Novel CAD gene mutations in a boy with developmental and epileptic encephalopathy 50 with dramatic response to uridine therapy: a case report and a review of the literature.

BACKGROUND: Developmental and epileptic encephalopathy-50 (DEE-50) is a rare clinical condition believed to be caused by a mutation in the CAD gene and is associated with a bleak prognosis. CAD-related diseases have a wide range of clinical manifestations and other symptoms that may be easily overlooked. Like other rare diseases, the clinical manifestations and the treatment of DEE-50 necessitate further investigation. CASE PRESENTATION: A 1-year-old male patient presented with developmental delay, seizures, and anaemia at 3 months of age. He further developed refractory status epilepticus (SE), rapid deterioration of cognitive and motor function, and even became comatose at 5 months of age. Whole-exome sequencing of trios (WES-trios) revealed a compound heterozygous variant in the CAD gene, with one locus inherited from his father (c.1252C>T: p.Q418* nonsense mutation) and one from his mother (c.6628G>A: p.G2210S, missense mutation). This compound heterozygous CAD variant was unreported in the Human Gene Mutation Database. After uridine treatment, his cognitive faculties dramatically improved and he remained seizure-free. Forty two cases with CAD gene mutation reported in the literatures were reviewed. Among them, 90% had onset before 3 years of age, with average of 1.6±1.8 years old. The average age of diagnosis was 7.7 ± 10 years. The mortality rate was approximately 9.5%, with all reported deaths occurring in patients without uridine treatment. The clinical entity could be improved dramatically when the patient treated with uridine. CONCLUSIONS: We present a boy with DEE 50 caused by novel CAD gene mutations and reviewed the clinical features of 42 patients reported previously. DEE 50 has early onset, refractory seizures, even status epilepticus leading to death, with favorable response to treatment with oral uridine. Early uridine treatment is recommended if CAD defect is suspected or genetically diagnosed. This study enhances the knowledge of DEE 50 and expands the spectrum of CAD gene mutations.

Complement C3-Deficiency-Induced Constipation in FVB/N-C3em1Hlee/Korl Knockout Mice Was Significantly Relieved by Uridine and Liriope platyphylla L. Extracts.

Complement component 3 (C3) deficiency has recently been known as a cause of constipation, without studies on the therapeutic efficacy. To evaluate the therapeutic agents against C3-deficiency-induced constipation, improvements in the constipation-related parameters and the associated molecular mechanisms were examined in FVB/N-C3em1Hlee/Korl knockout (C3 KO) mice treated with uridine (Urd) and the aqueous extract of Liriope platyphylla L. (AEtLP) with laxative activity. The stool parameters and gastrointestinal (GI) transit were increased in Urd- and AEtLP-treated C3 KO mice compared with the vehicle (Veh)-treated C3 KO mice. Urd and AEtLP treatment improved the histological structure, junctional complexes of the intestinal epithelial barrier (IEB), mucin secretion ability, and water retention capacity. Also, an improvement in the composition of neuronal cells, the regulation of excitatory function mediated via the 5-hydroxytryptamine (5-HT) receptors and muscarinic acetylcholine receptors (mAChRs), and the regulation of the inhibitory function mediated via the neuronal nitric oxide synthase (nNOS) and inducible NOS (iNOS) were detected in the enteric nervous system (ENS) of Urd- and AEtLP-treated C3 KO mice. Therefore, the results of the present study suggest that C3-deficiency-induced constipation can improve with treatment with Urd and AEtLP via the regulation of the mucin secretion ability, water retention capacity, and ENS function.

Two patients with fluoropyrimidine overdose successfully managed without uridine triacetate.

INTRODUCTION: In this case report we describe two patients with 5-fluorouracil (5-FU) overdose due to an unintentional increased infusion rate in which treatment with uridine triacetate was considered. Where previous case reports focus on the use of uridine triacetate in case of toxicity, this case report shows why it should be considered to abstain from the use of uridine triacetate. CASE REPORTS: The first patient is a 71-year-old woman who received 1200 mg/m2 5-FU in 2 h instead of 23 h. The second patient is a 74-year-old woman who received 2600 mg/m2 5-FU in 13 h instead of 24 h. The DPYD genotype of both patients was tested before the start of therapy and was found to be normal. MANAGEMENT & OUTCOME: Both patients received best supportive care and were admitted to the intensive care unit for monitoring of acute manifestations of toxicity. The first patient did not develop toxicity. The second patient did develop toxicity, but recovered completely. DISCUSSION: The rationale for abstaining from the use of uridine triacetate was the inadequacy of evidence backing its clinical and cost-effectiveness and the fact that uridine triacetate is not registered for the use in the European Union. Comparison of clinical outcomes of the already published open-label cohort with clinical outcomes of a comparable, well-described, best supportive care cohort is required before the added value of uridine triacetate can be determined. In addition, there is a need for a valid predictor of toxicity after fluoropyrimidine overdose.

