The U.S. Food and Drug Administration has alerted Merck of its intention to rescind the “breakthrough designation” for its investigatory hepatitis C virus (HCV) therapy grazoprevir/elbasvir (MK-5172/MK-8742). Such a designation is granted when research suggests a drug candidate may offer a substantial improvement over available therapies.

Merck’s fixed-dose tablet includes the investigational NS3/4A protease inhibitor grazoprevir and the investigational NS5A replication complex inhibitor elbasvir, to be taken once a day.

Wire service reports, including one from BloombergBusiness, have incorrectly stated that the breakthrough designation has already been rescinded. According to Merck spokesperson Sarra Herzog, the FDA has only alerted to the company of its intent to do so, apparently because the agency believes that grazoprevir/elbasvir will not provide a significant advancement over drugs for people with genotype 1 of hep C that have already been approved.


“Our company intends to discuss the matter with the agency in the coming weeks,” says Herzog. “And we’ll have the opportunity to provide additional information that might help the FDA determine the criteria for breakthrough designation to continue to be met.

“We certainly believe that our molecule has breakthrough attributes. We intend to offer ribavirin-free medicine for multiple genotypes,” irrespective of other health problems, Herzog continues. “That’s something that will be worthy for the FDA to review.”

Merck intends to file for approval of grazoprevir/elbasvir during the first half the year, regardless of the FDA’s decision regarding its breakthrough status.

To read the Bloomberg report, click here.