Leveraging the fluorescence enhancement effect of the G-triplex (G3)/thioflavin T (ThT) catalyzed by the adjacent double-stranded DNA positioned at the 5\' terminus of the G3, the G3-specific oligonucleotide (G3MB6) was utilized to facilitate the rapid detection of mercury (Hg(II)) through thymine-Hg(II)-thymine (T-Hg(II)-T) interactions. G3MB6 adopted a hairpin structure in which partially complementary strands could be disrupted with the presence of Hg(II). It prompted the formation of double-stranded DNA by T-Hg(II)-T, inducing the unbound single strand of G3MB6 to spontaneously form a parallel G3 structure, producing a solid fluorescence signal by ThT. Conversely, fluorescence was absent without Hg(II), since no double strand and formation of G3 occurred. The fluorescence intensity of G3MB6 exhibited a positive correlation with Hg(II) concentrations from 17.72 to 300 nM (R2 = 0.9954), boasting a notably low quality of limitation (LOQ) of 17.72 nM. Additionally, it demonstrated remarkable selectivity for detecting Hg(II). Upon application to detect Hg(II) in milk samples, the recovery rates went from 100.3% to 103.2%.

DNA base editing technologies predominantly utilize engineered deaminases, limiting their ability to edit thymine and guanine directly. In this study, we successfully achieve base editing of both cytidine and thymine by leveraging the translesion DNA synthesis pathway through the engineering of uracil-DNA glycosylase (UNG). Employing structure-based rational design, exploration of homologous proteins, and mutation screening, we identify a Deinococcus radiodurans UNG mutant capable of effectively editing thymine. When fused with the nickase Cas9, the engineered DrUNG protein facilitates efficient thymine base editing at endogenous sites, achieving editing efficiencies up to 55% without enrichment and exhibiting minimal cellular toxicity. This thymine base editor (TBE) exhibits high editing specificity and significantly restores IDUA enzyme activity in cells derived from patients with Hurler syndrome. TBEs represent efficient, specific, and low-toxicity approaches to base editing with potential applications in treating relevant diseases.

Fluorouracil is among the most used antimetabolite drugs for the chemotherapeutic treatment of various types of gastrointestinal malignancies. Dihydropyrimidine dehydrogenase (DPYD) genotyping prior to fluorouracil treatment is considered standard practice in most European countries. Yet, current pre-therapeutic DPYD genotyping procedures do not identify all dihydropyrimidine dehydrogenase (DPD)-deficient patients. Alternatively, DPD activity can be estimated by determining the DPD phenotype by quantification of plasma concentrations of the endogenous uracil and thymine concentrations and their respective metabolites dihydrouracil (DHU) and dihydrothymine (DHT). Liquid chromatography - mass spectrometry (LC-MS) detection is currently considered as the most adequate method for quantification of low-molecular weight molecules, although the sample preparation method is highly critical for analytical outcome. It was hypothesized that during protein precipitation, the recovery of the molecule of interest highly depends on the choice of precipitation agent and the extent of protein binding in plasma. In this work, the effect of protein precipitation using acetonitrile (ACN) compared to strong acid perchloric acid (PCA) on the recovery of uracil, thymine, DHU and DHT is demonstrated. Upon the analysis of plasma samples, PCA precipitation showed higher concentrations of uracil and thymine as compared to ACN precipitation. Using ultrafiltration, it was shown that uracil and thymine are significantly (60-65 %) bound to proteins compared to DHU and DHT. This shows that before harmonized cut-off levels of DPD phenotyping can be applied in clinical practice, the analytical methodology requires extensive further optimization.

