ABCC4 impacts megakaryopoiesis and protects megakaryocytes against 6-mercaptopurine induced cytotoxicity.

The role of ABCC4, an ATP-binding cassette transporter, in the process of platelet formation, megakaryopoiesis, is unknown. Here, we show that ABCC4 is highly expressed in megakaryocytes (MKs). Mining of public genomic data (ATAC-seq and genome wide chromatin interactions, Hi-C) revealed that key megakaryopoiesis transcription factors (TFs) interacted with ABCC4 regulatory elements and likely accounted for high ABCC4 expression in MKs. Importantly these genomic interactions for ABCC4 ranked higher than for genes with known roles in megakaryopoiesis suggesting a role for ABCC4 in megakaryopoiesis. We then demonstrate that ABCC4 is required for optimal platelet formation as in vitro differentiation of fetal liver derived MKs from Abcc4-/- mice exhibited impaired proplatelet formation and polyploidization, features required for optimal megakaryopoiesis. Likewise, a human megakaryoblastic cell line, MEG-01 showed that acute ABCC4 inhibition markedly suppressed key processes in megakaryopoiesis and that these effects were related to reduced cAMP export and enhanced dissociation of a negative regulator of megakaryopoiesis, protein kinase A (PKA) from ABCC4. PKA activity concomitantly increased after ABCC4 inhibition which was coupled with significantly reduced GATA-1 expression, a TF needed for optimal megakaryopoiesis. Further, ABCC4 protected MKs from 6-mercaptopurine (6-MP) as Abcc4-/- mice show a profound reduction in MKs after 6-MP treatment. In total, our studies show that ABCC4 not only protects the MKs but is also required for maximal platelet production from MKs, suggesting modulation of ABCC4 function might be a potential therapeutic strategy to regulate platelet production.

Visible Light-Mediated Late-Stage Thioetherification of Mercaptopurine Derivatives.

We disclose herein a novel and general radical approach to alkylthiopurines, encompassing 4 types of thiopurines, as well as their corresponding ribosides. This strategy is achieved through visible light-mediated late-stage functionalization of the sulfur atoms of mercaptopurines. The in situ-generated disulfide was proposed as the pivotal neutral intermediate for this transformation. We present herein a novel photo-mediated homolytic C-S bond formation for the preparation of alkylthiopurines and alkylthiopurine nucleosides. Despite the presence of reactive sites for the Minisci reaction, chemoselective S-alkylation remained the predominant pathway. This method allows for the late-stage introduction of a broad spectrum of alkyl groups onto the sulfur atom of unprotective mercaptopurine derivatives, encompassing 2-, 6-, and 8-mercaptopurine rings. Organoborons serve as efficient and eco-friendly alkylating reagents, providing advantages in terms of readily availability, stability, and reduced toxicity. Further derivatization of the thioetherified nucleosides, together with anti-tumor assays, led to the discovery of potent anti-tumor agents with an IC50 value reaching 6.1 µM (Comp. 31 for Jurkat).

Identification of Fasudil as a collaborator to promote the anti-tumor effect of lenvatinib in hepatocellular carcinoma by inhibiting GLI2-mediated hedgehog signaling pathway.

Lenvatinib is a frontline tyrosine kinase inhibitor for patients with advanced hepatocellular carcinoma (HCC). However, just 25% of patients benefit from the treatment, and acquired resistance always develops. To date, there are neither effective medications to combat lenvatinib resistance nor accurate markers that might predict how well a patient would respond to the lenvatinib treatment. Thus, novel strategies to recognize and deal with lenvatinib resistance are desperately needed. In the current study, a robust Lenvatinib Resistance index (LRi) model to predict lenvatinib response status in HCC was first established. Subsequently, five candidate drugs (Mercaptopurine, AACOCF3, NU1025, Fasudil, and Exisulind) that were capable of reversing lenvatinib resistance signature were initially selected by performing the connectivity map (CMap) analysis, and fasudil finally stood out by conducting a series of cellular functional assays in vitro and xenograft mouse model. Transcriptomics revealed that the co-administration of lenvatinib and fasudil overcame lenvatinib resistance by remodeling the hedgehog signaling pathway. Mechanistically, the feedback activation of EGFR by lenvatinib led to the activation of the GLI2-ABCC1 pathway, which supported the HCC cell's survival and proliferation. Notably, co-administration of lenvatinib and fasudil significantly inhibited IHH, the upstream switch of the hedgehog pathway, to counteract GLI2 activation and finally enhance the effectiveness of lenvatinib. These findings elucidated a novel EGFR-mediated mechanism of lenvatinib resistance and provided a practical approach to overcoming drug resistance in HCC through meaningful drug repurposing strategies.

