Flotetuzumab was found to demonstrate antileukemic activity in patients with primary induction failure (PIF) and early-relapse acute myeloid leukemia (ER-AML), and the treatment appears tolerable with infrequent neurologic adverse events, according to results from an updated analysis of an ongoing open-label phase 1/2 study (ClinicalTrials.gov Identifier: NCT02152956). The preliminary findings were presented by Ibrahim Aldoss, MD, of the Gehr Family Center for Leukemia Research at City of Hope in Duarte, California, at the virtual 62nd American Society of Hematology (ASH) Annual Meeting and Exposition.

CD123 is overexpressed on AML cells, including leukemia stem cells, as well as other hematological malignancies, said Dr Aldoss. Flotetuzumab is a humanized CD3 x CD123 bispecific T-cell engager that redirects T cells to kill tumor cells expressing CD123.

The open-label, single-arm, multicenter, phase 1/2 study previously identified the recommended phase 2 dosage of flotetuzumab as 500 ng/kg/d administered via continuous infusion in 28-day cycles following a step-up lead-in dose administered during cycle 1 in week 1 of treatment. The primary objective of the study was to assess safety and antileukemic activity of flotetuzumab in patients with PIF/ER-AML.

A total of 44 patients (PIF, n= 27; ER-AML, n=17) were included in the study. Median patient age was 63.5 years (range, 28.0-81.0), and most patient were men (70.5%). According to the European LeukemiaNet (ELN) 2017 risk stratification criteria, the majority of patients had nonfavorable risk (97.7%).

Evidence of antileukemic activity was documented in 59.1% of patients, with a median decrease of 81.0% in bone marrow blasts. Median time to first response was 1 cycle (range, 1-3).

The combined complete response rate (CR, <5% bone marrow blast) and CR with partial hematologic recovery (CRh) was 25.0% (PIF, 33.3%; ER-AML, 11.8%) and 31.8% when including CR with incomplete hematologic recovery (CRi). Among the 14 patients with CR/CRh/CRi, 8 patients subsequently underwent stem cell transplantation.

In addition, morphologic leukemia-free state was reported in 3 patients (PIF, n=1; ER-AML, n=2). Of the 10 patients with TP53 mutation, 5 were reported to have CRR/CRh/CRi, and 3 of those patients (60.0%) underwent stem cell transplantation.

For all patients who achieved CR/CRh/CRi, median duration of response was 8.13 months, and median overall survival was 10.7 months.

Cytokine release syndrome (CRS), the most frequently reported treatment-related adverse event, occurred in 100% of patients (n=44; all grade). One grade 3 CRS event occurred. Approximately half of CRS events (52%) occurred during step-up dosing in the first week of treatment, and the incidence of CRS progressively decreased over time.

Neurologic adverse events were reported as infrequent and of mild to moderate severity (all-grade headache, n=13; 29.5%). Neurologic treatment-related adverse events of grade 3 or more were confusional state (n=3) and dizziness (n=1).

Flotetuzumab demonstrated encouraging activity in patients with primary induction failure in early-relapse AML, a population with poor prognosis and high unmet medical need, Dr Aldoss concluded.

The study (ClinicalTrials.gov Identifier: NCT02152956) is currently enrolling patients.

Disclosure: Some authors have declared affiliations with or received funding from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.

Read more ofHematology Advisorscoverage of the ASH 2020 meeting by visiting theconference page.

Aldoss I, Uy G, Vey N, et al. Flotetuzumab as salvage therapy for primary induction failure and early relapse acute myeloid leukemia. Presented at: American Society of Hematology (ASH) 62nd Annual Meeting and Exposition; December 5-8, 2020. Abstract 331.

Read more:
Antileukemic Activity Seen With Flotetuzumab in Primary Induction Failure, Early-Relapse AML - Hematology Advisor