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

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.

Challenges and strategies associated with CAR-T cell therapy in blood malignancies

Cellular immunotherapy, particularly CAR-T cells, has shown potential in the improvement of outcomes in patients with refractory and recurrent malignancies of the blood. However, achieving sustainable long-term complete remission for blood cancer remains a challenge, with resistance and relapse being expected outcomes for many patients. Although many studies have attempted to clarify the mechanisms of CAR-T cell therapy failure, the mechanism remains unclear. In this article, we discuss and describe the current state of knowledge regarding these factors, which include elements that influence the CAR-T cell, cancer cells as a whole, and the microenvironment surrounding the tumor. In addition, we propose prospective approaches to overcome these obstacles in an effort to decrease recurrence rates and extend patient survival subsequent to CAR-T cell therapy.

Classic Hodgkin Lymphoma in Adolescents and Young Adults

Hodgkin lymphoma (HL) represents one of the more common cancers occurring in adolescent and young adults (AYAs) age 15-39 years. Despite a generally high cure rate, age-related differences in HL biology and the optimal therapeutic approaches including supportive care and risks for long-term adverse effects in the AYA population remain understudied. After an overview of HL epidemiology and biology in the AYA population, this review will cover frontline pediatric and adult treatment approaches. Recently completed and ongoing studies will foster harmonization of risk group definition and trial eligibility criteria across the AYA spectrum, enabling more rapid progress. In addition to treatment approaches, an evolving holistic care approach to AYA HL will result in enhanced understanding of unique challenges, and continued improved short- and long-term outcome for these patients.

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.

Pediatric oncology drug development and dosage optimization

Oncology drug discovery and development has always been an area facing many challenges. Phase 1 oncology studies are typically small, open-label, sequential studies enrolling a small sample of adult patients (i.e., 3-6 patients/cohort) in dose escalation. Pediatric evaluations typically lag behind the adult development program. The pediatric starting dose is traditionally referenced on the recommended phase 2 dose in adults with the incorporation of body size scaling. The size of the study is also small and dependent upon the prevalence of the disease in the pediatric population. Similar to adult development, the dose is escalated or de-escalated until reaching the maximum tolerated dose (MTD) that also provides desired biological activities or efficacy. The escalation steps and identification of MTD are often rule-based and do not incorporate all the available information, such as pharmacokinetic (PK), pharmacodynamic (PD), tolerability and efficacy data. Therefore, it is doubtful if the MTD approach is optimal to determine the dosage. Hence, it is important to evaluate whether there is an optimal dosage below the MTD, especially considering the emerging complexity of combination therapies and the long-term tolerability and safety of the treatments. Identification of an optimal dosage is also vital not only for adult patients but for pediatric populations as well. Dosage-finding is much more challenging for pediatric populations due to the limited patient population and differences among the pediatric age range in terms of maturation and ontogeny that could impact PK. Many sponsors defer the pediatric strategy as they are often perplexed by the challenges presented by pediatric oncology drug development (model of action relevancy to pediatric population, budget, timeline and regulatory requirements). This leads to a limited number of approved drugs for pediatric oncology patients. This review article provides the current regulatory landscape, incentives and how they impact pediatric drug discovery and development. We also consider different pediatric cancers and potential clinical trial challenges/opportunities when designing pediatric clinical trials. An outline of how quantitative methods such as pharmacometrics/modelling & simulation can support the dosage-finding and justification is also included. Finally, we provide some reflections that we consider helpful to accelerate pediatric drug discovery and development.

Early and Late Toxicities of Chimeric Antigen Receptor T-Cells

As chimeric antigen receptor (CAR) T-cell therapy is increasingly integrated into clinical practice across a range of malignancies, identifying and treating inflammatory toxicities will be vital to success. Early experiences with CD19-targeted CAR T-cell therapy identified cytokine release syndrome and neurotoxicity as key acute toxicities and led to unified initiatives to mitigate the influence of these complications. In this section, we provide an update on the current state of CAR T-cell-related toxicities, with an emphasis on emerging acute toxicities affecting additional organ systems and considerations for delayed toxicities and late effects.