Use of allopurinol to manage skewed 6-mercaptopurine metabolism in pediatric maintenance acute lymphoblastic leukemia treatment.

BACKGROUND: 6-mercaptopurine is a cornerstone of maintenance therapy for pediatric ALL. Response to 6MP is typically determined by the ANC. Therapeutic ANC range while receiving 6MP is between 500 and 1500/µL. In addition to desired myelosuppression, 6MP is associated with multiple adverse drug effects. Increased doses of 6MP can lead to therapeutic ANC values; however, patients may experience adverse effects before obtaining therapeutic myelosuppression, often deemed "skewed metabolism." Allopurinol may potentially correct skewed 6MP metabolism. PROCEDURE: Pediatric patients with ALL with 6MMP and 6TGN metabolites drawn during maintenance therapy were analyzed for allopurinol use. The primary outcome evaluated the percentage of time spent in therapeutic ANC range before and after allopurinol initiation. In addition, the difference in 6MMP:6TGN ratios before and after allopurinol initiation, incidence of hepatotoxicity, and rates of relapse, were analyzed. RESULTS: Ninety-five patients were included for analysis. Thirty-two (34%) patients received allopurinol. There were no significant differences in baseline demographics between the patients who received allopurinol and those who did not. When comparing ANC values pre- and post-allopurinol initiation, a statistically significant increase in the percentage of time spent in therapeutic range was observed (27% vs. 43%; p = .03). In addition, when comparing metabolite ratios pre- and post-allopurinol initiation, a statistically significant decrease in 6MMP:6TGN metabolite ratio values was observed (86.7 vs. 3.6; p < .0001). CONCLUSIONS: Allopurinol significantly increased the percent time in therapeutic ANC range and can be safely utilized to significantly lower the ratio of 6MMP:6TGN metabolites, alleviating the undesirable side effects of 6MMP, and optimizing the anti-leukemic effects associated with 6TGN.

Bioequivalence study followed by model-informed dose optimization of a powder for oral suspension of 6-mercaptopurine.

BACKGROUND: 6-Mercaptopurine (6MP) is the mainstay chemotherapy for acute lymphoblastic leukemia (ALL) and is conventionally available as 50 mg tablets. A new 6MP powder for oral suspension (PFOS 10 mg/mL) was developed recently by IDRS Labs, India, intended for pediatric use. A comparative pharmacokinetics of PFOS with T. mercaptopurine was conducted to determine the dose equivalence. METHODS: An open-label, randomized, two-treatment, two-period, two-sequence, single oral dose, crossover, bioequivalence study was conducted on 51 healthy adult subjects. Post hoc, a population pharmacokinetic (PopPK) model was developed using the healthy volunteer data to perform simulations with various PFOS doses and select a bioequivalent dose. Further, to confirm the safety of PFOS in pediatrics, a simulation of 6MP and 6-thioguanine exposures was performed by incorporating the formulation-specific parameters derived from the healthy volunteer study into the PopPK model in childhood ALL available in literature. RESULTS: The 6MP PFOS had 47% higher oral bioavailability compared to the reference product. Simulations using a two-compartmental PopPK model with dissolution and transit compartments showed that 40 mg of PFOS was found to be equivalent to 50 mg tablets. The simulated 6-thioguanine nucleotide concentrations in children using the dose adjusted for PFOS were between 114 and 703.6 pmol/8 × 108 RBC, which was within the range reported in pediatric ALL studies. CONCLUSION: 6MP PFOS 10 mg/mL should be administered at a 20% lower dose than the tablet to achieve comparable exposure. 6MP PFOS addresses an unmet medical need for a liquid formulation of 6MP in the Indian subcontinent.

