Design
In this multicenter, upfront randomized phase II trial, all patients receive quizartinib combined with HAM during salvage therapy. During consolidation therapy (chemotherapy as well as allo-HCT) patients receive either prophylactic quizartinib therapy or MRD-triggered preemptive continuation therapy with quizartinib according to up-front randomization. Efficacy is assessed by comparison to historical controls based on the matched threshold crossing approach.
Study setting and Randomization
In Germany, patients with r/r-AML are usually referred to academic hospitals. In this study, patients will be recruited in up to 20 academic centers registered in the Study Alliance Leukemia (SAL) group. Participating centers are contacted by study monitors and the medical coordinator monthly to promote patient recruitment. Furthermore, after protocol amendments or upon relevant updates during the study, a newsletter will be sent to all participating centers. Conferences with the participating centers of the SAL network are held regularly to share information regarding therapy responses and complications seen within the study. Expecting at least 5 eligible patients per year and center, approximately 2 years are required to recruit the anticipated number of patients.
Patients have to provide written informed consent and must meet all inclusion criteria before any protocol-specific procedures are performed.
Each patient must be registered in the electronic case report form (eCRF). Prior to this, each patient intended to be registered must be allotted a screening number by the study site. Patients are registered through the electronic case report form (Via eCRF) and a unique patient ID (PAT-ID) is assigned. The PAT-ID is composed of the aforementioned screening number and the site number. Following registration, all eligible patients are upfront 1:1 randomized. Forty patients are allocated to each arm via randomization using a centralized web-based tool (randomizer.at). Randomization is performed stratified according to previous treatment with midostaurin. Twenty or more centers are selected to recruit the intended number of patients. The treatment arms are (a) the MRD-triggered arm and (b) the prophylactic arm.
Post-randomization events
In case a patient prematurely withdraws from the trial or is lost to follow-up before measurement of the primary endpoint, this patient’s response is set to missing. In case a patient dies due to any cause before CR/ or CR with incomplete haematological recovery (CRi) measurement, the primary endpoint will be set to “no Composite Remission”.
Withdrawal of patients
A patient must be withdrawn from the trial i) at any time at the patient’s own request, ii) after salvage therapy if the patient fails to obtain CR/CRi, iii) at any time if unacceptable toxicity necessitating cessation of treatment is observed iv) at any time if there are changes in the medical status of the patient that compromise the patient’s safety or if the investigator considers that the withdrawal is in the patient’s best interest, v) in case of pregnancy, vi) at any time a patient’s protocol compliance turns out insufficient vii) if patient is lost to follow up.
If any of the aforementioned criteria are met, and patients agree to follow-up, previous unresolved AEs will continuously be followed. If cases iii and iv are met we will continue with the follow of the patient until end of study. However, if the patient withdraws from the trial and also from consent for disclosure of future information (e.g. follow-up visits), further data collection is prohibited.
Treatments and study procedures
Salvage Therapy
All patients are randomized upfront and receive one cycle of backbone salvage therapy with a standard HAM regimen. In patients aged 18-60 years, one cycle of cytarabine 3g/m² every 12 hours will be administered intravenously on days one to three, and in patients older than 60 years of age, cytarabine will be administered at a reduced dosage of 1g/m² bidaily on days one to three. Mitoxantrone will be administered irrespective of age group, intravenously at a dosage of 10mg/m² on days two and three. All patients will receive in addition 40 mg of quizartinib orally on days 1 to 28. If on day 28 no haematological recovery has occurred, and according to the first bone marrow examination no CR is achieved, quizartinib may be given until day 42 and a second remission control can be done if medically justified until day 42. If a therapy with a strong CYP3A4 inhibitor is initiated a dose reduction of quizartinib to 20mg per day will be initiated. Dose modifications in case of toxicities are described in Table 1 and Table 2.
Subjects who experience QT interval prolongation of more than 480msec corrected for heart rate (QTcF) will undergo dose interruption and/or reduction of quizartinb and will be monitored closely by ECGs, performed twice weekly for the first week of the QTcF prolongation and then weekly thereafter until the QTcF prolongation is resolved (Table 2). QTcF prolongation higher than grade 3 according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTC AE) will be recorded as AE including the Investigator’s assessment of seriousness, causality, and a detailed narrative.
In the event of significant toxicity grade 3 or 4, dosing must be interrupted, delayed and/or reduced by at least 50% [20]. In the event of unresolved or severe toxicities, administration will be interrupted and in case of multiple toxicities, dose modification should always be based on the worst toxicity observed. Quizartinib will be discontinued in case of non-hematological grade 4 toxicities including grade 4 QTcF prolongation.
Allogeneic hematopoietic cell transplantation
Subjects are permitted to undergo allo-HCT at any time after salvage therapy. Quizartinib should be discontinued at least 7 days before the start of a conditioning regimen. Maintenance therapy may be given starting the earliest at day 30 and the latest at day 100 after transplant according to initial randomization.
