What Achillion Pharmaceuticals does Achillion Pharmaceuticals is a developmental stage biotechnology company focused primarily on developing compounds to treat hepatitis C. It currently has four clinical-stage hepatitis C compounds -- three in phase 1 clinical trials and one in phase 2 trials. Its leading candidate, ACH-1625, showed 100% efficacy in early phase 2 clinical trials at high doses. Achillion also has one pre-clinical experimental drug aimed at being the next antibacterial drug.