Paediatric Strategy Forum for medicinal product development for acute myeloid leukaemia in children and adolescents: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

Paediatric strategy forum for medicinal product development of PI3-K, mTOR, AKT and GSK3β inhibitors in children and adolescents with cancer

Phosphatidylinositol 3-kinase (PI3-K) signalling pathway is a crucial path in cancer for cell survival and thus represents an intriguing target for new paediatric anti-cancer drugs. However, the unique clinical toxicities of targeting this pathway (resulting in hyperglycaemia) difficulties combining with chemotherapy, rarity of mutations in childhood tumours and concomitant mutations have resulted in major barriers to clinical translation of these inhibitors in treating both adults and children. Mutations in PIK3CA predict response to PI3-K inhibitors in adult cancers. The same mutations occur in children as in adults, but they are significantly less frequent in paediatrics. In children, high-grade gliomas, especially diffuse midline gliomas (DMG), have the highest incidence of PIK3CA mutations. New mutation-specific PI3-K inhibitors reduce toxicity from on-target PI3-Kα wild-type activity. The mTOR inhibitor everolimus is approved for subependymal giant cell astrocytomas. In paediatric cancers, mTOR inhibitors have been predominantly evaluated by academia, without an overall strategy, in empiric, mutation-agnostic clinical trials with very low response rates to monotherapy. Therefore, future trials of single agent or combination strategies of mTOR inhibitors in childhood cancer should be supported by very strong biological rationale and preclinical data. Further preclinical evaluation of glycogen synthase kinase-3 beta inhibitors is required. Similarly, even where there is an AKT mutation (∼0.1 %), the role of AKT inhibitors in paediatric cancers remains unclear. Patient advocates strongly urged analysing and conserving data from every child participating in a clinical trial. A priority is to evaluate mutation-specific, central nervous system-penetrant PI3-K inhibitors in children with DMG in a rational biological combination. The choice of combination, should be based on the genomic landscape e.g. PTEN loss and resistance mechanisms supported by preclinical data. However, in view of the very rare populations involved, innovative regulatory approaches are needed to generate data for an indication.

Navigating Treatment Options and Communication in Relapsed Pediatric AML

Despite improved outcomes in newly diagnosed pediatric AML, relapsed disease remains a therapeutic challenge. Factors contributing to slow progress in improving outcomes include inherent challenges in pediatric clinical trial accrual and the scarcity of novel targeted/immunotherapy agents available for pediatric development. This paradigm is changing, however, as international collaboration grows in parallel with the development of promising targeted agents. In this review, we discuss the therapeutic landscape of relapsed pediatric AML, including conventional chemotherapy, targeted therapies, and the challenges of drug approvals in this patient population. We highlight current efforts to improve communication among academia, industry, and regulatory authorities and discuss the importance of international collaboration to improve access to new therapies. Among the therapeutic options, we highlight the approach to second hematopoietic stem cell transplant (HSCT) and discuss which patients are most likely to benefit from this potentially curative intervention. Importantly, we acknowledge the challenges in providing these high-risk interventions to our patients and their families and the importance of shared communication and decision making when considering early-phase clinical trials and second HSCT.

Venetoclax Combination Treatment of Acute Myeloid Leukemia in Adolescents and Young Adult Patients

Over the past two decades, the prognosis in adolescents and young adults (AYAs) diagnosed with acute myeloid leukemia (AML) has significantly improved. The standard intensive cytotoxic treatment approach for AYAs with AML, consisting of induction chemotherapy with anthracycline/cytarabine combination followed by consolidation chemotherapy or stem cell transplantation, has lately been shifting toward novel targeted therapies, mostly in the fields of clinical trials. One of the most recent advances in treating AML is the combination of the B-cell lymphoma 2 (Bcl-2) inhibitor venetoclax with hypomethylating agents, which has been studied in elderly populations and was approved by the Food and Drug Administration (FDA) for patients over 75 years of age or patients excluded from intensive chemotherapy induction schemas due to comorbidities. Regarding the AYA population, venetoclax combination therapy could be a therapeutic option for patients with refractory/relapsed (R/R) AML, although data from real-world studies are currently limited. Venetoclax is frequently used by AYAs diagnosed with advanced hematologic malignancies, mainly acute lymphoblastic leukemia and myelodysplastic syndromes, as a salvage therapeutic option with considerable efficacy and safety. Herein, we aim to summarize the evidence obtained from clinical trials and observational studies on venetoclax use in AYAs with AML. Based on the available evidence, venetoclax is a safe and effective therapeutic option for R/R AML AYA patients. However, further research in larger cohorts is needed to confirm these data, establishing the benefits of a venetoclax-based regimen for this special population.

