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Equilibrative nucleoside transporters (ENTs) 1 and 2 facilitate nucleoside transport across the blood-testis barrier (BTB). Improving drug entry into the testes with drugs that use endogenous transport pathways may lead to more effective treatments for diseases within the reproductive tract. In this study, CRISPR/CRISPR-associated protein 9 was used to generate HeLa cell lines in which ENT expression was limited to ENT1 or ENT2. We characterized uridine transport in these cell lines and generated Bayesian models to predict interactions with the ENTs. Quantification of [(3)H]uridine uptake in the presence of the ENT-specific inhibitor S-(4-nitrobenzyl)-6-thioinosine (NBMPR) demonstrated functional loss of each transporter. Nine nucleoside reverse-transcriptase inhibitors and 37 nucleoside/heterocycle analogs were evaluated to identify ENT interactions. Twenty-one compounds inhibited uridine uptake and abacavir, nevirapine, ticagrelor, and uridine triacetate had different IC(50) values for ENT1 and ENT2. Total accumulation of four identified inhibitors was measured with and without NBMPR to determine whether there was ENT-mediated transport. Clofarabine and cladribine were ENT1 and ENT2 substrates, whereas nevirapine and lexibulin were ENT1 and ENT2 nontransported inhibitors. Bayesian models generated using Assay Central machine learning software yielded reasonably high internal validation performance (receiver operator characteristic > 0.7). ENT1 IC(50)-based models were generated from ChEMBL; subvalidations using this training data set correctly predicted 58% of inhibitors when analyzing activity by percent uptake and 63% when using estimated-IC(50) values. Determining drug interactions with these transporters can be useful in identifying and predicting compounds that are ENT1 and ENT2 substrates and can thereby circumvent the BTB through this transepithelial transport pathway in Sertoli cells. SIGNIFICANCE STATEMENT: This study is the first to predict drug interactions with equilibrative nucleoside transporter (ENT) 1 and ENT2 using Bayesian modeling. Novel CRISPR/CRISPR-associated protein 9 functional knockouts of ENT1 and ENT2 in HeLa S3 cells were generated and characterized. Determining drug interactions with these transporters can be useful in identifying and predicting compounds that are ENT1 and ENT2 substrates and can circumvent the blood-testis barrier through this transepithelial transport pathway in Sertoli cells.

A 56-year-old woman with history of hypertension, inadequately controlled on hydrochlorothiazide and nebivolol, presented with colorectal cancer with metastases to the liver in 2019. Genotypic testing revealed that her colorectal cancer was KRAS/NRAS wild-type and microsatellite stable. FOLFOX was

Fluoropyrimidine-based regimens are among the most commonly used chemotherapy combinations for the treatment of solid tumors. Several genetic polymorphisms that are implicated with fluoropyrimidine anabolism and catabolism have been associated with the development of life-threatening toxicities. Uridine triacetate is an FDA-approved antidote for 5-fluorouracil or capecitabine overdose and early-onset, life-threatening toxicity within 96 h of last chemotherapy dose. To date, it is not accessible for Greek patients as per the current summary of product characteristic's time restrictions. We report and discuss the course and outcome of capecitabine toxicity in a 66-year-old female colorectal cancer patient with heterozygous dihydropyrimidine dehydrogenase deficiency. This paper highlights the difficulty in timely access of this lifesaving medication for Greek and possibly other European patients.

Introduction: In 2015, vistogard was approved both the US FDA and the European Medicines Agency (EMA) as an antidote in the treatment of 5-FU poisoning following an overdose of 5-FU or capecitabine or in patients exhibiting early-onset, severe or life-threatening toxicity affecting the cardiac or central nervous system, and/or early-onset, unusually severe adverse reactions (e.g. gastrointestinal toxicity and/or neutropenia) within 96 h following the end of 5-FU or capecitabine administration.Areas covered: This paper reviews the history of the development of vistogard (uridine triacetate) to its current status in clinical practice. Vistogard is an orally active prodrug of uridine, which has made a more effective uridine administration technique possible to improve the tolerability of intravenous and oral fluoropyrimidines, including capecitabine. In addition to preclinical data, we also reviewed the data on all the published patients who received vistogard secondary to overdosed 5-FU or capecitab...

