Characterising a healthy adult with a rare HAO1 knockout to support a therapeutic strategy for primary hyperoxaluria

Abstract

By sequencing autozygous human populations, we identified a healthy adult woman with lifelong complete knockout of HAO1 (expected ~1 in 30 million outbred people). HAO1 (glycolate oxidase) silencing is the mechanism of lumasiran, an investigational RNA interference therapeutic for primary hyperoxaluria type 1. Her plasma glycolate levels were 12 times, and urinary glycolate 6 times, the upper limit of normal observed in healthy reference individuals (n = 67). Plasma metabolomics and lipidomics (1871 biochemicals) revealed 18 markedly elevated biochemicals (>5 sd outliers versus n = 25 controls) suggesting additional HAO1 effects. Comparison with lumasiran preclinical and clinical trial data suggested she has <2% residual glycolate oxidase activity. Cell line p.Leu333SerfsTer4 expression showed markedly reduced HAO1 protein levels and cellular protein mis-localisation. In this woman, lifelong HAO1 knockout is safe and without clinical phenotype, de-risking a therapeutic approach and informing therapeutic mechanisms. Unlocking evidence from the diversity of human genetic variation can facilitate drug development.

Optimizing the Intracellular Delivery of Therapeutic Anti-inflammatory TNF-α siRNA to Activated Macrophages Using Lipidoid-Polymer Hybrid Nanoparticles

“…In principle, any disease characterized by protein overexpression may be treated using synthetic molecules harnessing the RNAi pathway by Watson-Crick base-pairing, e.g., siRNA directed against a specific mRNA. Although the ability of double-stranded RNA to mediate silencing of gene expression was discovered in Caenorhabditis elegans more than two decades ago (Elbashir et al, 2001 ), only four drugs based on siRNA have been approved to date, i.e., patisiran (Adams et al, 2018 ), givosiran (Balwani et al, 2020 ), lumasiran (McGregor et al, 2020 ), and inclisiran (Raal et al, 2020 ; Ray et al, 2020 ) used for systemic treatment of the polyneuropathy of hereditary transthyretin amyloidosis, acute hepatic porphyria, and elevated LDL cholesterol respectively. Major hurdles for unlocking of the full potential of siRNA for therapeutic applications are delivery-related challenges (Dammes and Peer, 2020 ).…”

Small Molecule-Based Enzyme Inhibitors in the Treatment of Primary Hyperoxalurias

“…The latter could also benefit from economic reasons and an oral administration, among others. The inhibition of GO is also supported by the identification of a healthy adult with GO knockout [ 10 , 11 ].…”

“…Substrate reduction therapy (SRT) targeting glycolate oxidase (GO) was proposed as a novel therapeutic approach [ 7 , 8 ] with no nocive effects [ 9 , 10 , 11 ]. Recently, the FDA and EMA agencies have approved the first pharmacological treatment for PH1, based on siRNA inhibition of GO (lumasiran), after it has revealed promising results, meeting its primary efficacy endpoint and all tested secondary endpoints.…”

Transcriptional adaptation: a mechanism underlying genetic robustness

“…More recent analyses have reported that HLoF mutations are tolerated within outbred human populations, and exist at a frequency of approximately 18% in genes that do not show any disease association (Karczewski et al, 2020;Minikel et al, 2020). HLoF variants have also been identified in genes that affect disease risk (Karczewski et al, 2020), e.g., ACTN3, which is associated with ageing (Yang et al, 2003), HAO1, which is associated with kidney dysfunction (McGregor et al, 2020), and LRRK2, which is associated with Parkinson's disease (Whiffin et al, 2020). Similarly, in a recent analysis of 219 populations from 64 countries across Asia, it was reported that 43% of all proteincoding genes contain at least one protein-truncating variant, suggesting that HLoF variants can be well tolerated (Wall et al, 2019).…”