Study Of Palbociclib Combined With Chemotherapy In Pediatric Patients With Recurrent/Refractory Solid Tumors

Study Overview
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Brief Summary
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A study to learn about safety and find out maximum tolerable dose of palbociclib given in combination with chemotherapy (temozolomide with irinotecan or topotecan with cyclophosphamide) in children, adolescents and young adults with recurrent or refractory solid tumors (phase 1). Neuroblastoma tumor specific cohort to further evaluate antitumor activity of palbociclib in combination with topotecan and cyclophosphamide in children, adolescents, and young adults with recurrent or refractory neuroblastoma. Phase 2 to learn about the efficacy of palbociclib in combination with irinotecan and temozolomide when compared with irinotecan and temozolomide alone in the treatment of children, adolescents, and young adults with recurrent or refractory Ewing sarcoma (EWS).

Official Title
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PHASE 1/2 STUDY TO EVALUATE PALBOCICLIB (IBRANCE®) IN COMBINATION WITH IRINOTECAN AND TEMOZOLOMIDE OR IN COMBINATION WITH TOPOTECAN AND CYCLOPHOSPHAMIDE IN PEDIATRIC PATIENTS WITH RECURRENT OR REFRACTORY SOLID TUMORS

Conditions
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Ewing Sarcoma, Solid Tumors, Rhabdoid Tumor, Rhabdomyosarcoma, Neuroblastoma, Medulloblastoma, Diffuse Intrinsic Pontine Glioma

Intervention / Treatment
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* Drug: Palbociclib
* Drug: Temozolomide
* Drug: Irinotecan
* Drug: Topotecan
* Drug: Cyclophosphamide


Participation Criteria
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Eligibility Criteria
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Inclusion: Histologically confirmed relapsed or refractory solid tumor as follows: For dose escalation and dose determination parts: Histologically confirmed relapsed or refractory solid tumor (including CNS tumors but not lymphomas). Patients with Diffuse Intrinsic Pontine Glioma do not require histological only radiographic confirmed relapse to enroll. For dose expansion and tumor specific cohorts: Histologically confirmed relapsed or refractory solid tumor including but not limited to EWS, rhabdoid tumor, rhabdomyosarcoma, neuroblastoma, and medulloblastoma. Patients with Diffuse Intrinsic Pontine Glioma do not require histological only radiographic confirmed relapse to enroll. EWS is not eligible for TOPO and CTX tumor-specific cohorts. For randomized Phase 2 part: Histologically confirmed Ewing sarcoma at diagnosis or at relapse, with presence of EWSR1-ETS or FUS-ETS rearrangement. Histopathology confirmation of both EWSR1-ETS or FUS-ETS rearrangement partners is required OR availability of formalin fixed paraffin embedded (FFPE) tumor tissue sample for central testing. Patient must have relapsed or have refractory disease and at least evaluable disease in at least one site other than bone marrow that can be followed by imaging. Age ≥2 and <21 years at the time of study entry. Lansky performance status ≥50% for patients ≤16 years of age, or Eastern Cooperative Oncology Group (ECOG) 0, 1 or 2 for patients >16 years of age. Adequate bone marrow function. Absolute neutrophil count ≥1000/mm3; Platelet count ≥75,000/mm3 (transfusion independent, no platelet transfusion in past 7 days prior study entry); Hemoglobin ≥8.5 g/dL (transfusion allowed). Adequate renal function: Serum creatinine level based on age/gender must within protocol specified limits. Adequate liver function, including: Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × upper limit of normal (ULN) or ≤5 × ULN for age, if attributable to disease involvement of the liver; Total bilirubin ≤1.5 × ULN for age, unless the patient has documented Gilbert's syndrome.Patients with documented Gilbert's syndrome are eligible if direct bilirubin is within normal ranges (≤ULN). Patients enrolled to Phase 1 portion of the study and tumor specific cohorts must have measurable disease as defined by RECIST version 1.1 or modified RANO criteria for CNS disease or at least evaluable disease by INRC for neuroblastoma. The eligible patients with neuroblastoma must have at least one of the following at the time of study entry: Measurable tumor by CT or MRI that is avid on MIBG scan or demonstrates increased FDG uptake on PET scan; Avid lesion on MIBG scan with positive uptake at a minimum of one site; For disease that is not avid by MIBG-scan, at least one lesion that demonstrates increased FDG uptake on PET scan AND viable neuroblastoma confirmed by current or prior biopsy; bone marrow involvement with more than 5% neuroblastoma cells in at least one sample from bilateral bone marrow biopsies; In non MIBG-avid refractory soft tissue disease that does not demonstrate increased FDG uptake; lesion biopsy is required to document the presence of viable neuroblastoma, unless patient has a new soft tissue lesion (radiographic evidence of disease progression). Patients with EWS enrolled to Phase 2 portion