.15mg, .30mg, .60mg

Placebo

Primary objective using a flexible dosing titration regimen from 0.15mg Pagocolne BID, titrated at 2 weeks to 0.30mg Pagaclone BID for an additional 6 weeks versus placebo, on persistent developmental stuttering in patients 18 to 65 years of age over an 8 week, double blind treatment period, followed by five 53 week open label treatment extension periods. The primary efficacy variables will be based on data collected on the stuttering Severity Instrument-3 (SSI-3) Frequency and Duration Subscore, the Subjective Screening of Stuttering (SSS) Severity Subscore, and the treatment and week 8 visits. All efficacy assessments will evaluate change from pre-treatment to each on-treatment week.

SSI-3 Total overall Score and individual subscores (including frequency, duration, and physical concomitant subscores) Subjective Screening of Stuttering (SSS) test Speech Naturalness Scales (SNS) Liebowitz Social Anxiety Scale (LSAS) Stuttering Clinician's Global Impression-Improvement (CGI) Optional Neuropsychological Test Optional Functional Brain Imaging