A phase II study of bisantrene in patients with relapsed/refractory acute myeloid leukemia.

OBJECTIVES: To determine the current role of bisantrene, an anthracene with anthracycline-like activity which was shown in earlier studies to be effective therapy in relapsed/refractory acute myeloid leukemia with no discernible cardiotoxicity, in the treatment of patients with R/R AML. METHODS: This phase 2, single-center study (NCT03820908) enrolled adult R/R AML to receive bisantrene (250 mg/m2 daily for 7 days) which was administered via an intravenous infusion over 2 hours on days 1-7. Disease assessment included routine blood work and bone marrow studies. RESULTS: In all, 10 patients were enrolled with a median of 3 lines of prior therapy including seven patients who had relapsed following allogeneic stem cell transplantation. The most frequently reported grade ≥3 treatment-attributed hematologic AE was thrombocytopenia, whereas the most frequently reported grade ≥3 treatment-attributed non-hematologic AE was mucositis. Of the 10 patients, one (10%) achieved a complete remission and three patients achieved a partial remission resulting in an overall response rate of 40%. Next-generation sequencing of patient samples identified a wide array of mutations associated with activated signaling, splicing, and epigenetic modification. CONCLUSIONS: In view of the observed low toxicity, a follow-up study combining bisantrene with complementary anti-leukemic therapy is planned.

CXCR4 regulates migration and development of human acute myelogenous leukemia stem cells in transplanted NOD/SCID mice.

The chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 participate in the retention of normal hematopoietic stem cells within the bone marrow (BM) and their release into the circulation. Homing and engraftment of human stem cells in immunodeficient mice are dependent on cell surface CXCR4 expression and the production of BM SDF-1, which acts also as a survival factor for both human and murine stem cells. However, the role of SDF-1/CXCR4 interactions in the control of human acute myelogenous leukemia (AML) cell trafficking and disease progression is poorly understood. In this study, we report that although some AML cells do not express surface CXCR4, all AML cells tested express internal CXCR4 and SDF-1. Culture of AML cells with SDF-1 promoted their survival, whereas addition of neutralizing CXCR4 antibodies, SDF-1 antibodies, or AMD3100 significantly decreased it. Pretreatment of primary human AML cells with neutralizing CXCR4 antibodies blocked their homing into the BM and spleen of transplanted NOD/SCID/B2m(null) mice. Furthermore, weekly administrations of antihuman CXCR4 to mice previously engrafted with primary AML cells led to a dramatic decrease in the levels of human AML cells in the BM, blood, and spleen in a dose- and time-dependent manner. Interestingly, the same treatment did not affect significantly the levels of normal human progenitors engrafted into NOD/SCID mice. Taken together, our findings demonstrated the importance of the SDF-1/CXCR4 axis in the regulation of in vivo motility and development of human AML stem cells and identified CXCR4 neutralization as a potential treatment for AML.