FDA Sees Safety Issue With Merck Hepatitis Drug

A proposed Merck & Co medicine eliminated the liver-destroying hepatitis C virus although anemia and other safety concerns remained for the potential blockbuster drug, U.S. drug reviewers said on Monday.

Food and Drug Administration staff, in documents released on Monday, highlighted anemia as the main issue for an advisory panel that evaluates the Merck medicine on Wednesday. They also noted suicidal and homicidal thoughts reported by a small number of patients.

Industry analysts said they expected the panel to back the Merck drug, called boceprevir, given that it eliminated traces of the virus in a high percentage of patients.

Boceprevir and a proposed drug from Vertex Pharmaceuticals Inc are considered possible blockbuster products because of their potential to cure far more patients and in as little as half the time of standard drugs. Current therapies require almost a year of treatment and often cause flu-like symptoms that are tough to tolerate.Merck shares rose 0.2 percent to $34.25 in afternoon trading on the New York Stock Exchange. Vertex shares fell 2 percent to $48.32 on Nasdaq.

JPMorgan analyst Geoff Meacham said many Vertex investors were expecting "a materially worse review of boceprevir, which doesn't look like that may happen."

In two Merck-funded studies, 66 percent of patients given boceprevir plus standard therapy had a "sustained virologic response" (SVR), meaning the virus was not detectable in the blood. SVR is considered a cure.

For older therapies, the SVR rate was 38 percent. Patients had not been treated previously for hepatitis C.

The FDA staff said they generally agreed with Merck's assessment of the drug's effectiveness.Vertex has reported cure rates as high as 75 percent for its drug, telaprevir. The FDA is set to release its preliminary analysis of the Vertex data on Tuesday, and an advisory panel will review the medicine on Thursday.

SAFETY ISSUES NOT SEEN AS DEAL-BREAKERS

On the Merck drug, the FDA reviewers said they will ask outside advisers to consider an increase in the frequency and severity of anemia, a deficiency of red blood cells that can cause fatigue and other problems.

Another "potential safety signal" is a small number of reports of psychiatric symptoms such as suicidal and homicidal thoughts, the FDA reviewers said. But they added it was "difficult to make any meaningful clinical conclusions" about the cases. The same symptoms have been reported with pegylated interferon, one of the hepatitis treatments also given to patients in the studies.

Analyst Meacham said the staff comments were "in line with expectations" and supported a positive recommendation for approval. The focus on anemia was expected and the issue "doesn't look to be a deal-breaker," Meacham said in a research note.

He said the psychiatric issue was new but noted the symptoms already were linked with the other treatment.

About 1 percent of patients treated with boceprevir reported suicidal thoughts compared with less than 1 percent in a control group, the FDA staff said. Four out of 1,548 boceprevir patients reported homicidal thoughts, compared with none in the control group.

Dr. Eliav Barr, a Merck vice president, said there was no evidence boceprevir increased those problems and said other factors could explain them. For example, intravenous drug use is a main route of transmission for hepatitis C and drug abusers have higher rates of psychiatric symptoms.

About 3.2 million Americans are infected with hepatitis C, according to the Centers for Disease Control and Prevention.

(Editing by Gerald E. McCormick, Matthew Lewis and Steve Orlofsky)

((lisa.richwine@thomsonreuters.com; + 1 202 310-5691; Reuters Messaging: lisa.richwine.reuters.com@reuters.net))