Combination fedratinib and venetoclax has activity against human B-ALL with high FLT3 expression

Treatment of relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL) remains a challenge, particularly in patients who do not respond to traditional chemotherapy or immunotherapy. The objective of this study was to assess the efficacy of fedratinib, a semi selective JAK2 inhibitor and venetoclax, a selective BCL-2 inhibitor, on human B-ALL using both single-agent and combinatorial treatments. The combination treatment of fedratinib and venetoclax improved killing of the human B-ALL cell lines RS4;11 and SUPB-15 in vitro over single-agent treatments. This combinatorial effect was not detected in the human B-ALL cell line NALM-6, which was less responsive to fedratinib due to the absence of Flt3 expression. The combination treatment induces a unique gene expression profile relative to single-agent treatment and with an enrichment in apoptotic pathways. Finally, the combination treatment was superior to single agent treatment in an in vivo xenograft model of human B-ALL, with a two-week treatment regimen significantly improving overall survival while inducing CD19 expression. Overall, our data demonstrates the efficacy of a combinatorial treatment strategy of fedratinib and venetoclax against human B-ALL expressing high levels of Flt3.

Statement of Implication

The combination treatment of fedratinib and venetoclax has activity against human B-ALL with high FLT3 expression and has the potential to be a salvage therapy for patients with relapsed/refractory B-ALL.

CXCR4 allows T cell acute lymphoblastic leukemia to escape from JAK1/2 and BCL2 inhibition through CNS infiltration

Targeting the JAK/STAT and BCL2 pathways in patients with relapsed/refractory T cell acute lymphoblastic leukemia (T-ALL) may provide an alternative approach to achieve clinical remissions. Ruxolitinib and venetoclax show a dose-dependent effect on T-ALL individually, but combination treatment reduces survival and proliferation of T-ALL in vitro. Using a xenograft model, the combination treatment fails to improve survival, with death from hind limb paralysis. Despite on-target inhibition by the drugs, histopathology demonstrates increased leukemic infiltration into the central nervous system (CNS) as compared to liver or bone marrow. Liquid chromatography-tandem mass spectroscopy shows that ruxolitinib and venetoclax insufficiently cross into the CNS. The addition of the CXCR4 inhibitor plerixafor with ruxolitinib and venetoclax reduces clinical scores and enhances survival. While combination therapy with ruxolitinib and venetoclax shows promise for treating T-ALL, additional inhibition of the CXCR4-CXCL12 axis may be needed to maximize the possibility of complete remission.

Dietary administration of alpha-tocopheryloxyacetic acid induces CD4+ T cell activation and prolongs survival in murine rhabdomyosarcoma

Relapsed sarcomas remain essentially incurable for most children with cancer. Alpha-Tocopheryloxyacetic acid (αTEA) is a scalable semi-synthetic derivative of alpha-tocopherol that has shown promising activity preclinically and clinically in adult cancer, but has not yet been studied in pediatric sarcoma. We hypothesized that αTEA would mediate anti-tumor effects in rhabdomyosarcoma (RMS) by modulating the immunosuppressive milieu. Treatment of murine M3-9-M RMS in vitro with αTEA (2.5–100uM) resulted in increased apoptosis by flow cytometry (Annexin V+/7AAD+) and Incucyte analysis (Annexin V+) within 24 hours (p < 0.05). Using an established orthotopic luciferase+ M3-9-M in vivo RMS model, αTEA-supplemented chow administered for 21 days significantly reduced tumor volume (p < 0.001) and bioluminescence (p < 0.05) by 28 days, resulting in a significant prolongation of survival compared to matched control chow (p < 0.05), up to 4 weeks after the feed was stopped. Analysis of spleens from RMS mice fed αTEA-supplemented diets showed an increased percentage of Ki-67+ and IFNγ+CD4+ T cells (p < 0.01) at the end of treatment as compared to recipients of the control diet. In addition, a decrease in the percentage of CD11b+Arg-1+ (p < 0.01) and PD-L1+ (p < 0.05) cells within the spleen were observed in αTEA-treated RMS tumor-bearing mice. RNA-Seq analysis of RMS tumors is underway to explore changes in αTEA vs. control-treated mice. These results suggest that αTEA causes direct induction of apoptosis of RMS in vitro and in vivo, leading to prolonged survival through enhanced CD4+ T cell stimulation and reduced myeloid cell-mediated immunosuppression in RMS-bearing mice. Further investigation of αTEA as an immunomodulating agent is warranted.