Uridine Derivatives: Synthesis, Biological Evaluation, and In Silico Studies as Antimicrobial and Anticancer Agents.

Nucleoside analogs are frequently used in the control of viral infections and neoplastic diseases. However, relatively few studies have shown that nucleoside analogs have antibacterial and antifungal activities. In this study, a fused pyrimidine molecule, uridine, was modified with various aliphatic chains and aromatic groups to produce new derivatives as antimicrobial agents. All newly synthesized uridine derivatives were analyzed by spectral (NMR, FTIR, mass spectrometry), elemental, and physicochemical analyses. Prediction of activity spectra for substances (PASS) and in vitro biological evaluation against bacteria and fungi indicated promising antimicrobial capability of these uridine derivatives. The tested compounds were more effective against fungal phytopathogens than bacterial strains, as determined by their in vitro antimicrobial activity. Cytotoxicity testing indicated that the compounds were less toxic. In addition, antiproliferative activity against Ehrlich ascites carcinoma (EAC) cells was investigated, and compound 6 (2',3'-di-O-cinnamoyl-5'-O-palmitoyluridine) demonstrated promising anticancer activity. Their molecular docking against Escherichia coli (1RXF) and Salmonella typhi (3000) revealed notable binding affinities and nonbonding interactions in support of this finding. Stable conformation and binding patterns/energy were found in a stimulating 400 ns molecular dynamics (MD) simulation. Structure-activity relationship (SAR) investigation indicated that acyl chains, CH3(CH2)10CO-, (C6H5)3C-, and C2H5C6H4CO-, combined with deoxyribose, were most effective against the tested bacterial and fungal pathogens. Pharmacokinetic predictions were examined to determine their ADMET characteristics, and the results in silico were intriguing. Finally, the synthesized uridine derivatives demonstrated increased medicinal activity and high potential for future antimicrobial/anticancer agent(s).

Effect of Chronic Treatment with Uridine on Cardiac Mitochondrial Dysfunction in the C57BL/6 Mouse Model of High-Fat Diet-Streptozotocin-Induced Diabetes.

Long-term hyperglycemia in diabetes mellitus is associated with complex damage to cardiomyocytes and the development of mitochondrial dysfunction in the myocardium. Uridine, a pyrimidine nucleoside, plays an important role in cellular metabolism and is used to improve cardiac function. Herein, the antidiabetic potential of uridine (30 mg/kg/day for 21 days, i.p.) and its effect on mitochondrial homeostasis in the heart tissue were examined in a high-fat diet-streptozotocin-induced model of diabetes in C57BL/6 mice. We found that chronic administration of uridine to diabetic mice normalized plasma glucose and triglyceride levels and the heart weight/body weight ratio and increased the rate of glucose utilization during the intraperitoneal glucose tolerance test. Analysis of TEM revealed that uridine prevented diabetes-induced ultrastructural abnormalities in mitochondria and sarcomeres in ventricular cardiomyocytes. In diabetic heart tissue, the mRNA level of Ppargc1a decreased and Drp1 and Parkin gene expression increased, suggesting the disturbances of mitochondrial biogenesis, fission, and mitophagy, respectively. Uridine treatment of diabetic mice restored the mRNA level of Ppargc1a and enhanced Pink1 gene expression, which may indicate an increase in the intensity of mitochondrial biogenesis and mitophagy, and as a consequence, mitochondrial turnover. Uridine also reduced oxidative phosphorylation dysfunction and suppressed lipid peroxidation, but it had no significant effect on the impaired calcium retention capacity and potassium transport in the heart mitochondria of diabetic mice. Altogether, these findings suggest that, along with its hypoglycemic effect, uridine has a protective action against diabetes-mediated functional and structural damage to cardiac mitochondria and disruption of mitochondrial quality-control systems in the diabetic heart.

