• Comparison between treatment groups of the change from baseline in maximum cystometric bladder capacity
  

• Delay of the first involuntary detrusor contraction associated with symptomatic urgency
  
• Urgency, frequency and urge incontinence events as recorded in the Subject Micturition Diary
  
• Urgency Perception Scale
  

This is a Phase 2, randomized, double-blind, placebo-controlled trial to evaluate the safety and efficacy of AV608 in subjects with idiopathic detrusor overactivity. Female subjects between 18 and 65 years of age with a diagnosis of Overactive Bladder Syndrome and urodynamic observation of involuntary detrusor contractions during the filling phase will be eligible for the trial.

Eligible subjects will complete a baseline urodynamic assessment. All subjects who participate in the study will receive 3 weeks of treatment with AV608 or placebo. At the end of the treatment period, subjects will complete a second urodynamic assessment.

Inclusion Criteria:

• Female, 18 to 65 years of age, inclusive
• A current primary diagnosis of OAB
• Idiopathic detrusor overactivity, demonstrated by a urodynamic observation
• Evidence of frequency in combination with urinary urgency
• Written informed consent form
• Willingness to avoid pregnancy and practice adequate birth control
• Negative serum pregnancy test
• Agrees to refrain from blood donation during the course of the study

Exclusion Criteria:

• Subjects who are pregnant or lactating
• Clinically significant abnormality or clinically significant unstable medical condition
• QTc interval of 470 msec or greater at Visit 1
• Predominant stress urinary incontinence versus urge urinary incontinence based on subject history
• Neurogenic bladder (e.g. associated with spinal cord injury, multiple sclerosis, etc.)
• Anatomic or structural abnormalities possibly causing urinary incontinence or urgency, including but not limited to urogenital prolapse stage 2 or more according to the Pelvic Organ Prolapse Quantification (POP-Q) system
• Urological or gynecological surgery within 3 months of the baseline urodynamic assessment
• Current UTI or frequent UTIs (i.e., greater than or equal to 4 UTIs per year), interstitial cystitis, hematuria of unknown cause, or use of indwelling catheter
• Electro-stimulation therapy, bladder training, or physiotherapy for bladder control within 2 weeks of Visit 1
• History (within 1 year of Screening) of alcohol or substance dependence (except nicotine dependence) according to DSM‑IV‑TR criteria
• History of any kind of cancer within the last 2 years
• Existing non-malignant tumors that could compromise the function and/or anatomy of the lower urinary tract