A Study of the Effect of SYN-010 on Subjects With IBS-C

This is a Phase 2, randomized, multi-center, multi-dose study. Sixty subjects with irritable
bowel syndrome with constipation who are between the ages of 18 and 65, inclusive, will be
enrolled. The entire duration of the study may be up to 43 days (from Screening to the post
end-of-study [EOS] visit telephone call).

Inclusion Criteria:

- Subjects must have IBS-C and have a positive breath CH4 test result (> 10 ppm) at
Screening.

- Subject must meet the modified Rome III criteria for IBS-C.

- Subject must have an average abdominal pain intensity score of ≥ 3 (scale 0-10)
reported at Screening and Baseline.

- Subject must have an average of fewer than 3 complete spontaneous bowel movement
(CSBMs) per week.

- Subject must agree to refrain from making any lifestyle changes that may affect IBS-C
symptoms from the time of Screening to the end of the study.

Exclusion Criteria:

- Subject has taken IBS treatments (prescription or over-the-counter), proton pump
inhibitors, laxatives, antibiotics.

- Subject currently has any structural abnormality of the gastrointestinal (GI) tract or
a disease or condition that can affect GI motility, or any unexplained and clinically
significant symptoms such as lower GI bleeding, rectal bleeding, heme-positive stool,
iron-deficiency anemia, weight loss, or systemic signs of infection.

- Subject has been diagnosed with or has a family history of familial adenomatous
polyposis, hereditary nonpolyposis colorectal cancer, or any other form of familial
colorectal cancer.

- Subject reports loose (mushy) or watery stools (Bristol Stool Form Scale [BSFS] score
of 6 or 7).