DNA methyltransferase inhibition overcomes diphthamide pathway deficiencies underlying CD123-targeted treatment resistance
Katsuhiro Togami, … , Cory M. Johannessen, Andrew A. Lane
Katsuhiro Togami, … , Cory M. Johannessen, Andrew A. Lane
Published August 22, 2019
Citation Information: J Clin Invest. 2019;129(11):5005-5019. https://doi.org/10.1172/JCI128571.
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Research Article Hematology Oncology

DNA methyltransferase inhibition overcomes diphthamide pathway deficiencies underlying CD123-targeted treatment resistance

Abstract

The interleukin-3 receptor α subunit, CD123, is expressed in many hematologic malignancies including acute myeloid leukemia (AML) and blastic plasmacytoid dendritic cell neoplasm (BPDCN). Tagraxofusp (SL-401) is a CD123-targeted therapy consisting of interleukin-3 fused to a truncated diphtheria toxin payload. Factors influencing response to tagraxofusp other than CD123 expression are largely unknown. We interrogated tagraxofusp resistance in patients and experimental models and found that it was not associated with CD123 loss. Rather, resistant AML and BPDCN cells frequently acquired deficiencies in the diphthamide synthesis pathway, impairing tagraxofusp’s ability to ADP-ribosylate cellular targets. Expression of DPH1, encoding a diphthamide pathway enzyme, was reduced by DNA CpG methylation in resistant cells. Treatment with the DNA methyltransferase inhibitor azacitidine restored DPH1 expression and tagraxofusp sensitivity. We also developed a drug-dependent ADP-ribosylation assay in primary cells that correlated with tagraxofusp activity and may represent an additional novel biomarker. As predicted by these results and our observation that resistance also increased mitochondrial apoptotic priming, we found that the combination of tagraxofusp and azacitidine was effective in patient-derived xenografts treated in vivo. These data have important implications for clinical use of tagraxofusp and led to a phase 1 study combining tagraxofusp and azacitidine in myeloid malignancies.

Authors

Katsuhiro Togami, Timothy Pastika, Jason Stephansky, Mahmoud Ghandi, Amanda L. Christie, Kristen L. Jones, Carl A. Johnson, Ross W. Lindsay, Christopher L. Brooks, Anthony Letai, Jeffrey W. Craig, Olga Pozdnyakova, David M. Weinstock, Joan Montero, Jon C. Aster, Cory M. Johannessen, Andrew A. Lane

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Figure 5

Tagraxofusp is active in BPDCN patient–derived xenografts (PDXs) in vivo.

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Tagraxofusp is active in BPDCN patient–derived xenografts (PDXs) in vivo...
(A) Human CD45+CD123+ cells as a percentage of the peripheral blood mononuclear cells in NSG mice engrafted with 1 of 3 BPDCN PDXs, treated at day 0 (red arrow) with 5 days of tagraxofusp (red line) or vehicle (black line). A subset of animals in each group was re-treated with another cycle at the time when greater than 50% of animals showed progression (>5% in peripheral blood; blue lines represent animals that received 2 treatments and blue arrows are the time of the second treatment). (B) Peripheral blood disease burden measured by CD45+CD123+ flow cytometry and representative spleen size reduction in animals treated with tagraxofusp as compared to vehicle harvested 7 days after treatment (n = 4 each). (C) Sections from mouse spleens harvested on day 7 after treatment with tagraxofusp or vehicle and stained with hematoxylin & eosin (H&E) or the indicated antibodies by immunohistochemistry. Original magnification, ×40. (D) Kaplan-Meier overall survival curves for recipients of each PDX (left) and for all PDXs combined (right) that received tagraxofusp (red, n = 19) or vehicle (black, n = 15). Curves compared by log-rank test.