Mitochondrial Homeostasis and Mast Cells in Experimental Hepatic Ischemia-Reperfusion Injury of Rats.

BACKGROUND: Ischemia-reperfusion injury is a histopathological event and is an important cause of morbidity and mortality after hepatobiliary surgery. We aimed to investigate the protective effect of uridine on hepatic ischemia-reperfusion injury in rats. METHODS: The animals were divided into 4 groups (n = 8): group I (control), group II: ischemia-reperfusion (30 minutes ischemia and 120 minutes reperfusion), group III: ischemia-reperfusion+uridine (at the beginning of reperfusion), and group IV: ischemia-reperfusion+uridine (5 minutes before ischemia-reperfusion). Uridine was administered a single dose of 30 mg/kg IV. The 3 elements of the hepatoduodenal ligament (hepatic artery, portal vein, and biliary tract) were obliterated for 30 minutes. Then hepatic reperfusion was achieved for 120 minutes. RESULTS: In the ischemia-reperfusion group, both liver tissues and serum chymase activity and high-temperature requirement A2 levels were higher. Severe central vein dilatation and congestion, widening sinusoidal range, diffuse necrotic hepatocytes and dense erythrocyte accumulation in sinusoids, and strongly inducible nitric oxide synthase expression were seen in the ischemia-reperfusion group. A clear improvement was seen in both uridine co-administration and pretreatment groups. CONCLUSION: Our results revealed that uridine limits the development of liver damage under conditions of ischemia-reperfusion, thus contributing to an increase in hepatocyte viability.

[New Analogues of Uridine as Possible Anti-Viral Agents Specific to SARS-CoV-2].

The development of specific drugs against SARS-CoV-2 infection is a major challenge facing global science and healthcare. Despite numerous attempts, there are still no truly effective drugs. Currently, the main approach in the creation of drugs against COVID-19 is repurposing, i.e., re-profiling existing drugs approved for medical use, for example, the use of a drug for the treatment of Ebola-Remdesivir, and the use of a drug for the treatment of influenza-Favipiravir. However, it is already obvious that these drugs are not specific enough nor effective enough. Another promising approach is the creation of new molecules, but it should be noted immediately that implementation requires much more time and costs. However, the search for new SARS-CoV-2 specific antiviral agents continues. The aim of our work was the creation of new 5-substituted uridine derivatives as potential inhibitors of coronavirus RNA-dependent RNA polymerase. The substances were obtained in high yields by the Suzuki-Miyaura reaction and characterized using modern physicochemical methods. However, testing of their antiviral activity against SARS-CoV-2 did not reveal a significant inhibitory effect.

Uridine alleviates carbon tetrachloride-induced liver fibrosis by regulating the activity of liver-related cells.

At present, liver fibrosis is a major challenge of global health. When hepatocyte regeneration cannot compensate for hepatocyte death, it will develop into liver fibrosis in chronic liver disease. Initially, collagen produced by myofibroblasts plays a role in maintaining liver integrity, but excessive collagen accumulation can inhibit the residual liver function, leading to liver failure. At present, many scientists are actively looking for drugs to alleviate liver fibrosis. In the current study, we investigated the potential role of uridine in the treatment of liver fibrosis (uridine is a plant/animal-derived pyrimidine nucleoside, therefore uridine can also be ingested and absorbed by the body, accompanied by the process of food intake). For this, we systematically studied the effect of uridine on CCl4-induced liver fibrosis in vitro and in vivo through a series of technologies, such as Western blot, laser confocal scanning microscope, ELISA and immunohistochemistry. The experimental results showed that uridine can effectively reduce the accumulation of collagen in liver. Furthermore, uridine can improve the activity of liver cells and alleviate CCl4-induced liver injury. Furthermore, uridine can significantly alleviate the risk factors caused by hepatic stellate cell activation, uridine treatment significantly down-regulated the expression of α-SMA, collagen type-I and fibronectin. In conclusion, the current research shows that uridine can alleviate CCl4-induced liver fibrosis, suggesting that uridine can be used as a potential drug to alleviate liver fibrosis.

Oral hypomethylating agents: beyond convenience in MDS.

