Hepatic sinusoidal obstruction syndrome and short-term application of 6-thioguanine in pediatric acute lymphoblastic leukemia

Innovating Thiopurine Therapeutic Drug Monitoring: A Systematic Review and Meta-Analysis on DNA-Thioguanine Nucleotides (DNA-TG) as an Inclusive Biomarker in Thiopurine Therapy

BACKGROUND AND OBJECTIVE

Thioguanine (TG), azathioprine (AZA), and mercaptopurine (MP) are thiopurine prodrugs commonly used to treat diseases, such as leukemia and inflammatory bowel disease (IBD). 6-thioguanine nucleotides (6-TGNs) have been commonly used for monitoring treatment. High levels of 6-TGNs in red blood cells (RBCs) have been associated with leukopenia, the cutoff levels that predict this side effect remain uncertain. Thiopurines are metabolized and incorporated into leukocyte DNA. Measuring levels of DNA-incorporated thioguanine (DNA-TG) may be a more suitable method for predicting clinical response and toxicities such as leukopenia. Unfortunately, most methodologies to assay 6-TGNs are unable to identify the impact of NUDT15 variants, effecting mostly ethnic populations (e.g., Chinese, Indian, Malay, Japanese, and Hispanics). DNA-TG tackles this problem by directly measuring thioguanine in the DNA, which can be influenced by both TPMT and NUDT15 variants. While RBC 6-TGN concentrations have traditionally been used to optimize thiopurine therapy due to their ease and affordability of measurement, recent developments in liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques have made measuring DNA-TG concentrations in lymphocytes accurate, reproducible, and affordable. The objective of this systematic review was to assess the current evidence of DNA-TG levels as marker for thiopurine therapy, especially with regards to NUDT15 variants.

METHODS

A systematic review and meta-analysis were performed on the current evidence for DNA-TG as a marker for monitoring thiopurine therapy, including methods for measurement and the illustrative relationship between DNA-TG and various gene variants (such as TPMT, NUDT15, ITPA, NT5C2, and MRP4). PubMed and Embase were systematically searched up to April 2024 for published studies, using the keyword "DNA-TG" with MeSH terms and synonyms. The electronic search strategy was augmented by a manual examination of references cited in articles, recent reviews, editorials, and meta-analyses. A meta-analysis was performed using R studio 4.1.3. to investigate the difference between the coefficients (Fisher's z-transformed correlation coefficient) of DNA-TG and 6-TGNs levels. A meta-analysis was performed using RevMan version 5.4 to investigate the difference in DNA-TG levels between patients with or without leukopenia using randomized effect size model. The risk of bias was assessed using the Newcastle-Ottowa quality assessment scale.

RESULTS

In this systematic review, 21 studies were included that measured DNA-TG levels in white blood cells for either patients with ALL (n = 16) or IBD (n = 5). In our meta-analysis, the overall mean difference between patients with leukopenia (ALL + IBD) versus no leukopenia was 134.15 fmol TG/µg DNA [95% confidence interval (CI) (83.78-184.35), P < 0.00001; heterogeneity chi squared of 5.62, I2 of 47%]. There was a significant difference in DNA-TG levels for patients with IBD with and without leukopenia [161.76 fmol TG/µg DNA; 95% CI (126.23-197.29), P < 0.00001; heterogeneity chi squared of 0.20, I2 of 0%]. No significant difference was found in DNA-TG level between patients with ALL with or without leukopenia (57.71 fmol TG/µg DNA [95% CI (- 22.93 to 138.35), P < 0.80]). DNA-TG monitoring was found to be a promising method for predicting relapse rates in patients with ALL, and DNA-TG levels are likely a better predictor for leukopenia in patients with IBD than RBC 6-TGNs levels. DNA-TG levels have been shown to correlate with various gene variants (TPMT, NUDT15, ITPA, and MRP4) in various studies, points to its potential as a more informative marker for guiding thiopurine therapy across diverse genetic backgrounds.

