Treatment of Chronic Delta Hepatitis With Lonafarnib and Ritonavir

Background: \- Chronic hepatitis D is a liver disease caused by the hepatitis D virus (HDV). It can be severe and progressive. Most people with hepatitis D will develop scarring and damage to the liver. There is no FDA approved drug to treat chronic hepatitis D. Researchers want to know if the drugs lonafarnib and ritonavir can help people with chronic hepatitis D. Objective: \- To find out if treatment of hepatitis D with lonafarnib and ritonavir is safe and effective. Eligibility: \- People 18 years of age and older with chronic hepatitis D. They must not have HIV or other major illnesses. Design: * Participants will be screened with medical history, physical exams, and blood tests. * Participants will have 24 weeks of treatment. They will then have 24 weeks of follow-up. * Participants will be in 1 of 6 treatment groups. Those in each group will receive different doses of the study drugs. Some groups will start with placebo but will receive treatment after 3 months of placebo. * Participants will also take drugs to treat hepatitis B. * Participants will have many visits. These will include: * One three-day stay at the Clinical Center * Physical exams * EKG: small sticky patches will be put on the chest, arms, and legs to trace heart rhythm * Ultrasounds of the abdomen * Urine and blood tests * Stool samples * Eye exams * Evaluations by a reproductive endocrinologist (women) or urologist (men). Men may provide a sperm sample (optional).