Impact of ACCELERATE Paediatric Strategy Forums: a review of the value of multi-stakeholder meetings in oncology drug development

In a landscape of an increasing number of products and histology and age agnostic trials for rare patient cancer, prioritization of products is required. Paediatric Strategy Forums, organized by ACCELERATE and the European Medicines Agency with participation of the US Food and Drug Administration, are multi-stakeholder meetings that share information to best inform pediatric drug development strategies and subsequent clinical trial decisions. Academia, industry, regulators, and patient advocates are equal members, with patient advocates highlighting unmet needs of children and adolescents with cancer. The 11 Paediatric Strategy Forums since 2017 have made specific and general conclusions to accelerate drug development. Conclusions on product prioritization meetings, as well as global master protocols, have been outputs of these meetings. Forums have provided information for regulatory discussions and decisions by industry to facilitate development of high-priority products; for example, 62% of high-priority assets (agreed at a Forum) in contrast to 5% of those assets not considered high priority have been the subject of a Paediatric Investigational Plan or Written Request. Where there are multiple products of the same class, Forums have recommended a focused and sequential approach. Class prioritization resulted in an increase in waivers for non-prioritized B-cell products (44% to 75%) and a decrease in monotherapy trials, proposed in Paediatric Investigation Plans (PIP) submissions of checkpoint inhibitors from 53% to 19%. Strategy Forums could play a role in defining unmet medical needs. Multi-stakeholder forums, such as the Paediatric Strategy Forum, serve as a model to improve collaboration in the oncology drug development paradigm.

The PedAL/EuPAL Project: A Global Initiative to Address the Unmet Medical Needs of Pediatric Patients with Relapsed or Refractory Acute Myeloid Leukemia

The prognosis of children with acute myeloid leukemia (AML) has improved incrementally over the last few decades. However, at relapse, overall survival (OS) is approximately 40-50% and is even lower for patients with chemo-refractory disease. Effective and less toxic therapies are urgently needed for these children. The Pediatric Acute Leukemia (PedAL) program is a strategic global initiative that aims to overcome the obstacles in treating children with relapsed/refractory acute leukemia and is supported by the Leukemia and Lymphoma Society in collaboration with the Children's Oncology Group, the Innovative Therapies for Children with Cancer consortium, and the European Pediatric Acute Leukemia (EuPAL) foundation, amongst others. In Europe, the study is set up as a complex clinical trial with a stratification approach to allocate patients to sub-trials of targeted inhibitors at relapse and employing harmonized response and safety definitions across sub-trials. The PedAL/EuPAL international collaboration aims to determine new standards of care for AML in a first and second relapse, using biology-based selection markers for treatment stratification, and deliver essential data to move drugs to front-line pediatric AML studies. An overview of potential treatment targets in pediatric AML, focused on drugs that are planned to be included in the PedAL/EuPAL project, is provided in this manuscript.

Therapeutic targeting in pediatric acute myeloid leukemia with aberrant HOX/MEIS1 expression

Despite advances in the clinical management of childhood acute myeloid leukemia (AML) during the last decades, outcome remains fatal in approximately one third of patients. Primary chemoresistance, relapse and acute and long-term toxicities to conventional myelosuppressive therapies still constitute significant challenges and emphasize the unmet need for effective targeted therapies. Years of scientific efforts have translated into extensive insights on the heterogeneous spectrum of genetics and oncogenic signaling pathways of AML and identified a subset of patients characterized by upregulation of HOXA and HOXB homeobox genes and myeloid ecotropic virus insertion site 1 (MEIS1). Aberrant HOXA/MEIS1 expression is associated with genotypes such as rearrangements in Histone-lysine N-methyltransferase 2A (KMT2A-r), nucleoporin 98 (NUP98-r) and mutated nucleophosmin (NPM1c) that are found in approximately one third of children with AML. AML with upregulated HOXA/MEIS1 shares a number of molecular vulnerabilities amenable to recently developed molecules targeting the assembly of protein complexes or transcriptional regulators. The interaction between the nuclear scaffold protein menin and KMT2A has gained particular interest and constitutes a molecular dependency for maintenance of the HOXA/MEIS1 transcription program. Menin inhibitors disrupt the menin-KMT2A complex in preclinical models of KMT2A-r, NUP98-r and NPM1c acute leukemias and its occupancy at target genes leading to leukemic cell differentiation and apoptosis. Early-phase clinical trials are either ongoing or in development and preliminary data suggests tolerable toxicities and encouraging efficacy of menin inhibitors in adults with relapsed or refractory KMT2A-r and NPM1c AML. The Pediatric Acute Leukemia/European Pediatric Acute Leukemia (PedAL/EUPAL) project is focused to advance and coordinate informative clinical trials with new agents and constitute an ideal framework for testing of menin inhibitors in pediatric study populations. Menin inhibitors in combination with standard chemotherapy or other targeting agents may enhance anti-leukemic effects and constitute rational treatment strategies for select genotypes of childhood AML, and provide enhanced safety to avoid differentiation syndrome. In this review, we discuss the pathophysiological mechanisms in KMT2A-r, NUP98-r and NPM1c AML, emerging molecules targeting the HOXA/MEIS1 transcription program with menin inhibitors as the most prominent examples and future therapeutic implications of these agents in childhood AML.