Continuation therapy
All patients achieving CR are allocated according to randomization to either (a) the MRD-triggered arm or (b) the prophylactic arm receiving treatment with quizartinib. During consolidation therapy, patients allocated to the MRD-triggered arm (a) receive one cycle of HAM and are further allocated based on the MRD-results assessed by flow cytometry with a cut of level of 0.1%: if the MRD is negative they remain in the MRD-triggered arm for another HAM cycle, whereas MRD positive patients move to the prophylactic arm. All patients randomized to (b) the prophylactic arm will receive quizartinib during their two cycles of HAM therapy irrespective of MRD results.
Patients achieving MRD negativity in the MRD-triggered arm will not receive treatment during the maintenance phase. MRD positive patients have to move to the prophylactic arm receiving quizartinib as single-agent and will be continued for up to 12 cycles; arm monthly visits to assess the course of therapy are scheduled. Patients in the MRD-triggered arm are attending visits in 3-monthly intervals only. During maintenance therapy, starting from cycle 2, the quizartinib dosage will be increased up to 60mg orally, if the average QTcF of the triplicate ECGs is lower than 450msec on cycle 1, day 28. Once the dose is increased to 60mg/day, the subject may continue on this dose as long as no dose reduction is needed. In case of therapy with a strong CYP3A4 inhibitor a dose reduction to 20mg per day is required. The maintenance phase is followed by a safety follow-up of 28 days counted from end of treatment (EOT) for all patients from the prophylactic arm. Dose modifications are listed in Table 2 and 3.
Long-term follow-up
After EOT, all patients move to the observational follow-up with 3-monthly visits. For patients of the MRD-triggered arm, safety follow-up starts after the last visit of the last cycle of chemotherapy with subsequent transition to observational follow-up until end of study (EOS).
After the end of study visit, patients are routinely followed-up and treated as per standard of care at the discretion of the treating physician. Follow-up is planned to continue until the last patient alive has been observed for at least 2 years in total (study treatment including subsequent follow-up). Assuming 2 years of recruitment, the total observation period of the first patient may last up to 4 years. Event free and overall-survival follow-up is recorded until the end of the overall study.
Additional study procedures during salvage, maintenance therapy and follow-up
Patients undergo efficacy and safety assessments, including monitoring of Measurable Residual Disease (MRD), bone marrow specimen collection, blood and urine sampling and completion of patient reported outcome questionnaires before receiving study drug and at specified time points throughout the study (see supplementary Table 1).
Participants
Inclusion criteria
Inclusion criteria are outlined in Table 3. Key inclusion criteria are AML according to the 2016 WHO classification, relapse or refractory disease including to autologous or allogeneic hematopoietic cell transplantation, positivity for FLT3-ITD mutation defined as a ratio of mutant to wild-type alleles of at least 0.05, age between 18 and 75 years, Eastern Cooperative Oncology Group (ECOG) performance status between 0 and 2, adequate renal and hepatic function, and serum electrolytes (potassium, calcium, and magnesium) within normal limits. Refractoriness to induction therapy is defined as no CR, CRi, or partial remission (PR) after one or two intensive induction cycles of at least 7 days of cytarabine 100-200mg/m² continuously or an equivalent regimen with cytarabine with total dose not less than 700mg/m² per cycle and 2 days of an anthracycline (e.g. daunorubicin, idarubicin). Relapse after first line therapy is defined as relapsed AML after a first line therapy including at least one intensive induction and consolidation therapy including allo-HCT. The discontinuation of cytotoxic agents except hydroxyurea to control hyperleukocytosis or investigational treatments for at least 10 days or 28 days respectively is mandatory. Furthermore, all patients randomized into the study must be willing to use highly effective birth control and all female patients must have a negative serum pregnancy test.
Exclusion Criteria
Exclusion criteria are summarized in Table 3. Main exclusion criteria are diagnosis of acute promyelocytic leukemia (APL) French-American-British classification M3 or World Health Organization classification of APL with translocation t(15;17) (q22;q12), or BCR-ABL–positive leukemia. Other exclusion criteria are known active CNS leukemia, isolated extramedullary manifestation of AML, hyperleukocytosis (leukocytes > 30,000/µl), uncontrolled or significant cardiovascular disease, history of other malignancies (except adequately treated nonmelanoma skin cancer, curatively treated in situ disease, or other solid tumors curatively treated with no evidence of disease for at least 2 years), patients within the first 100 days posterior to allo-HCT, clinically relevant Graft-versus-Host-Disease, QTc interval >450 msec or any known relevant dysrhythmias.