Efficacy of optimised thiopurine therapy in patients with moderate-to-severe ulcerative colitis: retrospective long-term follow-up from two randomised trials.

OBJECTIVE: The long-term outcome of thiopurine therapy in patients with ulcerative colitis (UC) enrolled in prospective trials have not been evaluated. We aimed to assess the effects of optimised thiopurine maintenance therapy for UC. METHODS: Long-term data were obtained from patients from our center enrolled in two randomised, prospective, open-label, controlled studies comprising 66 thiopurine-naïve moderate-to-severe patients with UC consisting of a low dose azathioprine (AZA)/allopurinol combination or AZA monotherapy. Following the randomised trials, treatment was adjusted according to adverse effects and metabolites. Patients requiring optimisation initially on AZA monotherapy treatment were switched to low dose AZA in combination with allopurinol, low dose 6-mercaptopurin in combination with allopurinol, or 6-mercaptopurin treatment alone, and those treated with low dose AZA in combination with allopurinol were switched to low dose 6-mercaptopurin in combination with allopurinol or 6-mercaptopurin alone. RESULTS: A total of 62 patients were included in the analysis; 31 were initially treated with AZA monotherapy and 31 with low dose AZA in combination with allopurinol. Initial treatment was tolerated by 67% patients (7 AZA monotherapy and 28 low dose AZA in combination with allopurinol), increasing to 94% (58 patients) post-adjustment. After a median 52-month follow-up period, 38 (93%) out of the 41 primary responding patients-maintained clinical remission without steroids, biologics or surgery. The four intolerant patients and the 17 not responding to optimisation were more likely to require colectomy (odds ratio 16.36; 95% confidence interval 3.08-87.03, p < 0.0001). CONCLUSION: Optimised thiopurine therapy demonstrated effective long-term treatment for patients with ulcerative colitis.

Chemotherapeutic metabolism presenting as a recalcitrant case of hand-foot syndrome and mucositis.

INTRODUCTION: Mercaptopurine (6MP) and methotrexate (MTX) are commonly used for maintenance chemotherapy for acute lymphoblastic leukemia (ALL). These medications have been associated with various side effects such as myelosuppression, colitis, and thyroiditis in addition to numerous cutaneous adverse events. Cutaneous side-effects most reported include mucositis, alopecia, xerosis, and pruritus. We report an interesting case of hand-foot syndrome to 6MP in a child on maintenance therapy for B-cell ALL from an alteration in medication metabolism. CASE: We report a 10-year-old male on maintenance chemotherapy for pre-Bcell ALL who presented to the hospital with worsening oral lesions and erythematous, fissured plaques on the palms and soles. Maintenance therapy consisted of IV vincristine and 5-day pulse of steroids every 12 weeks, daily 6MP, and weekly MTX, which were increased to ≥ 150% of standard dosing due to persistent absolute neutrophil counts > 1500. Metabolites obtained on admission demonstrated elevated 6MMP metabolites at 35,761 (normal < 5700). TPMT and NUDT15 enzyme activity were normal and no alterations in genotyping were discovered. OUTCOME: Patient's oral chemotherapy, including both 6MP and MTX, were stopped and allopurinol 100 mg daily was initiated, which lead to overall improvement. DISCUSSION: Clinical findings of acute mucositis and worsening of hand-foot syndrome, in the setting of inadequate myelosuppression in a child on maintenance therapy for ALL should raise concerns to consider altered metabolism pathway leading to toxic metabolite buildup. Allopurinol can play in improving cutaneous manifestation and chemotherapeutic dosing in patients with altered metabolism.

Clinical pharmacists' knowledge, attitude, perception, and beliefs about the role of pharmacogenetic testing for genes polymorphisms when prescribing mercaptopurine.

