Insights into the pathogenesis of primary hyperoxaluria type I from the structural dynamics of alanine:glyoxylate aminotransferase variants.

Primary hyperoxaluria type I (PH1) is caused by deficient alanine:glyoxylate aminotransferase (AGT) activity. PH1-causing mutations in AGT lead to protein mistargeting and aggregation. Here, we use hydrogen-deuterium exchange (HDX) to characterize the wild-type (WT), the LM (a polymorphism frequent in PH1 patients) and the LM G170R (the most common mutation in PH1) variants of AGT. We provide the first experimental analysis of AGT structural dynamics, showing that stability is heterogeneous in the native state and providing a blueprint for frustrated regions with potentially functional relevance. The LM and LM G170R variants only show local destabilization. Enzymatic transamination of the pyridoxal 5-phosphate cofactor bound to AGT hardly affects stability. Our study, thus, supports that AGT misfolding is not caused by dramatic effects on structural dynamics.

Nedosiran: First Approval.

Nedosiran (RIVFLOZA™), a once-monthly subcutaneous small interfering RNA (siRNA) therapy, is being developed by Dicerna Pharmaceuticals, a Novo Nordisk company, for the treatment of primary hyperoxaluria (PH). It reduces oxalate overproduction by inhibiting the expression of the hepatic lactate dehydrogenase (LDH) enzyme. Nedosiran received its first approval on 29 September 2023 in the USA to lower urinary oxalate levels in children aged ≥ 9 years and adults with PH type 1 (PH1) and relatively preserved kidney function [e.g. estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m2]. This article summarizes the milestones in the development of nedosiran leading to this first approval for PH1.

HOGA1 gene pathogenic variants in primary hyperoxaluria type III: Spectrum of pathogenic sequence variants, and phenotypic association.

Primary hyperoxalurias (PH) are a group of rare heterogeneous disorders characterized by deficiencies in glyoxylate metabolism. To date, three genes have been identified to cause three types of PH (I, II, and III). The HOGA1 gene caused type III in around 10% of the PH cases. Disease-associated pathogenic variants have been reported from several populations and a comprehensive spectrum of these mutations and genotype-phenotype correlation has never been presented. In this study, we describe new cases of the HOGA1 gene pathogenic variants identified in our population. We report the first case of ESKD with successful kidney transplantation with 5 years of follow-up. Furthermore, a comprehensive overview of PH type III associated HOGA1 gene variants was carried out. Compiling the data from the literature, we reviewed 57 distinct HOGA1 gene pathogenic variants in 175 patients worldwide. The majority of reported variants are missense variants that predicted a loss of function mechanism as the underlying pathology. There has been evidence of the presence of founder mutations in several populations like Europeans, Ashkenazi Jews, Arab, and Chinese populations. No significant genotype-phenotype correlation was identified concerning the ages of onset of the disease and biochemical and metabolic parameters. Nephrocalcinosis was rare in patients with disease-associated variants. Most of the patients were presented with urolithiasis early in life; only five cases reported disease progression after the second decade of life. The establishment of impairment of renal function in 8% of all the reported cases makes this type a relatively severe form of primary hyperoxaluria, not a benign etiology as suggested previously.

Lactate dehydrogenase A inhibitors with a 2,8-dioxabicyclo[3.3.1]nonane scaffold: A contribution to molecular therapies for primary hyperoxalurias.