CD72 is a pan-tumor antigen associated to pediatric acute leukemia

In the development of novel immunotherapeutic approaches, the step of target identification is a challenging process, because it aims at identifying robust tumor-associated antigens (TAAs) specific for the pathological population and causing no off-target effects. Here we propose CD72 as a novel and robust TAA for pediatric acute leukemias. We provided an outline of CD72 expression assessed by flow cytometry on a variety of cancer cell lines and primary samples, including normal bone marrow (BM) samples and hematopoietic stem and progenitor cells. We analyzed CD 72 expression on a cohort of 495 pathological pediatric BM aspirates, including: 215 B-cell precursor acute lymphoblastic leukemias (BCP-ALL), 156 acute myeloid leukemias (AMLs), 88 T-lineage ALLs or lymphoblastic lymphomas with BM infiltration, 13 B-lineage lymphoblastic lymphomas with BM infiltration, 9 myelodysplastic syndromes with increased blasts (5%-9% blasts on BM: MDS-IB1) and 14 non-hematopoietic solid tumors infiltrating BM. Results showed that CD72 is highly expressed in almost all BCP-ALL and the majority of AML at diagnosis, including BCP-ALL cases characterized by CD19 loss. These findings support a potential role for advanced diagnostics and novel immunotherapy approaches, providing a pan-ALL and AML target.

Broadening the horizon: potential applications of CAR-T cells beyond current indications

Engineering immune cells to treat hematological malignancies has been a major focus of research since the first resounding successes of CAR-T-cell therapies in B-ALL. Several diseases can now be treated in highly therapy-refractory or relapsed conditions. Currently, a number of CD19- or BCMA-specific CAR-T-cell therapies are approved for acute lymphoblastic leukemia (ALL), diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), multiple myeloma (MM), and follicular lymphoma (FL). The implementation of these therapies has significantly improved patient outcome and survival even in cases with previously very poor prognosis. In this comprehensive review, we present the current state of research, recent innovations, and the applications of CAR-T-cell therapy in a selected group of hematologic malignancies. We focus on B- and T-cell malignancies, including the entities of cutaneous and peripheral T-cell lymphoma (T-ALL, PTCL, CTCL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), chronic lymphocytic leukemia (CLL), classical Hodgkin-Lymphoma (HL), Burkitt-Lymphoma (BL), hairy cell leukemia (HCL), and Waldenström's macroglobulinemia (WM). While these diseases are highly heterogenous, we highlight several similarly used approaches (combination with established therapeutics, target depletion on healthy cells), targets used in multiple diseases (CD30, CD38, TRBC1/2), and unique features that require individualized approaches. Furthermore, we focus on current limitations of CAR-T-cell therapy in individual diseases and entities such as immunocompromising tumor microenvironment (TME), risk of on-target-off-tumor effects, and differences in the occurrence of adverse events. Finally, we present an outlook into novel innovations in CAR-T-cell engineering like the use of artificial intelligence and the future role of CAR-T cells in therapy regimens in everyday clinical practice.

CAR-T cells for pediatric malignancies: Past, present, future and nursing implications

The treatment landscape for pediatric cancers over the last 11 years has undergone a dramatic change, especially with relapsed and refractory B-cell acute lymphoblastic leukemia (ALL), due to the introduction of chimeric antigen receptor-T (CAR-T) cell therapy. Because of the success of CAR-T cell therapy in patients with relapsed and refractory B-cell ALL, this promising therapy is undergoing trials in multiple other pediatric malignancies. This article will focus on the introduction of CAR-T cell therapy in pediatric B-cell ALL and discuss past and current trials. We will also discuss trials for CAR-T cell therapy in other pediatric malignancies. This information was gathered through a comprehensive literature review along with using first hand institutional experience. Due to the potential severe toxicities related to CAR-T cell therapy, safe practices and monitoring are key. These authors demonstrate that nurses have a profound responsibility in preparing and caring for patients and families, monitoring and managing side effects in these patients, ensuring that study guidelines are followed, and providing continuity for patients, families, and referring providers. Education of nurses is crucial for improved patient 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.

Engineering amino acid uptake or catabolism promotes CAR T-cell adaption to the tumor environment

Cancer cells take up amino acids from the extracellular space to drive cell proliferation and viability. Similar mechanisms are applied by immune cells, resulting in the competition between conventional T cells, or indeed chimeric antigen receptor (CAR) T cells and tumor cells, for the limited availability of amino acids within the environment. We demonstrate that T cells can be re-engineered to express SLC7A5 or SLC7A11 transmembrane amino acid transporters alongside CARs. Transporter modifications increase CAR T-cell proliferation under low tryptophan or cystine conditions with no loss of CAR cytotoxicity or increased exhaustion. Transcriptomic and phenotypic analysis reveals that downstream, SLC7A5/SLC7A11-modified CAR T cells upregulate intracellular arginase expression and activity. In turn, we engineer and phenotype a further generation of CAR T cells that express functional arginase 1/arginase 2 enzymes and have enhanced CAR T-cell proliferation and antitumor activity. Thus, CAR T cells can be adapted to the amino acid metabolic microenvironment of cancer, a hitherto recognized but unaddressed barrier for successful CAR T-cell therapy.