Children's Oncology Group's 2023 blueprint for research: Myeloid neoplasms

During the past decade, the outcomes of pediatric patients with acute myeloid leukemia (AML) have plateaued with 5-year event-free survival (EFS) and overall survival (OS) of approximately 46 and 64%, respectively. Outcomes are particularly poor for those children with high-risk disease, who have 5-year OS of 46%. Substantial survival improvements have been observed for a subset of patients treated with targeted therapies. Specifically, children with KMT2A-rearranged AML and/or FLT3 internal tandem duplication (FLT3-ITD) mutations benefitted from the addition of gemtuzumab ozogamicin, an anti-CD33 antibody-drug conjugate, in the AAML0531 clinical trial (NCT00372593). Sorafenib also improved response and survival in children with FLT3-ITD AML in the AAML1031 clinical trial (NCT01371981). Advances in characterization of prognostic cytomolecular events have helped to identify patients at highest risk of relapse and facilitated allocation to consolidative hematopoietic stem cell transplant (HSCT) in first remission. Some patients clearly have improved survival with HSCT, although the benefit is largely unknown for most patients. Finally, data-driven refinements in supportive care recommendations continue to evolve with meaningful and measurable reductions in toxicity and improvements in EFS and OS. As advances in application of targeted therapies, risk stratification, and improved supportive care measures are incorporated into current trials and become standard-of-care, there is every expectation that we will see improved survival with a reduction in toxic morbidity and mortality. The research agenda of the Children's Oncology Group's Myeloid Diseases Committee continues to build upon experience and outcomes with an overarching goal of curing more children with AML.

Relapsed pediatric acute myeloid leukaemia: state-of-the-art in 2023

Although outcomes of children and adolescents with newly diagnosed acute myeloid leukemia (AML) have improved significantly over the past two decades, more than one-third of patients continue to relapse and experience suboptimal long-term outcomes. Given the small numbers of patients with relapsed AML and historical logistical barriers to international collaboration including poor trial funding and drug availability, the management of AML relapse has varied among pediatric oncology cooperative groups with several salvage regimens utilized and a lack of universally defined response criteria. The landscape of relapsed pediatric AML treatment is changing rapidly, however, as the international AML community harnesses collective knowledge and resources to characterize the genetic and immunophenotypic heterogeneity of relapsed disease, identify biological targets of interest within specific AML subtypes, develop new precision medicine approaches for collaborative investigation in early-phase clinical trials, and tackle challenges of universal drug access across the globe. This review provides a comprehensive overview of progress achieved to date in the treatment of pediatric patients with relapsed AML and highlights modern, state-of-the-art therapeutic approaches under active and emerging clinical investigation that have been facilitated by international collaboration among academic pediatric oncologists, laboratory scientists, regulatory agencies, pharmaceutical partners, cancer research sponsors, and patient advocates.

Risk-Stratified Therapy for Pediatric Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) is the second most common type of leukemia in children. Recent advances in high-resolution genomic profiling techniques have uncovered the mutational landscape of pediatric AML as distinct from adult AML. Overall survival rates of children with AML have dramatically improved in the past 40 years, currently reaching 70% to 80% in developed countries. This was accomplished by the intensification of conventional chemotherapy, improvement in risk stratification using leukemia-specific cytogenetics/molecular genetics and measurable residual disease, appropriate use of allogeneic hematopoietic stem cell transplantation, and improvement in supportive care. However, the principle therapeutic approach for pediatric AML has not changed substantially for decades and improvement in event-free survival is rather modest. Further refinements in risk stratification and the introduction of emerging novel therapies to contemporary therapy, through international collaboration, would be key solutions for further improvements in outcomes.

Paediatric Strategy Forum for medicinal product development of DNA damage response pathway inhibitors in children and adolescents with cancer: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

DNA damage response inhibitors have a potentially important therapeutic role in paediatric cancers; however, their optimal use, including patient selection and combination strategy, remains unknown. Moreover, there is an imbalance between the number of drugs with diverse mechanisms of action and the limited number of paediatric patients available to be enrolled in early-phase trials, so prioritisation and a strategy are essential. While PARP inhibitors targeting homologous recombination-deficient tumours have been used primarily in the treatment of adult cancers with BRCA1/2 mutations, BRCA1/2 mutations occur infrequently in childhood tumours, and therefore, a specific response hypothesis is required. Combinations with targeted radiotherapy, ATR inhibitors, or antibody drug conjugates with DNA topoisomerase I inhibitor-related warheads warrant evaluation. Additional monotherapy trials of PARP inhibitors with the same mechanism of action are not recommended. PARP1-specific inhibitors and PARP inhibitors with very good central nervous system penetration also deserve evaluation. ATR, ATM, DNA-PK, CHK1, WEE1, DNA polymerase theta and PKMYT1 inhibitors are early in paediatric development. There should be an overall coordinated strategy for their development. Therefore, an academia/industry consensus of the relevant biomarkers will be established and a focused meeting on ATR inhibitors (as proof of principle) held. CHK1 inhibitors have demonstrated activity in desmoplastic small round cell tumours and have a potential role in the treatment of other paediatric malignancies, such as neuroblastoma and Ewing sarcoma. Access to CHK1 inhibitors for paediatric clinical trials is a high priority. The three key elements in evaluating these inhibitors in children are (1) innovative trial design (design driven by a clear hypothesis with the intent to further investigate responders and non-responders with detailed retrospective molecular analyses to generate a revised or new hypothesis); (2) biomarker selection and (3) rational combination therapy, which is limited by overlapping toxicity. To maximally benefit children with cancer, investigators should work collaboratively to learn the lessons from the past and apply them to future studies. Plans should be based on the relevant biology, with a focus on simultaneous and parallel research in preclinical and clinical settings, and an overall integrated and collaborative strategy.

