The GnG study is a randomized phase III trial with MRD after induction therapy and event-free survival (EFS) as primary endpoints. The two research questions are addressed in a 2 by 2 factorial design. The trial is designed to gain evidence of the anti-leukemic activity of GO and glasdegib in older patients with newly diagnosed AML.
Randomization, treatments, study procedures
Patients will be recruited in 25 centers part of the Study Alliance Leukemia (SAL) group. All patients are upfront randomized 1:1 to induction chemotherapy containing either fractionated GO treatment (GO-147) or one single dose of GO (GO-1) and again 1:1 either to glasdegib or placebo (double-blinded) as adjunct to consolidation therapy and as single-agent 6-months maintenance therapy. Randomization is stratified by the assumingly important prognostic factors age (≤70 years vs. >70 years) and Eastern Cooperative Oncology Group (ECOG) performance status (PS) (ECOG PS = 0 vs. ECOG PS > 0). Block randomization with varying block lengths is used and performed using a web tool (www.randomizer.at). Patients have to provide written informed consent before any protocol-specific procedures are performed.
Patients receive one cycle of backbone induction therapy with standard 7+3 regimen; cytarabine 200mg/m2 administered via continuous intravenous (IV) infusion for a total of 7 days and daunorubicin 60mg/m2 days 1, 2 and 3. Patients are randomized to receive in addition GO 3mg/m² IV over one hour (Mylotarg®), either on days 1,4 and 7 or only once on day 1 (GO-147 versus GO-1). Dose modification in case of CTC grade ≤2 toxicity is allowed in the GO-147 schedule to enable continued administration of GO on day 4 and day 7, respectively. In case of grade 3 toxicity on day 1 and/or 4, patients will receive GO on day 4 and 7, respectively, if the CTC grade has improved to grade <3 toxicity prior to infusion. In case of CTC grade 4 toxicity, GO is discontinued. Likewise, patients who develop anaphylaxis, pulmonary edema, acute respiratory distress syndrome or SOS after the first administration are not allowed to receive further doses of GO. On Day 15 and 28 (window day 28 to day 42), a bone marrow aspirate specimen is collected for local and central assessment. If this bone marrow specimen is not evaluable for assessment of response, the bone marrow aspiration has to be repeated upon count recovery or day 42 whichever occurs first. In case of bone marrow blast count >10% on day 15, or no CR or CR with incomplete neutrophil or platelet recovery (CRi) after induction therapy, one cycle of HAM (high dose cytarabine and mitoxantrone) as salvage therapy is allowed within the protocol.
Consolidation and maintenance therapy
During the consolidation phase, patients receive up to two cycles of cytarabine (1.0g/m2) administered by IV infusion every 12 hours on days 1, 2, and 3 . Study drug (glasdegib 100mg or placebo) is orally administered with approximately 8 ounces (240mL) of water in the morning, at the same time each day from cycle day 1 to 28. Cycle 2 of consolidation chemotherapy is scheduled to start immediately after the end of cycle 1 or within the next two weeks if blood count recovery is delayed. In case of hematologic toxicity, a dose reduction or delay of glasdegib is not required. Remission status assessments take place after each consolidation therapy cycle. Patients may undergo allo-HCT after induction or after any of the consolidation therapy cycles.
During maintenance therapy the dose of the study drug is the same as during consolidation therapy (glasdegib 100mg). Maintenance therapy with glasdegib or placebo begins after the end of the 2nd consolidation therapy cycle (includes recovery period of up to 14 days, if applicable) and after assessment of remission status or 180 days after allogeneic HCT. Patients receive up to 6 cycles of 28 days each (168 days in total) within the maintenance schedule.
All patients are asked to maintain a patient dosing diary throughout the study to record how they administer the study medication. Furthermore, patients are required to return all bottles, unused study drug and the patient dosing diary, after each cycle and at EOT visit for compliance assessment and drug accountability.