Human lactate dehydrogenase A (hLDHA) is one of the main enzymes involved in the pathway of oxalate synthesis in human liver and seems to contribute to the pathogenesis of disorders with endogenous oxalate overproduction, such as primary hyperoxaluria (PH), a rare life-threatening genetic disease. Recent published results on the knockdown of LDHA gene expression as a safe strategy to ameliorate oxalate build-up in PH patients are encouraging for an approach of hLDHA inhibition by small molecules as a potential pharmacological treatment. Thus, we now report on the synthesis and hLDHA inhibitory activity of a new family of compounds with 2,8-dioxabicyclo[3.3.1]nonane core (23-42), a series of twenty analogues to A-type proanthocyanidin natural products. Nine of them (25-27, 29-34) have shown IC50 values in the range of 8.7-26.7 µM, based on a UV spectrophotometric assay, where the hLDHA inhibition is measured according to the decrease in absorbance of the cofactor ß-NADH (340 nm). Compounds 25, 29, and 31 were the most active hLDHA inhibitors. In addition, the inhibitory activities of those nine compounds against the hLDHB isoform were also evaluated, finding that all of them were more selective inhibitors of hLDHA versus hLDHB. Among them, compounds 32 and 34 showed the highest selectivity. Moreover, the most active hLDHA inhibitors (25, 29, 31) were evaluated for their ability to decrease the oxalate production by hyperoxaluric mouse hepatocytes (PH1, PH2 and PH3) in vitro, and the relative oxalate output at 24 h was 16% and 19 % for compounds 25 and 31, respectively, in Hoga1-/- mouse primary hepatocyte cells (a model for PH3). These values improve those of the reference compound used (stiripentol). Compounds 25 and 31 have in common the presence of two hydroxyl groups at rings B and D and an electron-withdrawing group (NO2 or Br) at ring A, pointing to the structural features to be taken into account in future structural optimization.

New salicylic acid derivatives, double inhibitors of glycolate oxidase and lactate dehydrogenase, as effective agents decreasing oxalate production.

The synthesis and biological evaluation of double glycolate oxidase/lactate dehydrogenase inhibitors containing a salicylic acid moiety is described. The target compounds are obtained in an easily scalable two-step synthetic procedure. These compounds showed low micromolar IC50 values against the two key enzymes in the metabolism of glyoxylate. Mechanistically they behave as noncompetitive inhibitors against both enzymes and this fact is supported by docking studies. The biological evaluation also includes in vitro and in vivo assays in hyperoxaluric mice. The compounds are active against the three types of primary hyperoxalurias. Also, possible causes of adverse effects, such as cyclooxygenase inhibition or renal toxicity, have been studied and discarded. Altogether, this makes this chemotype with drug-like structure a good candidate for the treatment of primary hyperoxalurias.

Catabolism of Hydroxyproline in Vertebrates: Physiology, Evolution, Genetic Diseases and New siRNA Approach for Treatment.

Hydroxyproline is one of the most prevalent amino acids in animal proteins. It is not a genetically encoded amino acid, but, rather, it is produced by the post-translational modification of proline in collagen, and a few other proteins, by prolyl hydroxylase enzymes. Although this post-translational modification occurs in a limited number of proteins, its biological significance cannot be overestimated. Considering that hydroxyproline cannot be re-incorporated into pro-collagen during translation, it should be catabolized following protein degradation. A cascade of reactions leads to production of two deleterious intermediates: glyoxylate and hydrogen peroxide, which need to be immediately converted. As a result, the enzymes involved in hydroxyproline catabolism are located in specific compartments: mitochondria and peroxisomes. The particular distribution of catabolic enzymes in these compartments, in different species, depends on their dietary habits. Disturbances in hydroxyproline catabolism, due to genetic aberrations, may lead to a severe disease (primary hyperoxaluria), which often impairs kidney function. The basis of this condition is accumulation of glyoxylate and its conversion to oxalate. Since calcium oxalate is insoluble, children with this rare inherited disorder suffer from progressive kidney damage. This condition has been nearly incurable until recently, as significant advances in substrate reduction therapy using small interference RNA led to a breakthrough in primary hyperoxaluria type 1 treatment.

Therapeutic RNA interference: A novel approach to the treatment of primary hyperoxaluria.

RNA interference (RNAi) is a natural biological pathway that inhibits gene expression by targeted degradation or translational inhibition of cytoplasmic mRNA by the RNA induced silencing complex. RNAi has long been exploited in laboratory research to study the biological consequences of the reduced expression of a gene of interest. More recently RNAi has been demonstrated as a therapeutic avenue for rare metabolic diseases. This review presents an overview of the cellular RNAi machinery as well as therapeutic RNAi design and delivery. As a clinical example we present primary hyperoxaluria, an ultrarare inherited disease of increased hepatic oxalate production which leads to recurrent calcium oxalate kidney stones. In the most common form of the disease (Type 1), end-stage kidney disease occurs in childhood or young adulthood, often necessitating combined kidney and liver transplantation. In this context we discuss nedosiran (Dicerna Pharmaceuticals, Inc.) and lumasiran (Alnylam Pharmaceuticals), which are both novel RNAi therapies for primary hyperoxaluria that selectively reduce hepatic expression of lactate dehydrogenase and glycolate oxidase respectively, reducing hepatic oxalate production and urinary oxalate levels. Finally, we consider future optimizations advances in RNAi therapies.