of the study are eligible with evaluable disease (eg, bone only disease with no soft tissue component). Recovered to CTCAE Grade ≤1, or to baseline, from any non-hematological acute toxicities of prior surgery, chemotherapy, immunotherapy, radiotherapy, differentiation therapy or biologic therapy, with the exception of alopecia. Serum/urine pregnancy test (for all girls ≥8 years of age) negative at screening and at the baseline visit. Exclusion: Phase 1 and tumor specific cohorts: For palbociclib with IRN and TMZ combination, prior treatment with a CDK4/6 inhibitor or progression while on treatment with an IRN-containing regimen that includes TMZ. Patients who have received the combination of IRN and TMZ and did not progress while on these medications are eligible. For patients enrolling in the palbociclib with TOPO and CTX combination, prior treatment with a CDK4/6 inhibitor or progression while on treatment with a TOPO-containing regimen that includes CTX. Patients who have received the combination of TOPO and CTX and did not progress while on these medications are eligible. Phase 2 portion: prior treatment with a CDK4/6 inhibitor or progression while on treatment with an IRN-containing or TMZ-containing regimen. Patients who have received IRN and/or TMZ and did not progress while on these medications are eligible. Prior intolerability to IRN and/or TMZ plus/minus palbociclib with IRN and TMZ combination and prior intolerability to TOPO and/or CTX for TOPO and CTX combination. For patients enrolled in the UK, any contraindication for IRN and/or TMZ treatment, as per the local SmPC. Use of strong cytochrome P450 (CYP) 3A inhibitors or inducers within 12 days of study entry. Patients who are receiving strong uridine diphosphate-glucuronosyl transferase 1A1 (UGT1A1) inhibitors within 12 days of Cycle 1 Day 1 (C1D1) are not eligible for the palbociclib with IRN and TMZ combination. Patients who are receiving strong UGT1A1 inhibitors within 12 days of C1D1 are eligible for the palbociclib with TOPO and CTX combination (See Section 5.7.1 for list of products.) Systemic anti cancer therapy within 2 weeks prior to study entry and 6 weeks for nitrosoureas. Prior irradiation to >50% of the bone marrow (see Appendix 9). Participation in other studies involving investigational drug(s) within 2 weeks or 5 half lives, whichever is longer, prior to study entry. Major surgery within 4 weeks prior to study entry. Surgical biopsies or central line placement are not considered major surgeries. For IRN and TMZ with/without palbociclib combinations: known or suspected hypersensitivity to palbociclib, dacarbazine, IRN and/or TMZ. For combination of palbociclib with TOPO and CTX: known or suspected hypersensitivity to palbociclib, TOPO and/or CTX. Patients with known symptomatic brain tumors or brain metastases and require steroids, unless they have been on a stable or on a decreasing steroid dose for >14 days. Patients with previously diagnosed brain metastases are eligible if they have completed their prior treatment and have recovered from the acute effects of radiation therapy or surgery prior to study entry for these metastases for at least 14 days post radiation and 4 weeks post-surgery and are neurologically stable. Hereditary bone marrow failure disorder. QTc >470 msec. History of clinically significant or uncontrolled cardiac disease, including: History of or active congestive heart failure; if patient had congestive heart failure resolve and >1 year from resolution, patient will be considered eligible; Clinically significant ventricular arrhythmia (such as ventricular tachycardia, ventricular fibrillation or Torsades de Pointes); Diagnosed or suspected congenital or acquired prolonged QT syndrome; Need for medications known to prolong the QT interval; Uncorrected hypomagnesemia or hypokalemia because of potential effects on the QT interval; Left ventricular ejection fraction <50% or shortening fraction <28%. Recent or ongoing clinically significant gastrointestinal disorder that may interfere with absorption of orally administered drugs (eg, gastrectomy). Evidence of serious active or uncontrolled bacterial, fungal or viral infection or known history of hepatitis B virus, hepatitis C virus, or human immunodeficiency virus infection or acquired immunodeficiency syndrome-related illness. Screening for viral hepatitis and HIV is under discretion of investigator unless required by local regulation. Severe acute or chronic medical or laboratory test abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results, and in the judgment of the Investigator, would make the patient inappropriate for entry into this study. Investigator site staff members directly involved in the conduct of the study and their family members, site staff members otherwise supervised by the investigator, or patients who are Pfizer employees, including their family members, directly involved in the conduct of the study. Fertile male patients or female patients of childbearing potential who are unwilling or unable to follow contraceptive requirements. Pregnant or breastfeeding women.

