Magrolimab + azacitidine versus azacitidine + placebo in untreated higher risk (HR) myelodysplastic syndrome (MDS): The phase 3, randomized, ENHANCE study.

Abstract

TPS7055 Background: MDS is a clonal myeloid disorder characterized by cytopenia and ineffective hematopoiesis. The median age of diagnosis is approximately 70 yrs of age and prognosis and treatment are guided by the Revised International Prognostic Scoring System (IPSS-R) criteria. Patients with intermediate, high and very high risk MDS (HR-MDS) have a median overall survival (OS) of 0.8 to 3.7 years. Despite the high unmet need in this patient population, azacitidine (AZA) is the only approved therapy for HR-MDS which has improved overall survival in clinical trials to date. However, these agents lead to low complete response (CR) rates (10-17%) with limited OS ( = 2 years), indicating a need for alternative therapy. Magrolimab is a first-in-class monoclonal antibody that blocks the macrophage inhibitory immune checkpoint CD47, a “do not eat me” signal overexpressed on tumor cells. Binding of magrolimab to CD47 leads to phagocytosis of tumor cells. AZA increases expression of prophagocytic “eat me” signals, facilitating synergy with magrolimab. In an ongoing phase 1b study, the combination of magrolimab + AZA led to high response rates (ORR 91%, with a CR of 42%) and an acceptable safety profile without significant immune-related adverse events. ENHANCE (NCT04313881) is a phase 3 trial comparing the efficacy and safety of magrolimab + AZA with that of AZA + placebo (PBO) in previously untreated patients with HR-MDS. Methods: Patients ≥18 years old with previously untreated intermediate to very high risk MDS by IPSS-R are eligible for ENHANCE. Randomization is 1:1 to magrolimab + AZA or AZA + PBO with no crossover allowed. Magrolimab or placebo is administered intravenously (IV) with an initial 1 mg/kg priming dose to mitigate on target anemia. An intrapatient dose escalation regimen up to 30 mg/kg is then administered through Cycle 1, 30 mg/kg weekly dosing in Cycle 2, with 30 mg/kg Q2W dosing occurring in Cycle 3 and beyond. AZA is administered per regional prescribing information. Patients may remain on treatment until disease progression, relapse, loss of clinical benefit, or until unacceptable toxicities occur. Two primary efficacy endpoints are CR rate and OS. For patients undergoing allogeneic stem cell transplantation (ASCT), data for the CR rate will be censored at the time of ASCT and OS will be censored at the last known alive date. Secondary efficacy endpoints include RBC transfusion independence rate, event-free survival, minimal residual disease-negative rate, time to AML transformation, and patient-reported Functional Assessment of Cancer Therapy (FACT)-Anemia response rate. Biomarkers of immune cell recruitment, immune cell signaling, and bone marrow penetration of magrolimab will also be explored. Planned enrollment is approximately 520 patients globally, which began in September 2020. Accrual is ongoing. Clinical trial information: NCT04313881.