Reiji Fukano

Background/Objectives: Maternal systemic lupus erythematosus (SLE) is associated with preterm birth, but whether maternal disease activity influences early neonatal hematologic profiles beyond developmental immaturity remains unclear. We compared hematologic parameters between SLE-exposed preterm infants and maturity-matched controls and explored findings according to maternal SLE flare during pregnancy. Methods: This single-center retrospective matched-cohort study included 13 SLE-exposed preterm infants and 39 controls matched 1:3 by gestational age, birth weight, and sex. White blood cell (WBC) count, absolute neutrophil count (ANC), hemoglobin concentration, and platelet count were assessed at birth, around postnatal day 5, and at their nadir during hospitalization. Group differences were estimated using linear regression models including matched-set identifiers as fixed effects. Flare-stratified and hepatic analyses were exploratory, without adjustment for multiple comparisons. Results: Overall matched-set analyses showed no clear differences in WBC count, ANC, hemoglobin, or platelet values between SLE-exposed infants and controls. The estimated difference in nadir ANC was −405/μL (95% confidence interval [CI], −985 to 174/μL; p = 0.164). In the maternal-flare subgroup, nadir WBC count was lower than in its matched controls (difference, −2.31 × 10³/μL; 95% CI, −3.96 to −0.65 × 10³/μL; p = 0.009), as was nadir ANC (difference, −672/μL; 95% CI, −1260 to −85/μL; p = 0.028). Corresponding matched-set differences were not evident at birth or around postnatal day 5. The non-flare subgroup did not show a consistent pattern of leukocyte suppression. Conclusions: Maternal SLE exposure was not clearly associated with an overall difference in neonatal hematologic profiles within matched sets. Maternal SLE flare may identify a subgroup with lower WBC and neutrophil nadirs, but this exploratory finding requires confirmation in larger studies.

Clinical development of crizotinib in children with ALK‐positive anaplastic large cell lymphoma (ALCL) was advanced in the US but not in Japan. The objectives of phase 1 part of a clinical study in Japan were to assess the safety and pharmacokinetics and determine the recommended phase 2 dose (RP2D) of crizotinib in children with relapsed/refractory (R/R) ALK‐positive ALCL or neuroblastoma (NB). Two dose levels (165 and 280 mg/m ² twice daily (BID)) were planned to be evaluated. The aim of phase 2 part of the study was to assess the antitumor activity of crizotinib at the RP2D in children with R/R ALK‐positive ALCL. Seven patients were eligible for phase 1 part, 5 with ALCL and 2 with NB. All 7 patients received crizotinib at a starting dose of 165 mg/m ² BID, with 1 dose‐limiting toxicity observed (grade 3 gamma‐glutamyltransferase increased). The most common grade 3 or 4 adverse event was neutropenia (71%). The steady‐state C _max and AUC _tau of crizotinib at 165 mg/m ² BID were higher than expected. Considering the risk of a greater incidence of severe neutropenia, we decided that the 165 mg/m ² BID be the RP2D without evaluation at 280 mg/m ² BID. A total of 11 patients with ALK‐positive ALCL were enrolled in the phase 2 part. The objective response rate was 72.7% (90% CI, 43.6%–92.1%). One patient permanently discontinued crizotinib due to disease progression. Crizotinib at 165 mg/m ² BID was well tolerated and showed favorable antitumor activity in children with R/R ALK‐positive ALCL. Trial Registration: UMIN‐CTR: UMIN000028075

Background: The benefit of adding rituximab to standard lymphomes malins B (LMB) chemotherapy for children with high‐risk mature B‐cell non‐Hodgkin lymphoma (B‐NHL) has previously been demonstrated in an international randomized phase III trial, to which the Japanese Pediatric Leukemia/Lymphoma Study Group could not participate.Methods: To evaluate the efficacy and safety of rituximab in combination with LMB chemotherapy in Japanese patients, we conducted a single‐arm multicenter trial.Results: In this study, 45 patients were enrolled between April 2016 and September 2018. A total of 33 (73.3%), 5 (11.1%), and 6 (13.3%) patients had Burkitt lymphoma/leukemia, diffuse large B‐cell lymphoma, and aggressive mature B‐NHL, not otherwise specified, respectively. Ten (22.2%) and 21 (46.7%) patients had central nervous system disease and leukemic disease, respectively. The median follow‐up period was 47.5 months. Three‐year event‐free survival and overall survival were 97.7% (95% confidence interval, 84.9–99.7) and 100%, respectively. The only event was relapse, which occurred in a patient with diffuse large B‐cell lymphoma. Seven patients (15.6%) developed Grade 4 or higher non‐hematologic adverse events. Febrile neutropenia was the most frequent Grade 3 or higher adverse event after the pre‐phase treatment, with a frequency of 54.5%.Conclusion: The efficacy and safety of rituximab in combination with LMB chemotherapy in children with high‐risk mature B‐NHL was observed in Japan.