BACKGROUND: In the pivotal phase III RECOURSE trial, trifluridine/tipiracil (FTD/TPI) improved progression-free and overall survival (PFS, OS) of patients with pre-treated metastatic colorectal cancer (mCRC). Subsequently, the TALLISUR trial provided post-authorisation efficacy and safety data and patient-reported outcomes on quality of life (QoL) in a German patient cohort. The present analysis reports the final data on efficacy, safety and QoL and investigates the impact of baseline characteristics and associated prognostic subgroups on outcome.
METHODS: In this prospective, multi-centre, Germany-wide, phase IV study, patients with pre-treated mCRC were given the choice to receive either FTD/TPI or best supportive care (BSC). To assess the primary endpoint, QoL, EORTC QLQ-C30 questionnaires were employed. Secondary endpoints included QoL assessed through EQ-5D-5L questionnaires, OS, PFS and safety. Additionally, 3 subgroups were defined according to a post-hoc analysis of the RECOURSE trial: best, good and poor prognostic characteristics (BPC, GPC, PPC). Patients with < 3 metastatic sites at inclusion and/or ≥ 18 months from diagnosis to inclusion were considered to have GPC. GPC patients without liver metastasis at inclusion were considered to have BPC. All remaining patients were considered to have PPC.
RESULTS: Of 195 patients, 186 decided to receive FTD/TPI and 9 to receive BSC. The low number of patients in the BSC-arm did not allow statistically meaningful analyses. Treatment with FTD/TPI was associated with maintained QoL. For all patients, median OS was 6.9 months (95% CI 6.1 - 8.3) and for the defined subgroups (BPC n = 20 vs GPC n = 65 vs PPC n = 121) 12.2, 7.9 and 6.8 months (95% CI 6.0 - 18.2, 6.2 - 13.3, 5.4 - 8.1). The most frequent TEAEs were neutropenia (29.6%), anaemia (24.7%) and nausea (23.7%). Febrile neutropenia occurred in 1.1%.
CONCLUSIONS: Treatment of patients suffering from pre-treated mCRC with FTD/TPI was associated not only with prolonged survival and delayed progression, but also with maintained QoL. Independent of other baseline characteristics such as ECOG performance status and age, low metastatic burden and indolent disease were factors associated with favourable outcome.
BACKGROUND: EudraCT-Number 2017-000292-83, first registration 19/06/2017.

The stability of the human telomere G-quadruplex (G4) is directly linked to cancer disease. The human telomere is mostly associated with the flanking nucleobases, which can affect the stability of G4. Hence, in this study, the effect of the flanking nucleobases in the context of their chemical nature, number, and position on the structure and stability of G4 has been investigated in varying concentrations of KCl mimicking the normal and cancer KCl microenvironments. The addition of flanking nucleobases does not alter the G4 topology. However, the presence of merely a single flanking nucleobase destabilizes the telomeric G4. This destabilizing effect is more prominent for thymine than adenine flanking nucleobase, probably due to the formation of the intermolecular G4 topology by thymine. Interestingly, the change in the stability of the telomeric G4 in the presence of thymine flanking nucleobase is sensitive to the concentration of KCl relevant to the normal and cancerous microenvironments, in contrast to adenine. Flanking nucleobases have a greater impact at the 5\' end compared to the 3\' end, particularly noticeable in KCl concentrations resembling the normal microenvironment rather than the cancerous one. These findings indicate that the effect of the flanking nucleobases on telomeric G4 is different in the KCl salt relevant to normal and cancerous microenvironments. This study may be helpful in attaining molecular-level insight into the role of G4 in telomeric length regulation under normal and cancerous KCl salt conditions.