Hereditary orotic aciduria (HOA) is a very rare inborn error of pyrimidine metabolism. It results from a defect of the uridine-5-monophosphate synthase (UMPS) gene. To date, only about twenty patients have been described. We report a case of HOA with a novel variant in the UMPS gene. A 17-year-old Emirati girl was born to first-cousin parents. During the first year, she had recurrent, severe infections including disseminated varicella. After evaluation for immunodeficiency, an impression of immunodeficiency of unknown etiology was presumed. Frequent episodes of pancytopenia were also noted. Bone marrow biopsy showed trilineage megaloblastoid maturation with dysplastic changes that were refractory to hematinic therapy. Also, she was noted to have failure to thrive, developmental delay and epilepsy. She was referred to the Genetics clinic where whole-exome sequencing (WES) was done and showed a novel homozygous variant in the UMPS gene confirming a diagnosis of HOA. She was started on uridine triacetate after which she showed clinical, hematologic and biochemical improvement. Although extremely rare, hereditary orotic aciduria should be suspected in any child with megaloblastic bone marrow, immunodeficiency or when developmental delay and anemia coexist.

5-Fluorouracil (5-FU) remains to be the backbone of chemotherapy regimens approved for treatment of colorectal cancer and other gastrointestinal cancers and breast cancer. The incidence of cardiotoxicity associated with 5-FU ranges from 1.5–18%. Previous studies also concluded that rechallenging a patient with previous 5-FU cardiotoxicity with either lower dose or another mode of administration could result in repeat of cardiac complication in up to 45% of patients. Nearly 13% of patients died upon re-exposure to 5-FU. Clinical manifestations of cardiac complications of fluoropyrimidines including angina, myocardial infarction, arrhythmias, hypotension, Tako-Tsubo syndrome, heart failure, cardiogenic shock, pericarditis, and even sudden death have been reported. Cardiotoxicity is unpredictable and no alternative chemotherapeutics have been defined so far. The author describes here treatment options for patients with metastatic colorectal cancer who have encountered fluoropyrimidine-induced cardiotoxicity, including switching to a different fluoropyrimidine, switching to a different schedule of intravenous 5-FU, or switching to a non-fluoropyrimidine-containing chemotherapy regimen if one exists. Switching to a non-fluoropyrimidine-containing chemotherapy regimen is usually the most feasible choice for patients with metastatic disease as data on adjuvant setting is usually a fluoropyrimidine or its combination with oxaliplatin at present.

Purpose BiallelicCADvariants underlie CAD deficiency (or early infantile epileptic encephalopathy-50, [EIEE-50]), an error of pyrimidine de novo biosynthesis amenable to treatment via the uridine salvage pathway. We further define the genotype and phenotype with a focus on treatment. Methods Retrospective case series of 20 patients. Results Our study confirms CAD deficiency as a progressive EIEE with recurrent status epilepticus, loss of skills, and dyserythropoietic anemia. We further refine the phenotype by reporting a movement disorder as a frequent feature, and add that milder courses with isolated developmental delay/intellectual disability can occur as well as onset with neonatal seizures. With no biomarker available, the diagnosis relies on genetic testing and functional validation in patient-derived fibroblasts. Underlying pathogenic variants are often rated as variants of unknown significance, which could lead to underrecognition of this treatable disorder. Supplementation with uridine, uridine monophosphate, or uridine triacetate in ten patients was safe and led to significant clinical improvement in most patients. Conclusion We advise a trial with uridine (monophosphate) in all patients with developmental delay/intellectual disability, epilepsy, and anemia; all patients with status epilepticus; and all patients with neonatal seizures until (genetically) proven otherwise or proven unsuccessful after 6 months. CAD deficiency might represent a condition for genetic newborn screening.

Objectives Uridine was conjugated with fatty acids to improve the drug lipophilicity and the interaction with phospholipid bilayers. Methods The esterification reaction using carbodiimides compounds as coupling agents and a nucleophilic catalyst allowed us to synthesize tri-acyl ester derivatives of uridine with fatty acids. Analysis of molecular interactions between these tri-acyl ester derivatives and l-α-dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles (MLV) – as a mammalian cell membrane model – have been performed by differential scanning calorimetry (DSC). Key findings The DSC thermograms suggest that nucleoside and uridine triacetate softly interact with phospholipidic multilamellar vesicles which are predominantly located between the polar phase, whereas the tri-acyl ester derivatives with fatty acids (myristic and stearic acids) present a strongly interaction with the DMPC bilayer due to the nucleoside and aliphatic chains parts which are oriented towards the polar and lipophilic phases of the phospholipidic bilayer, respectively. However, the effects caused by the tri-myristoyl uridine and tri-stearoyl uridine are different. Conclusions We show how the structural changes of uridine modulate the calorimetric behaviour of DMPC shedding light on their affinity with the phospholipidic biomembrane model.

