In this study, we evaluated the association of NUDT15 *4 with mercaptopurine (6-MP) tolerance in a retrospective cohort of 1,399 patients with acute lymphoblastic leukemia (ALL) of diverse ancestries...In a separate retrospective validation study, six patients were identified as having NUDT15 *1/*4 by routine clinical pharmacogenetics testing and tolerated a 6-MP median dose of 38.7 mg/m2 (IQR, 33.7-54.0), confirming the need for dose reduction attributed to the NUDT15 *4 variant. These results point to the need to include NUDT15 *4 in pharmacogenetics-guided thiopurine dosing algorithms.

The observation that CAV1 inhibition modulated by 6-mercaptopurine, daidzin, and statins enhances the efficacy of bortezomib in vitro and in vivo highlights the translational significance of these FDA-approved drugs in improving MM outcomes. These data demonstrate that CAV1 serves as a potent therapeutic target for enhancing chemotherapy and immunotherapy for MM.

Preemptive pharmacogenomic testing for TPMT and NUDT15 polymorphisms before initiation of maintenance therapy for pediatric ALL patients yielded considerable cost savings.

None of the variants, except for NUDT15*3, were associated with cumulative thiopurine doses in ALL patients. However, these variants warrant further investigation in larger ALL cohorts.

P3, N=64, Not yet recruiting, Children's Oncology Group

After an initial response to antimetabolite therapy (6-mercaptopurine), she underwent haploidentical hematopoietic stem cell transplantation (HSCT) and is currently in complete remission. The goal of this review is to gain insight into the various hematological diseases associated with NS, starting from our unique case.

mAbcc4 expressed in HEK293 cells did not protect against any of the six arsenic species tested [arsenite, arsenate, MMAIII, monomethylarsonic acid, dimethylarsinous acid or DMAV], despite displaying remarkable resistance against the antimetabolite 6-mercaptopurine (>9-fold higher than hABCC4)...Here we used multiple cell models to demonstrate that mouse Abcc4 does not protect cells against, or transport, any arsenic species tested. Thus, differences between hABCC4 and mAbcc4 substrate selectivity likely contribute to differences in human and mouse arsenic toxicokinetics.

Despite great therapeutic advances in the field of biologics, small synthetic molecules such as thiopurines, including azathioprine, mercaptopurine, and thioguanine, remain an important therapeutic pillar in the treatment of inflammatory bowel disease, other autoimmune disorders, and cancer. In addition, the article takes a critical look at emerging research in the field of thiopurine pharmaco genomics featuring novel genetic markers and technological developments in genetic testing. Finally, the potential of integrated approaches that combine genetic, meta bolic, and clinical factors to further individualize thiopurine therapy is highlighted.

Patients were classified into a high DI phenotype (either 6-mercaptopurine [6-MP] or methotrexate [MTX] DI ≥110% during the first four study months, or 6-MPDI or MTXDI 100%-110% at study enrollment and ≥25% increase over the four study months) and normal DI phenotype (all others). While high DI was not associated with relapse in the entire cohort (adjusted hazard ratio [aHR]=1.4, 95%CI=0.8-2.4), it was associated with a greater hazard of relapse among adherent participants (aHR=2.4, 95%CI=1.0-5.5) but not among non-adherent participants (aHR=0.9, 95%CI=0.2-3.8). Dose escalation above protocol doses during maintenance therapy for ALL should be done cautiously after assessing adherence to prescribed therapy.

Additionally, gene-drug association analysis identified ciclosporin, ouabain and 6- mercaptopurine, which all exhibit immunosuppressive properties, as potential therapeutic options for tumor patients exhibiting high F3, PLAT or C1S expression, respectively. In summary, our findings provide a bioinformatics perspective on VRGs in pan-cancer, highlighting the pivotal roles of F3, PLAT and C1S, which could potentially be therapeutically exploited and targeted in several cancers, especially in GBMLGG.

All patients (5/5) treated with 5-azacitidine alone and one of the four treated with 6-mercaptopurine monotherapy had a reduction in mutant variant allele frequency. Among patients who received transplants, 7/13 are alive, and relapse post-transplant occurred in 3/13 with a median time to relapse of 3.55 months. This report provides insight into therapy responses and long-term outcomes across different genetic subsets of JMML and lends insight into the expected time to spontaneous resolution in patients with NS-MPD with germline PTPN11 mutations.

The observed high frequency of NUDT15 c.415C>T in our study population might explain the elevated prevalence of 6-MP-associated hematotoxicity in pediatric patients with ALL within the Indonesian population. Our study provides new insight regarding the NUDT15 gene polymorphism and its relation to hematotoxicity. Further studies are required to determine the necessity of adjusting the initial dose of 6-MP for Indonesian pediatric patients with ALL.

Sri Lankans are likely to show lower toxicity risk with sorafenib (rs7557402 c.84,131 C > G) and, higher toxicity risk with fluoropyrimidines (rs56038477 c.1236G > A) and mercaptopurine (rs116855232 c.415 C > T), and reduced effectiveness with tamoxifen (rs1065852 c.100 C > T) and platinum compounds (rs25487). These findings highlight the potential contribution of these genetic variations to the individual variability in anti-cancer dosage requirements among Sri Lankans.

