This is a Phase 1, randomized, double-blind (except for moxifloxacin), placebo- and positive-controlled, single-site, 4-way crossover study to investigate the effects of single therapeutic and supratherapeutic IV doses of difelikefalin (CR845) on the QTc interval in healthy adult subjects. Subjects will be randomized to a treatment sequence consisting of 4 treatment periods with a minimum 5-day washout between treatments. Subjects will receive each of the study treatments over the course of the study. Randomized subjects will receive the assigned study treatment as a single dose in the fasted state in the morning on Day 1 of each treatment period.

Key Inclusion Criteria:

• Body weight between 50 to 120 kg and body mass index within 18 to 29 kg/m2 at Screening;
• Current nonsmokers who have not used any tobacco- or nicotine-containing products (chewed or smoked) or replacement products, including, but not limited to, electronic cigarettes, in the 45 days prior to Screening.

Key Exclusion Criteria:

• Past or present diseases, which as judged by the Investigator, may affect the outcome of this study;
• Any condition or situation that, in the opinion of the Investigator, would prevent proper evaluation of the safety or efficacy of the study treatment according to the study protocol;
• History of hypersensitivity or allergy to moxifloxacin or any other study treatment or history of tendonitis or tendon rupture with moxifloxacin or any other quinolone type drug.