The primary objective of this study is to evaluate the safety of a single treatment of hMaxi-K compared to placebo (PBS-20% sucrose) administered by direct bladder wall injections. Two dose levels (16000 µg and 24000 µg -20 or 30 bladder wall injections, respectively) in females with moderate OAB/DO of ≥ six months duration will be evaluated. In each dose level, 6 participants will receive hMaxi-K and 3 will receive placebo. .