A Study to Assess FLX-787 in Subjects With Motor Neuron Disease Experiencing Muscle Cramps.

Inclusion Criteria:

- Documented diagnosis of Motor Neuron Disease (MND) [including Amyotrophic Lateral
Sclerosis (ALS), Primary Lateral Sclerosis (PLS) or Progressive Muscular Atrophy
(PMA)]

- Expected survival > 6 months

- 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 laryngospasm or significant swallowing problems

- Presence of percutaneous endoscopic gastrostomy, esophagogastroduodenoscopy, or G-tube

- 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