Ages Eligible for Study
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Minimum Age: 2 Years
Maximum Age: 20 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Phase 1 portion: The palbociclib plus irinotecan and temozolomide combination part of the study will comprise of a dose escalation cohort (following a rolling 6 design), a dose expansion cohort. The palbociclib plus topotecan and cyclophosphamide will comprise of a dose determination cohort(following a modified rolling 6 design), a dose expansion cohort, and Neuroblastoma tumor -specific cohort. Phase 2 open-label, randomized portion of the study will randomize patients in a 2:1 ratio to receive either palbociclib in combination with irinotecan and temozolomide (Arm A) or irinotecan and temozolomide chemotherapy alone (Arm B). Randomization will be stratified using block randomization by type and time of current disease recurrence (primary refractory or 1st recurrence < 2 years versus 1st recurrence ≥ 2 years or 2nd or greater recurrence).
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Phase 2 Arm A<br>Palbociclib in combination with irinotecan and temozolomide. | Drug: Palbociclib<br>* Phase 1: Administered (oral) at 55 mg/m2, 75 mg/m2, or 40 mg/m2, or 95 mg/m2 or 115 mg/m2 on days 1-14 of a 21-day cycle Phase 1 Tumor specific cohort-Neuroblastoma and Phase 2 : Administered (oral) at 75 mg/m2 on days 1-14 of a 21-day cycle<br>* Other names: Ibrance;Drug: Temozolomide<br>* Phase 1 and Phase 2: Administered at 100 mg/m2 (oral or intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Temodar;Drug: Irinotecan<br>* Phase 1 and Phase 2: Administered at 50 mg/m2 (intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Campto;|
| Experimental: Phase 1<br>Palbociclib in combination with temozolomide and irinotecan and/or with topotecan and cyclophosphamide. | Drug: Palbociclib<br>* Phase 1: Administered (oral) at 55 mg/m2, 75 mg/m2, or 40 mg/m2, or 95 mg/m2 or 115 mg/m2 on days 1-14 of a 21-day cycle Phase 1 Tumor specific cohort-Neuroblastoma and Phase 2 : Administered (oral) at 75 mg/m2 on days 1-14 of a 21-day cycle<br>* Other names: Ibrance;Drug: Temozolomide<br>* Phase 1 and Phase 2: Administered at 100 mg/m2 (oral or intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Temodar;Drug: Irinotecan<br>* Phase 1 and Phase 2: Administered at 50 mg/m2 (intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Campto;Drug: Topotecan<br>* Phase 1 only : Administered at 0.75 mg/m2 (intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Hycamtin;Drug: Cyclophosphamide<br>* Phase 1 only: Administered at 250 mg/m2 (intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Cytoxan;|
| Active Comparator: Phase 2 Arm B<br>Irinotecan and temozolomide alone. | Drug: Temozolomide<br>* Phase 1 and Phase 2: Administered at 100 mg/m2 (oral or intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Temodar;Drug: Irinotecan<br>* Phase 1 and Phase 2: Administered at 50 mg/m2 (intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Campto;|
| Experimental: Phase 1 Tumor specific cohort - Neuroblastoma<br>Palbociclib in combination with topotecan and cyclophosphamide. | Drug: Palbociclib<br>* Phase 1: Administered (oral) at 55 mg/m2, 75 mg/m2, or 40 mg/m2, or 95 mg/m2 or 115 mg/m2 on days 1-14 of a 21-day cycle Phase 1 Tumor specific cohort-Neuroblastoma and Phase 2 : Administered (oral) at 75 mg/m2 on days 1-14 of a 21-day cycle<br>* Other names: Ibrance;Drug: Topotecan<br>* Phase 1 only : Administered at 0.75 mg/m2 (intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Hycamtin;Drug: Cyclophosphamide<br>* Phase 1 only: Administered at 250 mg/m2 (intravenous), on days 1-5 of a 21-day cycle<br>* Other names: Cytoxan;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Phase 2 open-label, randomized: Event-free survival (EFS) based on Investigator assessment. | EFS is defined as the time from randomization until first event (ie, progression, recurrence following response, second malignancy or death without progression or recurrence). | Baseline to Month 24. | 
| Phase 1: First Cycle Dose-Limiting Toxicities (DLT) | For Dose Escalation/Determination Part: DLT defined as any of the following events occurring during the first treatment cycle and considered at least possibly-related to study medication:Grade 4 neutropenia lasting greater than 7 days;Grade 4 thrombocytopenia lasting greater than 7 days or need for platelet transfusion for a platelet count of < 20,000 per cubic millimeters twice within a 7-day period;greater than 14-day delay in the start of a subsequent course because of neutropenia or thrombocytopenia;Grade 3 or greater non-hematologic toxicities despite optimal treatment;any Grade 2 or greater non-hematologic toxicity requiring discontinuation or interruption of palbociclib for 7 or more consecutive days during the first cycle or any grade non-hematologic toxicity that delays the start of Cycle 2 by more than 14 days;clinically significant non-hematologic laboratory test abnormality Grade 3 or greater not resolving to Grade 1 or baseline within 7 days. | First cycle (cycle length is approximately 21 days) | 
