This is an open-label, single-center study to evaluate the mass-balance and pharmacokinetics of GB491 in 4-8 healthy male subjects receiving a single oral 150mg dose of GB491 containing approximately 50 uCi of [14C]GB491. This study will help understand how the drug appears in the blood, urine, and feces after it is administered.

In addition, this study will also evaluate the safety of a single dose of [14C]GB491 when given to healthy subjects.

Inclusion Criteria:

• A healthy male volunteer between 18 and 50 years of age inclusive
• A total body weight >=50kg, and a BMI of 19.0-26.0 kg/m2
• A signed informed consent document

Exclusion Criteria:

• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease
• Subjects with HBsAg-positive, or HCV-Ab-positive, or TPPA-positive, or HIV infection
• Subjects with a history of habitual constipation/diarrhea, irritable bowel syndrome, or inflammatory bowel disease