Endogenous Oxalate Production in Primary Hyperoxaluria Type 1 Patients.

BACKGROUND: Primary hyperoxaluria type 1 (PH1) is an inborn error of glyoxylate metabolism, characterized by increased endogenous oxalate production. The metabolic pathways underlying oxalate synthesis have not been fully elucidated, and upcoming therapies require more reliable outcome parameters than the currently used plasma oxalate levels and urinary oxalate excretion rates. We therefore developed a stable isotope infusion protocol to assess endogenous oxalate synthesis rate and the contribution of glycolate to both oxalate and glycine synthesis in vivo . METHODS: Eight healthy volunteers and eight patients with PH1 (stratified by pyridoxine responsiveness) underwent a combined primed continuous infusion of intravenous [1- 13 C]glycolate, [U- 13 C 2 ]oxalate, and, in a subgroup, [D 5 ]glycine. Isotopic enrichment of 13 C-labeled oxalate and glycolate were measured using a new gas chromatography-tandem mass spectrometry (GC-MS/MS) method. Stable isotope dilution and incorporation calculations quantified rates of appearance and synthetic rates, respectively. RESULTS: Total daily oxalate rates of appearance (mean [SD]) were 2.71 (0.54), 1.46 (0.23), and 0.79 (0.15) mmol/d in patients who were pyridoxine unresponsive, patients who were pyridoxine responsive, and controls, respectively ( P =0.002). Mean (SD) contribution of glycolate to oxalate production was 47.3% (12.8) in patients and 1.3% (0.7) in controls. Using the incorporation of [1- 13 C]glycolate tracer in glycine revealed significant conversion of glycolate into glycine in pyridoxine responsive, but not in patients with PH1 who were pyridoxine unresponsive. CONCLUSIONS: This stable isotope infusion protocol could evaluate efficacy of new therapies, investigate pyridoxine responsiveness, and serve as a tool to further explore glyoxylate metabolism in humans.

Discovery of Novel, Potent Inhibitors of Hydroxy Acid Oxidase 1 (HAO1) Using DNA-Encoded Chemical Library Screening.

Inhibition of hydroxy acid oxidase 1 (HAO1) is a strategy to mitigate the accumulation of toxic oxalate that results from reduced activity of alanine-glyoxylate aminotransferase (AGXT) in primary hyperoxaluria 1 (PH1) patients. DNA-Encoded Chemical Library (DECL) screening provided two novel chemical series of potent HAO1 inhibitors, represented by compounds 3-6. Compound 5 was further optimized via various structure-activity relationship (SAR) exploration methods to 29, a compound with improved potency and absorption, distribution, metabolism, and excretion (ADME)/pharmacokinetic (PK) properties. Since carboxylic acid-containing compounds are often poorly permeable and have potential active glucuronide metabolites, we undertook a brief, initial exploration of acid replacements with the aim of identifying non-acid-containing HAO1 inhibitors. Structure-based drug design initiated with Compound 5 led to the identification of a nonacid inhibitor of HAO1, 31, which has weaker potency and increased permeability.

Lumasiran: First Approval.

Lumasiran (Oxlumo™) is a subcutaneously administered small interfering RNA (siRNA) targeting the mRNA for hydroxyacid oxidase 1 gene (HAO1; encodes glycolate oxidase) and was developed by Alnylam Pharmaceuticals for the treatment of primary hyperoxaluria type 1 (PH1). By silencing the gene encoding glycolate oxidase, lumasiran depletes glycolate oxidase and thereby inhibits the synthesis of oxalate, which is the toxic metabolite that is directly associated with the clinical manifestations of PH1. On 19 November 2020, lumasiran received its first global approval in the EU for the treatment of PH1 in all age groups. On 23 November 2020, lumasiran was approved in the USA for the treatment of adult and paediatric patients with PH1. This article summarizes the milestones in the development of lumasiran leading to this first approval.

