A Multi-Center Trial to Determine the Safety and Efficacy of LX1033 in Subjects With Diarrhea-Predominant Irritable Bowel Syndrome

Inclusion Criteria:

- Male and female subjects, aged 18 to 70 years, with diarrhea-predominant IBS (IBS-D)
with symptom onset at least 6 months prior to diagnosis

- Two or more days per week with at least one stool with a consistency of Type 6 or 7
(Bristol Stool Form Scale)

- Weekly average of worst abdominal pain in past 24 hours score of greater than or
equal to 3.0 using a 0-10 point scale

- Ability to provide written, informed consent

Exclusion Criteria:

- Inability to discontinue any current drug therapy for IBS, with the exception of
bulking agents. Subjects will be allowed up to 2 doses of loperamide per week as
rescue medication.

- Subjects who score severe abdominal pain (rated 7 or higher) 5 or more days per week

- Concomitant use of opioid analgesic drugs or drugs that affect bowel motility

- Any abnormalities or conditions deemed by the investigator as clinically significant