Part B evaluations are based on the results of Part A. Part B will further consist of two subparts. In the first subpart, low single doses of 2 new isotopologs will be dosed to two groups of 4 subjects each, B1 and B2, respectively. Following assessment of safety and pharmacokinetics in the first subpart, the second subpart, which consists of three groups of 8 subjects (B3, B4, B5) each will be dosed. Subjects enrolled in B3, B4, and B5 will participate in a 3-way partial crossover study design.