This trial will evaluate the effect of ASP7147 on daily abdominal pain due to IBS-D during 4 weeks of treatment. It will also evaluate safety and tolerability in patients with IBS-D over the 4-week treatment period.

Inclusion Criteria:

• Ability to provide written informed consent
• Men or women aged 18-75 years
• Patient has IBS with diarrhea (IBS-D)
• Ability to communicate with the investigator

Exclusion Criteria:

• IBS with constipation (IBS-C) or mixed IBS (IBS-M)
• Other significant disease or condition that may interfere with trial completion
• Untreated lactose intolerance
• History of alcohol or drug abuse in past two years
• Participation in other clinical trials within prior month