Reshaping the Treatment Landscape of a Galactose Metabolism Disorder

Abstract

The Leloir pathway was elucidated decades ago, unraveling how galactose is metabolized in the body. Different inborn errors of metabolism in this pathway are known, the most frequent and well-studied being Classic Galactosemia (CG) (OMIM 230400) due to pathogenic variants in the GALT gene. Substrate reduction using dietary restriction of galactose is currently the only available treatment option. Although this burdensome diet resolves the life-threatening clinical picture in neonates, patients still face long-term complications, including cognitive and neurological deficits as well as primary ovarian insufficiency. Emerging therapies aim to address these challenges on multiple fronts: (1) restoration of GALT activity with nucleic acid therapies, pharmacological chaperones, or enzyme replacement; (2) influencing the pathological cascade of events to prevent accumulation of metabolites (Galactokinase 1 (GALK1) inhibitors, aldose reductase inhibitors), address myo-inositol deficiency, or alleviate cellular stress responses; (3) substrate reduction with synthetic biotics or galactose uptake inhibitors to eliminate the need for lifelong diet; and (4) novel approaches to mitigate existing symptoms, such as non-invasive brain stimulation and reproductive innovations. Early, personalized intervention remains critical for optimizing patient outcomes. We review the advances in the development of different treatment modalities for CG and reflect on the factors that need to be considered and addressed to reshape the landscape of treatment.

Keywords: GALK1 inhibitors; aldose reductase inhibitors; classic galactosemia; enzyme replacement; nucleic acid therapy; substrate reduction; symptom management.

FIGURE 1

Novel treatment modalities and considerations that reshape the treatment landscape of classic galactosemia. The treatment modalities currently being explored for CG can be grouped in multiple domains: Restoration of enzyme activity (top left), manipulation of the cascade of events (top right), substrate reduction and mitigation of symptoms (bottom left). Before, during and after the design of a new treatment modality, it is important to address several key questions and considerations (bottom right).