| Phase 1: Dose Expansion Parts: Frequency of adverse events | For Dose Expansion and Tumor-Specific Expansion Parts: Adverse events to be reported during treatment and for at least 28 days after last dose. | At least 28 days after last dose | 
| Phase 1: Dose Expansion Parts: Percentage of Participants With Complete Response or Partial Response | For Dose Expansion and Tumor-Specific Expansion Parts: patients with confirmed Complete Response or Partial Response per Response Evaluation Criteria in Solid Tumors (RECIST, v.1.1) or modified Response Assessment in Neuro-Oncology (RANO) for central nervous system malignancies, or International Neuroblastoma Response Criteria (INRC) for neuroblastoma, during study treatment, assessed approximately every 2 to 4 cycles (each cycle is approximately 21 days). | Through the end of treatment (up to at least 28 days after last dose) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Phase 1 and Phase 2: Frequency of adverse events | Adverse events to be reported during treatment and for at least 28 days after last dose. | At least 28 days after last dose | 
| Phase 1 and Phase 2: Percentage of participants with laboratory abnormalities | Magnesium, Calcium, Creatinine, Albumin, Alanine aminotransferase, Aspartate aminotransferase, Glucose, Phosphorus, Total Bilirubin, Blood urea nitrogen, Alkaline phosphatase, Sodium, Potassium, Chloride, Platelet Count, White Blood Cell Count (differential), hemoglobin, INR or prothrombin Time, HbA1c | At least 28 days after last dose | 
| Phase 1 and Phase 2: Number of Participants With Clinically Significant Treatment-emergent Electrocardiogram (ECG) Findings | Clinically significant ECG findings included: corrected QT (QTc) > 450 ms, QTc >500 ms, change in QTc between 30 and 60 ms, change in QTc greater than or equal to 60 ms. | At least 28 days after last dose | 
| Phase 1 and Phase 2: Number of Participants With Clinically Significant Change From Baseline in Vital Signs | systolic and diastolic blood pressure, pulse | At least 28 days after last dose | 
| Phase 2 open-label, randomized: Event-free survival (EFS) assessed by an independent review committee. | EFS is defined as the time from randomization until first event (ie, progression, recurrence following response, second malignancy or death without progression or recurrence). | Baseline to Month 24. | 
| Phase 1 and Phase 2: Percentage of Participants With Complete Response or Partial Response | Patients with confirmed Complete Response or Partial Response per Response Evaluation Criteria in Solid Tumors (RECIST, v.1.1) or modified Response Assessment in Neuro-Oncology (RANO) for central nervous system malignancies, or International Neuroblastoma Response Criteria (INRC) for neuroblastoma, during study treatment, assessed approximately every 2 to 4 cycles (each cycle is approximately 21 days). | Through the end of treatment (up to at least 28 days after last dose) | 
| Phase 1 and Phase 2: Duration of response (DoR) for Participants Who Achieved Complete Response or Partial Response | DoR defined as time from date of first response (Complete Response or Partial Response) in responders to date of progression or death | Up to 2 years | 
| Phase 1 and Phase 2: Progression Free Survival (PFS) | PFS defined as time from date of enrollment to earliest date of the death or progressive disease | Up to 2 years | 
| Phase 1 and Phase 2: Overall Survival (OS) | OS defined as the time from enrollment to date of death due to any cause. | Up to 2 years | 
| Phase 2 : comparison of PET-CT response assessment to objective response on CT/MRI. | PET-CT response assessment will be compared to objective response on MRI/CT, as data permit. | up to completion of Cycle 4 ( 12 weeks of therapy) | 
| Phase 2: the impact of the combination of palbociclib with TMZ and IRN treatment on the quality of life (QoL) of patients with refractory or recurrent EWS. | Results of QoL reported by patient at baseline and after 2 and 4 cycles using age-appropriate PROMIS tools will be summarized for both treatment arms, as data permit. Days of hospitalization will be compared in both treatment arms. | Up to Cycle 5 (completion of 12 weeks of treatment) | 
