A Study to Evaluate the Safety, Tolerability and Pharmacodynamics of DDP733 for IBS-c

Inclusion Criteria: * Subjects must have a history of IBS-c for at least 3 months prior to randomization as assessed using ROME criteria * Must have had endoscopic/radiologic bowel evaluation within the past 10 years * Must comply with completing a daily diary and be able to comply with GI transit measurements, including swallowing capsules containing small x-ray visible markers * Female subjects cannot be pregnant, post-partum for less than 1 year or breastfeeding Exclusion Criteria: * Serious underlying diseases, including psychiatric disorders * Current history of conditions affecting bowel transit * Recent history of biochemical or structural abnormalities of the gastrointestinal tract, gastrointestinal surgery, or gastrointestinal infection * Clinically significant abnormal examination findings or laboratory tests * Inability to stop taking certain medications, or a planned change in medications (including herbal remedies) which could interfere with study assessments * Use of drugs and or ethanol which may interfere with compliance of study procedures or influence study outcome * Presence of a medical condition which could interfere with the interpretation of study data * Significant use of nicotine or caffeine