ALLTogether is a European clinical treatment study for acute lymphoblastic leukaemia (ALL) in
      children and young adults. The aims are to improve survival and quality of survival for
      children and young adults with ALL. In young people, ALL has excellent outcome with an
      overall survival of about 92% in children and 75% in young adults. However, patients still
      die of disease - from relapse because of under-treatment and a large fraction of patients are
      also over-treated: All patients risk treatment-related death and some suffer long-term
      side-effects or secondary cancer. To show improvement with such good survival, large
      populations are needed.

      Study groups from Sweden, Norway, Iceland, Denmark, Finland, Estonia and Lithuania (NOPHO),
      the UK (UKALL), the Netherlands (DCOG), Germany (COALL), Belgium (BSPHO), Portugal (SHOP),
      Ireland (PHOAI), and France (SFCE), have designed a common treatment protocol for children
      and young adults with ALL.

      The study has a complex clinical trial design with sub-protocols (the randomisations /
      intervention) connected to a master protocol. The master protocol consists of well
      established therapy-elements and in its design typical for current ALL therapy. The master
      protocol therapy is in the study design considered as standard of care (SOC) therapy for
      children and young adults with ALL.

      The study structure is defined by a master protocol onto which randomised and interventional
      sub-protocols as well as sub-studies may be added, run and stop in a modular fashion.

      The randomisations / intervention may identify therapy that is less toxic, but equally
      efficacious for sub-groups of patients and innovative therapy that may reduce relapses and
      death from ALL. In the master protocol, improved risk-stratification is likely to increase
      survival and reduce unnecessary toxicity and the introduction of therapeutic drug monitoring
      (TDM) of Asparaginase activity will make the use of Asparaginase more rational and efficient
      and may thus improve overall outcomes.

      The investigators hypothesise that patients stratified to the standard-risk group are
      over-treated. Therefore, it will be tested if the treatment can be safely reduced. In the R1
      randomisation, patients will be randomised to receiving the Delayed Intensification (DI)
      phase of therapy with or without the anthracycline Doxorubicin.

      A similar hypothesis of over-treatment will also be tested in patients stratified to the
      intermediate risk-low group. In the R2 randomisation patients will be randomly assigned to
      either removal of Doxorubicin during the DI phase or removal of Vincristine and Dexamethasone
      pulses during the maintenance phase or to the control group, which will be treated with
      Doxorubicin in DI as well as Vincristine and Dexamethasone pulses during maintenance.
      Patients will only be randomised once.

      Randomisation R1 and R2 are only considered for children since adults have worse outcome and
      very poor survival after relapse, but the risk-stratification is likely to reduce the number
      of high-risk cases also in the adult-group.

      Patients stratified as intermediate risk-high (IR-high) are identified as having an increased
      risk of relapse and thus a less favourable prognosis than the standard- and intermediate
      risk-low groups, but a more favourable prognosis than the high risk patients. The majority of
      all relapses in childhood ALL is expected to occur in the IR-high group. Following a relapse,
      only approximately 40% of the children can be successfully treated again and for adults the
      corresponding figure is less than 20 %, so preventing relapses is very important. New
      treatment options that improves the antileukaemic efficacy and which have an improved safety
      profile are urgently needed.

      For IR-high patients Randomisation 3 (R3) is available. In R3 patients will be randomised to
      receive either:

        1. the addition of two cycles of Inotuzumab ozogamicin (InO) - Besponsa®, before start of
           the maintenance phase. After these cycles, the patients randomised to the InO arm will
           receive maintenance for the same duration as in the control arm.

        2. the addition of low dose 6-tioguanine (6TG) as an addition to the standard maintenance
           therapy.

        3. standard maintenance therapy

      Patients with ABL-class fusions in their leukaemic clone will, as a non-randomised
      experimental intervention, be treated with an addition of a tyrosine-kinase inhibitor during
      the induction phase (for patients <25 years) and from the consolidation phase (patients ≥25
      years). This intervention may shift therapy for previously resistant cases to lower intensity
      treatment with the associated reduced morbidity and may also reduce the number of relapses in
      analogy with the results in Ph+ ALL. The reason for not performing a randomised comparison is
      the rarity of the aberration and also the diversity of ABL-class fusions, reducing
      statistical power for any comparison further. For this reason, the results of this
      intervention may be pooled with other study-groups trying similar approaches.

      A new intervention is introduced for Down syndrome patients with CD19 positive ALL:
      ALLTogether1 DS (NRI2). For Down syndrome-ALL patients who have end of Induction MRD
      detectable but <25% two conventional chemotherapy consolidation blocks will be replaced with
      two blocks of Blinatumomab.

      For high-risk B-lineage patients, CAR-T therapy can be an alternative to high-risk blocks and
      stem-cell transplant, but in this case the intervention (CAR-T infusion) will be performed
      outside the ALLTogether1 study. However, the stratification-system in ALLTogether1 will
      define the population with a potential CAR-T indication.

      ALLTogether1 also includes five sub-studies:

      Efficacy of Imatinib in ABL-class fusion positive ALL

      Target population: All ABL-class patients enrolled in the ALLTogether study. Biomaterials to
      be collected at diagnosis, follow-up and relapse.