Paediatric Strategy Forum for medicinal product development in mitogen-activated protein kinase pathway inhibitors: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

As the mitogen-activated protein kinase (MAPK) signalling pathway is activated in many paediatric cancers, it is an important therapeutic target. Currently, a range of targeted MAPK pathway inhibitors are being developed in adults. However, MAPK signals through many cascades and feedback loops and perturbing the MAPK pathway may have substantial influence on other pathways as well as normal development. In view of these issues, the ninth Paediatric Strategy Forum focused on MAPK inhibitors. Development of MAPK pathway inhibitors to date has been predominantly driven by adult indications such as malignant melanoma. However, these inhibitors may also target unmet needs in paediatric low-grade gliomas, high-grade gliomas, Langerhans cell histiocytosis, juvenile myelomonocytic leukaemia and several other paediatric conditions. Although MAPK inhibitors have demonstrated activity in paediatric cancer, the response rates and duration of responses needs improvement and better documentation. The rapid development and evaluation of combination approaches, based on a deep understanding of biology, is required to optimise responses and to avoid paradoxical tumour growth and other unintended consequences including severe toxicity. Better inhibitors with higher central nervous systempenetration for primary brain tumours and cancers with a propensity for central nervous system metastases need to be studied to determine if they are more effective than agents currently being used, and the optimum duration of therapy with MAPK inhibition needs to be determined. Systematic and coordinated clinical investigations to inform future treatment strategies with MAPK inhibitors, rather than use outside of clinical trials, are needed to fully assess the risks and benefits of these single agents and combination strategies in both front-line and in the refractory/relapse settings. Platform trials could address the investigation of multiple similar products and combinations. Accelerating the introduction of MAPK inhibitors into front-line paediatric studies is a priority, as is ensuring that these studies generate data appropriate for scientific and regulatory purposes. Early discussions with regulators are crucial, particularly if external controls are considered as randomised control trials in small patient populations can be challenging. Functional end-points specific to the populations in which they are studied, such as visual acuity, motor and neuro psychological function are important, as these outcomes are often more reflective of benefit for lower grade tumours (such as paediatric low-grade glioma and plexiform neurofibroma) and should be included in initial study designs for paediatric low-grade glioma. Early prospective discussions and agreements with regulators are necessary. Long-term follow-up of patients receiving MAPK inhibitors is crucial in view of their prolonged administration and the important involvement of this pathway in normal development. Further rational development, with a detailed understanding of biology of this class of products, is crucial to ensure they provide optimal benefit while minimising toxicity to children and adolescents with cancer.

European regulatory strategy for supporting childhood cancer therapy developments

INTRODUCTION

Regulatory decisions on paediatric investigation plans (PIPs) aim at making effective and safe medicines timely available for children with high unmet medical need. At the same time, scientific knowledge progresses continuously leading frequently to the identification of new molecular targets in the therapeutic area of oncology. This, together with further efforts to optimise next generation medicines, results in novel innovative products in development pipelines. In the context of global regulatory development requirements for these growing pipelines of innovative products (e.g. US RACE for children Act), it is an increasing challenge to complete development efforts in paediatric oncology, a therapeutic area of rare and life-threatening diseases with high unmet needs.

OBJECTIVE

Regulators recognise feasibility challenges of the regulatory obligations in this context. Here, we explain the EU regulatory decision making strategy applied to paediatric oncology, which aims fostering evidence generation to support developments based on needs and robust science. Because there is a plethora of products under development within given classes of or within cancer types, priorities need to be identified and updated as evidence evolves. This also includes identifying the need for third or fourth generation products to secure focused and accelerated drug development.

CONCLUSION

An agreed PIP, as a plan, is a living document which can be modified in light of new evidence. For this to be successful, input from the various relevant stakeholders, i.e. patients/parents, clinicians and investigators is required. To efficiently obtain this input, the EMA is co-organising with ACCELERATE oncology stakeholder engagement platform meetings.

Access to early-phase clinical trials for children with relapsed and refractory neuroblastoma: A multicentre international study

OBJECTIVES

Neuroblastoma is the most common extracranial tumour in children, and prognosis for refractory and relapsed disease is still poor. Early-phase clinical trials play a pivotal role in the development of novel drugs. Ensuring adequate recruitment is crucial. The primary aim was to determine the rate of participation trials for children with refractory/relapsed neuroblastoma in two of the largest drug development European institutions.

