This is a medical research study to test a medication in adult patients with a disease called medium-chain acyl-CoA dehydrogenase (MCAD) deficiency caused by at least one copy of the 985A>G mutation. The medication is glycerol phenylbutyrate, called Ravicti, which is currently FDA approved for the treatment of urea cycle disorders. Previous research suggests that Ravicti may also be effective in the treatment MCAD deficiency. This study will investigate the safety and efficacy (how well it works) of Ravicti in patients with MCAD deficiency caused by having at least one copy of the 985A>G mutation.

Participation in the study will require one overnight admission and three outpatient visits at the Clinical and Translational Research Center at Children's Hospital of Pittsburgh of UPMC (also called the PCTRC). The total length of the study is 7 weeks.

Subjects will have blood work and an intravenous access line (IV) placed for several blood draws during the visit. Subjects will begin fasting at 8pm during the admission, which means they may consume only non-caloric fluids (water, unsweetened black coffee or tea, or sugar-free beverages). The next morning, fasting blood work will be obtained. The subject can then eat breakfast and will receive the study drug, Ravicti. The total time of fasting will be 12 hours.

Dosing for this study will begin at 2 grams/m2/day, which is about one-fifth (1/5) the dose used for other disorders. The reason for starting the dose lower in MCAD patients is that Ravicti is metabolized by the MCAD enzyme. Following the initial dose, blood will be drawn from the IV every two hours for 8 hours. These blood studies will check the levels of Ravicti in the subject's blood and monitor how the subject's body metabolizes them. The subject will be discharged 8 hours after drug administration. Following discharge, the subject will take Ravicti every day for two weeks.

Visit 2: After two weeks at a dose of 2 grams/m2/day, the subject will fast after 8 PM, and will come to the PCTRC the following morning to have an IV placed and blood draws. If the subject's blood work from the first visit shows that there is no concern, the subject's dose will be increased to 4 grams/m2/day. The subject will receive the first dose at this level in the PCTRC with breakfast, and blood samples will be collected from the IV every 2 hours for the next 8 hours. The subject will continue on this dose for two weeks.

Visit 3: After two weeks at a dose of 4 grams/m2/day, the subject will fast after 8 PM, and will come to the PCTRC the following morning to have an IV placed and blood draws. If the subject's blood work from the previous visit shows that there is no concern, the subject's dose will be increased to 6 grams/m2/day. The subject will receive the first dose at this level in the PCTRC with breakfast, and blood samples will be collected from the IV every 2 hours for the next 8 hours. The subject will continue on this dose for two weeks.

Visit 4 (final): After two weeks at a dose of 6 grams/m2/day, the subject will fast after 8 PM, and will come to the CTRC the following morning to have one blood draw. The subject will return any unused Ravicti, and their study participation will be completed.

All study procedures will be done at no cost to the subjects.

Inclusion Criteria:

• confirmation of a diagnosis of MCAD deficiency
• at least one copy of 985A>G MCAD mutation
• ability to follow protocol

Exclusion Criteria:

• positive pregnancy test
• currently breastfeeding
• currently taking any medication for which there is a potential drug interaction with Ravicti, includes corticosteroids, valproic acid, haloperidol, and probenecid
• liver or kidney insufficiency

Approximately 7 weeks

The definition of adverse event and a serious adverse event used to collect this information did not differ from the clinicaltrials.gov definition.

The purpose of this phase 1 trial was to establish a safe dose for treatment of patients with MCAD deficiency due to the common mutations, and to evaluate biomarkers of fatty acid metabolism in treated patients vs their pretreatment values.