Open-Label Fosmetpantotenate, a Phosphopantothenate Replacement Therapy in a Single Patient with Atypical PKAN

Objective. Pantothenate kinase-associated neurodegeneration (PKAN) is an autosomal recessive disorder with variable onset, rate of progression, and phenotypic expression. Later-onset, more slowly progressive PKAN often presents with neuropsychiatric as well as motor manifestations that include speech difficulties, progressive dystonia, rigidity, and parkinsonism. PKAN is caused by biallelic PANK2 mutations, a gene that encodes pantothenate kinase 2, a regulatory enzyme in coenzyme A biosynthesis. Current therapeutic strategies rely on symptomatic relief. We describe the treatment of the first, later-onset PKAN patient with oral fosmetpantotenate (previously known as RE-024), a novel replacement therapy developed to bypass the enzymatic defect. Methods. This was an open-label, uncontrolled, 12-month treatment with fosmetpantotenate of a single patient with a later-onset, moderately severe, and slowly progressive form of PKAN. Results. The patient showed improvement in all clinical parameters including the Unified Parkinson's Disease Rating Scale (UPDRS), Barry-Albright Dystonia Scale, the EuroQol five-dimensional three-level (EQ-5D-3L) scale, timed 25-foot walk test, and electroglottographic speech analysis. Fosmetpantotenate was well-tolerated with only transient liver enzyme elevation which normalized after dose reduction and did not recur after subsequent dose increases. Conclusions. Fosmetpantotenate showed promising results in a single PKAN patient and should be further studied in controlled trials.