Uridine triacetate (Vistogard®) provides a much-needed emergency treatment for fluorouracil and capecitabine overdose or early-onset severe toxicity, both of which are associated with significant morbidity and mortality. In two pooled open-label clinical studies, uridine triacetate initiated as soon as possible within 96 h of fluorouracil or capecitabine overdose or toxicity was associated with 30-day survival rates of 94% (96 and 81% in patients with overdose and early-onset severe toxicity, respectively), which compares very favourably with the rate of 16% in a historical cohort of patients who received best supportive care following fluorouracil overdose. Approximately one-third of cancer patients resumed chemotherapy in

BACKGROUND Increased susceptibility to 5-fluorouracil (5-FU)/capecitabine can lead to rapidly occurring toxicity caused by impaired clearance, dihydropyrimidine dehydrogenase deficiency, and other genetic variations in the enzymes that metabolize 5-FU. Life-threatening 5-FU overdoses occur because of infusion pump errors, dosage miscalculations, and accidental or suicidal ingestion of capecitabine. Uridine triacetate (Vistogard) was approved in 2015 for adult and pediatric patients who exhibit early-onset severe or life-threatening 5-FU/capecitabine toxicities or present with an overdose. Uridine triacetate delivers high concentrations of uridine, which competes with toxic 5-FU metabolites. METHODS In 2 open-label clinical studies, patients who presented with a 5-FU/capecitabine overdose or an early onset of severe toxicities were treated. Patients received uridine triacetate as soon as possible (most within the first 96 hours after 5-FU/capecitabine). Outcomes included survival, resumption of chemotherapy, and safety. Their survival was compared with the survival of a historical cohort of overdose patients who received only supportive care. RESULTS A total of 137 of 142 overdose patients (96%) treated with uridine triacetate survived and had a rapid reversal of severe acute cardiotoxicity and neurotoxicity; in addition, mucositis and leukopenia were prevented, or the patients recovered from them. In the historical cohort, 21 of 25 patients (84%) died. Among the 141 uridine triacetate–treated overdose patients with a diagnosis of cancer (the noncancer patients included 6 intentional or accidental pediatric overdoses), 53 resumed chemotherapy in

5-Fluorouracil (5-FU), an analog of uracil, is one of the most commonly used chemotherapeutic agents and like other agents has a narrow therapeutic index limited by toxicity. Compared to previous attempts, uridine triacetate (Vistogard) has shown to increase the potential efficacy of 5-FU by allowing administering a higher dose and decreasing the toxicity. Recently, Vistogard received orphan drug designation from the FDA as an antidote in the treatment of 5-FU poisoning and from the European Medicines Agency as a treatment for 5-FU overdose. However, no data have been published to date in humans who were rescued by this agent following severe toxicity associated with 5-FU due to dihydropyrimidine dehydrogenase (DPYD) deficiency, the enzyme which is responsible for the elimination of approximately 80 % of the administered dose of 5-FU. We identified two patients with advanced pancreatic cancer who were referred to us for testing of DPYD status following severe toxicity associated with 5-FU administered at a dose of 1400 mg/m2 weekly bolus high-dose 5-FU followed by oral uridine triacetate as a part of a clinical trail. One patient developed grade 3 thrombocytopenia and grade 3 skin rash that resolved with discontinuation of 5-FU and supportive care, while second patient developed grade 4 thrombocytopenia, grade 3 coagulopathy and grade 3 neurological toxicity with a fatal outcome. DPYD status was evaluated as we have previously published. The first patient was found to have an abnormally low DPYD activity of 0.087-nmol/min/mg protein by radioisotopic assay (reference normal range 0.182–0.688 nmol/min/mg protein). Because of pancytopenia, DPYD enzyme activity could not be assessed in patient 2; genotypic analysis of DPYD during autopsy revealed the presence of the heterozygous mutation, IVS14+1 G>A, DPYD*2A, now recognized as the most common cause of DPYD deficiency. These two patients present the first two cases of DPYD deficiency that had either delay in severe toxicity or recovered from severe toxicity as they received oral Vistogard as a part of the conical trial. Toxicity was delayed in both patients by a mean of 3.5 weeks (range 3–4 weeks), indicating that Vistogard might be able to delay 5-FU toxicity despite higher doses than standard bolus dose of 5-FU used in gastrointestinal malignancies and the appearance of a potentially less toxic adverse effect of 5-FU at an unusual site (cutaneous) in one patient. The role of uridine triacetate with 5-FU in DPYD-deficient patients needs further investigation.

