Abstract C139: The IRAK4 inhibitor emavusertib (CA-4948) synergizes with second generation BTK inhibitors acalabrutinib and zanubrutinib in MYD88-L265P mutated lymphoma cell lines
Authors: Guidetti Francesca , Arribas Alberto J. , Cannas Eleonora , Zucca Emanuele , Stathis Anastasios , von Roemeling Reinhard , Bertoni Francesco 
Published: December 2023

Abstract
Background. IRAK4 is a protein kinase downstream the Toll-like receptor (TLR), activated through the adaptor protein MYD88, crucial for the signaling cascade that leads to NF-κB-mediated cytokine and survival factor expression. Somatic mutations in the gene coding for the adaptor protein MYD88 are common in lymphoid tumors. In particular, the MYD88-L265P mutations, known to sustain NF-κB activation, is specifically observed in a fraction of the activated B cell (ABC) diffuse large B-cell lymphomas (DLBCL), in the vast majority of lymphoplasmacytic lymphoma (LPL), and in rare marginal zone lymphomas (MZLs). So far, no success has been achieved to directly inhibit MYD88. Emavusertib (CA-4948) is an IRAK4 inhibitor, which has shown preclinical activity in ABC DLBCL and MZL models, especially in cases bearing the MYD88-L265P. We and others have shown synergism when combining emavusertib with the first generation BTK inhibitor ibrutinib. Clinical trials are on-going exploring emavusertib as single agent or in combination in patients with hematological cancers or solid tumors. Since ibrutinib is associated with possible toxicities that can outbalance its clinical efficacy, here, we have tested the combination of emavusertib with acalabrutinib and zanubrutinib, two 2nd generation BTK inhibitors that have shown improved safety profile in clinical trials.
Methods. Cell lines were exposed to five increasing concentrations of each compound as single agent or in combination for 72 h, followed by MTT assay. The beneficial effect of the combinations compared to the single agents was considered both as synergism according to the Chou-Talalay combination index and as potency and efficacy according to the MuSyC algorithm.
Results. Cell lines bearing the MYD88-L265P mutation and derived from ABC DLBCL (OCI-Ly-10, TMD8, HBL1) or MZL/LPL (Karpas-1718) were exposed to emavusertib, acalabrutinib or zanubrutinib as single agent or in combination. Synergism, defined as a median Chou-Talalay index &lt; 0.9, was observed for both the combination of emavusertib plus acalabrutinib and for the combination of emavusertib plus zanubrutinib in all four cell lines. Based on the MuSyC algorithm, the synergistic activity of emavusertib was mainly due to an improved efficacy (i.e., maximal effect) rather than improved potency (i.e., minimal active dose) of the BTK inhibitors.
Conclusions. In MYD88-L265P mutated lymphoma cell lines, synergism is observed combining the IRAK4 inhibitor emavusertib with the 2nd generation BTK inhibitors acalabrutinib and zanubrutinib. Our data sustain further clinical exploration of the combination of IRAK4 and BTK inhibitors for lymphoma patients.
Citation Format: Francesca Guidetti, Alberto J. Arribas, Eleonora Cannas, Emanuele Zucca, Anastasios Stathis, Reinhard von Roemeling, Francesco Bertoni. The IRAK4 inhibitor emavusertib (CA-4948) synergizes with second generation BTK inhibitors acalabrutinib and zanubrutinib in MYD88-L265P mutated lymphoma cell lines [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C139.