METHODS

Data from patients diagnosed with refractory/relapsed neuroblastoma between January 2012 and December 2018 at the two institutions were collected and analysed.

RESULTS

Overall, 48 patients were included. A total of 31 (65%) refractory/relapsed cases were enrolled in early-phase trials. The main reasons for not participating in clinical trials included not fulfilling eligibility criteria prior to consent (12/17, 70%) and screening failure (2/17, 12%). Median time on trial was 4.3 months (range 0.6-13.4). Most common cause for trial discontinuation was disease progression (67.7%). Median overall survival was longer in refractory (28 months, 95% CI: 20.9-40.2) than in relapsed patients (14 months, 95% CI: 8.1-20.1) (p = .034).

CONCLUSIONS

Although two thirds of children with refractory/relapsed neuroblastoma were enrolled in early-phase trials, recruitment rates can still be improved. The main cause for not participating on trials was not fulfilling eligibility criteria prior to consent, mainly due to performance status and short life expectancy. This study highlights the hurdles to access to innovative therapies for children with relapsed/refractory neuroblastomas, and identifies key areas of development to improve recruitment to early-phase trials.

Paediatric Strategy Forum for medicinal product development of multi-targeted kinase inhibitors in bone sarcomas: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

The eighth Paediatric Strategy Forum focused on multi-targeted kinase inhibitors (mTKIs) in osteosarcoma and Ewing sarcoma. The development of curative, innovative products in these tumours is a high priority and addresses unmet needs in children, adolescents and adults. Despite clinical and investigational use of mTKIs, efficacy in patients with bone tumours has not been definitively demonstrated. Randomised studies, currently being planned or in progress, in front-line and relapse settings will inform the further development of this class of product. It is crucial that these are rapidly initiated to generate robust data to support international collaborative efforts. The experience to date has generally indicated that the safety profile of mTKIs as monotherapy, and in combination with chemotherapy or other targeted therapy, is consistent with that of adults and that toxicity is manageable. Increasing understanding of relevant predictive biomarkers and tumour biology is absolutely critical to further develop this class of products. Biospecimen samples for correlative studies and biomarker development should be shared, and a joint academic-industry consortium created. This would result in an integrated collection of serial tumour tissues and a systematic retrospective and prospective analyses of these samples to ensure robust assessment of biologic effect of mTKIs. To support access for children to benefit from these novel therapies, clinical trials should be designed with sufficient scientific rationale to support regulatory and payer requirements. To achieve this, early dialogue between academia, industry, regulators, and patient advocates is essential. Evaluating feasibility of combination strategies and then undertaking a randomised trial in the same protocol accelerates drug development. Where possible, clinical trials and development should include children, adolescents, and adults less than 40 years. To respond to emerging science, in approximately 12 months, a multi-stakeholder group will meet and review available data to determine future directions and priorities.

Relapsed acute myeloid leukemia in children and adolescents: current treatment options and future strategies

Pediatric acute myeloid leukemia (AML) develops from clonal expansion of hematopoietic precursor cells and is characterized by morphologic and cytomolecular heterogeneity. Although the past 40 years have seen significant improvements in overall survival, the prevailing treatment challenges in pediatric AML are the prevention of relapse and the management of relapsed disease. Approximately 25% of children and adolescents with AML suffer disease relapse and face a poor prognosis. Our greater understanding of the genomic, epigenomic, metabolomic, and immunologic pathophysiology of relapsed AML allows for better therapeutic strategies that are being developed for pediatric clinical trials. The development of biologically rational agents is critical as conventional chemotherapeutic salvage regimens are not effective for all patients and pose risk of organ toxicity in heavily pretreated patients. Another major barrier to improvement in outcomes for relapsed pediatric AML is the historic lack of availability and participation in clinical trials. There are ongoing efforts to launch multinational clinical trials of emerging therapies. The purpose of this review is to summarize currently available and newly developed therapies for relapsed pediatric AML.

Targeted inhibitors and antibody immunotherapies: Novel therapies for paediatric leukaemia and lymphoma

