Basel-based Roche says it will pay $3.70 per share, a premium of more than 250 percent on Anadys’s closing price Friday.

Roche said in a statement Monday that the acquisition would boost its portfolio of drugs to treat hepatitis C.

San Diego-based Anadys has developed an oral drug called Setrobuvir that is currently being trialed for treatment of chronic hepatitis C infections.

Roche last week reported third-quarter sales of 9.82 billion Swiss francs ($10.98).