CONCLUSIONS

This systematic review strongly supports the further investigation of DNA-TG as a marker for monitoring thiopurine therapy. Its correlation with treatment outcomes, such as relapse-free survival in ALL and the risk of leukopenia in IBD, underscores its role in enhancing personalized treatment approaches. DNA-TG effectively identifies NUDT15 variants and predicts late leukopenia in patients with IBD, regardless of their NUDT15 variant status. The recommended threshold for late leukopenia prediction in patients with IBD with DNA-TG is suggested to be between 320 and 340 fmol/µg DNA. More clinical research on DNA-TG implementation is mandatory to improve patient care and to improve inclusivity in thiopurine treatment.

6-Mercaptopurine-associated Sinusoidal Obstructive Syndrome During Interim Maintenance I: A Case Report

Thiopurine-methyltransferase (TPMT) and nudix-hydrolase-15 (NUDT15) are enzymes relevant to the metabolism of thiopurine medications, used to treat immunologic disorders and malignancies. Standard dosing administered in the setting of TPMT/NUDT15 dysfunction can cause excessive cytotoxic metabolites and life-threatening complications. We describe an adolescent with high-risk B-cell acute lymphoblastic leukemia (ALL) whose TPMT/NUDT15 status was unknown due to lack of insurance approval for genetic testing. He subsequently developed myelosuppression and severe veno-occlusive disease (VOD) after receiving 6-mercaptopurine (6-MP). Our patient provides an example of a very rare 6-MP-related toxicity and the potential benefit of TPMT/NUDT15 screening before initiating thiopurine therapy.

Veno-Occlusive Disease: A Life-saving Novel Approach With Plasma Exchange, IVIG, and Steroid, Without Defibrotide

INTRODUCTION

Hepatic veno-occlusive disease (VOD) is a critical medical emergency with a high mortality rate of up to 90% if not promptly treated. Defibrotide is the only approved medication for VOD treatment, exhibiting anti-inflammatory, antithrombotic, and anti-ischemic properties. This report presents a case of severe VOD in a patient undergoing acute lymphoblastic leukemia (ALL) treatment.

CASE PRESENTATION

We describe the successful and rapid treatment of severe VOD in an ALL patient using therapeutic plasma exchange (TPE), intravenous immunoglobulin (IVIG), and methylprednisolone (MPZ). The patient showed significant clinical and laboratory improvement after this combined therapeutic approach.

CONCLUSION

This case highlights the effectiveness of TPE, IVIG, and MPZ in the treatment of severe VOD in ALL patients, providing insights into alternative therapeutic strategies in the absence of Defibrotide.

Primary Budd-Chiari syndrome versus sinusoidal obstruction syndrome: a review

Budd-Chiari syndrome (BCS) and sinusoidal obstruction syndrome (SOS) are two major vascular disorders of the liver, of which both can cause portal hypertension related complications, but their locations of obstruction are different. BCS refers to the obstruction from the hepatic vein to the junction between the inferior vena cava and right atrium, which is the major etiology of post-sinusoidal portal hypertension; by comparison, SOS is characterized as the obstruction at the level of hepatic sinusoids and terminal venulae, which is a cause of sinusoidal portal hypertension. Both of them can cause hepatic congestion with life-threatening complications, especially acute liver failure and chronic portal hypertension, and share some similar features in terms of imaging and clinical presentations, but they have heterogeneous risk factors, management strategy, and prognosis. Herein, this paper reviews the current evidence and then summarizes the difference between primary BCS and SOS in terms of risk factors, clinical features, diagnosis, and treatment.

Transjugular intrahepatic portosystemic shunt for the treatment of hepatic sinusoidal obstruction syndrome caused by pyrrolizidine alkaloids: A multicenter retrospective study

Purpose

To assess the impact of transjugular intrahepatic portosystemic shunt (TIPS) on clinical outcomes and liver histology in patients with hepatic sinusoidal obstruction syndrome (HSOS) caused by pyrrolizidine alkaloids (PA), and compare these results with those of patients who received supportive treatment alone.