| Phase 1 and Phase 2:Palbociclib Pharmacokinetics, Maximum observed plasma concentration during a dosing interval at steady state (Css, max) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5, 6, 14) and Cycle 2 (day 5 and 14). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Palbociclib Pharmacokinetics, Maximum plasma concentration time (Tmax) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5, 6, 14) and Cycle 2 (day 5 and 14). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Palbociclib Pharmacokinetics, Area under the concentration-time curve during a dosing interval at steady state (AUCss,t) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2,5, 6,14) and Cycle 2 (day 5 and 14). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Palbociclib Pharmacokinetics, Measured concentration at the end of a dosing interval at steady state (taken directly before next administration) (Css,trough) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5, 6, 14) and Cycle 2 (day 5 and 14). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Palbociclib Pharmacokinetics, Oral plasma clearance (CL/F) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5, 6, 14) and Cycle 2 (day 5 and 14). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Temozolomide Pharmacokinetics, Maximum observed plasma concentration during a dosing interval at steady state (Css, max) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 5) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Temozolomide Pharmacokinetics, Maximum plasma concentration time (Tmax) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 5) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Temozolomide Pharmacokinetics, Area under the concentration-time curve during a dosing interval at steady state (AUCss,t) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 5) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Temozolomide Pharmacokinetics, Measured concentration at the end of a dosing interval at steady state (taken directly before next administration) (Css,trough) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 5) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Temozolomide Pharmacokinetics, Oral plasma clearance (CL/F) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 5) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Irinotecan (and active metabolites) Pharmacokinetics, Maximum observed plasma concentration during a dosing interval at steady state (Css, max) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Irinotecan (and active metabolites) Pharmacokinetics, Maximum plasma concentration time (Tmax) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Irinotecan (and active metabolites) Pharmacokinetics, Area under the concentration-time curve during a dosing interval at steady state (AUCss,t) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Irinotecan (and active metabolites), Measured concentration at the end of a dosing interval at steady state (taken directly before next administration) (Css,trough) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1 and Phase 2: Irinotecan (and active metabolites) Pharmacokinetics, Oral plasma clearance (CL/F) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Topotecan (and active metabolites) Pharmacokinetics, Oral plasma clearance (CL/F) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Topotecan (and active metabolites), Measured concentration at the end of a dosing interval at steady state (taken directly before next administration) (Css,trough) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Topotecan (and active metabolites) Pharmacokinetics, Area under the concentration-time curve during a dosing interval at steady state (AUCss,t) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Topotecan (and active metabolites) Pharmacokinetics, Maximum plasma concentration time (Tmax) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Topotecan (and active metabolites) Pharmacokinetics, Maximum observed plasma concentration during a dosing interval at steady state (Css, max) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Cyclophosphamide Pharmacokinetics, Oral plasma clearance (CL/F) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Cyclophosphamide Pharmacokinetics, Maximum observed plasma concentration during a dosing interval at steady state (Css, max) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Cyclophosphamide Pharmacokinetics, Maximum plasma concentration time (Tmax) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Cyclophosphamide Pharmacokinetics, Area under the concentration-time curve during a dosing interval at steady state (AUCss,t) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 
| Phase 1: Cyclophosphamide Pharmacokinetics, Measured concentration at the end of a dosing interval at steady state (taken directly before next administration) (Css,trough) | Multiple Dose (assuming steady state is achieved), as data permit | PK sampling at time points during Cycle 1 (day 2, 5 and 6) and Cycle 2 (day 5). Each cycle is 21 days. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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EWS, Pediatric Cancer, Ewing Sarcoma, Neuroblastoma, Recurrent Neuroblastoma, Solid Tumor, Recurrent Solid Tumors, Refractory Solid Tumors, Bone Cancer, Bone Tumor, Bone Sarcoma, Soft Tissue Cancer, Soft Tissue Sarcoma, Recurrent Ewing Sarcoma, Refractory Ewing Sarcoma, Relapsed Ewing Sarcoma, Childhood Cancer, Ewing Sarcoma Treatment, Palbociclib, CDK4/6 Inhibitor, Irinotecan, Temozolomide, Topotecan, Cyclophosphamide