Oral hypomethylating agents (HMAs) represent a substantial potential boon for patients with myelodysplastic syndrome (MDS) who have previously required between 5 and 7 visits per month to an infusion clinic to receive therapy. For patients who respond to treatment, ongoing monthly maintenance visits represent a considerable burden to quality of life, and for those who are early in therapy, these sequential visits may tax transportation and financial resources that would be optimally distributed over the treatment cycle to facilitate transfusion support. The availability of oral HMAs may support the optimal application of these agents by contributing to adherence and lessening the burden of therapy, potentially encouraging patients to stay on longer-term treatment. Distinct pharmacokinetic profiles for the recently approved oral HMAs (oral azacitidine and decitabine-cedazuridine) result in differential toxicity profiles and have prompted their clinical trial development in lower- and higher-risk MDS, respectively.

Uridine Treatment of the First Known Case of SLC25A36 Deficiency.

SLC25A36 is a pyrimidine nucleotide carrier playing an important role in maintaining mitochondrial biogenesis. Deficiencies in SLC25A36 in mouse embryonic stem cells have been associated with mtDNA depletion as well as mitochondrial dysfunction. In human beings, diseases triggered by SLC25A36 mutations have not been described yet. We report the first known case of SLC25A36 deficiency in a 12-year-old patient with hypothyroidism, hyperinsulinism, hyperammonemia, chronical obstipation, short stature, along with language and general developmental delay. Whole exome analysis identified the homozygous mutation c.803dupT, p.Ser269llefs*35 in the SLC25A36 gene. Functional analysis of mutant SLC25A36 protein in proteoliposomes showed a virtually abolished transport activity. Immunoblotting results suggest that the mutant SLC25A36 protein in the patient undergoes fast degradation. Supplementation with oral uridine led to an improvement of thyroid function and obstipation, increase of growth and developmental progress. Our findings suggest an important role of SLC25A36 in hormonal regulations and oral uridine as a safe and effective treatment.

Uridine treatment prevents myocardial injury in rat models of acute ischemia and ischemia/reperfusion by activating the mitochondrial ATP-dependent potassium channel.

The effect of uridine on the myocardial ischemic and reperfusion injury was investigated. A possible mechanism of its cardioprotective action was established. Two rat models were used: (1) acute myocardial ischemia induced by occlusion of the left coronary artery for 60 min; and (2) myocardial ischemia/reperfusion with 30-min ischemia and 120-min reperfusion. In both models, treatment with uridine (30 mg/kg) prevented a decrease in cell energy supply and in the activity of the antioxidant system, as well as an increase in the level of lipid hydroperoxides and diene conjugates. This led to a reduction of the necrosis zone in the myocardium and disturbances in the heart rhythm. The blocker of the mitochondrial ATP-dependent potassium (mitoKATP) channel 5-hydroxydecanoate limited the positive effects of uridine. The data indicate that the cardioprotective action of uridine may be related to the activation of the mitoKATP channel. Intravenously injected uridine was more rapidly eliminated from the blood in hypoxia than in normoxia, and the level of the mitoKATP channel activator UDP in the myocardium after uridine administration increased. The results suggest that the use of uridine can be a potentially effective approach to the management of cardiovascular diseases.

Anti-Apoptotic and Anti-Oxidant Effects of Systemic Uridine Treatment in an Experimental Model of Sciatic Nerve Injury.

AIM: To investigate the anti-apoptotic and anti-oxidant effects of systemic uridine treatment in a rat model of sciatic nerve injury. MATERIAL AND METHODS: Thirty-two adult male rats were equally randomized to Sham, Control, U100, and U500 groups. Sham rats received a sham operation by exposing the right sciatic nerve without transection, while those in the Control, U100, and U500 groups underwent right sciatic nerve transection followed by immediate primary anostomosis. Sham and Control groups received saline (0.9% NaCl) injections intraperitoneally (i.p.), while U100 and U500 groups received 100 mg/kg and 500 mg/kg uridine injections (i.p.), respectively, once a day for 7 days after the surgery. Rats in all the groups were sacrificed on the eighth day; sciatic nerve samples were analyzed for apoptosis by Western Blotting and for oxidation parameters including myeloperoxidase (MPO), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) by Enzyme-Linked Immunosorbent Assay (ELISA). RESULTS: Uridine treatment at the dose of 500 mg/kg significantly decreased as apoptosis determined by Caspase-3/Actin ratio and exhibited significant anti-oxidant effects as determined by decreased levels of MPO and MDA as well as increased levels of SOD, GPx, and CAT compared to controls. Uridine at 100 mg/kg was only found to decrease the Caspase-3/Actin ratio, although it significantly decreased MDA and increased CAT levels compared to controls. CONCLUSION: Treatment with uridine reduces apoptosis and oxidation in a rat model of sciatic nerve injury dose-dependently. Thus, uridine may be beneficial in peripheral nerve regeneration by exhibiting anti-apoptotic and anti-oxidant effects.

