Progress towards drug discovery for Friedreich’s Ataxia: Identifying synthetic oligonucleotides that more potently activate expression of human frataxin protein

Xiulong Shen, Johnathan Wong, Thahza P. Prakash, Frank Rigo, Yanjie Li, Marek Napierala, David R. Corey; Bioorganic & Medicinal Chemistry,
2020, 115472, doi:10.1016/j.bmc.2020.115472.

We have previously demonstrated that synthetic antisense oligonucleotides or duplex RNAs that are complementary to the expanded repeat can activate expression of FXN and return levels of FXN protein to near normal. The potency of these compounds, however, was too low to encourage vigorous pre-clinical development. We now report testing of “gapmer” oligonucleotides consisting of a central DNA portion flanked by chemically modified RNA that increases binding affinity. We find that gapmer antisense oligonucleotides are several fold more potent activators of FXN expression relative to previously tested compounds. The potency of FXN activation is similar to a potent benchmark gapmer targeting the nuclear noncoding RNA MALAT-1, suggesting that our approach has potential for developing more effective compounds to regulate FXN expression in vivo.

High levels of frataxin overexpression leads to mitochondrial and cardiac toxicity in mouse models

Brahim Belbellaa, Laurence Reutenauer, Nadia Messaddeq, Laurent Monassier, Helene Puccio; bioRxiv 2020.03.31.015255; doi:10.1101/2020.03.31.015255

AAV-mediated gene therapy constitutes a promising approach for FA, as demonstrated in cardiac and neurological mouse models. While the minimal therapeutic level of FXN protein to be restored and biodistribution have recently been defined for the heart, it is unclear if FXN overexpression could be harmful. Indeed, depending on the vector delivery route and dose administrated, the resulting FXN protein level could reach very high levels in the heart, cerebellum, or in off-target organs such as the liver. The present study demonstrates safety of FXN cardiac overexpression up to 9-fold the normal endogenous level, but significant toxicity to the mitochondria and heart above 20-fold. We show gradual severity with increasing FXN overexpression, ranging from subclinical cardiotoxicity to left ventricle dysfunction. This appears to be driven by impairment of mitochondria respiratory chain, ultrastructure and homeostasis, which lead to myofilaments alteration, cell death and fibrosis. Overall, this study underlines the need, during the development of gene therapy approaches, to consider appropriately vector potency, long term safety and biomarkers to monitor such events.

Disarrangement of Endoplasmic reticulum-mitochondria communication impairs Ca2+ homeostasis in FRDA

Laura R Rodríguez, Pablo Calap-Quintana, Tamara Lapeña-Luzón, Federico V Pallardó, Stephan Schneuwly, Juan Antonio Navarro Langa, Pilar Gonzalez-Cabo; bioRxiv 2020.03.27.011528; doi:10.1101/2020.03.27.011528

Friedreich ataxia (FRDA) is a neurodegenerative disorder characterized by neuromuscular and neurological manifestations. It is caused by mutations in gene FXN, which results in loss of the mitochondrial protein frataxin. Endoplasmic Reticulum-mitochondria associated membranes (MAMs) are inter-organelle structures involved in the regulation of essential cellular processes, including lipid metabolism and calcium signaling. In the present study, we have analyzed in both, unicellular and multicellular models of FRDA, an analysis of calcium management and of integrity of MAMs. We observed that function of MAMs is compromised in our cellular model of FRDA, which was improved upon treatment with antioxidants. In agreement, promoting mitochondrial calcium uptake was sufficient to restore several defects caused by frataxin deficiency in Drosophila Melanogaster. Remarkably, our findings describe for the first time frataxin as a member of the protein network of MAMs, where interacts with two of the main proteins implicated in endoplasmic reticulum-mitochondria communication. These results suggest a new role of frataxin, indicate that FRDA goes beyond mitochondrial defects and highlight MAMs as novel therapeutic candidates to improve patient's conditions.