Background: Single nucleotide polymorphisms in the gene encoding proteins involved in mercaptopurine metabolism can influence drug efficacy and safety. This study aims to assess clinical pharmacists' knowledge about mercaptopurine-related genes and their polymorphisms and investigate their attitudes, perceptions, and beliefs about the need for and importance of pharmacogenetic testing for mercaptopurine. Methods: A cross-sectional descriptive study was conducted among oncology/hematology clinical pharmacists in Saudi Arabia using an online-questionnaire developed by experts in the field. The questionnaire consists of four-sections exploring clinical pharmacists' knowledge, attitudes, perceptions, and beliefs about the importance of gene testing and genes polymorphism when prescribing mercaptopurine. Descriptive statistics were used to analyze the data in the study. Results: A total of 41 oncology/hematology clinical pharmacists responded to the survey invitation. Almost half of them had more than 10 years of work experience, but only 17 % of them received formal training in pharmacogenetics. The overall level of knowledge about pharmacogenetics among participants was low, with a mean score of 2.8 points (1.7) out of 8 items. However, around 76 % agreed that it is important to perform pharmacogenetic screening prior to prescribing mercaptopurine, and almost 93 % state that it will influence their dosage recommendation. Most of the participants had a good perception (95.1 %) of their role in genetic testing for medication selection, dosing, and monitoring; however, about 10 % of surveyed pharmacists reported not being completely responsible about recommending pharmacogenetic testing. The surveyed pharmacists had a good belief in the importance of pharmacogenetic testing and their overall attitude was positive toward the use of pharmacogenetic testing, with emphasis on the importance of training on the proper assessment and interpretation of pharmacogenetic tests. Conclusions: Pharmacists demonstrated good perception and positive attitude toward pharmacogenetic testing, despite the low level of knowledge and limited formal training. Thus, more attention to developing national guidelines on pharmacogenetic testing is warranted to ensure successful pharmacogenetic testing implementation.

6-Mercaptopurine potently inhibits recruitment of SHP2 by phosphorylated PD-1 to inhibit PD-1 signalling and enhance T cell function.

Antibody inhibitors that block PD-1/PD-L1 interaction have been approved for oncological clinics, yielding impressive treatment effects. Small molecules inhibiting PD-1 signalling are at various stages of development, given that small molecular drugs are expected to outperform protein drugs in several ways. Currently, a significant portion of these small molecular inhibitors achieve this purpose by binding to a limited region of the PD-L1 protein, thereby limiting the choice of chemical structures. Alternative strategies for developing small-molecular PD-1 inhibitors are urgently needed to broaden the choice of chemical structures. Here, we report that 6-mercaptopurine (6-MP) inhibits PD-1 signalling, activates T cell function in vitro and in vivo and shrinks tumours by activating cytotoxic T cells. 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.

Combination Therapy With Immunomodulators Improves the Pharmacokinetics of Infliximab But Not Vedolizumab or Ustekinumab.

BACKGROUND AND AIMS: The aim of this study was to assess how 6-thioguanine nucleotide (6-TGN) levels and use of oral methotrexate relate to the pharmacokinetics of biologics. METHODS: This was a prospective cohort study including patients with inflammatory bowel diseases on maintenance doses of infliximab, vedolizumab, or ustekinumab on monotherapy or combination with a thiopurine or oral methotrexate. We collected 6-TGN concentrations, biomarker levels, and clinical and endoscopic disease activity. The primary outcomes were infliximab, vedolizumab, and ustekinumab concentrations as well as anti-drug antibodies (ADAs). RESULTS: A total of 369 patients were recruited (113 infliximab, 133 vedolizumab, and 123 ustekinumab). Patients with 6-TGN levels ≥146 pmol per 8 × 108 red blood cells (RBCs), and those receiving combination therapy with thiopurine or oral methotrexate had significantly higher infliximab concentrations when compared with monotherapy (median levels of 17.4 µg/mL on thiopurine with 6-TGN ≥146 pmol per 8 × 108 RBCs, 17.1 on methotrexate, and 3.9 on infliximab monotherapy; P = .001 for both comparisons). However, there was no association between the use of immunomodulators and 6-TGN concentrations with vedolizumab (median levels of 8.8 on thiopurine with 6-TGN ≥152 pmol per 8 × 108 RBCs, 6.8 on methotrexate, and 10.5 on vedolizumab monotherapy; P > .05 for both comparisons) or ustekinumab median concentrations (median levels of 5.0 on thiopurine with 6-TGN ≥154 pmol per 8 × 108 RBCs, 5.2 on methotrexate and 7.0 on ustekinumab monotherapy; P > .05 for both comparisons). Fourteen (12%) patients had anti-infliximab antibodies, while 1 patient had ADAs in each of the other drug cohorts. CONCLUSIONS: Achieving higher 6-TGN levels or the use of methotrexate improved the pharmacokinetics of infliximab. Conversely, these data do not support the use of combination therapy to augment pharmacokinetics with vedolizumab or ustekinumab.

