After making nearly $10 billion in 2014 with the hepatitis C virus (HCV) treatment Sovaldi (sofosbuvir), many of Gilead Sciences’ top developers have moved on to curing the hepatitis B virus (HBV), Bloomberg reports.

Michael Sofia, Sovaldi’s principle inventor, recently founded OnCore Biopharma, which focuses on hep B. He’s joined by a sales executive from Pharmasset Inc., the biotech that originally held the patent for sofosbuvir, the main compound in the hep C drug Sovaldi, before selling the patent to Gilead in 2012.

James Sapirstein, a researcher who helped build Gilead’s antiviral portfolio, started a new firm named ContraVir, which also focuses on HBV. Michelle Berrey, the former chief medical officer of Pharmasset, heads Chimerix, which is Contravir’s partner firm.

About 240 million people are living with HBV around the world, which is more than the global HCV population. The World Health Organization estimates that at least 780,000 people die from HBV every year.