Materials and methods

From June 2015 to August 2022, 164 patients diagnosed with PA-HSOS in six tertiary care centers were retrospectively included in this study and divided into TIPS group (n = 69) and supportive treatment (ST) group (n = 95). The main endpoint was to determine whether TIPS placement could improve survival in PA-HSOS patients. The clinical symptoms associated with portal hypertension were also evaluated in this study. Additionally, a small TIPS-subgroup of 7 patients received liver biopsies before and after TIPS for histological analysis.

Results

The incidence of death was markedly lower in the TIPS group than in the ST group (log-rank p = 0.026). Multivariate Cox model revealed that group assignment (hazard ratio (HR) 5.146; 95 % confidence interval (CI) 1.587-16.687; p = 0.006), total bilirubin (HR 1.029; 95 % CI 1.020-1.038; p < 0.001), and INR (HR 13.291; 95 % CI 3.637-48.566; p < 0.001) were independent predictors for mortality. In addition, TIPS placement reduced the risk of complications associated with portal hypertension but did not increase the rate of overt hepatic encephalopathy (log-rank p = 0.731). Furthermore, six of 7 TIPS patients receiving liver biopsies improved after TIPS placement, and one patient developed fibrosis.

Conclusions

TIPS placement decreased the mortality and risk of complications associated with portal hypertension. Histological evaluation in a few patients showed a potential improvement by TIPS.

A Review of Acute Lymphocytic Leukemia (ALL) in the Pediatric Population: Evaluating Current Trends and Changes in Guidelines in the Past Decade

Acute lymphocytic leukemia (ALL) is a commonly diagnosed cancer in children. Despite technological advancements to improve treatment and survival rates, there has been a steady increase in the incidence of ALL and treatment failures. This paper discusses the pathogenic interaction between genetic and environmental factors leading to childhood ALL. It evaluates the current treatment guidelines and notable obstacles leading to resistance, relapse, and treatment toxicities. The review evaluates a 10-year trend in the management guidelines of pediatric ALL through a systematic literature review of records from 2012 to 2023. Findings show that improvement in the five-year survival rates, notwithstanding rates of relapse and incurable diseases, is still high. Furthermore, several risk factors, including an interplay between genetic and environmental factors, are largely contributory to the outcome of ALL treatments and its overall incidence. Moreover, huge financial costs have remained a significant challenge in outcomes. There remains a need to provide individualized treatment plans, shared decision-making, and goals of care as parts of the management guidelines for the best possible outcomes. We expect that future advancements will increase overall survival rates and disease-free years.

Safety and efficacy of personalized versus standard initial dosing of thiopurines: Systematic review and meta-analysis of randomized trials

BACKGROUND

Pretherapy assessment of specific genetic polymorphism (TPMT, NUDT15, FTO, RUNX1, etc) or enzyme levels (for TPMT) may help personalize the dose of thiopurines and avoid adverse effects.

RESEARCH DESIGN AND METHODS

A systematic review of randomized controlled trials (RCTs) comparing personalized versus standard strategy for initial thiopurine dosing was performed. The electronic databases were searched on 27 September 2022. The outcomes were overall adverse effects, myelotoxicity, drug interruptions, and therapeutic efficacy with either strategy. The certainty of evidence was assessed using GRADE methodology.

RESULTS

We included six randomized trials, done dominantly in patients with inflammatory bowel disease (IBD). The personalized strategies were genotype testing in 4 trials (TPMT in three trials, NUDT15 in two) and enzyme levels for TPMT in two trials. The pooled risk of myelotoxicity in personalized dosing was lower [RR = 0.72 (95%CI, 0.55-0.94, I2 = 0%)]. The pooled risk of pancreatitis (RR = 1.10I, 0.78-1.56, I2 = 0%), hepatotoxicity (RR = 1.13, 0.69-1.88, I2 = 45), and GI intolerance (RR = 1.01, 0.92-1.10, I2 = 0) were similar in two groups. The pooled risk of drug interruption in individualized dosing was similar to the standard dosing group (RR = 0.97, I2 = 68%).

CONCLUSION

Personalized testing-based initial thiopurine dosing is protective against myelotoxicity as compared to standard weight-based dosing.