Nucleoside O-glycosylation represents an archetypal problem in chemical selectivity, inasmuch as the nucleobase (an undesired site of reaction) is usually more nucleophilic than the hydroxyl (the desired site of reaction). Optimized reaction conditions have been developed for the efficient O-glycosylation of nucleoside hydroxyls. Both thioglycoside and Schmidt imidate donors (1.5 equiv) have been employed successfully. Interference by the nucleobase is minimized by the use of indium(III) triflate as the donor activating reagent; the In(OTf)3 serves to promote apparent transfer of the donor glycosyl moiety from nucleobase to hydroxyl. Glycosylation of uridine triacetate gives products resulting from O- and N-glycosylation of the pyrimidine ring.

Background Uncommon early-onset severe toxicities from 5-fluorouracil (5-FU) and capecitabine can be fatal if early warning signs are not recognized and treated promptly. Objectives This article delineates the differences between expected side effects and uncommon early-onset severe toxicities from 5-FU and capecitabine. It also provides background for understanding the reasons patients may develop these toxicities and reviews the efficacy of standard supportive care against a novel therapy (uridine triacetate). Methods A panel of nurses convened to review the literature about toxicities associated with 5-FU and capecitabine administration and determined methods to educate nurses about toxicities and treatment. Findings Standard supportive care for 5-FU and capecitabine toxicities is associated with high fatality rates. Uridine triacetate treatment within 96 hours of administration is associated with survival.

Fluoropyrimidines (5-fluorouracil and capecitabine) are antimetabolite drugs, widely used for the treatment of a variety of cancers, both in adjuvant and in metastatic setting. Although the most common toxicities of these drugs have been extensively studied, robust data and comprehensive characterization still lack concerning fluoropyrimidine-induced cardiotoxicity (FIC), an infrequent but potentially life-threatening toxicity. This review summarizes the current state of knowledge of FIC with special regard to proposed pathogenetic models (coronary vasospasm, endothelium and cardiomyocytes damage, toxic metabolites, dihydropyrimidine dehydrogenase deficiency); risk and predictive factors; efficacy and usefulness in detection of laboratory markers, electrocardiographic changes and cardiac imaging; and specific treatment, including a novel agent, uridine triacetate. The role of alternative chemotherapeutic options, namely raltitrexed and TAS-102, is discussed, and, lastly, we overview the most promising future directions in the research on FIC and development of diagnostic tools, including microRNA technology.

Fluorouracil and capecitabine are fluoropyrimidine chemotherapy agents that are commonly used for various cancers. These agents are generally well tolerated at standard doses; however, it has been reported that 31–34% of patients develop dose-limiting toxicities. Dihydropyrimidine dehydrogenase and thymidylate synthase play a major role in fluorouracil and capecitabine activity and toxicity. Uridine triacetate has shown promising results for the emergency treatment of patients who either receive an overdose of the cancer treatment fluorouracil or capecitabine or to treat patients who exhibit early-onset, severe, or life-threatening toxicity. We describe a case of a patient who developed capecitabine toxicity and was unsuccessfully treated with uridine triacetate.

According to the NIH, about 275 000 patients receive treatment with 5-Fluorouracil (5-FU) and more than 1300 die from 5-FU toxicity every year from life-threatening myelosuppression, gastrointestinal complications, and neurotoxicity. Immunocompromised persons are at higher risk of developing toxicity. Recently uridine triacetate (Vistagard®) has been approved by the Food and Drug Administration (FDA) as the only specific antidote available for 5-FU poisoning. In a clinical trial (n = 135), 96% of patients with 5-FU toxicity recovered after treatment, where as in a historical control group only 10% survived. This is the first published case report of survival after 5-FU overdose who also was immunocompromised from HIV/AIDs. A 52 year old male with history of HIV/AIDS (CD4 70), CNS toxoplasmosis and anal cancer presented to the emergency department after realizing he had received an entire course of 5-FU in 24 instead of 96 h. Treatment with uridine triacetate was arranged in the emergency department. After receiving treatment the patient was asymptomatic and had an uncomplicated hospital course. 5-FU poisoning must be recognized early as uridine triacetate is approved by the FDA for use within 96 h following the end of 5-FU administration. Emergency medicine physicians should promptly recognize and treat 5-FU poisoning. However, this may be challenging as patients may not seek medical attention until many hours or several days after last administration since symptoms are often delayed with 5-FU poisoning.

