The Bruton tyrosine kinase inhibitor zanubrutinib (BGB-3111) demonstrated synergies with other anti-lymphoma targeted agents Inhibition of Bruton tyrosine kinase (BTK) is a wellestablished therapeutic approach in B-cell malignancies and two BTK inhibitors, ibrutinib and acalabrutinib, have been approved by the U.S. Food and Drug Administration for use in this setting. 1 Zanubrutinib (BGB-3111) is an investigational second-generation irreversible BTK inhibitor that has been shown to have lower off-target inhibitory activity on other kinases, including interleukin-2-inducible T-cell kinase (ITK), Janus kinase 3 (JAK3) and epidermal growth factor receptor (EGFR). 2 Zanubrutinib is under active clinical investigation for use in lymphoid neoplasms. Here, we evaluated the effects of zanubrutinib in combination with other targeted agents in human lymphoma cell lines. Cell lines derived from activated B-cell (ABC) diffuse large B-cell lymphoma (DLBCL; n=3) or mantle cell lymphoma (MCL; n=2) were exposed for 72 h to increasing doses of zanubrutinib (provided by BeiGene) alone and in combination with increasing doses of other compounds (acquired from Selleckem), as previously described. 3 Cell line identity was assessed by short tandem repeat DNA fingerprinting (Promega GenePrint 10 System kit). Synergism was defined in the presence of a Chou-Talalay combination index between 0.3 and 0.9, additivity for a combination index between 0.9 and 1.1, and antagonism/no benefit for a combination index >1.1. 3 As determined by the half maximal inhibitory concentration (IC50), single-agent zanubrutinib showed antitumor activity in the nanomolar range in one MCL line (REC1, IC50 0.9 nM) and two ABC DLBCL lines (TMD8,

Introduction. BGB-3111 is a novel generation irreversible BTK inhibitor (Hu et al AACR2017) under active clinical investigation for lymphoid tumors. Here, we evaluated BGB-3111 in combination with other anti-cancer agents on a panel of human lymphoma cell lines. Methods. Cell lines derived from activated B cell (ABC) diffuse large B cell lymphoma (DLBCL) (n=3), mantle cell lymphoma (MCL) (n=2) and chronic lymphocytic leukemia (CLL) (n=2) were exposed to increasing doses of BGB-3111 alone and in combination with increasing doses of other compounds (72h). Synergy was assessed with Chou-Talalay combination index (CI): synergism (<0.9), additive (0.9-1.1), antagonism/no benefit (> 1.1). Cell cycle analysis was performed after 24h of treatment. Results. As single agent BGB-3111 showed anti-tumor activity in the nanomolar range in two ABC-DLBCL (TMD8, IC50 0.4 nM; OCI-LY-10, 1.5 nM) and in one MCL (REC1, IC50 0.9 nM) cell lines, while the remaining four cell lines resulted resistant (IC50s > 5µM). The pattern of activity was similar to what seen with ibrutinib and other 2nd generation BTK inhibitors (Gaudio et al, ENA 2016). BGB-3111 was then valuated in combination with targeted agents. In ABC-DLBCL, synergism was achieved in 3/3 cell lines when BGB-3111 was combined with the MEK inhibitor pimasertib or with BCL2 inhibitor venetoclax. The combination with BET inhibitor OTX-015 was synergistic in 2/3 cell lines, while the combination with the XPO1 antagonist selinexor was beneficial in 2/3 (1 synergism, 1 additive). In CLL cell lines, the best combinations were BGB-3111 with OTX015 or with selinexor with 2/2 synergisms. The results of the combinations with pimasertib or venetoclax were discordant (pimasertib, 1 synergism, 1 no benefit; venetoclax, 1 synergism, 1 no benefit). Both MCL cell lines achieved synergism combining BGB-3111 with pimasertib, or selinexor, or venetoclax. The combination with OTX-015 was also beneficial, but synergism was observed in only one of the two cell lines, and additive in the remaining. The improved anti-tumor activity of the combination versus the single agents were confirmed performing cell cycle analysis in an ABC-DLBCL (OCI-LY-10) with an increased subG0 phase when BGB3111 was combined with venetoclax, pimasertib and OTX-015. Conclusion. BGB-3111 was active as single and the combination with inhibitors of key regulatory pathways in cell lines derived from ABC-DLBCL, CLL and MCL. Citation Format: Chiara Tarantelli, Lu Zhang, Elisabetta Curti, Filippo Spriano, Eugenio Gaudio, Luciano Cascione, Alberto Arribas, Emanuele Zucca, Anastasios Stathis, Davide Rossi, Francesco Bertoni. The BTK inhibitor BGB-3111 is synergistic with other anti-lymphoma targeted agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 796.