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Clin Cancer Res. 2018 Sep 11. pii: clincanres.0098.2018. doi: 10.1158/1078-0432.CCR-18-0098. [Epub ahead of print]

The Novel Bromodomain and Extraterminal Domain Inhibitor INCB054329 Induces Vulnerabilities in Myeloma Cells That Inform Rational Combination Strategies.

Author information

1
In vivo pharmacology, Incyte Corporation mstubbs@incyte.com.
2
Drug Discovery, Incyte Corporation.
3
Discovery Chemistry, Incyte Corporation.
4
Chemistry, Incyte Corporation.
5
Incyte Corporation.
6
In vivo pharmacology, Incyte Corporation.
7
Translational Sciences, Incyte Corporation.
8
In Vitro Pharmacology, Incyte Corporation.
9
Applied Technology, Incyte Research Institute.
10
Pharmacology, Incyte Corporation.

Abstract

INTRODUCTION:

Bromodomain and extraterminal domain (BET) proteins regulate the expression of many cancer-associated genes and pathways; BET inhibitors have demonstrated activity in diverse models of hematologic and solid tumors. We report the preclinical characterization of INCB054329, a structurally distinct BET inhibitor that has been investigated in Phase 1 clinical trials.

METHODS:

We used multiple myeloma models to investigate vulnerabilities created by INCB054329 treatment that could inform rational combinations.

RESULTS:

In addition to c-MYC, INCB054329 decreased expression of oncogenes FGFR3 and NSD2/MMSET/WHSC1 that are deregulated in t(4;14) rearranged cell lines. The profound suppression of FGFR3 sensitized the t(4;14)-positive cell line OPM-2 to combined treatment with a fibroblast growth factor receptor inhibitor in vivo In addition, we show that BET inhibition across multiple myeloma cell lines resulted in suppressed interleukin (IL)-6 Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling. INCB054329 displaced binding of BRD4 to the promoter of IL-6 receptor (IL-6R) leading to reduced levels of IL-6R and diminished signaling through STAT3. Combination with JAK inhibitors (ruxolitinib or itacitinib) further reduced JAK-STAT signaling and synergized to inhibit myeloma cell growth in vitro and in vivo This combination potentiated tumor growth inhibition in vivo, even in the MM1.S model of myeloma that is not intrinsically sensitive to JAK inhibition alone.

CONCLUSION:

Preclinical data reveal insights into vulnerabilities created in myeloma cells by BET protein inhibition and potential strategies that can be leveraged in clinical studies to enhance the activity of INCB054329.

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