Terbium-triggered aggregation-induced emission of bimetallic nanoclusters for anticancer drugs sensing via the inner filter effect

The development of accurate and sensitive detection methods of anticancer drugs is of significant importance because they play vital roles in biological systems. In recent years, bimetallic nanoclusters (BMNCs) incorporating the advantages of two metals have gained more and more attention, and can be widely applied in sensing applications. In this work, for the first time, we designed a sensing platform based on terbium ion (Tb³⁺) triggered aggregation-induced emission (AIE) of BMNCs. Tb³⁺ hybrid glutathione (GS) protected Ag/Cu nanoclusters (Tb³⁺@GS-AgCuNCs) were facilely fabricated according to the complexation reaction between Tb³⁺ and the carboxyl group of GS. Due to the inner filter effect (IFE), the fluorescence of Tb³⁺@GS-AgCuNCs decreased significantly in the presence of anticancer drugs with 6-thioguanine and methotrexate as representatives. In addition, the sensing platform was applied to monitor 6-thioguanine and methotrexate in real serum samples, indicating that it has great potential in anticancer drugs related applications.

Sinusoidal Obstruction Syndrome of the Liver Associated With 6-Mercaptopurine During Maintenance in a Child With T-cell Acute Lymphoblastic Leukemia

Sinusoidal obstruction syndrome (SOS) of the liver is a complication of chemotherapy most often encountered with hematopoietic stem cell transplant due to high-dose conditioning regimens, but it can also occur with regimens outside of the transplant setting. Mild-to-moderate SOS is a well-described 6-thioguanine toxicity; however, it has rarely been reported as secondary to 6-mercaptopurine, a related thiopurine. This report details a case of a 10-year-old male with T-cell acute lymphoblastic leukemia who developed severe SOS during maintenance therapy with 6-mercaptopurine, and a review of the related literature.

Maintenance therapy for acute lymphoblastic leukemia: basic science and clinical translations

Maintenance therapy (MT) with oral methotrexate (MTX) and 6-mercaptopurine (6-MP) is essential for the cure of acute lymphoblastic leukemia (ALL). MTX and 6-MP interfere with nucleotide synthesis and salvage pathways. The primary cytotoxic mechanism involves the incorporation of thioguanine nucleotides (TGNs) into DNA (as DNA-TG), which may be enhanced by the inhibition of de novo purine synthesis by other MTX/6-MP metabolites. Co-medication during MT is common. Although Pneumocystis jirovecii prophylaxis appears safe, the benefit of glucocorticosteroid/vincristine pulses in improving survival and of allopurinol to moderate 6-MP pharmacokinetics remains uncertain. Numerous genetic polymorphisms influence the pharmacology, efficacy, and toxicity (mainly myelosuppression and hepatotoxicity) of MTX and thiopurines. Thiopurine S-methyltransferase (encoded by TPMT) decreases TGNs but increases methylated 6-MP metabolites (MeMPs); similarly, nudix hydrolase 15 (encoded by NUDT15) also decreases TGNs available for DNA incorporation. Loss-of-function variants in both genes are currently used to guide MT, but do not fully explain the inter-patient variability in thiopurine toxicity. Because of the large inter-individual variations in MTX/6-MP bioavailability and metabolism, dose adjustments are traditionally guided by the degree of myelosuppression, but this does not accurately reflect treatment intensity. DNA-TG is a common downstream metabolite of MTX/6-MP combination chemotherapy, and a higher level of DNA-TG has been associated with a lower relapse hazard, leading to the development of the Thiopurine Enhanced ALL Maintenance (TEAM) strategy-the addition of low-dose (2.5-12.5 mg/m²/day) 6-thioguanine to the 6-MP/MTX backbone-that is currently being tested in a randomized ALLTogether1 trial (EudraCT: 2018-001795-38). Mutations in the thiopurine and MTX metabolism pathways, and in the mismatch repair genes have been identified in early ALL relapses, providing valuable insights to assist the development of strategies to detect imminent relapse, to facilitate relapse salvage therapy, and even to bring about changes in frontline ALL therapy to mitigate this relapse risk.