Anti-inflammation and anti-aging mechanisms of mercaptopurine in vivo and in vitro.

Skin is the biggest organ of the human body, which easily gets irritated by exposure to the sun. Skin photoaging and acute photodamage are caused by intense UV-B radiation. Therefore, it is imperative to find new compounds to prevent skin damage and aging. Mercaptopurine is an immunologic agent commonly used for treating Acute lymphoblastic leukemia and inflammatory bowel disease. The beneficial effects of mercaptopurine on the skin have not been reported, and its intrinsic mechanism of action is unclear. Therefore, this study was to explore mercaptopurine when exposed to UV-B radiation in HacaT cells and C57BL6 mice aging and damage effects. The model of in vivo UV-B-induced skin damage and skin photoaging was established, and the impact of mercaptopurine on cell and animal skin was studied. The study found that mercaptopurine, on the one hand, inhibits cellular and animal senescence. On the other, it inhibits the expression of mitogen-activated protein kinase (MAPK) and the nuclear factor κB (NF-κB), which are important signaling molecules in the early UV-B reaction signaling pathway. In addition, mercaptopurine downregulates matrix metalloproteinase expression, increases collagen fiber content, and facilitates collagen synthesis. Treatment with mercaptopurine also inhibits the expression of inflammatory factors and reduces inflammatory cell infiltration of the skin. In conclusion, our study elucidates mercaptopurine's anti-photoaging and anti-inflammatory activity in cellular and animal models.

Mercaptopurine induced myelosuppression in a child with a NUDT15 rs116855232 homozygous variant.

INTRODUCTION: Mercaptopurine (6-MP) is the backbone of the consolidation and maintenance therapy for paediatric acute lymphoblastic leukaemia (ALL). Nevertheless, it can cause critical myelosuppression. Predicting adverse reactions to 6-MP often involves the investigation of pharmacogenetic variants; in particular thiopurine S-methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15). Lately, NUDT15 variants have been shown to play a significant pharmacogenetic role in predicting 6-MP intolerance in children of Asian descent. CASE REPORT: We present a six-year-old male child of Indian origin with persistent cytopenia after treatment. This prompted targeted sequencing of the genes TPMT and NUD15. The results revealed two copies of the variant of NUD15 rs116855232, that is, NUDT15*2 genotype. MANAGEMENT AND OUTCOME: Since the NUDT15*2 allele classified the patient as a poor metabolizer, he was restarted on a low dose of 6-MP, which he tolerated. DISCUSSION: Individuals with the NUDT15*2allele (*2/*2 genotype) are poor metabolizers of thiopurines which results in an adverse reaction to 6-MP. About 3.5% of Indians show variations in the TPMT gene as compared to 19.4% variations observed in NUDT15, which makes the latter a more reliable disease marker.

A validated ecofriendly chromatographic method for determination of myasthenia gravis combined medications in spiked human plasma.

Recently, the main interest of analytical chemistry researchers has been the development of green analytical methods to minimize harmful effects on the environment and natural life. Therefore, an RP-HPLC method was developed and assessed regarding its greenness criteria using three greenness assessment tools: an analytical eco-scale, an analytical greenness metric approach and a green analytical procedure index. This method aims to separate and quantitatively determine three co-administered drugs, namely pyridostigmine bromide (PYR), 6-mercaptopurine (MRC) and prednisolone (PRD), in their tertiary mixture and spiked human plasma. These drugs are co-administered to manage myasthenia gravis autoimmune disease. The separation was done using a C18 column and a gradient elution of a mixture of 0.1% H3 PO4 aqueous solution (pH 2.3) and methanol. The flow rate was adjusted to 1 ml/min and detection was done at 254 (for PYR and PRD) and at 330 nm (for MRC). The lower limits of quantitation were 15, 2, and 5 µg/ml for PYR, MER and PRD, respectively. Linear correlations were obtained and found to be near 1. In addition, the proposed method was validated according to the US Food and Drug Administration's instructions, and the results proved its success to determine the three studied drugs in their tertiary mixture and spiked human plasma.