Effect of alanine supplementation on oxalate synthesis.

The Primary Hyperoxalurias (PH) are rare disorders of metabolism leading to excessive endogenous synthesis of oxalate and recurring calcium oxalate kidney stones. Alanine glyoxylate aminotransferase (AGT), deficient in PH type 1, is a key enzyme in limiting glyoxylate oxidation to oxalate. The affinity of AGT for its co-substrate, alanine, is low suggesting that its metabolic activity could be sub-optimal in vivo. To test this hypothesis, we examined the effect of L-alanine supplementation on oxalate synthesis in cell culture and in mouse models of Primary Hyperoxaluria Type 1 (Agxt KO), Type 2 (Grhpr KO) and in wild-type mice. Our results demonstrated that increasing L-alanine in cells decreased synthesis of oxalate and increased viability of cells expressing GO and AGT when incubated with glycolate. In both wild type and Grhpr KO male and female mice, supplementation with 10% dietary L-alanine significantly decreased urinary oxalate excretion ~30% compared to baseline levels. This study demonstrates that increasing the availability of L-alanine can increase the metabolic efficiency of AGT and reduce oxalate synthesis.

Oxalosis Crystals' Redeposition in Cardiac Tissue Leading to New-Onset Fatal Cardiac Complication After Liver Transplant in Primary Oxalosis Patient: Case Report.

Primary oxalosis is a rare hereditary disorder of metabolism resulting in accumulation of calcium oxalate in almost all tissues of the body. All published data point out the improvement of cardiac function after transplant. Here, we report the first case in the literature of an 8-year-old patient with primary oxalosis in which oxalosis implantations increased in cardiac tissue after liver transplant and manifested as new-onset ventricular tachycardia and cardiomyopathy, leading to death.

Stiripentol identifies a therapeutic target to reduce oxaluria.

PURPOSE OF REVIEW: Oxalate is a metabolic end-product promoting the formation of calcium oxalate crystals in urine. Massive urine oxalate excretion occurs in genetic diseases, mainly primary hyperoxaluria type I and II, threatening renal function. Ethylene glycol poisoning may induce the precipitation of calcium oxalate crystals in renal tubules, leading to acute renal failure. In both cases, oxalate results from glyoxylate transformation to oxalate in the liver, by lactate dehydrogenase (LDH) enzymes, especially the LDH-5 isoenzyme. The purpose of the review is to highlight LDH as a potential therapeutic target according to recent publications. RECENT FINDINGS: Genetic therapy targeting LDH metabolism decreases urine oxalate excretion in rodents. Stiripentol is an antiepileptic drug that has been shown recently to inhibit neuronal LDH-5 isoenzyme. Stiripentol was hypothesized to reduce hepatic oxalate production and urine oxalate excretion. In vitro, stiripentol decreases oxalate synthesis by hepatocytes. In vivo, stiripentol oral administration decreases urine oxalate excretion in rats and protects renal function and renal tissue against ethylene glycol intoxication and chronic calcium oxalate crystalline nephropathy. SUMMARY: The use of stiripentol in-vitro and in-vivo highlights that targeting hepatic LDH by pharmacological or genetic tools may decrease oxalate synthesis, deserving clinical studies.

Diffuse Hypermetabolic Bone Marrow Infiltration in Severe Primary Hyperoxaluria on FDG PET.

A 24-year-old man, with type 1 primary hyperoxaluria (diagnosed at age 20 years after repeated renal lithiasis, due to a I244T mutation frequently encountered in Mediterranean countries) complicated by end-stage renal failure requiring dialysis, was admitted for pancytopenia, refractory to erythropoietin injections. On clinical examination, he presented a hepatosplenomegaly without palpable adenopathy. F-FDG PET/CT revealed intense and diffuse bone marrow uptake in the axial skeleton and preferential long bone metaphyseal uptake. Bone marrow aspiration showed Gaucher-like cells infiltration due to oxalate accumulation in macrophages, leading to the diagnosis of bone marrow involvement by primary hyperoxaluria.

Urinary monocyte chemoattractant protein 1 associated with calcium oxalate crystallization in patients with primary hyperoxaluria.

