ERG/5-HTP in Fragile X Syndrome (FXS)

5-HTP will be over-encapsulated in identical size 00 capsules. During the 5-HTP Treatment Period (Period 3) and 5-HTP/EM Treatment Period (Period 2), subjects will take 1 capsule of 5-HTP 3 times per day.

Ergoloid mesylates 1 mg will be mixed with methyl cellulose and placed in a size 00 capsule. During the EM Treatment Period (Period 1) and 5-HTP/EM Treatment Period (Period 2), subjects will take 1 capsule of EM 3 times per day.

Matching placebo for Ergoloid mesylates will be ascorbic acid powder in identical size 00 capsules. During the 5-HTP Treatment Period (Period 3) and Placebo Treatment Period (Period 4), subjects will take 1 capsule of matching placebo for EM 3 times per day.

Matching placebo for 5-Hydroxytryptophan will be ascorbic acid powder in identical size 00 capsules. During the EM Treatment Period (Period 2) and Placebo Treatment Period (Period 4), subjects will take 1 capsule of matching placebo for 5-HTP 3 times per day.