OBJECTIVE: This phase I trial is to determine the recommended dose of the TAS-102, irinotecan plus bevacizumab regimen and assess its safety and efficacy in patients with metastatic colorectal cancer refractory to fluoropyrimidine and oxaliplatin treatment.
METHODS: A 3 + 3 designed dose escalation was performed. Patients were administered TAS-102 (30-35 mg/m2 twice daily on days 1-5) and irinotecan (150-165 mg/m2 on day 1) combined with a fixed dose of bevacizumab (5 mg/kg on day 1) every two weeks. The primary endpoint was the determination of the recommended phase II dose.
RESULTS: Eighteen patients were enrolled: 6 at the Level 1 (TAS-102 30 mg/m2 twice daily, irinotecan 150 mg/m2 plus bevacizumab 5 mg/kg), six at the Level 2 (TAS-102 35 mg/m2 twice daily, irinotecan 150 mg/m2 plus bevacizumab 5 mg/kg), and six at the Level 3 (TAS-102 30 mg/m2 twice daily, irinotecan 165 mg/m2 plus bevacizumab 5 mg/kg). Five dose-limiting toxicities occurred: one observed at Level 1 (thrombocytopenia), two at Level 2 (neutropenia and diarrhea), and two at Level 3 (fatigue and neutropenia). The RP2D was established as TAS-102 30 mg/m2 twice daily and irinotecan 150 mg/m2 plus bevacizumab 5 mg/kg. The most frequent grade 3/4 treatment-related adverse events were neutropenia (33.3%), diarrhea (16.7%), and thrombocytopenia (11.1%). No treatment-related death occurred. Two patients (11.1%) experienced partial responses and 14 (77.8%) had stable disease.
CONCLUSIONS: The regimen of TAS-102, irinotecan, and bevacizumab is tolerable with antitumor activity for metastatic colorectal cancer patients refractory to first-line fluoropyrimidines and oxaliplatin treatment.

Aim: The objective of this study was to compare adverse event (AE) management costs for fruquintinib, regorafenib, trifluridine/tipiracil (T/T) and trifluridine/tipiracil+bevacizumab (T/T+bev) for patients with metastatic colorectal cancer (mCRC) previously treated with at least two prior lines of therapy from the US commercial and Medicare payer perspectives. Materials & methods: A cost-consequence model was developed to calculate the per-patient and per-patient-per-month (PPPM) AE costs using rates of grade 3/4 AEs with incidence ≥5% in clinical trials, event-specific management costs and duration treatment. Anchored comparisons of AE costs were calculated using a difference-in-differences approach with best supportive care (BSC) as a common reference. AE rates and treatment duration were obtained from clinical trials: FRESCO and FRESCO-2 (fruquintinib), RECOURSE (T/T), CORRECT (regorafenib) and SUNLIGHT (T/T, T/T+bev). AE management costs for the commercial and Medicare perspectives were obtained from publicly available sources. Results: From the commercial perspective, the AE costs (presented as per-patient, PPPM) were: $4015, $1091 for fruquintinib (FRESCO); $4253, $1390 for fruquintinib (FRESCO-2); $17,110, $11,104 for T/T (RECOURSE); $9851, $4691 for T/T (SUNLIGHT); $8199, $4823 for regorafenib; and $11,620, $2324 for T/T+bev. These results were consistent in anchored comparisons: the difference-in-difference for fruquintinib based on FRESCO was -$1929 versus regorafenib and -$11,427 versus T/T; for fruquintinib based on FRESCO-2 was -$2257 versus regorafenib and -$11,756 versus T/T. Across all analyses, results were consistent from the Medicare perspective. Conclusion: Fruquintinib was associated with lower AE management costs compared with regorafenib, T/T and T/T+bev for patients with previously treated mCRC. This evidence has direct implications for treatment, formulary and pathways decision-making in this patient population.

OBJECTIVE: Dihydropyrimidinase deficiency is a rare autosomal recessive disorder of the pyrimidine degradation pathway, with fewer than 40 patients published. Clinical findings are variable and some patients may remain asymptomatic. Global developmental delay and increased susceptibility to 5-fluorouracil are commonly reported. Here we present atrioventricular septal defect as a novel feature in dihydropyrimidinase deficiency.
METHODS: A four-year-old male with global developmental delay, dysmorphic facies, autistic features and a history of seizures was diagnosed with dihydropyrimidinase deficiency based on strikingly elevated urinary dihydrouracil and dihydrothymine and a homozygous pathogenic nonsense variant in DPYS gene. He had a history of complete atrioventricular septal defect corrected surgically in infancy.
CONCLUSIONS: This is the second report of congenital heart disease in dihydropyrimidinase deficiency, following a single patient with a ventricular septal defect. The rarity of the disease and the variability of the reported findings make it difficult to describe a disease-specific clinical phenotype. The mechanism of neurological and other systemic findings is unclear. Dihydropyrimidinase deficiency should be considered in patients with microcephaly, developmental delay, epilepsy and autistic traits. We suggest that congenital heart disease may also be a rare phenotypic feature.