BACKGROUND: Patients with primary hyperoxaluria (PH) often develop kidney stones and chronic kidney disease. Noninvasive urine markers reflective of active kidney injury could be useful to gauge the effectiveness of ongoing treatments. METHODS: A panel of biomarkers that reflect different nephron sites and potential mechanisms of injury (clusterin, neutrophil gelatinase-associated lipocalin (NGAL), 8-isoprostane (8IP), monocyte-chemoattractant protein 1(MCP-1), liver-type fatty acid binding protein (L-FABP), heart-type fatty acid binding protein (H-FABP), and osteopontin (OPN)) were measured in 114 urine specimens from 30 PH patients over multiple visits. Generalized estimating equations were used to assess associations between biomarkers and 24 h urine excretions, calculated proximal tubular oxalate concentration (PTOx), and eGFR. RESULTS: Mean (±SD) age at first visit was 19.5 ± 16.6 years with an estimated glomerular filtration rate (eGFR) of 68.4 ± 21.0 ml/min/1.73m2. After adjustment for age, sex, and eGFR, a higher urine MCP-1 concentration and MCP-1/creatinine ratio was positively associated with CaOx supersaturation (SS). Higher urine NGAL and NGAL/creatinine as well as OPN and OPN/creatinine were associated with higher eGFR. 8IP was negatively associated with PTOx and urinary Ox, but positively associated with CaOx SS. CONCLUSION: In PH patients greater urine MCP-1 and 8IP excretion might reflect ongoing collecting tubule crystallization, while greater NGAL and OPN excretion may reflect preservation of kidney mass and function. CaOx crystals, rather than oxalate ion may mediate oxidative stress in hyperoxaluric conditions. Further studies are warranted to determine whether urine MCP-1 excretion predicts long term outcome or is altered in response to treatment.

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

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.

[Clinical analysis of seven cases with primary hyperoxaluria type 1 in children].

Objective: To investigate the clinical, imaging and molecular characteristics of primary hyperoxaluria type 1 (PH1) in children and to sum up existing evidence for further understanding the phenotype-genotype correlation of infantile PH1. Methods: This retrospective analysis was based on the medical records of children with PH1 diagnosed by gene test in the Department of Nephrology, Guangzhou Women and Children's Medical Center from June 2016 to May 2019. Targeted exome sequencing was performed on tubular disease-related genes of the probands and Sanger sequencing was conducted to validate suspected pathogenic variants of family members. Logistic regression analysis of NC and CCr was adopted to show the relation between NC and renal function. The literature review was conducted, and the clinical, imaging and molecular biogenetic characteristics of the disease were analyzed and summarized. Results: A total of 7 children from 6 families were enrolled. The median age of onset was 5 months. The median age of diagnosis was 8 months. Five cases had progressed to end-stage renal disease (ESRD), one case had chronic kidney disease (CKD) stage 1, and the other one had CKD stage 2. Four cases died, one case maintained on hemodialysis, and the other two non-dialysis cases were followed up. Among the 7 cases, 4 patients had infantile PH1, 1 patient had child and adolescent type, 1 patient had family type and the other one had unknown classification. There were two siblings (the younger brother had uremia and the sister had normal renal function) who had the delayed diagnosis for 5 and 3 years respectively. All patients in this cohort had proteinuria and microscopic hematuria, but no patients had gross hematuria. Three cases had hypercalciuria. Comprehensive diagnostic imaging evaluation include CT scan, MR scan, radiography and ultrasound led to the diagnosis of nephrocalcinosis (NC) in 5 cases, including 4 cases of simple NL and 1 case of NC with nephrolithiasis (NL), 1 case of multiple NL and 1 case of microcrystal deposition in renal medulla. However, only one case of NC was identified by ultrasound, the other 4 cases of NC were identified by radiograph examination. In the logistic regression analysis involving NC and creatinine clearnce rate (CCr), the results showed that NC was an independent risk factor for renal dysfunction (OR 2.5, 95%CI 0.7-1.2, P<0.05). All the 7 cases had AGXT gene variant, including homozygous variant in 4 cases and compound heterozygous variant in 3 cases. A total of 9 variant genotypes were found, and exon 6 variants were found in 4 children. Among them, there were 3 cases with c.679_680delAA. To our knowledge, both c.679_680delAA and c.190A>T in the cohort have not been reported previously. Conclusions: Infantile PH1 is the most common type of PH1 in children, which progresses rapidly or even begins with renal failure, with poor prognosis. It is also highly heterogeneous in phenotype and genotype. NC is an independent risk factor leading to renal failure. Radiograph examination showed high specificity for the diagnosis of NC. At present, the misdiagnosis and delayed diagnosis of PH1 are still common in China. It is of great significance to carry out quantitative determination of uric oxalate in order to reduce the misdiagnosis rate and enhance follow-up technologies for evaluating the therapeutic effect.