      Aims

        1. To determine the efficacy of imatinib in the treatment of ABL-class leukemia

        2. To find the best discriminative biomarkers for TKI response in ABL-class ALL

        3. To determine the frequency of intrinsic (at diagnosis) and acquired TKI resistance (due
           to treatment)

        4. To find causes of TKI resistance in ABL-class patients

      Objectives

        1. To determine the percent of ABL-class patients who need to switch from IR-high to HR
           because of high MRD levels

        2. To determine the effect of imatinib exposure on clinical outcome

        3. To determine the molecular response to imatinib by monitoring fusion transcript levels
           and mutational spectrum at diagnosis and during follow up

        4. To determine whether the molecular response parameters reflect the Ig/TCR MRD or
           flow-MRD response or are a better predictor of therapy failure than Ig/TCR or flow-based
           MRD monitoring

        5. To determine the phosphorylation status of ABL-class proteins and presence of
           TKI-resistance associated mutations in ABL genes prior to imatinib treatment and the
           emergence of such mutations during treatment with imatinib

        6. To determine the presence of mutations in regulatory /other genes before and during
           imatinib treatment and functionally address the importance of these mutations in TKI
           resistance

        7. To determine whether the efficacy of TKIs depends on the type of fusion gene

      Biomarkers to Reform Approaches to therapy-Induced Neurotoxicity (BRAIN)

      Target population: All patients registered on ALLTogether1 aged ≥ 4 years at end of therapy
      and without:

        1. Pre-existing neurodevelopmental disorder (e.g Trisomy 21, ADHD) prior to diagnosis of
           ALL

        2. Significant visual or motor impairment preventing use of a touch screen ipad

      Aims

        1. To institute universal screening of all children for adverse neurocognitive outcomes at
           the end of treatment using a validated user-friendly computer software programme
           (CogState) and compare neurocognitive outcomes by treatment allocation.

        2. To identify risk factors for adverse outcomes including whether acute neurotoxic events
           are associated with poor performance on cognitive tests at end of therapy compared to
           patients without acute neurotoxicity.

      Primary end-point

      a. Proportion of children with a z-score <1.5 on detection and/or identification CogState
      tasks in each treatment arm at the end of anti-leukaemic therapy. A z-score < 1.5 correlates
      with moderate cognitive impairment at a level that may require additional support.

      Secondary and exploratory end-points

        1. Association between CogState scores at end of treatment and overt neurotoxic episodes as
           recorded on the trial adverse event database.

        2. Association between Cogstate scores and clinical and demographic variables - age, sex,
           ethnicity, CNS status.

        3. Proportion of children with scores <1.5SD for one card learning (learning), one back
           (working memory) and Groton's maze (executive function) on different treatment arms.

        4. Association between CogState scores and patient reported outcome measures/Quality of
           life measurements collected as part of the main ALLTogether1 trial.

      Association between asparaginase activity levels and outcome

      Target population: All patients included in the ALLTogether1 protocol are eligible for
      participation.

      Primary aim

      To study the association between asparaginase activity levels and outcome (MRD, relapse,
      survival)

      Secondary aims

        1. To evaluate the association between asparaginase activity levels and toxicities, such as
           pancreatitis, infections and deep venous thrombosis (DVT)

        2. To evaluate the association between asparaginase activity levels and hepatotoxicity in a
           subset of patients

      CSF-Flow

      Target population: All patients included in the ALLTogether1 protocol are eligible for
      participation

      Aims

        1. To use cerebrospinal fluid (CSF) flow cytometry (FCM) to improve the accuracy of
           diagnostic tests for CNS leukaemia compared to conventional CSF cytology. An associated
           objective will be to develop a recommended protocol for CSF flow cytometry with external
           quality assessment to ensure uniformity of measurement across the ALLTogether
           consortium.

        2. To investigate whether negative FCM identifies a group of children at very low risk of
           CNS relapse, suitable for testing de-escalation of CNS-directed therapy in future
           trials.

        3. To investigate whether positive FCM can identify children at increased risk of CNS
           relapse and whether patients with persistent positivity (FCM positive at day 15 onwards)
           might benefit from studies testing escalated CNS-directed therapy or a switch to more
           intensive treatment arms.

        4. To collect matching CSF supernatant for studies comparing CSF FCM with soluble
           biomarkers (e.g. metabolic, cell-free DNA, proteomic and microRNA) in selected centres.

      Maintenance therapy pharmacokinetics/-dynamics study

      Target population: All patients included in the ALLTogether1 protocol are eligible for
      participation. For IR-high patients participating in the randomised InO- and TEAM
      sub-protocols, the monitoring of 6-mercaptopurine (6MP)/Methotrexate (MTX) metabolites at
      three months intervals is mandatory.

      Aims and specific objectives

        1. To map pharmacokinetics of 6MP and MTX during maintenance therapy in all patients in the
           ALLTogether protocol.

        2. To associate metabolite profiles with TPMT and NUDT15 variants, as routinely analysed in
           ALLTogether.

        3. To explore the association of event-free survival with DNA-TG and other 6MP/MTX
           metabolites.

        4. To explore the association between risk of second cancers with DNA-TG and other 6MP/MTX
           metabolites.

        5. To explore the association of risk of invasive infections with DNA-TG and other 6MP/MTX
           metabolites.

        6. To explore the association of risk of osteonecrosis with DNA-TG and other 6MP/MTX
           metabolites.

        7. To explore the association of sinusoidal obstruction syndrome with DNA-TG and other
           6MP/MTX metabolites.