Evaluation of tolerance to mercaptopurine in patients with inflammatory bowel disease and gastrointestinal intolerance to azathioprine.

BACKGROUND: Thiopurines such as azathioprine (AZA) and mercaptopurine (MP) are commonly utilized to treat inflammatory bowel disease (IBD). Their use is frequently restricted due to gastrointestinal intolerance (GI). Previous retrospective studies have reported that AZA-intolerant patients may benefit from a switch to MP; yet the effectiveness of this strategy has not been prospectively evaluated. AIMS: To assess GI tolerance to MP in patients who are intolerant to AZA, and to identify clinical predictors of GI intolerance to AZA or MP. METHODS: A prospective, observational, single-cohort study was performed in 92 thiopurine-naïve IBD patients. They were started on a 50mg dose of AZA and escalated to 2.5mg/kg per day by week 2. Those with GI intolerance were rechallenged with a 50% dose of AZA, after which another dose escalation attempt was made. If symptoms persisted, they were switched to MP. RESULTS: Thirty (32.6%) of the recruited patients suffered from GI intolerance to AZA. Of these, 15 did not present recurrence of symptoms after rechallenge with lower doses. Of 15 intolerant patients, 14 were switched to MP. Within the MP cohort, 8 patients (57%) were also intolerant to MP, 5 (36%) had no symptoms, and 1 (7%) was lost to follow-up. Female gender was the only independent predictor of GI intolerance to AZA. CONCLUSIONS: Up to half of the AZA-intolerant patients tolerated a 50% dose rechallenge that was successfully escalated. A switch to MP was tolerated in over a third of cases whom rechallenge failed. Our strategy (challenge-rechallenge-switch) achieved an overall GI tolerance to thiopurines in most of the patients.

Screening for mercaptopurine intolerance in ALL - target the genes or their product?

To avoid toxicity, patients with inherited intolerance to thiopurines require major dose reductions of six mercaptopurine (6MP) for acute lymphoblastic leukaemia (ALL) maintenance treatment. Germline variants in the NUDT15 gene are emerging as the most common cause of 6MP intolerance in East Asian populations. New approaches are being developed to identify susceptibility to 6MP toxicity in order to appropriately tailor dosing schedules for at-risk patients. Commentary on: Tanaka et al. Prominence of NUDT15 genetic variation associated with 6-mercaptopurine tolerance in a genome-wide association study of Japanese children with acute lymphoblastic leukaemia. Br J Haematol 2022;199:260-269 and Yoshida et al. Low NUDT15 expression levels due to biallelic NUDT15 variants and 6-mercaptopurine intolerance. Br J Haematol 2022;199:270-276.

Prominence of NUDT15 genetic variation associated with 6-mercaptopurine tolerance in a genome-wide association study of Japanese children with acute lymphoblastic leukaemia.

Inherited genetic variation is associated with 6-mercaptopurine (6-MP) dose reduction and frequent toxicities induced by 6-MP. However, the tolerable dose for 6-MP is not fully predicted by the known variation in NUDT15 and TPMT among Asian children with acute lymphoblastic leukaemia (ALL). We performed a genome-wide association study (GWAS) related to 6-MP dose among Japanese children with ALL. This GWAS comprised 224 patients previously enrolled in Tokyo Children's Cancer Study Group clinical studies with replication attempted in 55 patients. Genome-wide single nucleotide polymorphism (SNP) genotypes were evaluated for association with average 6-MP dose during the initial 168 days of maintenance therapy. Possible associations were observed across five gene-coding regions, among which only variants at 13q14.2 were significant and replicated genome-wide (rs116855232, NUDT15, ß = -10.99, p = 3.7 × 10-13 ). Notable findings were observed for variants in AFF3 (rs75364948, p = 2.05 × 10-6 ) and CHST11 (rs1148407, p = 2.09 × 10-6 ), but were not replicated possibly due to small numbers. A previously reported candidate SNP in MTHFR was associated with higher average 6-MP dose (rs1801133, p = 0.045), and FOLH1 (rs12574928) was associated in an evaluation of candidate regions (padjust  = 0.013). This study provides strong evidence that rs116855232 in NUDT15 is the genetic factor predominantly associated with 6-MP tolerable dose in children in Japan.

