• This is a single-center, open-label, single-arm study with a double-blind, placebo-controlled, randomized withdrawal extension. Patients are initiated on a DCCR dose of about 1.5 mg/kg (maximum starting dose of 145 mg) and are titrated every 14 days to about 2.4 mg/kg, 3.3 mg/kg, 4.2 mg/kg, and 5.1 mg/kg (maximum dose of 507.5 mg). These DCCR doses are equivalent to diazoxide doses of 1.03, 1.66, 2.28, 2.9, and 3.52 mg/kg. The administered dose will be as close to the mg/kg dosing as can be achieved by the available dose strengths of DCCR. Patients will be up-titrated at each visit at the discretion of the investigator. All patients will be continued in the double-blind, placebo-controlled, randomized withdrawal extension. Any patient who showed an increase in resting energy expenditure and/or a reduction in hyperphagia from Baseline through Day 55 or Day 69 will be designated a responder, whereas all others will be designated non-responders. Responders will be randomized in a 1:1 ratio either to continue on active treatment at the dose they were treated with on Day 69 or to the placebo equivalent of that dose for an additional 4 weeks. Non-responders will continue open label treatment during the extension.