The aim of this double blind, placebo controlled, study is to evaluate activity consistent with efficacy provided by 14 days administration of GI270384X, and to provide preliminary pharmacokinetics and safety/tolerability of 14 days administration of GI270384X in patients with mild to moderate active ulcerative colitis (UC).

Inclusion criteria:

• Females can be of childbearing or non-childbearing potential
• Subjects who have relapsing (relapsed = 6 weeks ago; this being at least a second episode) mild to moderate UC (score of 4 - 11 on the MTWI at Screening and with an endoscopy score of = 2). Diagnosis of UC originally must be established by sigmoidoscopy or colonoscopy, and have compatible histology.
• As confirmed through signed informed consent, the subject must understand and be able, willing and likely to fully comply with study procedures and restrictions

Exclusion criteria:

• Subjects with severe UC according to the MTWI (score >11) and subjects who have been in relapse for > 6 weeks.
• Subjects are not eligible for this study if they have Crohn's Disease, proctitis (where the extent of inflammation = 15 cm), bleeding disorders, or active ulcer disease.
• Positive stool culture for enteric pathogens (including Salmonella, Shigella, Yersinia, Aeromonas, Plesiomonas or Campylobacter).
• Presence of Clostridium difficile toxin present or with ova or parasites as detected by microscopy.