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.

Reduction in 6-MP dose intensity was observed in patients with both rs73189762 and known no-function variants in the NUDT15 and TPMT genes. This finding supports the initial observation and suggests that 6-MP dose reduction might be beneficial for individuals with this genotype combination.

This study provides the first comprehensive pharmacogenetic characterization of cancer therapy-related SNPs and highlights significant disparities in SNP frequencies within the Chilean population. Our findings underscore the necessity for inclusive research and personalized therapeutic strategies to ensure the equitable and effective application of precision medicine across diverse global communities.

The mercaptopurine dose intensity was considerably low in NUDT15 rs116855232 TT genotype compared with CT and CC. The dosage of mercaptopurine should be adjusted according to the NUDT15 genotype in pediatric patients with ALL.

It is revealed that increased tetrahydrofolate consumption via histidine catabolism partially explains the re-sensitization ability of histidine. More importantly, this work provides fresh insights into that desuccinylation mediated by SIRT5 is an indispensable and synergistic requirement for histidine combination therapy against 6-MP resistance, which is undisclosed previously and demonstrates a rational strategy to ameliorate chemoresistance and protect pediatric patients with B-ALL from disease progression or relapse.

P1/2, N=27, Recruiting, The First Affiliated Hospital with Nanjing Medical University

We recommend more substantial dose reductions to individualize MP therapy and mitigate toxicity in TPMT/NUDT15 IM/IM patients.

P1/2, N=48, Not yet recruiting, Haukeland University Hospital

To test the possibility that HBB acted in generating a persistor cell phenotype, cell lines were placed in mercaptopurine and prednisone for 10-14 days at two different concentrations and counted throughout drug exposure and for an additional 10-14 days following removal of drug. The increased clonal potential upon overexpression of HBB could be indicative of the ability to reconstitute a tumor from a small subpopulation following treatment. Additionally, our data suggests that protein is not required for increased clonal growth leading us to hypothesize that catalytic RNA is responsible. We are also currently analyzing RNAseq data from the cell lines and will compare differential gene expression between the empty vector and HBB expressing cells to discover downstream pathways impacted by HBB.

Introduction: Current COG protocols for childhood ALL recommend increasing 6-mercaptopurine (6MP) and methotrexate (MTX) dose intensity (DI=prescribed therapy dose/ planned protocol dose) to >100% during maintenance for patients exhibiting inadequate myelosuppression (surrogate for systemic exposure to 6MP/MTX). High antimetabolite dose intensity in children with ALL who adhere to oral 6MP during maintenance therapy is associated with higher odds of hematologic toxicities as well as increased hazard of relapse. These findings inform clinicians about the issues related to dose escalation beyond protocol doses, especially among adherent patients.

The maintenance cycle consists of 12 weeks of daily 6MP at an individualized dosage, weekly methotrexate (MTX) at a dosage of 20 mg/m2, and monthly vincristine and steroid pulses. A decrease in the initial dosage from 50 mg/m2/day to 30 mg/m2/day has the potential to reduce febrile toxicity in the patient group exhibiting intermediate activity of the NUDT15 enzyme, which is observed in approximately 20% of individuals in East Asia. Through this research, we expect to provide the dosing guidelines for 6MP in patients with ALL in East Asia.

Intermittent cycles of exposure, particularly at the 10 and 20 mg/kg, decreased body and organ weights, increased micronucleated cells in the peripheral blood, induced oxidative/nitrosative stress, altered sperm chromatin quality, reduced serum testosterone and follicle stimulating hormone (FSH) levels, increased testicular structural aberrations, DNA damage, and apoptosis, and upregulated TNF-α expression and downregulated p-AMPK and β-catenin expressions. Conclusively, intermittent cycles of exposure at 10 and 20 mg/kg doses to the juvenile rats significantly induced oxidative stress, genotoxicity, and cellular and molecular perturbations in the testes and sperm of adult rats.

The dose intensity of 6-MP in ALL patients with NUDT15 c.415C>T variants was significantly lower than that in wild type patients. This research provided a basis for further investigation into relations between NUDT15 gene and adverse reaction, treatment efficacy and dose intensity of 6-MP.

TPMT- and NUDT15-based dosing of 6-MP will significantly contribute toward further reducing the incidence of leukopenia in Chinese children with ALL. This trial is registered at www.clinicaltrial.gov as #NCT04228393.

The anti-inflammatory response of 6-MP influenced by intestinal microbiota and its metabolites SCFAs, especially butyrate, played an essential role in improving ALL progression.

Due to worsening of the disease, patient was treated with mercaptopurine (50 mg QID per os)#for 7 days, which caused an initial regression of WBC (<30x10⁹)... Leukemia cutis is a rare occurrence in patients with CMML, associated with blast transformation and poor prognosis. LC is also a predictive factor in CMML patents, for progression to acute myeloid leukemia (AML).#Histopathology is essential for establishing the diagnosis, especially as the dermatological manifestation can be polymorphic and imitate other diseases. Clinicans should be aware of this rare manifestation, because its early diagnosis has important prognostic implications, so further hematological intervention can be instituted.

