Karsten Nysom

Adding blinatumomab to standard chemotherapy for infants with KMT2A ‐rearranged acute B‐cell lymphoblastic leukemia ( KMT2A ‐r B‐ALL) improves outcomes. Although blinatumomab impairs immunoglobulin G (lgG) production, increasing infection susceptibility, IgG recovery remains poorly understood. Thirty infants received Interfant‐06 protocol chemotherapy with one course of blinatumomab added post‐induction. We screened 169 IgG levels post‐blinatumomab and IVIg supplementation timepoints. An increase in IgG was subsequently noted until maintenance, where practically all available values returned to normal (>4 g/L). Blinatumomab leads to an IgG reduction, with near‐complete recovery occurring before end of treatment. Future trials should monitor immunoglobulin recovery post‐blinatumomab to guide infection‐preventing strategies. Trial Registration : EudraCT no: 2016‐004674‐17

Diffuse intrinsic pontine glioma (DIPG) is the pediatric tumor with the worst prognosis. BIOMEDE was a randomized phase 2 trial comparing the efficacy in terms of overall survival (OS) (primary endpoint) of epidermal growth factor receptor (EGFR) inhibitor erlotinib, mTOR inhibitor everolimus and multitargeted tyrosine kinase inhibitor dasatinib in combination with radiotherapy in patients with a biopsy-proven DIPG. Tumors were assessed centrally for immunohistochemical biomarkers (EGFR overexpression or PTEN loss) together with whole-exome and RNA sequencing. A cohort of 66 children with the same inclusion criteria and treated previously with temozolomide-based regimen was used to compare outcome. Treatment allocation was performed by randomization in 233 patients, designed so that a drug could not be allocated if the corresponding biomarker was absent: 36 received erlotinib, 102 received dasatinib and 95 received everolimus. The trial was ended for futility of the primary endpoint following the recommendations of the independent data monitoring committee: OS from biopsy was not different from the control cohort (median OS = 10.8 months (95% confidence interval (CI): 9.5−13.0)) in any of the three arms (median OS = 9.7 months (95% CI: 7.8−14.6) for erlotinib; 9.9 months (95% CI: 8.8−11.2) for dasatinib; and 11.9 months (95% CI: 10.7−14.2) for everolimus). Everolimus showed significantly less ocular, renal, skin and gastrointestinal side effects and treatment discontinuation for toxicity (secondary endpoint). TP53 mutations, frequently linked to multiple structural chromosomal aberrations, were the strongest predictor for poor survival in multivariate analysis (hazard ratio = 2.8 (95% CI: 1.9−4.2), P < 0.0001). Both mutations in and activation of the mTOR pathway were associated with a better response to everolimus. Four long-term survivors treated with an mTOR inhibitor were alive free of treatment over 6 years from diagnosis. With comprehensive tumor profiling, BIOMEDE validated prognostic biomarkers as well as informative theranostic biomarkers for future trials. ClinicalTrials.gov: NCT02233049.

Rhabdoid tumours (RT) are malignancies of the central nervous system, kidneys, liver and soft tissues that most commonly affect very young children with survival rates below 30% in high-risk cohorts. Treatment entails surgery, intensive chemotherapy and radiotherapy, associated with substantial short- and long-term toxicities. There is an unmet need to develop targeted therapies for RT to improve patient outcomes and mitigate the toxicities of current therapy. Detailed research followed by a workshop had the objective of enabling the development of targeted therapeutics for RT. Given the inherent commonality of their biology (i.e. biallelic inactivation of SMARCB1 or more rarely SMARCA4 ) the therapeutic approach should be similar for intra-cranial and extra-cranial tumours. DDB1–CUL4-associated factor 5 is a promising target, and the development of small molecule binders/degraders is a priority. Enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) degraders may have greater therapeutic potential than inhibitors. Fibroblast growth factor receptor and platelet-derived growth factor receptor inhibitors may have value in subgroups. Mouse double minute 2 homologue (MDM2) is a priority target for novel therapeutic development and combination trials. Combinations of EZH2, MDM2 inhibitors and selective inhibitors of nuclear export should be evaluated robustly preclinically and drive early clinical studies.

KMT2A -rearranged infant ALL ( KMT2A -r ALL) has a poor prognosis. Adding blinatumomab, a bispecific T-cell engager targeting CD19, to standard chemotherapy for infants with KMT2A -r ALL improved short-term outcomes. Here, we present long-term results, toxicity, and pharmacokinetics of blinatumomab from this study. Thirty infants received Interfant-06 protocol chemotherapy with one additional postinduction blinatumomab course. Disease-free survival (DFS) and overall survival (OS) were compared with a historical Interfant-06–selected cohort without blinatumomab. Infection and administration of intravenous immunoglobulin (IVIg) and granulocyte-colony stimulating factor (G-CSF) were documented. Blinatumomab's steady-state concentration (Css) and clearance (CL) were analyzed. The median follow-up was 4.2 years (range, 3.2-6.0). Blinatumomab significantly improved outcomes compared with controls, with a 4-year DFS of 83.3% versus 44.0% and a 4-year OS of 93.3% versus 60.2%. No infection-related fatality occurred postinduction, in contrast to 4% in Interfant-06. IVIg was administered in 19 (63%) patients, and G-CSF in five (17%). The mean Css of blinatumomab was 706 ± 194 pg/mL/d, and the median CL was 0.89 L/h/m ² (range, 0.57-2.66). Adding blinatumomab to standard treatment for infants with KMT2A -r ALL resulted in sustained improvement in outcome. Pharmacokinetics were comparable across pediatric age groups. The benefit of blinatumomab in frontline therapy remains promising and awaits further confirmation in ongoing trials.