The effects of the inactivation of Hydroxyproline dehydrogenase on urinary oxalate and glycolate excretion in mouse models of primary hyperoxaluria.

The major clinical manifestation of the Primary Hyperoxalurias (PH) is increased production of oxalate, as a consequence of genetic mutations that lead to aberrant glyoxylate and hydroxyproline metabolism. Hyperoxaluria can lead to the formation of calcium-oxalate kidney stones, nephrocalcinosis and renal failure. Current therapeutic approaches rely on organ transplants and more recently modifying the pathway of oxalate synthesis using siRNA therapy. We have recently reported that the metabolism of trans-4-hydroxy-L-proline (Hyp), an amino acid derived predominantly from collagen metabolism, is a significant source of oxalate production in individuals with PH2 and PH3. Thus, the first enzyme in the Hyp degradation pathway, hydroxyproline dehydrogenase (HYPDH), represents a promising therapeutic target for reducing endogenous oxalate production in these individuals. This is supported by the observation that individuals with inherited mutations in HYPDH (PRODH2 gene) have no pathological consequences. The creation of mouse models that do not express HYPDH will facilitate research evaluating HYPDH as a target. We describe the phenotype of the Prodh2 knock out mouse model and show that the lack of HYPDH in PH mouse models results in lower levels of urinary oxalate excretion, consistent with our previous metabolic tracer and siRNA-based knockdown studies. The double knockout mouse, Grhpr KO (PH2 model) and Prodh2 KO, prevented calcium-oxalate crystal deposition in the kidney, when placed on a 1% Hyp diet. These observations support the use of the Grhpr KO mice to screen HYPDH inhibitors in vivo. Altogether these data support HYPDH as an attractive therapeutic target for PH2 and PH3 patients.

Development and Validation of a New Gas Chromatography-Tandem Mass Spectrometry Method for the Measurement of Enrichment of Glyoxylate Metabolism Analytes in Hyperoxaluria Patients Using a Stable Isotope Procedure.

Primary hyperoxalurias (PH) are inborn errors of glyoxylate metabolism characterized by an increase in endogenous oxalate production. Oxalate overproduction may cause calcium-oxalate crystal formation leading to kidney stones, nephrocalcinosis, and ultimately kidney failure. Twenty-four hour urine oxalate excretion is an inaccurate measure for endogenous oxalate production in PH patients and not applicable in those with kidney failure. Treatment efficacy cannot be assessed with this measure during clinical trials. We describe the development and validation of a gas chromatography-tandem mass spectrometry method to analyze the samples obtained following a stable isotope infusion protocol of 13C2-oxalate and 1-13C-glycolate in both healthy individuals and PH patients. Isotopic enrichments of plasma oxalate, glycolate, and glyoxylate were measured on a gas chromatography-triple quadrupole mass spectrometry system using ethylhydroxylamine and N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) for analyte derivatization. Method precision was good for oxalate and glycolate (coefficients of variation [CV] were <6.3% and <4.2% for inter- and intraday precision, respectively) and acceptable for glyoxylate (CV <18.3% and <6.7% for inter- and intraday precision, respectively). The enrichment curves were linear over the specified range. Sensitivity was sufficient to accurately analyze enrichments. This new method allowed calculation of kinetic features of these metabolites, thus enabling a detailed analysis of the various pathways involved in glyoxylate metabolism. The method will further enhance the investigation of the metabolic PH derangements, provides a tool to accurately assess the therapeutic efficacy of new promising therapeutic interventions for PH, and could serve as a clinical tool to improve personalized therapeutic strategies.