(Reuters) - The U.S. Food and Drug Administration (FDA) warned on Thursday that Intercept Pharmaceuticals Inc’s drug Ocaliva was being incorrectly dosed in some patients with a rare liver disease, increasing the risk of liver injury and death.

The U.S. drugmaker’s shares fell 10.4 percent to $87.90 in afternoon trading following the news.

The FDA warning comes two weeks after Intercept gave healthcare providers prescribing information for Ocaliva and flagged reports of liver failure and deaths. (bit.ly/2xudehJ)

Ocaliva, approved last May, is used to treat primary biliary cholangitis (PBC), a rare, chronic liver disease that causes bile ducts in the liver to become inflamed, damaged and destroyed.

Nineteen deaths and 11 cases of serious liver injury were associated with the use of Ocaliva, the FDA said. Some patients were receiving higher doses of the drug, particularly due to a higher frequency of dosing than recommended in the label, the agency added. (bit.ly/2hiUvil)

“FDA’s narrative about the high number of deaths and worsening of PBC cases strikes us as particularly concerning, and could tilt the FDA more toward a black box warning,” Leerink analyst Joseph Schwartz said in a report to clients.

A black box warning is the strictest warning by the FDA that appears on a prescription drug’s label, calling attention to serious or life-threatening risks of a drug.

However, RBC Capital Markets analysts said the risks flagged by the FDA were already known and included on the drug’s label. The affected patients represent under 5 percent of the overall PBC population, limiting likely commercial impact to Intercept, they said.

In the quarter ended June 30, Intercept generated $30.4 million in worldwide sales from Ocaliva.

The New York-based company was reviewing the FDA’s warning, Intercept said via email.