PURPOSE: Outcomes for children with relapsed and refractory high-risk neuroblastoma (RR-HR-NBL) remain dismal. Here, we investigate addition of the anti-GD2 monoclonal antibody, dinutuximab beta (dB), to temozolomide (T)-based chemotherapy. MATERIALS AND METHODS: Patients with RR-HR-NBL were randomly assigned in a 1:2 ratio to receive chemotherapy alone or chemotherapy with dB, given concurrently as a 7-day infusion (10 mg/m ² /24 h). The trial had a factorial design, with some patients also randomly assigned between chemotherapy regimens (T v T-topotecan [TTo]). Crossover to dB with To/cyclophosphamide was allowed for patients randomly assigned to chemotherapy alone with disease progression (PD). The primary outcome was best objective response (complete or partial) rate (overall response rate [ORR]) during six cycles of treatment. Progression-free (PFS), overall survival (OS), and safety were secondary outcomes. RESULTS: Sixty-five patients were randomly assigned to chemotherapy alone (3 T, 19 TTo) or with dB (6 dBT, 37 dBTTo). The median age was 4 years; 28 and 37 patients had refractory and relapsed diseases, respectively. Baseline characteristics were balanced between arms. The ORR was 30.2% (13 of 43) and 18.2% (4 of 22) in dB and non-dB arms, the median PFS was 11.1 months (95% CI, 4.3 to 15.5) for dB patients and 3.8 months (95% CI, 1.9 to 7.9) for non-dB patients, respectively. The median OS was 25.7 months (95% CI, 11.4 to not reached [NR]) for dB patients and 17.1 months (95% CI, 7.6 to 54.6) for non-dB patients (upper 95% CI, NR in dB arm). Thirteen of 22 patients in the non-dB arm crossed over to dB with cyclophosphamide/To because of PD. Neurotoxicity was more common in the dB arm (grade 1 and 2: 26% v 9%, grade 3: 2.3% v 4.5%), but other toxicities were similar. CONCLUSION: Within a randomized phase II setting, results observed with addition of dB to T-based chemotherapy in RR-HR-NB warrant further evaluation.

PURPOSE: High levels of DNA replication stress and defects in the DNA damage response (DDR) pathways are vulnerabilities of many poor prognosis childhood malignancies. Ataxia telangiectasia and Rad3-related protein (ATR) is a key regulator of these pathways and constitutes an attractive target, especially in combination. However, the malignancies where ATR inhibitors have maximum benefit and synergistic combinations differ between adults and children. DESIGN: ACCELERATE convened a multistakeholder meeting and conducted review and analysis to propose the optimal pathway for the development of ATR inhibitors in pediatric malignancies. RESULTS: Considering the lack of identified biomarkers, the initial evaluation of ATR inhibitors should focus on Ewing sarcoma, rhabdomyosarcoma, and neuroblastoma in view of their high levels of DNA replication stress and defects in DDR pathways. Early phase trials of ATR inhibitors should be iterative, based on a clear hypothesis with responders and nonresponders undergoing detailed molecular analysis and a revised new hypothesis generated. Trial designs should restrict monotherapy evaluation to a brief exposure in a small number of patients and progress rapidly to combinations. Highlighted combination partners are poly(ADP-ribose) polymerase inhibitors and antibody drug conjugates with topoisomerase I inhibitor payloads. Combinations with ALK inhibitors (in ALK / MYCN -aberrant neuroblastoma) and aurora A kinase (in MYCN -amplified) are supported by robust mechanisms of action and preclinical data. Early interactions with regulators are crucial, and early phase clinical trials should be conducted in regulatory-approved, academic-sponsored, industry-supported, platform trials. CONCLUSION: ATR inhibitors are a prototype for the development of medicinal products in a limited pediatric population. For the substantial potential of ATR inhibitors in children with malignancy to be realized, strategic planning between academia, industry, regulators, and patient advocates is vital.

Children with relapsed acute leukemia have a poor prognosis; current relapse treatments are toxic, and novel treatments are needed. The anti‐CD38 antibody isatuximab is approved for relapsed‐refractory multiple myeloma in adults. We present results of the ISAKIDS study (NCT03860844) investigating isatuximab in children with relapsed‐refractory acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML). This Phase 2, single‐arm, multicenter, open‐label study enrolled children aged 28 days to −4 sensitivity threshold for ALL and 10 ⁻³ sensitivity threshold for AML. One event of fatal cytokine release syndrome was reported in a patient with a high baseline white blood cell count, leading to trial adaptation. The toxicity of isatuximab with chemotherapy was otherwise manageable. Despite initial evidence of efficacy of isatuximab combined with intensive chemotherapy, CR/CRi rates did not meet stringent prespecified criteria to proceed to ISAKIDS Stage 2 (≥60% [T‐ALL] and ≥70% [B‐ALL and AML]).

Summary: EWOG‐MESRAT (European Working Group—Methylation Signatures and Response to Azacitidine Therapy; DRKS00007185) is an investigator‐initiated trial that studied EPIC array‐based DNA methylation patterns and next generation sequencing (NGS)‐based variant allele frequencies (VAFs) of driver mutations in peripheral blood (PB) and bone marrow (BM) of 11 patients with newly diagnosed juvenile myelomonocytic leukaemia (JMML) during therapy with azacitidine. We demonstrate that the pharmacodynamic activity of azacitidine can efficiently be monitored in PB and BM. DNA methylation subgroup classification was linked to clinical response after three cycles of azacitidine and found to be conserved between PB and BM in all patients. In contrast, neither changes in VAFs nor changes in DNA methylation patterns during the course of therapy correlated with therapy outcome among the 11 study patients. This work thus supports the value of DNA methylation subgroup classification from PB samples for response prediction of single‐agent azacitidine in patients with JMML.