Raffaele, S.; Bonifacino, T.; Mannella, F. C.; Nguyen, N.; Torazza, C.; Marangon, D.; Chinosi, E. M.; Schroder, H. D.; Hejbol, E. K.; Madsen, K.; Marchetti, L.; Trincavelli, M. L.; Milanese, M.; Lecca, D.; Lambertsen, K. L.; Bonanno, G.; Abbracchio, M. P.; Fumagalli, M.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no definitive disease-modifying therapies available, underscoring the urgent need to identify novel druggable targets. The G protein-coupled receptor GPR17 is a critical regulator of oligodendrocyte maturation and has emerged as a candidate target in ALS, yet its relevance to human disease and therapeutic potential remain unclear. Here, we demonstrate that pathological GPR17 upregulation defines a conserved, pathologically immature oligodendroglial state in human ALS that can be pharmacologically leveraged to restore myelin integrity and improve functional outcome in vivo. Publicly available transcriptomics datasets and histological analysis revealed an increased abundance of GPR17-expressing immature oligodendrocytes in post-mortem human spinal cord tissue from ALS cases compared with non-neurological controls. Moreover, sustained activation of GPR17 with a selective agonist was able to induce GPR17 internalization in heterologous expression systems. In line with this mechanism, treatment with the same agonist promoted the differentiation of primary oligodendrocyte precursor cells derived from SOD1G93A mice. Translating these findings in vivo, chronic treatment with a brain-penetrant GPR17 agonist derived from the same pharmacological class significantly extended survival, delayed body weight loss, and improved motor performance in female SOD1G93A mice, whereas male mice showed no therapeutic benefit. These effects were associated with restored oligodendrocyte maturation, preserved myelin integrity, motor neuron survival, and attenuated reactive gliosis in the spinal cord of female SOD1G93A mice, while milder effects were observed in males. Together, these findings establish oligodendroglial GPR17 as a conserved and pharmacologically actionable target in ALS and show that sustained in vivo GPR17 agonism can reprogram altered oligodendroglial states and slow disease progression in a sex-dependent manner.