Abstract 1050: Mechanistic studies investigating the synergistic combination of Loncastuximab Tesirine and Ibrutinib in pre-clinical models of B-cell non-Hodgkin lymphoma

Loncastuximab tesirine-lpyl (formerly ADCT-402) is a pyrrolobenzodiazepine dimer-based antibody-drug conjugate directed against human CD19 which has been recently approved by the United States Food and Drug Administration for the treatment of relapsed or refractory diffuse large B-cell lymphoma (DLBCL). Pre-clinically, loncastuximab tesirine has shown potent and specific anti-tumor activity in lymphoma models both as single agent and in combination with other approved drugs. Clinically, loncastuximab tesirine is being tested in multiple clinical trials, either as monotherapy or in combination with other anti-lymphoma drugs including ibrutinib. Ibrutinib is a small molecule inhibitor of Bruton’s tyrosine kinase, approved for treatment of mantle cell lymphoma (MCL), chronic lymphocytic leukaemia and other haematological malignancies.Here, we investigated the combined effect of loncastuximab tesirine (lonca) and ibrutinib in pre-clinical models of B-cell non-Hodgkin lymphoma (NHL).In vitro, the combination of lonca and ibrutinib was tested in a panel of 5 NHL-derived cell lines covering activated B-cell-DLBCL (TMD8 and OCI-Ly3), germinal center B-cell-DLBCL (WSU-DLCL2) and MCL (REC-1 and Granta-519) subtypes and showed synergistic activity in all but one cell line (WSU-DLCL2), as assessed by the Chou-Talalay method.Quantification of cell viability (propidium iodide [PI]-negative and Annexin V-negative), early apoptosis (Annexin V-positive and PI-negative) and late apoptosis (Annexin V-positive and PI-positive) showed a statistically significant reduction of viable cells accompanied by an increase in early apoptotic cells after 72-hour treatment with the combination compared to the single agents.Analysis of γH2AX and cleaved PARP protein expression revealed that ibrutinib drives the increase in both γH2AX and cleaved PARP after 24 hours of treatment, while lonca is largely responsible for the upregulation of both markers after 72 hours of treatment, suggesting that the two drugs work with different kinetics. Interestingly, increased γH2AX was detected in the combination setting compared to the two single agents at the 72-hour time-point.Gene expression profiling of TMD8 cells treated with lonca, ibrutinib or their combination revealed that the cytokine-cytokine receptor interaction pathway and the nuclear factor kappa light chain enhancer of activated B cells pathway were among the most affected by the drug combination. Interleukin-10 (IL-10) was one of the most downregulated genes. Interestingly, quantitative gene and protein expression analysis revealed that IL-10 downregulation was more effective in the combination setting compared to the single agents. In conclusion, these preclinical data support the ongoing clinical investigation of lonca and ibrutinib in patients with advanced DLBCL or MCL. Citation Format: Danilo Cucchi, Nikoleta Sachini, Patrick H. van Berkel, Francesca Zammarchi. Mechanistic studies investigating the synergistic combination of Loncastuximab Tesirine and Ibrutinib in pre-clinical models of B-cell non-Hodgkin lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1050.