A Study to Assess the Safety and Effectiveness of FLX-787 in Subjects With Charcot-Marie-Tooth Disease Experiencing Muscle Cramps.

Inclusion Criteria: * Presence of symptoms of CMT since at least 6 months prior to Screening, and confirmed diagnosis of CMT as defined by: 1. Genetic confirmation of a mutation known to cause CMT, or 2. Clinical and electrophysiological evidence of CMT and a genetic confirmation in a family member. Clinical features include length dependent sensory and motor loss, with sensorimotor axonal or demyelinating changes on a nerve conduction study. * Weekly muscle cramping (defined as: a sustained muscle contraction that's most often painful and lasts seconds to minutes) Exclusion Criteria: * Presence of major gastrointestinal disorders, such as inflammatory bowel disease, diverticulitis, active peptic ulcer disease, or significant gastroesophageal reflux disease (i.e., not well-controlled on antacids or proton pump inhibitors), or oral or esophageal lesions/ulcers * Presence of significant swallowing problems * Unable or unwilling to discontinue medications for cramps and/or opiates * Inability to tolerate a spicy sensation in the mouth or stomach * Actively using illicit drugs or history of chronic substance abuse within the past year prior to screening, including abuse of alcohol * Intention to change the current level of tobacco use or use of nicotine-containing products (i.e., new smokers or those actively trying to quit may not enrolled) * Participated in a clinical study (except natural history studies without administration of an investigational product) within 30 days prior to screening