Nucleoside O-glycosylation represents an archetypal problem in chemical selectivity, inasmuch as the nucleobase (an undesired site of reaction) is usually more nucleophilic than the hydroxyl (the desired site of reaction). Optimized reaction conditions have been developed for the efficient O-glycosylation of nucleoside hydroxyls. Both thioglycoside and Schmidt imidate donors (1.5 equiv) have been employed successfully. Interference by the nucleobase is minimized by the use of indium(III) triflate as the donor activating reagent; the In(OTf)3 serves to promote apparent transfer of the donor glycosyl moiety from nucleobase to hydroxyl. Glycosylation of uridine triacetate gives products resulting from O- and N-glycosylation of the pyrimidine ring.

On December 11, 2015, the FDA approved uridine triacetate (VISTOGARD; Wellstat Therapeutics Corporation) for the emergency treatment of adult and pediatric patients following a fluorouracil or capecitabine overdose regardless of the presence of symptoms, and of those who exhibit early-onset, severe, or life-threatening toxicity affecting the cardiac or central nervous system, and/or early onset, unusually severe adverse reactions (e.g., gastrointestinal toxicity and/or neutropenia) within 96 hours following the end of fluorouracil or capecitabine administration. Uridine triacetate is not recommended for the nonemergent treatment of adverse reactions associated with fluorouracil or capecitabine because it may diminish the efficacy of these drugs, and the safety and efficacy of uridine triacetate initiated more than 96 hours following the end of administration of these drugs has not been established. The approval is based on data from two single-arm, open-label, expanded-access trials in 135 patients receiving uridine triacetate (10 g or 6.2 g/m2 orally every 6 hours for 20 doses) for fluorouracil or capecitabine overdose, or who exhibited severe or life-threatening toxicities within 96 hours following the end of fluorouracil or capecitabine administration. Ninety-six percent of patients met the major efficacy outcome measure, which was survival at 30 days or survival until the resumption of chemotherapy, if prior to 30 days. The most common adverse reactions were vomiting, nausea, and diarrhea. This article summarizes the FDA review of this New Drug Application, the data supporting approval of uridine triacetate, and the unique regulatory situations encountered by this approval. Clin Cancer Res; 22(18); 4545–49. ©2016 AACR.

Adverse drug reactions can be unpredictable. However, pharmacogenomic testing can help identify patients who may be more susceptible to the toxic effects of certain drugs. Genetic variations in the dihydropyrimidine dehydrogenase and thymidylate synthase genes have been shown to increase the risk of 5-fluorouracil toxicity. 5-Fluorouracil toxicity can be life threatening. Fortunately, there is treatment available for 5-fluorouracil toxicity, called uridine triacetate. Although, the indications for its use limit its administration to within 96 h of receiving 5-fluorouracil, we report a case of effective therapy in a patient started on uridine triacetate beyond the recommended 96 h, who was found to carry a thymidylate synthase gene variation but no dihydropyrimidine dehydrogenase mutations. This provides important implications for pharmacogenomic testing.

Nitrogen-containing compounds have been subjected to electrochemical oxidation with Et3N-3HF as an electrolyte. Caffeine afforded 8-fluorocaffeine as a sole product in 40.3% yield. Guanosine tetraacetate and uridine triacetate gave the fluorinated compounds in 17.5 and 4.6% yields, rspectively. Similar electrochemical oxidation of caffeine with methanol, KCl, or KCN afforded 8-methoxycaffeine, 8-chlorocaffeine, or 8-cyanocaffeine, respectively.

e21689Background: Uridine triacetate was approved by FDA in 2015 for adult and pediatric patients who exhibit early-onset, severe or life-threatening toxicities or who receive an overdose of 5-fluo...

e18232Background: Oral uridine triacetate improves survival and reduces toxicity when administered after serious overdoses of 5-fluorouracil (5-FU) in preclinical animal models and in humans. It ac...

e21612Background: Uridine triacetate was approved by FDA in 2015 for adult and pediatric patients who receive an overdose of 5-fluorouracil or capecitabine or who exhibit early-onset, severe or lif...

Nitrogen-containing compounds have been subjected to electrochemical oxidation with Et3N-3HF as an electrolyte. Caffeine afforded 8-fluorocaffeine as a sole product in 40.3% yield. Guanosine tetraacetate and uridine triacetate gave the fluorinated compounds in 17.5 and 4.6% yields, rspectively. Similar electrochemical oxidation of caffeine with methanol, KCl, or KCN afforded 8-methoxycaffeine, 8-chlorocaffeine, or 8-cyanocaffeine, respectively.