Single Arm Open-label Clinical Trial in Ataxia-telangiectasia to Test the Effects of Nicotinamide Riboside on Ataxia Scales, Immune Function, and Neurofilament Light Chain.

Ataxia Telangiectasia (A-T) is a rare, genetic, progressive, life-limiting, neuro-degenerative condition affecting a variety of body systems resulting in ataxia, immune deficiency, respiratory complications and a predisposition to cancer. Currently there is no cure for A-T.

Over the years, a number of small clinical trials using steroids, antioxidants and anti-inflammatory agents have had little success. The disease natural history is relentless leading to early death. A-T generates a significant disease burden for the individuals, their extended families and on health care resources. With palliative care being the only current option for families, a treatment trial for A-T meets an unmet need. Our group previously demonstrated compelling evidence of reversible mitochondrial dysfunction and preventable cell death in A-T patient cells and the beneficial effects of heptanoate (C7), the primary metabolite of triheptanoin. C7 corrects a defect in endoplasmic reticulum (ER)-mitochondrial signalling in A-T cells and has great potential for application in treating patients. C7 has been utilised with efficacy and safety over the last 15 years for inborn errors of metabolism (IEM) such as long chain fatty acid defects (LC-FAOD).

A-T is due to a genetic defect that results in a defective serine/threonine protein kinase, known as ATM. Normally, ATM, plays a central role in protecting the genome against damage. It is increasingly evident that ATM protects cells against oxidative stress. This protein is also present outside the nucleus, where it is activated by oxidative stress through a separate mechanism from DNA damage, providing an explanation why anti-oxidants have a protective role in A-T cells in culture and in animal models. From these and other studies, it is evident that mitochondrial abnormalities characterise ATM and it has been suggested that A-T should be considered, at least in part, as a mitochondrial disease.

We have added substance to that claim by showing that ATM-deficient (B3) cells are exquisitely sensitive to inhibition of glycolysis by glucose deprivation, compared to controls (HBEC). We have also shown this increased sensitivity to nutrient deprivation for primary epithelial cells from patients and in immortalised patient cells. We demonstrated that this was caused by defective assembly of the VDAC1-GRP75-IP3R1 calcium channel and less ER-mitochondria contact points as determined by transmission electron microscopy. This in turn resulted in reduced calcium release from the ER and less transfer to mitochondria providing further evidence for mitochondrial dysfunction in A-T cells. We have recently completed a Phase 2A/B clinical trial exploring the efficacy and tolerability of C7 in AT patients (https://classic.clinicaltrials.gov/NCT04513002).

Nicotinamide adenine dinucleotide (NAD+) is an essential cofactor for many cellular enzymes, including those involved in mitochondrial biogenesis and maintenance. Nicotinamide adenine dinucleotide exists in two forms, including an oxidized (NAD+) and a reduced (NADH) form, and plays a key role in intermediary metabolism, as obligatory partner in numerous oxidation/reduction reactions. The cellular pool of NAD+ and NADH is tightly regulated through a careful balance between its biosynthesis and its breakdown by NAD+-consuming enzymes. NAD+ deficiency plays a role in disease mechanisms underlying DNA repair disorders. Mitochondrial damage and NAD+ depletion are key features in ataxia telangiectasia.