Administration of MELPIDA to Determine the Safety and Efficacy for Patients With Spastic Paraplegia Type 50

Inclusion Criteria: * Age \< 5 years old * Confirmed diagnosis of SPG50 disease by: * Genomic DNA mutation analysis demonstrating homozygous or compound heterozygous, pathogenic and/or potentially pathogenic variants in the AP4M1 gene * Clinical history or examination features consistent with SPG50 and that include neurologic dysfunction * Parent/legal guardian willing to provide written informed consent for their child prior to participation in the study * Subject able to comply with all protocol requirements and procedures Exclusion Criteria: * Inability to participate in study procedures (as determined by the site investigator) * Presence of a concomitant medical condition that precludes lumbar puncture (LP) or use of anesthetics * History of bleeding disorder or any other medical condition or circumstance in which lumbar puncture is contraindicated according to local institutional policy * Inability to be safely sedated in the opinion of the clinical anesthesiologist * Active infection, at the time of dosing, based on clinical observations * Concomitant illness or requirement for chronic drug treatment that in the opinion of the PI creates unnecessary risks for gene transfer * Inability of the patient to undergo MRI according to local institutional policy * Inability of the patient to undergo any other procedure required in this study * The presence of significant non-SPG50 related central nervous system (CNS) impairment or behavioral disturbances that would confound t…