CAR immune cells: design principles, resistance and the next generation

The remarkable clinical activity of chimeric antigen receptor (CAR) therapies in B cell and plasma cell malignancies has validated the use of this therapeutic class for liquid cancers, but resistance and limited access remain as barriers to broader application. Here we review the immunobiology and design principles of current prototype CARs and present emerging platforms that are anticipated to drive future clinical advances. The field is witnessing a rapid expansion of next-generation CAR immune cell technologies designed to enhance efficacy, safety and access. Substantial progress has been made in augmenting immune cell fitness, activating endogenous immunity, arming cells to resist suppression via the tumour microenvironment and developing approaches to modulate antigen density thresholds. Increasingly sophisticated multispecific, logic-gated and regulatable CARs display the potential to overcome resistance and increase safety. Early signs of progress with stealth, virus-free and in vivo gene delivery platforms provide potential paths for reduced costs and increased access of cell therapies in the future. The continuing clinical success of CAR T cells in liquid cancers is driving the development of increasingly sophisticated immune cell therapies that are poised to translate to treatments for solid cancers and non-malignant diseases in the coming years.

Paediatric drug development and evaluation: Existing challenges and recommendations

Despite various international regulatory initiatives over the last 20 years, many challenges remain in the field of paediatric drug development and evaluation. Indeed, drug research and development is still focused essentially on adult indications, thereby excluding many paediatric patients, limiting the feasibility of trials and favouring competing developments. Off-label prescribing persists and the development of age-appropriate dosage forms for children remains limited. Against this background, the members of this panel (TR) recommend the launch of multi-partner exchange forums on specific topics in order to focus new drug research and development on the real, unmet medical needs of children and adolescents, and in keeping with the underlying mechanisms of action. Scientific information sharing and cooperation between stakeholders are also essential for defining reference evaluation methods in each medical field. These forums can be organised through existing paediatric facilities and research networks at the French and European level. The latter are specifically dedicated to paediatric research and can facilitate clinical trial implementation and patient enrolment. Moreover, specific grants and public/private partnerships are still needed to support studies on the repositioning of drugs in paediatric indications, and pharmacokinetic studies aimed at defining appropriate dosages. The development of new pharmaceutical forms, better suited for paediatric use, and the promotion of resulting innovations will stimulate future investments. Initiatives to gather observational safety and efficacy data following off-label and/or derogatory early access should also be encouraged to compensate for the lack of information available in these situations. Finally, the creation of Ethics Committees (EC) with a specific "mother-child" advisory expertise should be promoted to ensure that the current regulation (Jardé law in France) is implemented whilst also taking into account the paediatric specificities in medical trials.

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.

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.

Review: Sustainable Clinical Development of CAR-T Cells – Switching From Viral Transduction Towards CRISPR-Cas Gene Editing

T cells modified for expression of Chimeric Antigen Receptors (CARs) were the first gene-modified cell products approved for use in cancer immunotherapy. CAR-T cells engineered with gammaretroviral or lentiviral vectors (RVs/LVs) targeting B-cell lymphomas and leukemias have shown excellent clinical efficacy and no malignant transformation due to insertional mutagenesis to date. Large-scale production of RVs/LVs under good-manufacturing practices for CAR-T cell manufacturing has soared in recent years. However, manufacturing of RVs/LVs remains complex and costly, representing a logistical bottleneck for CAR-T cell production. Emerging gene-editing technologies are fostering a new paradigm in synthetic biology for the engineering and production of CAR-T cells. Firstly, the generation of the modular reagents utilized for gene editing with the CRISPR-Cas systems can be scaled-up with high precision under good manufacturing practices, are interchangeable and can be more sustainable in the long-run through the lower material costs. Secondly, gene editing exploits the precise insertion of CARs into defined genomic loci and allows combinatorial gene knock-ins and knock-outs with exciting and dynamic perspectives for T cell engineering to improve their therapeutic efficacy. Thirdly, allogeneic edited CAR-effector cells could eventually become available as “off-the-shelf” products. This review addresses important points to consider regarding the status quo, pending needs and perspectives for the forthright evolution from the viral towards gene editing developments for CAR-T cells.