The citrate transporter SLC13A5 as a therapeutic target for kidney disease: evidence from Mendelian randomization to inform drug development

Abstract

AbstractBackgroundSolute carrier family 13 member 5 (SLC13A5) is a Na -coupled citrate co-transporter that mediates the entry of extracellular citrate into the cytosol. SLC13A5 inhibition has been proposed as a therapeutic target for reducing progression of kidney disease via its effects on citrate metabolism. However, evidence of its efficacy in humans is limited. The aim of this study was to leverage the Mendelian randomization paradigm to gain insight into the effects of SLC13A5 inhibition in humans, towards prioritizing and informing clinical development efforts.MethodsThe primary Mendelian randomization analyses investigated the effect of SLC13A5 inhibition on measures of kidney function, including creatinine and cystatin C based measures of estimated glomerular filtration rate (creatinine-eGFR and cystatin C-eGFR), blood urea nitrogen (BUN), urine albumin-creatinine ratio (uACR), and risk of chronic kidney disease and microalbuminuria. Secondary analyses included a paired plasma and urine metabolome-wide association study, investigation of secondary traits related to SLC13A5 biology, a phenome-wide association study (PheWAS), and a proteome-wide association study. All analyses were compared to the effect of genetically predicted plasma citrate levels using variants selected from across the genome, and statistical sensitivity analyses robust to the inclusion of pleiotropic variants were also performed. Data were obtained from large scale genetic consortia and biobanks, with sample sizes ranging from 5,023 to 1,320,016 individuals.ResultsWe found evidence of associations between genetically proxied SLC13A5 inhibition and higher creatinine-eGFR (p=0.002), cystatin C-eGFR (p=0.005), and lower BUN (p=3×10-3). Statistical sensitivity analyses robust to the inclusion of pleiotropic variants suggested that these effects may be a consequence of higher plasma citrate levels. There was no strong evidence of associations of genetically proxied SLC13A5 inhibition with uACR or risk of CKD or microalbuminuria. Secondary analyses also identified evidence of associations with higher plasma calcium levels (p=6×10-13) and lower fasting glucose (p=0.02). PheWAS did not identify any safety concerns.ConclusionThis Mendelian randomization analysis provides human-centric insight to guide clinical development of an SLC13A5 inhibitor. We identify plasma calcium and citrate as biologically plausible biomarkers of target engagement, and plasma citrate as a potential biomarker of mechanism of action. Our human genetic evidence corroborates evidence from various animal models to support effects of SLC13A5 inhibition on improving kidney function. Further study in the form of early-stage clinical trials may now be warranted to help translate these findings towards improving patient care.