Nutritional support is essential for patients with severe motor and intellectual disabilities (SMID) to ensure the smooth provision of medical care. These patients often require long-term tube feeding with enteral formulas, potentially leading to deficiencies in vitamins and trace elements. Additionally, frequent antibiotic use for infections often disrupts gut microbiota, inhibiting vitamin K2 production by intestinal bacteria. We assessed the serum protein induced by vitamin K absence or antagonists-II (PIVKA-II) and undercarboxylated osteocalcin (ucOC) levels to assess the vitamin K status in 20 patients with SMID (median age: 44.1 years, 11 men and 9 women) undergoing long-term tube feeding for durations ranging from 3 to 31 years. Thirteen (65%) and nine (45%) patients had elevated PIVKA-II (<40 mAU/mL) and serum ucOC levels (reference value < 4.50 ng/mL), respectively. Dietary vitamin K1 intake did not differ between patients with and without elevated PIVKA-II levels. Vitamin K2 supplementation for 3 months decreased serum PIVKA-II levels near those within the reference range. Approximately half of the patients with SMID on tube feeding had subclinical vitamin K deficiency. Further studies are needed to ascertain if long-term vitamin K2 supplementation effectively prevents vitamin K deficiency-induced hypercoagulation, osteoporosis, and vascular calcification in patients with SMID.

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.

Summary: Peripheral T‐cell lymphoma (PTCL) is a group of heterogeneous non‐Hodgkin lymphomas showing a mature T‐cell or natural killer cell phenotype, but its molecular abnormalities in paediatric patients remain unclear. By employing next‐generation sequencing and multiplex ligation‐dependent probe amplification of tumour samples from 26 patients, we identified somatic alterations in paediatric PTCL including Epstein–Barr virus (EBV)‐negative (EBV^–) and EBV‐positive (EBV⁺) patients. As recurrent mutational targets for PTCL, we identified several previously unreported genes, including TNS1, ZFHX3, LRP2, NCOA2 and HOXA1, as well as genes previously reported in adult patients, e.g. TET2, CDKN2A, STAT3 and TP53. However, for other reported mutations, VAV1‐related abnormalities were absent and mutations of NRAS, GATA3 and JAK3 showed a low frequency in our cohort. Concerning the association of EBV infection, two novel fusion genes: STAG2‐AFF2 and ITPR2‐FSTL4, and deletion and alteration of CDKN2A/2B, LMO1 and HOXA1 were identified in EBV^– PTCL, but not in EBV⁺ PTCL. Conversely, alterations of PCDHGA4, ADAR, CUL9 and TP53 were identified only in EBV⁺ PTCL. Our observations suggest a clear difference in the molecularmechanism of onset between paediatric and adult PTCL and a difference in the characteristics of genetic alterations between EBV^– and EBV⁺ paediatric PTCL.

Acute erythroid leukemia (AEL) is characterized by a distinct morphology, mutational spectrum, lack of preclinical models, and poor prognosis. Here, using multiplexed genome editing of mouse hematopoietic stem and progenitor cells and transplant assays, we developed preclinical models of AEL and non-erythroid acute leukemia and describe the central role of mutational cooperativity in determining leukemia lineage. Different combination of mutations in Trp53, Bcor, Dnmt3a, Rb1, and Nfix resulted in the development of leukemia with an erythroid phenotype, accompanied by the acquisition of alterations in signaling and transcription factor genes that recapitulate human AEL by cross-species genomic analysis. Clonal expansion during tumor evolution was driven by mutational cooccurrence, with clones harboring a higher number of founder and secondary lesions (eg, mutations in signaling genes) showing greater evolutionary fitness. Mouse and human AEL exhibited deregulation of genes regulating erythroid development, notably Gata1, Klf1, and Nfe2, driven by the interaction of mutations of the epigenetic modifiers Dnmt3a and Tet2 that perturbed methylation and thus expression of lineage-specific transcription factors. The established mouse leukemias were used as a platform for drug screening. Drug sensitivity was associated with the leukemia genotype, with the poly (ADP-ribose) polymerase inhibitor talazoparib and the demethylating agent decitabine efficacious in Trp53/Bcor–mutant AEL, CDK7/9 inhibitors in Trp53/Bcor/Dnmt3a–mutant AEL, and gemcitabine and bromodomain inhibitors in NUP98-KDM5A leukemia. In conclusion, combinatorial genome editing has shown the interplay of founding and secondary genetic alterations in phenotype and clonal evolution, epigenetic regulation of lineage-specific transcription factors, and therapeutic tractability in erythroid leukemogenesis.