Remission status assessments take place every three months for two years after beginning maintenance therapy. The overall treatment schedule is summarized in Figure 1.
Glasdegib and placebo are interrupted in patients experiencing adverse events of grade 3 or 4. Appropriate follow-up assessments are performed until adequate recovery from toxicity. In patients recovering within 21 days from dose interruption, glasdegib/placebo may be resumed. If hematological recovery parameters are not met after 21 days of dose interruption, permanent discontinuation of treatment with glasdegib/placebo is advised. Criteria for dose interruption and dose reductions in cases of non-hematological toxicities including applicable doses in milligrams are summarized in Tables 1 and 2.
The period of observation under therapy ends with the last visit of the sixth cycle of maintenance therapy. After the end of treatment visit, patients are routinely followed-up according to standard of care. Follow-up is intended until the last patient alive has been observed for at least 2 years (study treatment including subsequent follow-up). Assuming 2 years of linear recruitment, total observation of the first patient may last up to 4 years and a median follow-up of 3 years at end of study is expected.
Event free survival and OS observational follow-up is recorded until the end of the study. After achieving an observation period of 2 years counted from day 1, the follow-up may be performed by contacting the treating physician instead of in house-visits.
Additional study procedures during induction, consolidation and continuation phases
Patients undergo efficacy and safety assessments, including monitoring of MRD, bone marrow specimen collection, blood and urine sampling and patient reported outcomes before receiving study drug and at specified time points throughout the study.
Inclusion criteria are outlined in Table 3. Key inclusion criteria are newly diagnosed AML according to the 2016 WHO classification, no prior chemotherapy for leukemia except hydroxyurea for up to 7 days to control hyperleukocytosis, age 60 years and older and ECOG PS between 0 and 2.
Exclusion criteria are summarized in Table 3. Main exclusion criteria are diagnosis of acute promyelocytic leukemia (APL) with translocation t(15;17)(q22;q12) or BCR-ABL–positive AML. Other exclusion criteria are known active CNS leukemia, HIV, viral hepatitis, prior treatment with a smoothened inhibitor (SMOi) and/or hypomethylating agent, as well as known liver cirrhosis or history of SOS.
The GnG trial has two efficacy endpoints. The first is MRD-negativity after sequential or single-dose GO in combination with intensive induction therapy. MRD-negativity is defined as the absence of leukemic cells at the end of the induction therapy assessed by flow cytometry with a sensitivity of 10-4-10-5. If MRD-negativity cannot be measured, or if patients drop out of the study before MRD measurements, missing values will be replace using multiple imputation. Patients who die from any cause before MRD measurement will be regarded as MRD-positive. The second endpoint is EFS after two years; EFS is defined as the time from randomization until one of the following events, whichever occurs first: a) failure to obtain CR or CR with incomplete neutrophil or platelet recovery (CRi) after induction therapy, b) relapse from CR/CRi or c) death from any cause. Patients without an event are censored at last follow-up. 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 induction therapy. Relapse after CR or CRi is characterized by ≥5% blast cells in the bone marrow aspirate and/or biopsy not attributable to any other cause, the reappearance of leukemic blasts in the peripheral blood, appearance of extramedullary leukemia, or presence of Auer rods. Platelet (≥100 G/l) and neutrophil (≥1.0 G/l) counts for the assessments of CR and CRi are assessed according to standard criteria .
Secondary survival endpoints are OS (defined as time from randomization until death from any cause) and relapse-free survival (RFS) (measured from first CR/CRi to time of recurrence of the disease or death from any cause, whichever occurs first). Patients without an event are censored at the last date of follow-up. Further secondary endpoints are response (CR/CRi) after induction therapy, patient reported outcomes (PROs) and pharmacoeconomics. PROs include assessments of a) health-related quality of life (QoL), calculated as the EORTC QLQ-C30 Summary Score , b) the quality of sleep or sleep disorders, calculated with the “Sleep Quality Index” from the PSQI according to the corresponding scoring guidelines , and c) anxiety and depression, calculated from the PHQ-4 according to the corresponding scoring manual ; pharmacoeconomics with health care resource utilization is assessed by self-administered resource utilization questionnaire and the SF-36  questionnaires for health economic analyses with patient-reported information on personal traits and experiences are collected at baseline.
