Background:
LGMD2I/R9 is an autosomal-recessive neuromuscular disorder caused by pathogenic variants in the FKRP gene, which leads to impaired glycosylation of α dystroglycan (αDG). There are no approved therapies for LGMD2I/R9, representing a significant unmet medical need.
Methods:
Preclinical work in disease pathophysiology expanded the understanding of the mechanism of disease in LGMD 2I/R9 and identified a viable therapeutic entry point (Kanagawa 2016). BBP-418 is a small molecule that is a glycosylation substrate therapy targeting the FKRP enzyme and is currently being evaluated in a Phase 3 Clinical Trial (NCT05775848) as a mechanistically based treatment for LGMD2I/R9.
Results:
Oral BBP-418 provides supraphysiological level of pharmaceutical-grade substrate and drives the residual activity of the FKRP enzyme, increasing glycosylation of αDG. Glycosylated αDG is a critical component of the dystrophin-associated glycoprotein complex, which is responsible for anchoring the muscle cell cytoskeleton to the extracellular matrix (ECM). Complete glycosylation of αDG supports the physical link between the ECM and the muscle cell membrane, conferring stability and resistance to activity-induced damage. Preclinically, treatment with BBP-418 increased glycosylated αDG in FKRP P448L rodents (Wu et al. 2025). The increase in glycosylated αDG led to functional improvements in skeletal muscle function and respiratory function in treated mice (Cataldi 2018). To measure changes in glycosylated αDG levels in skeletal muscle, a validated quantitative Western Blot Assay was developed (Rajasingham 2024).
The clinical development program utilized BBP-418 in an open label safety and efficacy Phase 2 study, which showed promising data in a small study population. The placebo-controlled Phase 3 study was designed to further evaluate the mechanism of action of BBP-418, measuring glycosylated αDG and other key biomarkers of muscular damage and functional endpoints.
Conclusion: Over a decade of foundational research has elucidated LGMD2I/R9 pathophysiology, identified a potential disease-modifying therapy, and enabled biomarker-driven clinical evaluation of BBP-418.