Genetic Variation in ABCC4 and CFTR and Acute Pancreatitis during Treatment of Pediatric Acute Lymphoblastic Leukemia

Background: Acute pancreatitis (AP) is a serious, mechanistically not entirely resolved side effect of L-asparaginase-containing treatment for acute lymphoblastic leukemia (ALL). To find new candidate variations for AP, we conducted a genome-wide association study (GWAS). Methods: In all, 1,004,623 single-nucleotide variants (SNVs) were analyzed in 51 pediatric ALL patients with AP (cases) and 1388 patients without AP (controls). Replication used independent patients. Results: The top-ranked SNV (rs4148513) was located within the ABCC4 gene (odds ratio (OR) 84.1; p = 1.04 × 10⁻¹⁴). Independent replication of our 20 top SNVs was not supportive of initial results, partly because rare variants were neither present in cases nor present in controls. However, results of combined analysis (GWAS and replication cohorts) remained significant (e.g., rs4148513; OR = 47.2; p = 7.31 × 10⁻⁹). Subsequently, we sequenced the entire ABCC4 gene and its close relative, the cystic fibrosis associated CFTR gene, a strong AP candidate gene, in 48 cases and 47 controls. Six AP-associated variants in ABCC4 and one variant in CFTR were detected. Replication confirmed the six ABCC4 variants but not the CFTR variant. Conclusions: Genetic variation within the ABCC4 gene was associated with AP during the treatment of ALL. No association of AP with CFTR was observed. Larger international studies are necessary to more conclusively assess the risk of rare clinical phenotypes.

Advances in Thiopurine Drug Delivery: The Current State-of-the-Art

Thiopurines (mercaptopurine, azathioprine and thioguanine) are well-established maintenance treatments for a wide range of diseases such as leukemia, inflammatory bowel disease (IBD), systemic lupus erythematosus (SLE) and other inflammatory and autoimmune diseases in general. Worldwide, millions of patients are treated with thiopurines. The use of thiopurines has been limited because of off-target effects such as myelotoxicity and hepatotoxicity. Therefore, seeking methods to enhance target-based thiopurine-based treatment is relevant, combined with pharmacogenetic testing. Controlled-release formulations for thiopurines have been clinically tested and have shown promising outcomes in inflammatory bowel disease. Latest developments in nano-formulations for thiopurines have shown encouraging pre-clinical results, but further research and development are needed. This review provides an overview of novel drug delivery strategies for thiopurines, reviewing modified release formulations and with a focus on nano-based formulations.

Understanding thiopurine methyltransferase polymorphisms for the targeted treatment of hematologic malignancies

INTRODUCTION

Thiopurine methyltransferase (TPMT) catalyzes the S-methylation of thiopurines (mercaptopurine (MP) and tioguanine (TG)), chemotherapeutic agents used in the treatment of acute lymphoblastic leukemia (ALL). Polymorphisms in TPMT gene encode diminished activity enzyme, enhancing accumulation of active metabolites, and partially explaining the inter-individual differences in patients' clinical response.

AREAS COVERED

This review gives an overview on TPMT gene and function, and discusses the pharmacogenomic implications of TPMT variants in the prevention of severe thiopurine-induced hematological toxicities and the less known implication on TG-induced sinusoidal obstruction syndrome. Additional genetic and non-genetic factors impairing TPMT activity are considered. Literature search was done in PubMed for English articles published since1990, and on PharmGKB.

EXPERT OPINION

To titrate thiopurines safely and effectively, achieve the right degree of lymphotoxic effect and avoid excessive myelosuppression, the optimal management will combine a preemptive TPMT genotyping to establish a safe initial dose with a close phenotypic monitoring of TPMT activity and/or of active metabolites during long-term treatment. Compared to current ALL protocols, replacement of TG by MP during reinduction phase in TPMT heterozygotes and novel individualized TG regimens in maintenance for TPMT wild-type subjects could be investigated to improve outcomes while avoiding risk of severe hepatotoxicity.