Cofilin dysregulation alters actin turnover in frataxin-deficient neurons

Diana C. Muñoz-Lasso, Belén Mollá, Pablo Calap-Quintana, José Luis García-Giménez, Federico V. Pallardo, Francesc Palau & Pilar Gonzalez-Cabo; Sci Rep 10, 5207 (2020). https://doi.org/10.1038/s41598-020-62050-7.

In this work, we demonstrate the dysregulation of the actin cytoskeleton in frataxin-deficient neurites of DRG neurons from the YG8R mice as a result of hyperactivation of cofilin-1 and the complex ARP2/3, which could affect the dynamics of growth cones and neurite growth. Recent work has determined that cofilin hyperactivation is age-dependent57, so it would be interesting to analyze these results at the embryonic stage. Assessing if there is a dysregulation of cofilin that could contribute to a failure in the neurite growth of embryonic neurons would help to understand the hypoplastic phenomena previously described in FRDA patients1. As a whole, our results show for the first time an imbalance in the activity of cofilin that could explain, at least partially, the neuropathy of FRDA. Future research will determine if cofilin is a potential molecular target for a therapeutic approach in FRDA.

Inhibition of the SUV4-20 H1 histone methyltransferase increases frataxin expression in Friedreich's ataxia patient cells

Gabriela Vilema-Enríquez, Robert Quinlan, Peter Kilfeather, Roberta Mazzone, Saba Saqlain, Irene del Molino del Barrio, Annalidia Donato, Gabriele Corda, Fengling Li, Masoud Vedadi, Andrea H Németh, Paul E Brennan, Richard Wade-Martins; bioRxiv 2020.03.26.010439; doi:10.1101/2020.03.26.010439

Finally, based on the structural activity relationship and crystal structure of A-196, novel small molecule A-196 analogues were synthesized and shown to give a 20-fold increase in potency for increasing FXN expression. Overall, our results suggest that histone methylation is important in the regulation of FXN expression, and highlight SUV4-20 H1 as a potential novel therapeutic target for FRDA.

Neurophysiologic intraoperative monitoring (NIOM) in pediatric patients with polyneuropathy

McKinney JL, Islam MP. Child's Nervous System : Chns : Official Journal of the International Society for Pediatric Neurosurgery. 2020 Mar DOI: 10.1007/s00381-020-04571-0.

Neurophysiologic intraoperative monitoring (NIOM) abnormalities during scoliosis surgery led to a diagnosis of Friedreich’s ataxia in this illustrative case. This prompted the retrospective examination of NIOM for pediatric scoliosis surgery in polyneuropathy patients.

Onset features and time to diagnosis in Friedreich's Ataxia

Elisabetta Indelicato, Wolfgang Nachbauer, Andreas Eigentler, Matthias Amprosi, Raffaella Matteucci Gothe, Paola Giunti, Caterina Mariotti, Javier Arpa, Alexandra Durr, Thomas Klopstock, Ludger Schöls, Ilaria Giordano, Katrin Bürk, Massimo Pandolfo, Claire Didszdun, Jörg Schulz, Sylvia Boesch; Research Square; 2020. DOI: 10.21203/rs.3.rs-18562/v1.

Background: In rare disorders diagnosis may be delayed due to limited awareness and unspecific presenting symptoms. Herein, we address the issue of diagnostic delay in Friedreich´s Ataxia (FRDA), a genetic disorder caused by homozygous GAA-repeat expansions.

Inherited Metabolic Diseases and Cardiac Pathology in Adults: Diagnosis and Prevalence in a CardioMetabo Study

Brailova, M.; Clerfond, G.; Trésorier, R.; Minet-Quinard, R.; Durif, J.; Massoullié, G.; Pereira, B.; Sapin, V.; Eschalier, R.; Bouvier, D.; J. Clin. Med. 2020, 9, 694. Doi:10.3390/jcm9030694

