Treatment with the copper compound CuATSM has no significant effect on motor neuronal pathology in patients with ALS

Aims Although the orally available brain‐penetrant copper compound CuATSM has demonstrated promising effects in SOD1‐linked mouse models, the impact of CuATSM on disease pathology in patients with amyotrophic lateral sclerosis (ALS) remains unknown. Methods The present study set out to address this deficit by performing the first pilot comparative analysis of ALS pathology in patients that had been administered CuATSM and riluzole [N = 6 cases composed of ALS‐TDP (n = 5) and ALS‐SOD1 (n = 1)] versus riluzole only [N = 6 cases composed of ALS‐TDP (n = 4) and ALS‐SOD1 (n = 2)]. Results Our results revealed no significant difference in neuron density or TDP‐43 burden in the motor cortex and spinal cord of patients that had received CuATSM compared with patients that had not. In patients that had received CuATSM, p62‐immunoreactive astrocytes were observed in the motor cortex and reduced Iba1 density was found in the spinal cord. However, no significant difference in measures of astrocytic activity and SOD1 immunoreactivity was found with CuATSM treatment. Discussion These findings, in this first postmortem investigation of patients with ALS in CuATSM trials, demonstrate that in contrast to that seen in preclinical models of disease, CuATSM does not significantly alleviate neuronal pathology or astrogliosis in patients with ALS. This study performs the first postmortem investigation into patients treated with CuATSM during life. Our results demonstrate no significant difference in neuron density or pTDP‐43 burden in patients that had received CuATSM compared to patients that had not.