The ICCTG RCT2 study was a randomized, placebo-controlled, two-arm clinical trial that investigated the efficacy and safety of intravesical Bacillus Calmette-Guerin (BCG) therapy in treating patients with treatment refractory Interstitial Cystitis (IC). IC is a bladder syndrome characterized as painful, debilitating and chronic, with no widely accepted effective treatment. Characteristic symptoms include pain with bladder filling, and marked urinary frequency (to relieve pain). The presentation of symptoms can be quite variable among patients, suggesting that IC is a multi-factorial syndrome with several proposed etiologies, some of which may be interrelated.

Subjects with IC were randomized to 6 weekly double-blinded intravesical instillations of either BCG or placebo, and then followed for a total of 34 weeks. The primary outcome was a patient reported global response assessment at week 34, supplemented with medications for IC during weeks 31 to 34 recorded in a diary. Although the safety profile for BCG was acceptable, the therapy did not show significant benefit compared to placebo.

The primary objective of the ICCTG RCT2 study was to evaluate the efficacy and safety of BCG therapy in treating patients with treatment refractory interstitial cystitis (IC).

The primary outcome measure was a patient- reported Global Response Assessment (GRA) at week 34, supplemented with medications for IC during weeks 31 to 34. Secondary outcome measures included a 24-hour voiding diary, pain, urgency, validated IC symptom indexes and adverse events.

The study enrolled participants who met the National Institutes of Health-National Institute for Diabetes and Digestive and Kidney Diseases criteria for IC, and reported at least moderate pain and frequency for a minimum of 24 weeks before study entry.

Small improvements were observed for all secondary outcomes, some more so with BCG, but these differences were of borderline statistical significance. Although the safety profile for BCG was acceptable, the therapy did not show significant benefit compared to placebo.