Despite improved outcomes achieved in the last decades for children with newly diagnosed leukaemia and lymphoma, treatment of patients with refractory/relapsed disease remains a challenge. The cure rate is still unsatisfactory and often achieved at the cost of significant morbidity. Exploring treatment with novel agents should offer less toxic therapeutic options, without compromising efficacy. Bispecific and antibody-drug conjugates targeting CD19 and CD22 (blinatumomab and inotuzumab ozogamicin) play an important role in the treatment of relapsed and refractory B-cell precursor acute lymphoblastic leukaemia (BCP-ALL); antibodies targeting CD123 and CD38 are also under investigation for acute myeloid leukaemia (AML) and T-ALL, respectively. Targeted therapy with small molecules is of primary importance for specific genetic subtypes, such as BCR-ABL-positive ALL, FLT3-ITD AML and anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma. KMT2A-directed targeted therapy with menin inhibitors holds promise to be of relevance in KMT2A-rearranged leukaemias, known to have dismal prognosis. Target inhibition in cellular pathways such as BCL-2, RAS, MEK, Bruton's tyrosine kinase, JAK-STAT or CDK4/CDK6 inhibition may be suitable for different diseases with common mutated pathways. Nevertheless, development and approval of new agents for paediatric cancers lags behind adult therapeutic options. New regulations were implemented to accelerate drug development for children. Considering the number of oncology medicinal products available for adults and the rarity of paediatric cancers, prioritisation based on scientific evidence and medical need, as well as international collaboration, is critical. Herein, we review the current status of drug development for children with leukaemia and lymphoma, excluding cellular therapy despite its well-known significance.

Efficacy of Flotetuzumab in Combination with Cytarabine in Patient-Derived Xenograft Models of Pediatric Acute Myeloid Leukemia

Children with acute myeloid leukemia (AML) have a poor prognosis despite the intensification of chemotherapy. Future efforts to improve outcomes should focus on more precise targeting of leukemia cells. CD123, or IL3RA, is expressed on the surface of nearly all pediatric AML samples and is a high-priority target for immunotherapy. The efficacy of an investigational dual-affinity retargeting antibody (DART) molecule (CD123 × CD3; MGD006 or flotetuzumab) was assessed in two distinct patient-derived xenograft (PDX) models of pediatric AML. MGD006 simultaneously binds to CD123 on target cells and CD3 on effector T cells, thereby activating T cells and redirecting them to induce cytotoxicity in target cells. The concurrent treatment of cytarabine and MGD006 was performed to determine the effect of cytarabine on T-cell counts and MGD006 activity. Treatment with MGD006 along with an allogeneic human T-cell infusion to act as effector cells induced durable responses in both PDX models, with CD123 positivity. This effect was sustained in mice treated with a combination of MGD006 and cytarabine in the presence of T cells. MGD006 enhanced T-cell proliferation and decreased the burden of AML blasts in the peripheral blood with or without cytarabine treatment. These data demonstrate the efficacy of MGD006 in prolonging survival in pediatric AML PDX models in the presence of effector T cells and show that the inclusion of cytarabine in the treatment regimen does not interfere with MGD006 activity.

Pediatric Acute Myeloid Leukemia—Past, Present, and Future

This review reports about the main steps of development in pediatric acute myeloid leukemia (AML) concerning diagnostics, treatment, risk groups, and outcomes. Finally, a short overview of present and future approaches is given.

Diagnostic challenges in acute monoblastic/monocytic leukemia in children

Acute monoblastic/monocytic leukemia (AMoL), previously defined as M5 according to FAB classification, is one of the most common subtypes of Acute Myeloid Leukemia (AML) in children, representing ~15-24% of all pediatric AMLs. Currently, the characterization of monocytic-lineage neoplasia at diagnosis includes cytomorphology, cytochemistry, immunophenotyping by multiparametric flow cytometry, cytogenetics, and molecular biology. Moreover, measurable residual disease (MRD) detection is critical in recognizing residual blasts refractory to chemotherapy. Nonetheless, diagnosis and MRD detection may still be challenging in pediatric AMoL since the morphological and immunophenotypic features of leukemic cells potentially overlap with those of normal mature monocytic compartment, as well as differential diagnosis can be troublesome, particularly with Juvenile Myelomonocytic Leukemia and reactive monocytosis in infants and young children. A failure or delay in diagnosis and inaccuracy in MRD assessment may worsen the AMoL prognosis. Therefore, improving diagnosis and monitoring techniques is mandatory to stratify and tailor therapies to the risk profile. This Mini Review aims to provide an updated revision of the scientific evidence on pediatric AMoL diagnostic tools.

Paediatric Strategy Forum for medicinal product development of chimeric antigen receptor T-cells in children and adolescents with cancer: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

