Inclusion Criteria:

Subjects will be included in the study only if they meet all the following criteria:

1. Subject must satisfy DSM-V criteria for childhood onset fluency disorder (stuttering).
2. The nature of stuttering must be developmental in origin with the onset prior to 8 years of age.
3. Subject must have a score of moderate or higher on the MLGSSS.
4. Subject agrees to use an acceptable method of contraception for the duration of the study.
5. Subject must be able to speak English.
6. Subjects must be adults between the ages of 18 - 65.

Exclusion Criteria:

Subjects will be excluded from the study if they meet one or more of the following criteria:

1. Subject has an unstable neurologic, psychiatric, or medical condition in the judgement of the investigator.
2. Subject (female) is pregnant.
3. Subject has evidence of moderate or severe renal or hepatic impairment at Screening.
4. Subjects currently taking any moderate or strong CYP3A4 inhibitor medications.
5. Subject who meets the DSM-5 criteria for moderate to severe substance use disorder within twelve months prior to study inclusion.
6. Subject has a positive pregnancy test at screening or on Day 1 prior to the start of study drug.
7. Subject that is lactating at screening or Day 1, prior to the start of study drug and does not agree to cease giving breast milk to child(ren), donating breast milk and/or providing breast milk to anyone for consumption, from Day 1 until 14 days after the last dose of study medication.
8. Any history of neuroleptic malignant syndrome (NMS).
9. Subject with a glycosylate hemoglobin (A1c) of greater than 6.4 percent.