has refused to cover Gilead’s other expensive hepatitis C drug Harvoni, and instead negotiated a deal with rival drugmaker Abbvie to get its hepatitis C drug Viekira at a discount.

The benefits manager, which covers about 85 million Americans, has also complained about pricey cancer drugs. Bristol-Myers Squibb’s melanoma drug Yervoy can keep patients with terminal melanoma alive for a year or longer but it costs $120,000 for a course of treatment.

Patients are almost never bearing these high costs. Insurance plans covered more than 98 percent of the costs for patients whose drugs cost $100,000 or more in 2014. “Across the cost spectrum, patients in 2014 paid an average of 13.5 percent of their total medication costs, down from 14.9 percent in 2013,” the report reads.

"Patients are overwhelmingly taking specialty medications, and have multiple comorbidities, prescriptions and prescribers."

Express Scripts used data from 31.5 million insured Americans covered by commercial insurers, Medicare and Medicaid for its report.

“The profile emerging from this research shows these patients are overwhelmingly taking specialty medications, and have multiple comorbidities, prescriptions and prescribers,” said Dr. Glen Stettin, senior vice president for clinical research at Express Scripts.

The report found that 90 percent of patients with drug costs of $50,000 used specialty medications, which are expensive treatments for complex conditions. More than a third of them were being treated for 10 or more different medical conditions.