This is a multicenter, randomized, double-blind, placebo-controlled, parallel-design, exploratory study of orally administered ERB-041 in subjects with active IC. The primary objectives of this study will be to investigate ERB-041's activity on levels of urinary APF, explore the gene expression response in peripheral blood mononuclear cells (PBMC), and to evaluate the safety of ERB-041 in women with active IC.

Inclusion Criteria:

• Subjects seeking medical treatment for symptoms consistent with IC that have been ongoing for > 9 months or seeking medical treatment for a previous documented diagnosis of IC
• Subjects who are not surgically sterile or postmenopausal (amenorrheic > 12 months) must agree and commit to the use of a medically acceptable, highly-effective (i.e. double-barrier or IUD), non-hormonal form of birth control during the study and for 30 days after the last dose of test

Exclusion Criteria:

• Use of herbal supplements (except for a daily multivitamin/mineral supplement not containing herbal components)
• History of cancer (other than resected cutaneous basal or squamous cell carcinoma or in situ cervical cancer) with less than 5 years documentation of a disease-free state
• Vaginitis or vaginal infection within 1 month before randomization