Efficacy Endpoints
The primary endpoint of the study is achievement of complete remission or CR with incomplete neutrophil or platelet recovery (CRi) after salvage therapy with HAM in combination with quizartinib. CR is defined as bone marrow blasts <5%, absence of circulating blasts and blasts with Auer rods, absence of extramedullary disease, neutrophil count ≥1000/µl, and platelet count ≥100000/µl. CRi is defined as CR with residual neutropenia (neutrophils < 1000/µl) and thrombocytopenia (platelets < 100 000/µl).
Refractory disease or treatment failure is defined as failure to achieve CR or CRi, presence of Auer rods, or appearance of new or worsening extramedullary disease after one course of intensive treatment. Relapse after CR or CRi is characterized by ≥5% blasts in the bone marrow aspirate and/or biopsy not attributable to any other cause, the reappearance of leukemic blasts in the peripheral blood, the new appearance of extramedullary leukemia, or presence of Auer rods. Platelet and neutrophil counts for the assessments of CR and CRi are delineated based on the 2017 recommendations from the International Working Group commissioned by the European Leukemia Net [25].
Secondary survival endpoints are event free survival (EFS), defined from study inclusion as one of the following events, whichever occurs first: a) failure to obtain complete remission (CR) or complete remission with incomplete hematological recovery (CRi) after Q-HAM therapy, b) relapse from CR/CRi or c) death from any cause. Patients without an event are censored at last follow-up. Overall survival (OS) is defined as time from randomization until death from any cause and relapse-free survival (RFS) is measured from first CR/CRi to time of recurrence of the disease or death from any cause, whichever occurs first. Patients without event are censored at the last date of follow-up. Cumulative incidence of relapse (CIR) is defined as the time from achievement of a CR/CRi after salvage therapy to the recurrence of the disease, whereby death from any cause is a competing event. Cumulative incidence of death (CID), defined as the time from achievement of a CR/CRi after salvage therapy to death from any cause whereby recurrence of the disease is a competing event.
Further secondary endpoints are patient reported outcomes (PROs). PROs include assessments of a) health-related quality of life (QoL), calculated as the EORTC QLQ-C30 Summary Score [26], b) the quality of sleep or sleep disorders, calculated with the “Sleep Quality Index” from the PSQI according to the corresponding scoring guidelines [27], and c) anxiety and depression, calculated from the PHQ-4 according to the corresponding scoring manual [28].
Safety Assessments
All adverse events (AEs) that occur after the screening visit (or as soon as the medical history of the patient has been examined) are documented. The period of observation ends with the last study visit. All patients who have AEs, whether considered associated with the use of the investigational medical products or not, are monitored for outcome determination. The Data Monitoring Committee (DMC)is composed of three independent experts, meets regularly to review all data relevant to safety, and provides the sponsor with recommendations regarding trial modification, continuation, or termination.
Auditing
Audits are planned to be performed based on regular risk-based evaluation. Regulatory authorities and auditors authorized by the sponsor may request access to all source documents, the CRF, and other trial documentation. Investigators are contractually bound to enable direct access to these documents and to support audit activities.
Protocol Amendments
Decisions regarding protocol amendments will be taken by the study core team encompassing the coordinating investigator, trial coordinator, trial statistician, medical coordinator, and data management. Meetings for reviewing all available findings and information are scheduled every 2 weeks.
Sample collection
The samples will be collected at the following time points: i) at baseline, ii) after salvage therapy, iii) after consolidation therapy, iv) after each cycle of consolidation therapy, v) after each cycle of maintenance therapy, vi) at the end of treatment, vii) every three months during observational follow up, and at end of study.
Data Collection and Handling
All data required as per the study protocol, including clinical and laboratory data are documented by the investigator or an authorized member of the study team in the medical record of the patient and in the eCRF. Access to the eCRF is password protected and an audit trail is in place. Any entries are tracked and locked to prevent further editing. The investigator at the clinical site is responsible for ensuring that all sections of the eCRF are completed correctly. Entries are checked for plausibility and consistency via eCRF-inherent edit checks and visually by the monitors where necessary. Implausibility and missing entries are queried and to be clarified with the responsible investigator. All relevant documents and data collected within the study will be archived for at least 10 years after termination of the study.
Ancillary and Post trial care
For all patients in the prophylactic arm, treatment ends after the 12th cycle of maintenance therapy (EOT). For all patients randomized to the MRD-triggered arm, who did not cross-over in the prophylactic arm, treatment ends after the 2nd cycle of consolidation therapy (EOT). After EOT patients are routinely followed-up and treated as per standard of care at the discretion of the treating physician. The period of observation (and the overall study) ends for all patients when the last patient being included and alive has been followed for at least 730 days (2 years) counted from this patient’s day 1 (EOS).