This is the first pharmacogenetics study carried out in a black Zimbabwean leukemia patient cohort. The high defective TPMT*3C (9.8%) allele frequency points to the potential utility of pharmacogenetics testing for safe usage of 6-mercaptopurine in this population.

In contrast, after multivariate analysis, relapse hazard ratio (HR) increased in ALL children of the intermediate risk arm compared to those in standard risk arm (3.44, 95% confidence interval (CI), 1.31-9.05, p= 0.012), and in carriers of the PACSIN2 rs2413739 T allele compared to those with the CC genotype (heterozygotes CT: HR, 2.32; 95% CI, 0.90-5.97; p=0.081; homozygous TT: HR, 4.14; 95% CI, 1.54-11.11; p=0.005). Future studies are needed to confirm the lack of impact of TGN levels and variability on relapse in the AIEOP-BFM ALL trials, and to clarify the mechanism of PACSIN2 rs2413739 on outcome.

Inhibition of HPRT1 by 6-mercaptopurine (6-MP) in combination with methotrexate (MTX), which blocks the de novo purine synthesis pathway, attenuated the growth of SCLC in mouse xenograft models. Moreover, modulation of host glutamine anabolism with the glutamine synthetase inhibitor methionine sulfoximine (MSO) in combination with 6-MP and MTX treatment resulted in marked tumor suppression and prolongation of host survival. Our results thus suggest that modulation of host glutamine anabolism combined with simultaneous inhibition of the de novo and salvage purine synthesis pathways may be of therapeutic benefit for SCLC.

Thiopurines, such as 6-mercaptopurine (6-MP), are widely used as cytotoxic agents and immunosuppressants for leukemia and autoimmune or inflammatory diseases...The loss of NUDT15 thiopurine detoxification enhances thiopurine-mediated DNA damage via the Trp53 networks in HSCs. Therefore, caution is required in long-term thiopurine use in patients with NUDT15 R139C in view of its adverse effects on HSCs in the form of DNA damage.

The cornerstone of ALL-MT is the daily administration of oral 6-mercaptopurine (6MP), a purine analogue. 6MP is combined with weekly oral methotrexate (MTX), an antifolate drug, to augment therapeutic activity. Some protocols include additional chemotherapy drugs (such as vincristine and corticosteroids) during MT...Management of MT thus requires close supervision to ensure treatment adherence, periodic drug dose modifications, and treatment to tolerance, while minimizing treatment interruptions due to toxicity. The review highlights these challenges and discusses approaches and strategies for the management of MT, focusing on the Indian context.

Optimum formulation exhibited significantly higher cytotoxic effects on HEP3G than on pure 6-MCP. These results demonstrated that solid lipid nanodrug delivery systems have great potential for formulation of 6-MCP.

The material also released small amounts of zinc, which are important in the treatment of the disease because these ions can prevent some of the adverse effects of chemotherapy. The results obtained are promising and have great application potential.

Three patients (4%) ceased thiopurine therapy due to thiopurine-related AEs, while no laboratory toxicity required therapy adjustments. Monitoring frequency of every 6 months seems feasible in patients with stable IBD on long-term (median duration > 6 years) maintenance thiopurine therapy and may contribute to reduced patient-burden and health care costs.

Polymorphism in FTO-rs16952570 did not show any correlation with thiopurine related toxicity in ALL patients.

In conclusion, child's age and day 1 maintenance white blood cell/absolute neutrophil counts significantly affected the occurrence of grade 4 hematotoxicity. Close monitoring for white blood cell and absolute neutrophil counts during maintenance phase treatment is recommended for early diagnosis of hematotoxicity.

Mechanistically, 6-MP potently inhibited PD-1 signalling by blocking the recruitment of SHP2 by PD-1. Considering that 6-MP is a chemotherapeutic agent already approved by the FDA for childhood leukaemia, our work revealed a novel anti-tumour mechanism for this drug and suggests that 6-MP warrants further clinical evaluation for other tumour types.

In conclusion, in this cohort, XDH rs2281547 was identified as a genetic risk factor for grade 4 hematologic toxicities in ALL patients treated with 6-MP. Genetic polymorphisms in enzymes other than TPMT involved in the 6-mercaptopurine pathway should be considered during its use to avoid hematological toxicity.

SIGNIFICANCE STATEMENT: Mimicking the initiation process of relapse-specific mutations of the NT5C2 and PRPS1 genes in childhood acute lymphoblastic leukemia treated with 6-mercaptopurine (6-MP), this study sought to introduce NT5C2-R39Q and PRPS1-S103N mutations into a human lymphoid leukemia cell line by homologous recombination using the CRISPR/Cas9 system. In the resultant 6-MP-resistant sublines, the intended mutations and diverse in-frame small insertions/deletions were confirmed, indicating that the obtained sublines are useful for molecular pharmacological evaluation of the NT5C2 and PRPS1 gene mutations.