Objective To investigate whether a histone deacetylase inhibitor (HDACi) would be effective in an in vitro model for the neurodegenerative disease Friedreich ataxia (FRDA) and to evaluate safety and surrogate markers of efficacy in a phase I clinical trial in patients. Methods We used a human FRDA neuronal cell model, derived from patient induced pluripotent stem cells, to determine the efficacy of a 2-aminobenzamide HDACi (109) as a modulator of FXN gene expression and chromatin histone modifications. FRDA patients were dosed in 4 cohorts, ranging from 30mg/day to 240mg/day of the formulated drug product of HDACi 109, RG2833. Patients were monitored for adverse effects as well as for increases in FXN mRNA, frataxin protein, and chromatin modification in blood cells. Results In the neuronal cell model, HDACi 109/RG2833 increases FXN mRNA levels and frataxin protein, with concomitant changes in the epigenetic state of the gene. Chromatin signatures indicate that histone H3 lysine 9 is a key residue for gene silencing through methylation and reactivation through acetylation, mediated by the HDACi. Drug treatment in FRDA patients demonstrated increased FXN mRNA and H3 lysine 9 acetylation in peripheral blood mononuclear cells. No safety issues were encountered. Interpretation Drug exposure inducing epigenetic changes in neurons in vitro is comparable to the exposure required in patients to see epigenetic changes in circulating lymphoid cells and increases in gene expression. These findings provide a proof of concept for the development of an epigenetic therapy for this fatal neurological disease.

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Resveratrol is a naturally occurring stilbene which has shown promising results as treatment for several neurodegenerative diseases. However, its application is limited due to its low efficacy and bioavailability. Here, we have designed and synthesized alkylated resveratrol prodrugs combining structural modification to improve antioxidant and anti-inflammatory properties and the preparation of prodrugs to extend drug bioavailability. For comparison we also studied resveratrol prodrugs and alkylated resveratrol derivatives. Methylated and butylated resveratrol derivatives showed the best in vitro neuroprotective and anti-inflammatory activity. The glucosyl- and glucosyl-acyl- prodrugs of these derivatives showed lower toxicity on zebra fish embryo. When neuroprotection was examined on pentylenetetrazole challenged zebra fish, they were capable of reverting neuronal damage but to a lower extent than resveratrol. Nevertheless, 3-O-(6'-O-octanoyl)-β-d-glucopyranoside resveratrol (compound 8) recovered AChE activity over 100% whereas resveratrol only up to 92%. In a 3-nitropropionic acid mice model of Huntington's disease, resveratrol derivative 8 delayed the onset and reduced the severity of HD-like symptoms, by improving locomotor activity and protecting against weight loss. Its effects involved an equal antioxidant but better anti-inflammatory profile than resveratrol as shown by SOD2 expression in brain tissue and circulating levels of IL-6 (11 vs 18 pg/mL), respectively. Finally, the octanoyl chain in compound 8 could be playing a role in inflammation and neuronal development indicating it could be acting as a double-drug, instead of as a prodrug.

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