The seventh multi-stakeholder Paediatric Strategy Forum focused on chimeric antigen receptor (CAR) T-cells for children and adolescents with cancer. The development of CAR T-cells for patients with haematological malignancies, especially B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), has been spectacular. However, currently, there are scientific, clinical and logistical challenges for use of CAR T-cells in BCP-ALL and other paediatric malignancies, particularly in acute myeloid leukaemia (AML), lymphomas and solid tumours. The aims of the Forum were to summarise the current landscape of CAR T-cell therapy development in paediatrics, too identify current challenges and future directions, with consideration of other immune effector modalities and ascertain the best strategies to accelerate their development and availability to children. Although the effect is of limited duration in about half of the patients, anti-CD19 CAR T-cells produce high response rates in relapsed/refractory BCP-ALL and this has highlighted previously unknown mechanisms of relapse. CAR T-cell treatment as first- or second-line therapy could also potentially benefit patients whose disease has high-risk features associated with relapse and failure of conventional therapies. Identifying patients with very early and early relapse in whom CAR T-cell therapy may replace haematopoietic stem cell transplantation and be definitive therapy versus those in whom it provides a more effective bridge to haematopoietic stem cell transplantation is a very high priority. Development of approaches to improve persistence, either by improving T cell fitness or using more humanised/fully humanised products and co-targeting of multiple antigens to prevent antigen escape, could potentially further optimise therapy. Many differences exist between paediatric B-cell non-Hodgkin lymphomas (B-NHL) and BCP-ALL. In view of the very small patient numbers with relapsed lymphoma, careful prioritisation is needed to evaluate CAR T-cells in children with Burkitt lymphoma, primary mediastinal B cell lymphoma and other NHL subtypes. Combination trials of alternative targets to CD19 (CD20 or CD22) should also be explored as a priority to improve efficacy in this population. Development of CD30 CAR T-cell immunotherapy strategies in patients with relapsed/refractory Hodgkin lymphoma will likely be most efficiently accomplished by joint paediatric and adult trials. CAR T-cell approaches are early in development for AML and T-ALL, given the unique challenges of successful immunotherapy actualisation in these diseases. At this time, CD33 and CD123 appear to be the most universal targets in AML and CD7 in T-ALL. The results of ongoing or planned first-in-human studies are required to facilitate further understanding. There are promising early results in solid tumours, particularly with GD2 targeting cell therapies in neuroblastoma and central nervous system gliomas that represent significant unmet clinical needs. Further understanding of biology is critical to success. The comparative benefits of autologous versus allogeneic CAR T-cells, T-cells engineered with T cell receptors T-cells engineered with T cell receptor fusion constructs, CAR Natural Killer (NK)-cell products, bispecific T-cell engager antibodies and antibody-drug conjugates require evaluation in paediatric malignancies. Early and proactive academia and multi-company engagement are mandatory to advance cellular immunotherapies in paediatric oncology. Regulatory advice should be sought very early in the design and preparation of clinical trials of innovative medicines, for which regulatory approval may ultimately be sought. Aligning strategic, scientific, regulatory, health technology and funding requirements from the inception of a clinical trial is especially important as these are very expensive therapies. The model for drug development for cell therapy in paediatric oncology could also involve a 'later stage handoff' to industry after early development in academic hands. Finally, and very importantly, strategies must evolve to ensure appropriate ease of access for children who need and could potentially benefit from these therapies.

Second Paediatric Strategy Forum for anaplastic lymphoma kinase (ALK) inhibition in paediatric malignancies: ACCELERATE in collaboration with the European Medicines Agency with the participation of the Food and Drug Administration

The first (2017) and sixth (2021) multistakeholder Paediatric Strategy Forums focused on anaplastic lymphoma kinase (ALK) inhibition in paediatric malignancies. ALK is an important oncogene and target in several paediatric tumours (anaplastic large cell lymphoma [ALCL], inflammatory myofibroblastic tumour [IMT], neuroblastoma and hemispheric gliomas in infants and young children) with unmet therapeutic needs. ALK tyrosine kinase inhibitors have been demonstrated to be active both in ALK fusion-kinase positive ALCL and IMT. ALK alterations differ, with fusions occurring in ALCL, IMT and gliomas, and activating mutations and amplification in neuroblastoma. While there are many ALK inhibitors in development, the number of children diagnosed with ALK driven malignancies is very small. The objectives of this ALK Forum were to (i) Describe current knowledge of ALK biology in childhood cancers; (ii) Provide an overview of the development of ALK inhibitors for children; (iii) Identify the unmet needs taking into account planned or current ongoing trials; (iv) Conclude how second/third-generation inhibitors could be evaluated and prioritised; (v) Identify lessons learnt from the experience with ALK inhibitors to accelerate the paediatric development of other anti-cancer targeted agents in the new regulatory environments. There has been progress over the last four years, with more trials of ALK inhibitors opened in paediatrics and more regulatory submissions. In January 2021, the US Food and Drug Administration approved crizotinib for the treatment of paediatric and young adult patients with relapsed or refractory ALCL and there are paediatric investigation plans (PIPs) for brigatinib and for crizotinib in ALCL and IMT. In ALCL, the current goal is to investigate the inclusion of ALK inhibitors in front-line therapy with the aim of decreasing toxicity with higher/similar efficacy compared to present first-line therapies. For IMT, the focus is to develop a joint prospective trial with one product in children, adolescents and adults, taking advantage of the common biology across the age spectrum. As approximately 50% of IMTs are ALK-positive, molecular analysis is required to identify patients to be treated with an ALK inhibitor. For neuroblastoma, crizotinib has not shown robust anti-tumour activity. A focused and sequential development of ALK inhibitors with very good central nervous system (CNS) penetration in CNS tumours with ALK fusions should be undertaken. The Forum reinforced the strong need for global academic collaboration, very early involvement of regulators with studies seeking possible registration and early academia-multicompany engagement. Innovations in study design and conduct and the use of 'real-world data' supporting development in these rare sub-groups of patients for whom randomised clinical trials are not feasible are important initiatives. A focused and sequenced development strategy, where one product is evaluated first with other products being assessed sequentially, is applicable for ALK inhibitors and other medicinal products in children.