Study Monitoring
Study monitoring is done by the Heidelberg Clinical Studies Coordination Center (KKS). The first monitoring visit at each study center is scheduled to occur at the end of the second patient's induction therapy. Further monitoring visits at each study site will depend on the i) recruitment success of study participants, ii) the monitor's assessment of the trial site’s compliance with applicable stipulations (e.g., number and severity of protocol deviations or deficiencies detected during study visits), iii) the deficiencies detected via Central Data Review and iv) the assessment of the coordinating team. The monitoring is carried out according to a monitoring manual giving comprehensive guidance on monitoring activities (Source Data Verification rules, corrective and preventive actions, documentation of protocol violations, escalation of findings etc.).
Ethical and legal aspects
All the procedures set out in the trial protocol are designed to ensure that all persons involved in the trial abide by Good Clinical Practice (GCP) and the ethical principles described in the current version of the Declaration of Helsinki. The trial is carried out in keeping with local legal and regulatory requirements. Before being admitted to the clinical trial, all patients must consent in writing to their participation after having understood the nature, scope, and possible consequences of the clinical trial.
All planned substantial changes to the study (protocol amendments) are to be submitted to the EC and the competent federal authority requesting their approval. Records of relevant communication with the EC and the regulatory authorities are kept by the coordinating investigator.
Access to data and dissemination policy
After publication of the complete trial, access to selected raw data is intended. This must be done in accordance with the European data protection act and informed consent given by the patients.
The results from this trial will be presented at national (e.g., annual meeting of the German Society of Hematology/Oncology); meetings of the Competence Net “Acute and Chronic Leukemias” and international meetings (e.g., meetings of the European Leukemia-Net; annual congresses of the European Hematology Association, the American Society of Hematology and the American Society of Clinical Oncology). The full results will be published in high-impact peer-reviewed medical journals.
Sample Size calculation and statistics
To assess the efficacy with respect to the primary endpoint CR/CRi of Q-HAM during salvage therapy we will compare the patients in the study to historical controls based on the matched threshold-crossing approach [10][29][30]. The latter is a novel approach to enhance the classic single-arm trial design by including matched control patients. This design overcomes common disadvantages of single-armed and small randomized studies [31], since the expected outcome of the observed study population can be adjusted based on the matched controls with a comparable distribution of known prognostic and predictive factors. Furthermore, balanced treatment groups lead to stable statistical models.
The proposed adaptive design consists of two stages with an interim analysis after the first stage. At the interim analysis, historical control patients are matched to the enrolled intervention patients with regard to known prognostic and predictive factors. The treatment effect of the intervention as compared to the control group is then estimated based on the enrolled intervention patients and the selected historical control patients. In case the estimated treatment effect is below a pre-specified threshold, the trial will be stopped for futility. However, in case the estimated treatment effect is above a pre-specified threshold, the sample size for the second stage of the trial will be recalculated to obtain a sufficiently high conditional power based on the results of the interim analysis and the trial continues to the second stage with the recalculated sample size.
In the proposed design, matched control patients will be drawn from two large IPD meta-analyses datasets of r/r-AML patients (“historical control”) [6][7]. For matching, the variables age, and high-risk cytogenetics are used in refractory patients. Additionally, first CR duration shorter than 18 months will be used in relapsed patients. After the enrolment of 30 patients, the a priori unknown matching rate and the number of matched controls per patient in the intervention group are determined at the interim analysis using an iterative procedure [30]. An (non-binding) interim stop for futility is done in case the odds ratio, estimated using a logistic regression model adjusting for the matching parameters, does not exceed a threshold of 1.3. If the trial continues to a second stage, a sample size recalculation is performed using a conditional power argument taking number of matched partners and observed treatment effect into account. In the final analysis, historical control patients are also matched to the patients from the second stage, and the p-values from the two stages are combined using the inverse normal approach and tested at a one-sided significance level of α=0.05.
The sample size required for a fixed design, assuming CR/Cri rates of 0.50 for the enrolled patients and 0.30 for the historical controls, would be a minimum of 74 assuming a logistic regression is performed at one-sided significance level α=0.05, the aspired power is 0.8, and number of matching partners per intervention patient is at least 1. Thus, a maximum of 80 patients will be enrolled. The trial sample size is recalculated based on a conditional power argument in an interim analysis after enrolling 30 patients and will hence range between 30 and 80.
Due to the adaptive nature of the trial, two separate logistic models will be fitted for the two trial stages and be combined using the inverse normal function approach. Determination of p-values, point and interval estimates will take the adaptive nature of the trial into account. Analysis of the primary endpoint will be based on the full analysis population. Concerning the secondary endpoints: EFS, OS, and RFS endpoints will be analyzed using a Cox regression model and Kaplan-Meier-Plots, CIR, and CID will be analyzed according to Gray 1988 [32] and via cumulative incidence plots, and quality of life will be analyzed descriptively according to the corresponding guidelines and EORTC recommendations. Statistical analysis will be performed using SAS v9.4 or higher.