All adverse events (AEs) that occur after the clinical 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. All AEs are coded using the latest version of the Medical Dictionary for Regulatory Activities and assigned grades based on National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.00. The Data Monitoring Committee (DMC) reviews all data relevant to safety. The DMC, which is composed of three independent experts meets regularly, and provides the sponsor with recommendations regarding trial modification, continuation, or termination.
Data Collection and Handling
All the information collected during the study 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 electronic case report form (eCRF). The eCRF is password protected and every entry is 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. Every entry is controlled for plausibility and consistency. All missing data or inconsistencies are clarified with the responsible investigator. The discrepancy clarifications are done by the monitor manager. All relevant documents and data collected within the study will be archived for at least 10 years after termination of the study.
Ethical and legal aspects
All the procedures set out in this 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 written form to participate after the nature, scope, and possible consequences of the clinical trial have been understood by the patient.
Sample size calculation and statistics
Addressing two primary endpoints, MRD-negativity after induction therapy and EFS, 252 evaluable patients are needed to reject each of the two null hypotheses at a two-sided significance level of 2.5% with a power of at least 85%.
The first primary endpoint evaluation involves the comparison of rates of MRD-negativity assessed by flow-cytometry after induction therapy between GO-147 and GO-1. Assuming a rate of MRD-negativity of 45% for GO-147 and 20% for GO-1, as well as a 3% dropout rate, a total number of 252 evaluable patients are needed to reject the null hypothesis of no difference regarding the MRD-negativity rate for patients receiving GO-147 as compared to patients receiving GO-1 during induction therapy at a two-sided significance level of 2.5% with a power of at least 85% using a chi-squared test.
The second primary endpoint evaluation involves a two-group comparison of EFS between the experimental arm of glasdegib as well as the control arm of placebo both as adjunct to standard consolidation therapy. Assuming a 2-year EFS of 38.5% for the experimental arm and a 2-year EFS of 21% for the control arm (resulting in a hazard ratio of HR=0.612), as well as an exponentially distributed dropout rate of 5% at 2 years, a total number of 224 evaluable patients (based on a number of d=178 required events) are needed to reject the null hypothesis assuming no difference regarding EFS for patients receiving glasdegib as compared to patients receiving placebo at a two-sided significance level of 2.5% with a power of at least 85% using a log-rank test, assuming an accrual time of 24 months, as well as a follow-up time of 24 months. This leads to a total sample size of N=max(252, 224)=252 patients to be enrolled for the whole trial to ensure a power of at least 85% for both primary endpoints.
The MRD-negativity after induction therapy is analyzed using a generalized linear mixed model and EFS with a Cox regression frailty model. Both models are adjusted for the following fixed factors: treatment (MRD-negativity: GO-1 vs. GO-147 and EFS: glasdegib vs. placebo), age, sex, and ECOG PS, as well as for the random factor “recruiting center”. The primary analysis is based on the full analysis set including all randomized patients. Adjustment for multiple testing is done using the Bonferroni-Holm procedure in order to control the family-wise error rate at a two-sided significance level of 5% in the strong sense. Missing values for the short-term primary endpoint MRD-negativity are replaced using multiple imputation by using of the fully conditional specification method . Odds and hazard ratios are reported alongside with two-sided 97.5% and 95% confidence intervals, and a possible center effect is assessed by calculating the intra-class correlation coefficient and by presenting the results stratified for center. A sensitivity analysis of the long-term primary endpoint additionally includes the interaction between maintenance therapy and induction therapy. Statistical analysis is performed using SAS v9.4 or higher.