Low NUDT15 expression levels due to biallelic NUDT15 variants and 6-mercaptopurine intolerance.

6-Mercaptopurine (6-MP) is widely used for the treatment of paediatric leukaemia and lymphoma. Recently, germline variants in the NUDT15 gene have been identified as one of the major genetic causes for 6-MP-associated adverse effects such as myelosuppression. Patients with hypomorphic NUDT15 variants accumulate excessive levels of DNA-incorporated thioguanine in white blood cells, resulting in severe myelosuppression. Although preclinical studies suggest that these variants may influence the protein stability of NUDT15, this has not been directly characterised in patients. In this study, we report the development of a series of novel monoclonal antibodies against NUDT15, using which we quantitatively assessed NUDT15 protein levels in 37 patients with acute lymphoblastic leukaemia treated with 6-MP, using sandwich enzyme-linked immunosorbent assay (ELISA). The NUDT15 genotype was highly correlated with its protein levels (p < 0.0001), with homozygous and compound heterozygous patients showing exceedingly low NUDT15 expression. There was a positive correlation between NUDT15 protein level and 6-MP tolerance (r = 0.631, p < 0.0001). In conclusion, our results point to low NUDT15 protein abundance as the biochemical basis for NUDT15-mediated 6-MP intolerance, thus providing a phenotypic readout of inherited NUDT15 deficiency.

Risk Prediction and Comparative Efficacy of Anti-TNF vs Thiopurines, for Preventing Postoperative Recurrence in Crohn's Disease: A Pooled Analysis of 6 Trials.

BACKGROUND & AIMS: The superiority of anti-TNF-α agents to thiopurines for the prevention of postoperative recurrence of Crohn's disease (CD) after ileocolonic resection remains controversial. In this meta-analysis of individual participant data (IPD), the effect of both strategies was compared and assessed after risk stratification. METHODS: After a systematic literature search, IPD were requested from randomized controlled trials investigating thiopurines and/or anti-TNF-α agents after ileocolonic resection. Primary outcome was endoscopic recurrence (ER) (Rutgeerts score ≥i2) and secondary outcomes were clinical recurrence (Harvey-Bradshaw Index/Crohn's Disease Activity Index score) and severe ER (Rutgeerts score ≥i3). A fixed effect network meta-analysis was performed. Subgroup effects were assessed and a prediction model was established using Poisson regression models, including sex, smoking, Montreal classification, CD duration, history of prior resection and previous exposure to anti-TNF-α or thiopurines. RESULTS: In the meta-analysis of IPD, 645 participants from 6 studies were included. In the total population, a superior effect was demonstrated for anti-TNF-α compared with thiopurine prophylaxis for ER (relative risk [RR], 0.52; 95% confidence interval [CI], 0.33-0.80), clinical recurrence (RR, 0.50; 95% CI, 0.26-0.96), and severe ER (RR, 0.41; 95% CI, 0.21-0.79). No differential subgroup effects were found for ER. In Poisson regression analysis, previous exposure to anti-TNF-α and penetrating disease behavior were associated with ER risk. The advantage of anti-TNF-α agents as compared with thiopurines was observed in low- and high-risk groups. CONCLUSIONS: Anti-TNF-α is superior to thiopurine prophylaxis for the prevention of endoscopic and clinical postoperative CD recurrence after ileocolonic resection. The advantage of anti-TNF-α agents was confirmed in subgroup analysis and after risk stratification.

Thiopurine Enhanced ALL Maintenance (TEAM): study protocol for a randomized study to evaluate the improvement in disease-free survival by adding very low dose 6-thioguanine to 6-mercaptopurine/methotrexate-based maintenance therapy in pediatric and adult patients (0-45 years) with newly diagnosed B-cell precursor or T-cell acute lymphoblastic leukemia treated according to the intermediate risk-high group of the ALLTogether1 protocol.

