A deficient activity of one or more of the mitochondrial oxidative phosphorylation (OXPHOS) enzyme complexes leads to devastating diseases, with high unmet medical needs. Mitochondria, and more specifically the OXPHOS system, are the main cellular production sites of Reactive Oxygen Species (ROS). Increased ROS production, ultimately leading to irreversible oxidative damage of macromolecules or to more selective and reversible redox modulation of cell signalling, is a causative hallmark of mitochondrial diseases. Here we report on the development of a new clinical-stage drug KH176 acting as a ROS-Redox modulator. Patient-derived primary skin fibroblasts were used to assess the potency of a new library of chromanyl-based compounds to reduce ROS levels and protect cells against redox-stress. The lead compound KH176 was studied in cell-based and enzymatic assays and in silico. Additionally, the metabolism, pharmacokinetics and toxicokinetics of KH176 were assessed in vivo in different animal species. We demonstrate that KH176 can effectively reduce increased cellular ROS levels and protect OXPHOS deficient primary cells against redox perturbation by targeting the Thioredoxin/Peroxiredoxin system. Due to its dual activity as antioxidant and redox modulator, KH176 offers a novel approach to the treatment of mitochondrial (-related) diseases. KH176 efficacy and safety are currently being evaluated in a Phase 2 clinical trial.

The endogenous nucleoside adenosine has profound tissue protective effects in situations of ischaemia or inflammation. Animal studies have shown that various drugs can activate this protective mechanism by interfering with the metabolism of adenosine. Translation of this concept to the clinical arena is hampered by the difficulties encountered in measuring the adenosine concentration, due to the rapid cellular uptake and degradation of adenosine, which continues unabated after blood sampling, and due to the metabolically active endothelial barrier for adenosine. In the current paper, we critically discuss the various methods to measure the adenosine concentration in humans in vivo. For the measurement of circulating adenosine, we conclude that the use of a pharmacological blocker solution (containing inhibitors of the enzymes ecto-5'-nucleotidase, adenosine deaminase, and adenosine kinase, and of the equilibrative nucleoside transporter) and a purpose-built syringe which mixes the blood with this solution immediately at the tip of the needle, seems to be the most sensitive technique. However, for the measurement of adenosine concentrations in interstitial tissue, microdialysis is a suitable method, when used with an appropriate method to determine the recovery of adenosine across the semipermeable membrane to calculate the absolute adenosine concentration. Consistent use of these methods could help in the comparison of the various studies focussed on endogenous adenosine and could help to facilitate the use of drugs that modulate the adenosine concentration to protect tissues in the clinical arena.

The PTEN-induced putative kinase 1 knockout rat (Pink1−/−) is marketed as an established model for Parkinson’s disease, characterized by development of motor deficits and progressive degeneration of half the dopaminergic neurons in the substantia nigra pars compacta by 8 months of age. In this study, we address our concerns about the reproducibility of the Pink1−/− rat model. We evaluated behavioural function, number of substantia nigra dopaminergic neurons and extracellular striatal dopamine concentrations by in vivo microdialysis. Strikingly, we and others failed to observe any loss of dopaminergic neurons in 8-month-old male Pink1−/− rats. To understand this variability, we compared key experimental parameters from the different studies and provide explanations for contradictory findings. Although Pink1−/− rats developed behavioural deficits, these could not be attributed to nigrostriatal degeneration as there was no loss of dopaminergic neurons in the substantia nigra and no changes in neurotransmitter levels in the striatum. To maximize the benefit of Parkinson’s disease research and limit the unnecessary use of laboratory animals, it is essential that the research community is aware of the limits of this animal model. Additional research is needed to identify reasons for inconsistency between Pink1−/− rat colonies and why degeneration in the substantia nigra is not consistent.

No abstract