Targeted Therapy in Pediatric AML: An Evolving Landscape

The outcomes associated with pediatric acute myeloid leukemia (AML) have improved over the last few decades, with the implementation of intensive chemotherapy, hematopoietic stem cell transplant, and improved supportive care. However, even with intensive therapy and the use of HSCT, both of which carry significant risks of short- and long-term side effects, approximately 30% of children are not able to be cured. The characterization of AML in pediatrics has evolved over time and it currently involves use of a variety of diagnostic tools, including flow cytometry and comprehensive genomic sequencing. Given the adverse effects of chemotherapy and the need for additional therapeutic options to improve outcomes in these patients, the genomic and molecular architecture is being utilized to inform selection of targeted therapies in pediatric AML. This review provides a summary of current, targeted therapy options in pediatric AML.

Treatment of acute myeloid leukemia in children: A practical perspective

Pediatric acute myeloid leukemia (AML) is a heterogeneous disease that requires a multifaceted treatment approach. Although outcomes for low-risk AML have improved significantly over recent decades, high-risk AML continues to be associated with an adverse prognosis. Recent advances in molecular diagnostics, risk stratification, and supportive care have contributed to improvements in outcomes in pediatric AML. Targeted approaches, for example, the use of tyrosine kinase inhibitors to treat FLT3-ITD AML, offer promise and are currently undergoing clinical investigation in pediatric patients. New approaches to hematopoietic stem cell transplantation, including the use of haploidentical donors, are significantly expanding donor options for patients with high-risk AML. This review provides an overview of recent advances in the treatment of pediatric AML that are likely to have clinical impact and reshape the standard of care.

Paediatric Strategy Forum for medicinal product development of epigenetic modifiers for children: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

The fifth multistakeholder Paediatric Strategy Forum focussed on epigenetic modifier therapies for children and adolescents with cancer. As most mutations in paediatric malignancies influence chromatin-associated proteins or transcription and paediatric cancers are driven by developmental gene expression programs, targeting epigenetic mechanisms is predicted to be a very important therapeutic approach in paediatric cancer. The Research to Accelerate Cures and Equity (RACE) for Children Act FDARA amendments to section 505B of the FD&C Act was implemented in August 2020, and as there are many epigenetic targets on the FDA Paediatric Molecular Targets List, clinical evaluation of epigenetic modifiers in paediatric cancers should be considered early in drug development. Companies are also required to submit to the EMA paediatric investigation plans aiming to ensure that the necessary data to support the authorisation of a medicine for children in EU are of high quality and ethically researched. The specific aims of the forum were i) to identify epigenetic targets or mechanisms of action associated with epigenetic modification relevant to paediatric cancers and ii) to define the landscape for paediatric drug development of epigenetic modifier therapies. DNA methyltransferase inhibitors/hypomethylating agents and histone deacetylase inhibitors were largely excluded from discussion as the aim was to discuss those targets for which therapeutic agents are currently in early paediatric and adult development. Epigenetics is an evolving field and could be highly relevant to many paediatric cancers; the biology is multifaceted and new targets are frequently emerging. Targeting epigenetic mechanisms in paediatric malignancy has in most circumstances yet to reach or extend beyond clinical proof of concept, as many targets do not yet have available investigational drugs developed. Eight classes of medicinal products were discussed and prioritised based on the existing level of science to support early evaluation in children: inhibitors of menin, DOT1L, EZH2, EED, BET, PRMT5 and LSD1 and a retinoic acid receptor alpha agonist. Menin inhibitors should be moved rapidly into paediatric development, in view of their biological rationale, strong preclinical activity and ability to fulfil an unmet clinical need. A combination approach is critical for successful utilisation of any epigenetic modifiers (e.g. EZH2 and EED) and exploration of the optimum combination(s) should be supported by preclinical research and, where possible, molecular biomarker validation in advance of clinical translation. A follow-up multistakeholder meeting focussing on BET inhibitors will be held to define how to prioritise the multiple compounds in clinical development that could be evaluated in children with cancer. As epigenetic modifiers are relatively early in development in paediatrics, there is a clear opportunity to shape the landscape of therapies targeting the epigenome in order that efficient and optimum plans for their evaluation in children and adolescents are developed in a timely manner.

European research networks to facilitate drug research in children

Paediatric drug development faces several barriers. These include fragmentation of stakeholders and inconsistent processes during the conduct of research. This review summarises recent efforts to overcome these barriers in Europe. Two exemplar initiatives are described. The European Paediatric Translational Research Infrastructure facilitates preclinical research and other work that underpins clinical trials. conect4children facilitates the design and implementation of clinical trials. Both these initiatives listen to the voices of children and their advocates. Coordination of research needs specific effort that supplements work on science, resources and the policy context.