Triacetyluridine treats epileptic encephalopathy from CAD mutations: a case report and review.

Refractory epilepsy and encephalopathy are frequently encountered in patients with inborn errors of metabolism. We report a case of an 8-year-old girl with history of developmental delay, autism and intractable epilepsy that was found to have a pathogenic variant in CAD. We briefly review the biochemical pathway of CAD and the preclinical and clinical studies that suggest uridine supplementation can rescue the CAD deficiency phenotypes. Our case demonstrates a relatively late-onset case of refractory epilepsy with a rapid response to treatment using the uridine pro-drug triacetyluridine (TAU), the FDA-approved treatment for hereditary orotic aciduria.

Prospects for the use of regulators of oxidative stress in the comprehensive treatment of the novel Coronavirus Disease 2019 (COVID-19) and its complications.

Some surface proteins of the newly identified severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can bind to the hemoglobin molecule of an erythrocyte, which leads to the destruction of the structure of the heme and the release of harmful iron ions to the bloodstream. The degradation of hemoglobin results in the impairment of oxygen-carrying capacity of the blood, and the accumulation of free iron enhances the production of reactive oxygen species. Both events can lead to the development of oxidative stress. In this case, oxidative damage to the lungs leads then to the injuries of all other tissues and organs. The use of uridine, which preserves the structure of pulmonary alveoli and the air-blood barrier of the lungs in the course of experimental severe hypoxia, and dihydroquercetin, an effective free radical scavenger, is promising for the treatment of COVID-19. These drugs can also be used for the recovery of the body after the severe disease.

Decitabine/Cedazuridine: First Approval.

A fixed dose oral combination (FDC) of decitabine and cedazuridine (Inqovi®), is being developed by Astex Pharmaceuticals (a subsidiary of Otsuka Pharmaceuticals) for the treatment of various cancers like myelodysplastic syndromes (MDS), chronic myelomonocytic leukaemia (CMML), acute myeloid leukaemia (AML), glioma and solid tumours. Decitabine, a DNA methyltransferase inhibitor approved for the treatment of MDS and CMML, is degraded by cytidine deaminase in the gastrointestinal tract and liver, thereby limiting oral bioavailability. Cedazuridine is a proprietary, patented cytidine deaminase inhibitor that, when added to decitabine, increases oral bioavailability of the drug. In July 2020, decitabine/cedazuridine received its first approval in the USA and Canada for the treatment of MDS and CMML. In the USA, it is indicated for use in adults with MDS and CMML, including previously treated and untreated, de novo and secondary MDS with the following French-American-British subtypes (refractory anaemia, refractory anaemia with ringed sideroblasts, refractory anaemia with excess blasts and CMML) and intermediate-1, intermediate-2 and high-risk International Prognostic Scoring System groups. Clinical studies for AML, glioma and solid tumours are underway in several countries worldwide. This article summarizes the milestones in the development of decitabine/cedazuridine leading to this first approval for the treatment of MDS and CMML.

Oral Azacitidine and Cedazuridine Approximate Parenteral Azacitidine Efficacy in Murine Model.