Single-agent TAS102 (trifluridine/tipiracil) and regorafenib are FDA-approved treatments for metastatic colorectal cancer (mCRC). We previously reported that regorafenib combined with a fluoropyrimidine can delay disease progression in clinical case reports of multidrug-resistant mCRC patients. We hypothesized that the combination of TAS102 and regorafenib may be active in CRC and other gastrointestinal (GI) cancers and may in the future provide a treatment option for patients with advanced GI cancer. We investigated the therapeutic effect of TAS102 in combination with regorafenib in preclinical studies employing cell culture, colonosphere assays that enrich for cancer stem cells, and in vivo. TAS102 in combination with regorafenib has synergistic activity against multiple GI cancers in vitro including colorectal and gastric cancer, but not liver cancer cells. TAS102 inhibits colonosphere formation and this effect is potentiated by regorafenib. In vivo anti-tumor effects of TAS102 plus regorafenib appear to be due to anti-proliferative effects, necrosis and angiogenesis inhibition. Growth inhibition by TAS102 plus regorafenib occurs in xenografted tumors regardless of p53, KRAS or BRAF mutations, although more potent tumor suppression was observed with wild-type p53. Regorafenib significantly inhibits TAS102-induced angiogenesis and microvessel density in xenografted tumors, as well inhibits TAS102-induced ERK1/2 activation regardless of RAS or BRAF status in vivo. TAS102 plus regorafenib is a synergistic drug combination in preclinical models of GI cancer, with regorafenib suppressing TAS102-induced increase in microvessel density and p-ERK as contributing mechanisms. The TAS102 plus regorafenib drug combination may be further tested in gastric and other GI cancers.

OBJECTIVE: Trifluridine/tipiracil, registered for the treatment of patients with metastatic gastric and colorectal cancer, is a substrate and inhibitor for the organic cation transporter 2 (OCT2) and the multidrug and toxin extrusion protein 1 (MATE1), which raises the potential for drug-drug interactions with other OCT2/MATE1 modulators. Therefore, we prospectively examined the effect of an OCT2/MATE1 inhibitor (cimetidine) and substrate (metformin) on the pharmacokinetics of trifluridine.
METHODS: In this three-phase crossover study, patients with metastatic colorectal or gastric cancer were sequentially treated with trifluridine/tipiracil alone (phase A), trifluridine/tipiracil concomitant with metformin (phase B) and trifluridine/tipiracil concomitant with cimetidine (phase C). The primary endpoint was the relative difference in exposure of trifluridine assessed by the area under the curve from timepoint zero to infinity. A > 30% change in exposure was considered clinically relevant. A p-value of < 0.025 was considered significant because of a Bonferroni correction.
RESULTS: Eighteen patients were included in the analysis. Metformin did not significantly alter the exposure to trifluridine (- 12.6%; 97.5% confidence interval - 25.0, 1.8; p = 0.045). Cimetidine did alter the exposure to trifluridine significantly (+ 18.0%; 97.5% confidence interval 4.5, 33.3; p = 0.004), but this increase did not meet our threshold for clinical relevance. Metformin trough concentrations were not influenced by trifluridine/tipiracil.
CONCLUSIONS: Our result suggests that the OCT2/MATE1 modulators cimetidine and metformin can be co-administered with trifluridine/tipiracil without clinically relevant effects on drug exposure.
BACKGROUND: NL8067 (registered 04-10-2019).