Safety and Pharmacodynamic Study of Sobetirome in X-Linked Adrenoleukodystrophy (X-ALD)

Subjects will have a screening visit within 6 weeks prior to the Baseline visit. At Baseline
visit blood will be drawn and to establish baseline values for plasma and red blood cell
(RBC) very long chain fatty acids (VLCFA; C22, C24, and C26). Subjects will receive an oral
dose of 50 mcg sobetirome once daily for 14 days beginning on Day 1. Subjects will be kept
in the clinic on Day 1 for 16 hours following their initial dose of sobetirome for repeat
blood sampling for pharmacokinetic analysis. Subjects will return to the clinic on days 7,
15, 21 and 28 for blood collection for VLCFA measurements. On day 15, after safety
assessment, subjects will receive an increased dose of 100 mcg and this dose will be
continued once daily through Day 28. Subjects will continue to return to the clinic weekly
for blood and urine collection and safety assessments. Subjects will return to the clinic
on day 42 for an End of Study visit that will involve a final measurement of VLCFA and blood
and urine safety labs to check for reversibility. Safety labs will include serum chemistry,
free fatty acid profile, hematology, urinalysis, and thyroid function. Subjects will be
monitored with ECGs, vital signs, physical exams and assessment of adverse events.

Inclusion Criteria:

- males 18-65 years old

- X-ALD diagnosis by either elevated VLCFAs or DNA testing

- must sign informed consent and agree to complete required clinic visits.

Exclusion Criteria:

- female gender

- abnormal laboratory test results (except VLCFA) at screening visit

- history of coronary artery disease

- use of triiodothyronine therapy

- abnormal thyroid function test at screening visit

- untreated adrenal insufficiency

- currently taking Lorenzo's Oil or other VLCFA lowering agent

- participation in investigational drug study within 30 days