Many inherited metabolic diseases (IMD) have cardiac manifestations. The aim of this study was to estimate the prevalence of IMD in adult patients with hypertrophic cardiomyopathy (HCM) and cardiac rhythm abnormalities that require cardiac implantable electronic devices (CIEDs). The study included a review of the medical files of patients aged 18 to 65 years who were followed in our cardiology department during the period 2010–2017. Metabolic explorations for Fabry disease (FD), mitochondrial cytopathies, and fatty-acid metabolism disorders were carried out in patients with unexplained etiology. The prevalence of IMD in patients with HCM was 5.6% (confidence interval (CI): 2.6–11.6). Six cases of IMD were identified: 1 mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome, 1 Hurler syndrome, 2 Friedreich’s ataxia, 1 FD, and 1 short-chain acyl-CoA dehydrogenase deficiency. Three cases of IMD were identified in patients requiring CIEDs: 1 patient with Leber hereditary optic neuropathy, 1 FD, and 1 short chain acyl-CoA dehydrogenase (SCAD) deficiency. IMD prevalence in patients with CIEDs was 3.1% (CI: 1.1–8.8). IMD evaluation should be performed in unexplained HCM and cardiac rhythm abnormalities adult patients, since the prevalence of IMD is relatively important and they could benefit from specific treatment and family diagnosis.

Design Therapeutics Launches with $45 Million to Develop a New Class of Disease-Modifying Therapies for Serious Degenerative Disorders

SAN DIEGO--(BUSINESS WIRE)--Mar 20, 2020
Design Therapeutics announced today that it is launching to create and develop a new class of therapies for patients with serious degenerative disorders caused by nucleotide repeat expansions. The company has closed a $45 million Series A financing led by SR One, with participation from Cormorant Asset Management, Quan Capital and WestRiver Group, to advance its lead therapeutic candidate into clinical development for the treatment of Friedreich’s ataxia, and support advancement of its discovery programs for multiple other degenerative diseases, including fragile X syndrome and myotonic dystrophy.
Design Therapeutics has developed a novel program that unblocks transcription, thereby restoring the natural production and function of frataxin. With the use of proceeds from the Series A fundraising, Design Therapeutic intends to conduct IND-enabling studies and initiate clinical development for its program for Friedreich’s ataxia.

ENDOTHELIAL FRATAXIN DEFICIENCY DRIVES NUCLEAR REPLICATION STRESS-INDUCED SENESCENCE AND MITOCHONDRIAL DYSFUNCTION ACROSS MULTIPLE SUBTYPES OF PULMONARY HYPERTENSION

Miranda K. Culley, Jingsi Zhao, Ying Tang, Yi Yin Tai, Dror Perk, Vinny Negi, Yen-Chun Lai, Qiujun Yu, Adam Handen, Gil Speyer, Seungchan Kim, Taijyu Satoh, Michael Reynolds, Sruti Shiva, Annie Watson, Yassmin Al Aaraj, John Sembrat, Mauricio Rojas, Karen Norris, Aditi Gurkar, Mingxia Gu, Marlene Rabinovitch, Thomas Bertero and Stephen Chan; Journal of the American College of Cardiology, Volume 75, Issue 11 Supplement 1, March 2020 DOI: 10.1016/S0735-1097(20)34284-4

Endothelial DNA damage and metabolic dysfunction are linked to pulmonary hypertension (PH). Their joint regulation, control of cellular senescence, and relevance across PH subtypes are unknown. Mutations in the iron-sulfur (Fe-S) biogenesis gene frataxin (FXN) disrupt DNA integrity and metabolism, causing Friedreich’s ataxia (FRDA) and hypertrophic cardiomyopathy, often complicated by PH. Because Fe-S loss promotes PH, we hypothesized endothelial FXN deficiency induces genotoxic and metabolic dysregulation and predisposes to PH, particularly vascular remodeling due to ventricular stiffening.

FXN deficiency promotes replication stress-induced senescence and metabolic reprogramming across PH subtypes, including a predisposition to PH in FRDA. Our data endorse developing PH diagnostics and therapeutics related to Fe-S biology and genotoxic stress, namely for PH due to left heart disease.