Vertex plans to soon begin mid-stage trials involving more than 200 patients to verify the VX-950's impressive earlier effectiveness and its lack of side effects.
Boger said he is hopeful VX-950 in larger trials will also eliminate the virus in the lion's share of patients.
"I wouldn't be surprised if it was 90 plus (percent)," Boger said.
An estimated 4 million Americans are infected with hepatitis C, which quietly attacks the liver for decades and is the leading cause of liver transplants."
However, if NM283 is approved so it could be used alongside the Vertex pill in a "cocktail" of therapies.
Later on Tuesday, Idenix Chief Executive Jean-Pierre Sommadossi said NM283 indeed would be a key component of hepatitis C cocktail therapy.
Sommadossi said it and a drug being developed by Roche are the only ones he knows of in clinical trials that block polymerase, a protein the virus requires to replicate.
By contrast, the Vertex drug and hepatitis C treatments being developed by other companies block another protein, known as protease.