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The new $84,000 hepatitis C treatment is losing momentum, for now

(AP Photo/Courtesy of Gilead Sciences)

After recording the best launch of any drug in history, it looks like the pace is starting to slow down for Gilead Sciences' Sovaldi — the new $84,000 hepatitis C cure that's sparking a new focus on specialty drug costs.

Data released by CVS Health on Tuesday show that use of Sovaldi has slowed down since May after the drug's record-setting start last December. The slowdown can partly be explained by the health-care industry's anticipation of more hepatitis C treatments soon hitting the market, including another one from Gilead that could gain FDA approval any day now. This CVS chart shows how Sovaldi's launch compares to other recent launches for hepatitis C treatments.

The CVS data also provide some insight into how the new drug, which is priced at $1,000 per day, is being used in the real world. Looking at nearly 2,000 of its pharmacy patients, CVS found 8.1 percent (or about 1 in 12) discontinued their treatment. That's four times higher than the 2 percent discontinuation rate that occurred in Sovaldi's clinical trials.

Clinical trials have much more controlled environments, so it's easier to ensure that those patients follow through on the full course of treatment. Even so, the discontinuation rate for Sovaldi clinical trials was still "really impressively low," said CVS chief scientific officer William Shrank.

With nearly a 95 percent cure rate in clinical trails, Sovaldi is being hailed as a major breakthrough for a disease that more than 3 million Americans carry. The drug's price tag, though, is spooking health insurers and state Medicaid programs at a time when there's a heightened effort to diagnose the liver disease.

As a result, an 8 percent discontinuation rate "is still pretty good," Shrank said. "But when you're talking about a medication that costs $1,000 a day, when the investment is so great, we really want to make sure we're getting the most value out of that investment."

The 8 percent discontinuation rate since Sovaldi hit the shelves is still much lower than previous treatments for hepatitis C, which weren't as effective and had more severe side effects. A study of U.S. veterans with hepatitis C released this year found that 54 percent discontinued the most common treatment before these new medications hit the market.

People stop taking medication for a number of reasons — whether it's cost, side effects, or if they don't see improvement. However, the CVS data can't speak to why people stopped taking Sovaldi. CVS did report that people who hadn't tried previous treatments had higher discontinuation rates than those who had.

"My expectation would be that patients that failed other regimens are likely to be sicker and more likely to see a greater sense in urgency around the treatment," Shrank said.