This is a two-part dose-finding trial of MK-7680 in participants with Hepatitis C Virus (HCV) infection of genotype (GT)1 (Part I) and GT3 (Part 2). The primary hypothesis is that daily administration of a safe and well tolerated dose of MK-7680 will produce a decrease in HCV viral load.

Parts 1 and 2 will each consist of 4 panels. In the first panel, a 200 mg dose of MK-7680 will be administered. In each of the following 3 panels, higher or lower doses of MK-7680 will be administered. Each panel will only begin once the safety and tolerability data from the preceding panel have been evaluated.

Inclusion Criteria:

• Is in good health except for HCV infection
• Is male or is a female of non-childbearing potential
• Clinical diagnosis of HCV GT1 or GT3 with no evidence of mixed-GT or non-typeable infection

Exclusion Criteria:

• Has a history of clinically significant and not stably controlled endocrine, gastrointestinal, cardiovascular, hematological, hepatic (excepting HCV infection), immunological, renal, respiratory, genitourinary, or major neurological abnormality or disease
• Has a history of cancer
• Has a history of significant multiple and/or severe allergies
• Is positive for hepatitis B or human immunodeficiency virus
• Has had major surgery, donated or lost 1 unit (500 mL) of blood within 4 weeks prior to screening
• Consumes more than 2 alcoholic beverages per day or is currently a regular user of any illicit drug(s) or has a history of alcohol/drug abuse within 12 months prior to screening
• Has chronic hepatitis not caused by HCV (e.g., nonalcoholic steatohepatitis [NASH])
• Has clinical or laboratory evidence of advanced or decompensated liver disease, or evidence of bridging or higher grade fibrosis