Nomlabofusp Treatment Produces Frataxin Levels That Correlate Across Peripheral Tissues: Preclinical and Clinical Support for Surrogate Tissue Sampling.

Nomlabofusp is a recombinant, cell-penetrating human frataxin (hFXN) fusion protein in development for the treatment of Friedreich's ataxia (FRDA). This study evaluated whether nomlabofusp-derived hFXN concentrations covary across accessible peripheral matrices and FRDA-relevant tissues, supporting the feasibility of surrogate tissue sampling to monitor drug-derived hFXN exposure. Following subcutaneous administration in mice, rats, non-human primates, and patients with FRDA, we quantified nomlabofusp-derived hFXN and assessed cross-tissue correlations across target tissues (brain, heart, skeletal muscle, dorsal root ganglia) and accessible peripheral matrices (skin, buccal cells, platelets). We observed significant and consistent cross-tissue correlations, with concordant relationships among heart, skeletal muscle, dorsal root ganglia, skin, buccal cells, liver, and mitochondrial fractions, indicating coordinated distribution and/or retention of nomlabofusp-derived hFXN across these matrices. Correlation patterns were maintained across species, supporting the robustness and translational relevance of the observed relationships. Collectively, these data support the use of peripheral tissues-particularly skin and buccal cells-for cross-sectional and longitudinal monitoring of hFXN supplementation in FRDA.