This is a Phase 1/2 randomized, blinded, dose-escalation study to evaluate the safety and efficacy of intrathecal (IT) administration of SBT101, a recombinant adeno-associated virus serotype 9 (AAV9) containing a functional copy of the human adenosine triphosphate (ATP)-binding cassette transporter subfamily D member 1 (ABCD1; hABCD1) gene, in adult patients with adrenomyeloneuropathy (AMN) aged 18-65 years. Patients will receive a single dose of SBT101 via IT route (or an imitation procedure) and will be followed for safety and efficacy for 2 years. Patients receiving SBT101 will be followed for an additional 3 years (5 total) for Safety. Patients receiving an imitation procedure will be offered the opportunity to receive SBT101 after 2 years, as data indicate.