The bromodomain and extra-terminal domain degrader MZ1 exhibits preclinical anti-tumoral activity in diffuse large B-cell lymphoma of the activated B cell-like type

Chiara Tarantelli; Eleonora Cannas; Hillarie Ekeh; Carmelo Moscatello; Eugenio Gaudio; Luciano Cascione; Sara Napoli; Cesare Rech; Andrea Testa; Chiara Maniaci; Andrea Rinaldi; Emanuele Zucca; Anastasios Stathis; Alessio Ciulli; Francesco Bertoni

doi:10.37349/etat.2021.00065

The bromodomain and extra-terminal domain degrader MZ1 exhibits preclinical anti-tumoral activity in diffuse large B-cell lymphoma of the activated B cell-like type

Explor Target Antitumor Ther. 2021;2(6):586-601. doi: 10.37349/etat.2021.00065. Epub 2021 Dec 31.

Authors

Chiara Tarantelli¹, Eleonora Cannas¹, Hillarie Ekeh¹, Carmelo Moscatello^{1

2}, Eugenio Gaudio¹, Luciano Cascione^{1

3}, Sara Napoli¹, Cesare Rech¹, Andrea Testa⁴, Chiara Maniaci⁴, Andrea Rinaldi¹, Emanuele Zucca^{1

5}, Anastasios Stathis^{5

6}, Alessio Ciulli⁴, Francesco Bertoni^{1

5}

Affiliations

¹ Institute of Oncology Research, Faculty of Biomedical Sciences, USI, 6500 Bellinzona, Switzerland.
² Department of Medical, Oral and Biotechnological Sciences, "G. d'Annunzio" University of Chieti-Pescara, I-66100 Chieti, Italy.
³ SIB Swiss Institute of Bioinformatics, 1000 Lausanne, Switzerland.
⁴ Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, Scotland, UK.
⁵ Oncology Institute of Southern Switzerland, Ente Ospedaliero Cantonale, 6500 Bellinzona, Switzerland.
⁶ Faculty of Biomedical Sciences, USI, 6900 Lugano, Switzerland.

Abstract

Aim: Bromodomain and extra-terminal domain (BET) proteins are epigenetic readers that play a fundamental role in transcription regulation. Preclinical and early clinical evidence sustain BET targeting as an anti-cancer approach. BET degraders are chimeric compounds comprising of a BET inhibitor, which allows the binding to BET bromodomains, linked to a small molecule, binder for an E3 ubiquitin ligase complex, triggering BET proteins degradation via the proteasome. These degraders, called proteolysis-targeting chimeras (PROTACs), can exhibit greater target specificity compared to BET inhibitors and overcome some of their limitations, such as the upregulation of the BET proteins themselves. Here are presented data on the anti-tumor activity and the mechanism of action of the BET degrader MZ1 in diffuse large B cell lymphoma (DLBCL) of the activated B-cell like (ABC, ABC DLBCL), using a BET inhibitor as a comparison.

Methods: Established lymphoma cell lines were exposed for 72 h to increasing doses of the compounds. Cell proliferation was evaluated by using an 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazoliumbromide (MTT) assay. Fluorescent-Activated Cell Sorter (FACS) analysis was performed to measure apoptotic activation and RNA sequencing (RNA-Seq) to study the transcriptional changes induced by the compounds.

Results: MZ1, and not its negative control epimer cisMZ1, was very active with a median half maximal inhibitory concentration (IC₅₀) of 49 nmol/L. MZ1 was more in vitro active than the BET inhibitor birabresib (OTX015). Importantly, MZ1 induced cell death in all the ABC DLBCL cell lines, while the BET inhibitor was cytotoxic only in a fraction of them. BET degrader and inhibitor shared partially similar changes at transcriptome level but the MZ1 effect was stronger and overlapped with that caused cyclin-dependent kinase 9 (CDK9) inhibition.

Conclusions: The BET degrader MZ1 had strong cytotoxic activity in all the ABC DLBCL cell lines that were tested, and, at least in vitro, it elicited more profound effects than BET inhibitors, and encourages further investigations.

Keywords: BET; bromodomain; bromodomain-containing protein 4; diffuse large B-cell lymphoma; epigenetics; immuno-oncology; lymphoma; proteolysis-targeting chimeras.