BACKGROUND: DNA methyltransferase inhibitors (DNMTis) improve survival for patients with myelodysplastic syndromes (MDS) and those with acute myeloid leukemia (AML) unable to receive standard cytotoxic chemotherapy and are, accordingly, the backbone of standard-of-care treatment for these conditions. Standard regimens with DNMTIs, decitabine (DEC) or azacitidine (AZA) include daily subcutaneous (s.c.) or intravenous (i.v.) administration for 5-7 consecutive days. Attempts to provide the therapy orally have been limited given rapid clearance of the agents by the enzyme cytidine deaminase (CDA), which is ubiquitous in the gut and liver as part of first-pass metabolism. Recently, cedazuridine (CDZ), an oral inhibitor of CDA, was successfully combined with DEC to approximate the pharmacokinetics of i.v. DEC in patients. OBJECTIVE: To determine if an oral dosing strategy might be feasible in the clinic with AZA, we attempted to increase the bioavailability of oral AZA through the use of CDZ, in a murine model. METHODS: Following pharmacokinetic and pharmacodynamic assessment of oral AZA dosed with CDZ in murine and monkey models, we tested this regimen in vivo with a human cell line-derived xenograft transplantation experiment (CDX). Following this we combined the regimen with venetoclax (VEN) to test the efficacy of an all-oral regimen in a patient-derived xenograft (PDX) model. RESULTS: Parenteral AZA and oral AZA + CDZ exhibited similar pharmacokinetic profiles, and efficacy against human AML cells. Tumor regression was seen with AZA + CDZ in MOLM-13 CDX and PDX models. CONCLUSIONS: We conclude that oral AZA when combined with CDZ achieves successful tumor regression in both CDX and PDX models. Furthermore, the combination of AZA + CDZ with VEN in a PDX model emulated responses seen with VEN + AZA in the clinic, implying a potential all-oral VEN-based therapy opportunity in myeloid diseases.

Uridine as a protector against hypoxia-induced lung injury.

The effect of the activation of the mitochondrial ATP-dependent potassium channel (mitoKATP) on the ultrastructure of rat lung in acute hypoxic hypoxia (7% of oxygen in nitrogen, exposure 30 min) was studied. It was shown that uridine, a precursor of the mitoKATP activator UDP, exerted a protective effect against hypoxic damage to the lung. The administration of uridine to animals prior to hypoxia decreased the number of mitochondria with altered ultrastructure and prevented the hypoxia-induced mitochondrial swelling. Uridine also protected the epithelial, interstitial and endothelial layers of the air-blood barrier from the hypoxia-induced hyperhydration. The protective action of uridine against hypoxia-induced lung injury was eliminated by the selective blocker of mitoKATP 5-hydroxydecanoate. These data suggest that one of the mechanisms of the positive effect of uridine is related to the activation of the mitoKATP channel, which, according to the literature and our data, is involved in the protection of tissues from hypoxia and leads to adaptation to it. A possible role of uridine in the maintenance of the mitochondrial structure upon hypoxia-induced lung injury and the optimization of oxygen supply of the organism is discussed.

Efficacy and safety of a two-drug direct-acting antiviral agent regimen ruzasvir 180 mg and uprifosbuvir 450 mg for 12 weeks in adults with chronic hepatitis C virus genotype 1, 2, 3, 4, 5 or 6.

Ruzasvir (MK-8408, an NS5A inhibitor) and uprifosbuvir (MK-3682, a nonstructural protein 5B nucleotide inhibitor) are highly potent direct-acting antiviral agents for the treatment of hepatitis C virus (HCV) infection. A phase III clinical trial evaluating the two-drug combination of ruzasvir 60 mg plus uprifosbuvir 450 mg suggested suboptimal efficacy in certain HCV genotypes (C-BREEZE 1; NCT02759315). The aim of the present study was to evaluate the efficacy and safety of ruzasvir in combination with uprifosbuvir administered at a higher dose than that assessed in the earlier study (C-BREEZE 2: NCT02956629/Merck protocol PN041). Treatment-naïve or interferon (with or without ribavirin)-experienced participants with or without compensated cirrhosis were enrolled. All participants received ruzasvir 180 mg plus uprifosbuvir 450 mg once daily for 12 weeks. The primary objectives were the proportion of participants with HCV RNA <15 lU/mL at 12 weeks after the end of study therapy (SVR12), and safety and tolerability of the study drug. Overall, 282 participants were enrolled. SVR12 (n/N) was 91.3% (42/46) in participants infected with HCV genotype (GT) 1a; GT1b, 96.7% (29/30); GT2, 91.5% (43/47); GT3, 73.8% (45/61); GT4, 98.2% (55/56); GT5, 100.0% (18/18); and GT6, 90.9% (20/22). Adverse events (AEs) were reported by 61.3% of participants; drug-related AEs were reported by 33.3%. The most frequent (≥5% of participants) drug-related AEs in all participants were fatigue (7.8%) and headache (7.4%). In conclusion, the two-drug combination of ruzasvir 180 mg plus uprifosbuvir 450 mg for 12 weeks was highly effective and well tolerated in participants infected with HCV GT1, GT2, GT4, GT5 and GT6, with a lower efficacy in GT3-infected persons.