BACKGROUND: A critical challenge in current acute lymphoblastic leukemia (ALL) therapy is treatment intensification in order to reduce the relapse rate in the subset of patients at the highest risk of relapse. The year-long maintenance phase is essential in relapse prevention. The Thiopurine Enhanced ALL Maintenance (TEAM) trial investigates a novel strategy for ALL maintenance. METHODS: TEAM is a randomized phase 3 sub-protocol to the ALLTogether1 trial, which includes patients 0-45 years of age with newly diagnosed B-cell precursor or T-cell ALL, and stratified to the intermediate risk-high (IR-high) group, in 13 European countries. In the TEAM trial, the traditional methotrexate (MTX)/6-mercaptopurine (6MP) maintenance backbone (control arm) is supplemented with low dose (2.5-12.5 mg/m2/day) oral 6-thioguanine (6TG) (experimental arm), while the starting dose of 6MP is reduced from 75 to 50 mg/m2/day. A total of 778 patients will be included in TEAM during ~ 5 years. The study will close when the last included patient has been followed for 5 years from the end of induction therapy. The primary objective of the study is to significantly improve the disease-free survival (DFS) of IR-high ALL patients by adding 6TG to 6MP/MTX-based maintenance therapy. TEAM has 80% power to detect a 7% increase in 5-year DFS through a 50% reduction in relapse rate. DFS will be evaluated by intention-to-treat analysis. In addition to reducing relapse, TEAM may also reduce hepatotoxicity and hypoglycemia caused by high levels of methylated 6MP metabolites. Methotrexate/6MP metabolites will be monitored and low levels will be reported back to clinicians to identify potentially non-adherent patients. DISCUSSION: TEAM provides a novel strategy for maintenance therapy in ALL with the potential of improving DFS through reducing relapse rate. Potential risk factors that have been considered include hepatic sinusoidal obstruction syndrome/nodular regenerative hyperplasia, second cancer, infection, and osteonecrosis. Metabolite monitoring can potentially increase treatment adherence in both treatment arms. TRIAL REGISTRATION: EudraCT, 2018-001795-38. Registered 2020-05-15, Clinicaltrials.gov , NCT04307576 . Registered 2020-03-13, https://clinicaltrials.gov/ct2/show/NCT04307576.

Effects of immunosuppressive drugs on COVID-19 severity in patients with autoimmune hepatitis.

BACKGROUND: We investigated associations between baseline use of immunosuppressive drugs and severity of Coronavirus Disease 2019 (COVID-19) in autoimmune hepatitis (AIH). PATIENTS AND METHODS: Data of AIH patients with laboratory confirmed COVID-19 were retrospectively collected from 15 countries. The outcomes of AIH patients who were on immunosuppression at the time of COVID-19 were compared to patients who were not on AIH medication. The clinical courses of COVID-19 were classified as (i)-no hospitalization, (ii)-hospitalization without oxygen supplementation, (iii)-hospitalization with oxygen supplementation by nasal cannula or mask, (iv)-intensive care unit (ICU) admission with non-invasive mechanical ventilation, (v)-ICU admission with invasive mechanical ventilation or (vi)-death and analysed using ordinal logistic regression. RESULTS: We included 254 AIH patients (79.5%, female) with a median age of 50 (range, 17-85) years. At the onset of COVID-19, 234 patients (92.1%) were on treatment with glucocorticoids (n = 156), thiopurines (n = 151), mycophenolate mofetil (n = 22) or tacrolimus (n = 16), alone or in combinations. Overall, 94 (37%) patients were hospitalized and 18 (7.1%) patients died. Use of systemic glucocorticoids (adjusted odds ratio [aOR] 4.73, 95% CI 1.12-25.89) and thiopurines (aOR 4.78, 95% CI 1.33-23.50) for AIH was associated with worse COVID-19 severity, after adjusting for age-sex, comorbidities and presence of cirrhosis. Baseline treatment with mycophenolate mofetil (aOR 3.56, 95% CI 0.76-20.56) and tacrolimus (aOR 4.09, 95% CI 0.69-27.00) were also associated with more severe COVID-19 courses in a smaller subset of treated patients. CONCLUSION: Baseline treatment with systemic glucocorticoids or thiopurines prior to the onset of COVID-19 was significantly associated with COVID-19 severity in patients with AIH.