Abstract 3324: Optimizing the therapeutic potential of tyrosine kinase inhibitors in chemo-immunotherapy of B-cell acute lymphoblastic leukemia involving rituximab
Authors: Domka Krzysztof , Poprzeczko Martyna , Urbanska Zuzanna , Komorowski Lukasz , Pastorczak Agata , Fidyt Klaudyna , Dabkowska Agnieszka , Lachota Mieszko , Winiarska Magdalena , Siudakowska Karolina , Patkowska Elzbieta , Sędek Łukasz , Perkowski Bartosz , Krzymieniewska Beata , Firczuk Malgorzata 
Published: June 2022

Abstract
B-cell acute lymphoblastic leukemia (B-ALL) is a malignancy caused by accumulation of immature B cells. Advances in the field, especially in genomic studies and new treatment development, significantly improved the prognosis of B-ALL over the last decades. However, the B-ALL subtype harboring Philadelphia chromosome t(9;22)(q34;q11) (Ph+ B-ALL) still remains a therapeutic challenge despite available targeted treatment with tyrosine kinase inhibitors (TKIs). The novel therapeutic regimens for adult B-ALL often include rituximab (RTX) - a monoclonal anti-CD20 antibody - for patients with &gt;20% CD20+ blasts. Moreover, drug combinations including approved TKIs and antibodies are being tested in clinical trials. Since some TKIs display immune effector cell inhibition, investigating their immunomodulatory effects in the context of combined chemo-immunotherapies is clinically relevant for the rational combination design. We found that blasts isolated from Ph+ B-ALL patients showed the highest CD20 expression on mRNA level among defined B-ALL genetic subtypes. As Ph+ CD20+ patients may be qualified for treatment with TKIs along with RTX, this result prompted the need of investigating the effects of TKIs on immune effectors. We therefore compared how first-, second- and third-generation TKIs (imatinib, dasatinib, nilotinib, bosutinib, ponatinib) and allosteric inhibitor asciminib recently approved for the treatment of chronic myeloid leukemia (CML) affect innate and antibody-mediated cytotoxicity. B-ALL cell lines, patient-derived lymphoblasts propagated in NSG mice (primografts) and ex vivo whole blood assays were used for testing the efficacy of effector cell-mediated mechanisms in the presence of TKIs. The TKIs were compared in NK-cell based natural cytotoxicity tests, antibody-dependent cytotoxicity (ADCC) tests and phagocytosis assays with monocyte-derived macrophages. Dasatinib was also tested using whole blood ex vivo ADCC assays before and after administration of the TKI. Out of six tested TKIs, asciminib presented the most favorable profile, causing slight or no effector cell inhibition in both innate and antibody-mediated responses. In contrast, dasatinib significantly decreased the immune cells activity in all tests, reducing natural and RTX-mediated cytotoxicity of NK cells against B-ALL blasts. Dasatinib and ponatinib significantly inhibited in vitro phagocytosis of primograft B-ALL cells. To a lesser extent, cytotoxicity and phagocytosis were suppressed by imatinib, bosutinib and nilotinib. Importantly, we confirmed that the orally administered dasatinib impairs the NK cell activity in patients’ blood. Our findings indicate that the TKIs differentially impact RTX-mediated effector mechanisms. The novel, allosteric TKI asciminib could be preferentially used in combination with RTX-based immunotherapy. This work was supported by the Polish National Science Centre grant 2019/35/B/NZ5/01428 and by the Ministry of Education and Science within “Regional Initiative of Excellence” program 013/RID/2018/19."
Citation Format: Krzysztof Domka, Martyna Poprzeczko, Zuzanna Urbanska, Lukasz Komorowski, Agata Pastorczak, Klaudyna Fidyt, Agnieszka Dabkowska, Mieszko Lachota, Magdalena Winiarska, Karolina Siudakowska, Elzbieta Patkowska, Łukasz Sędek, Bartosz Perkowski, Beata Krzymieniewska, Malgorzata Firczuk. Optimizing the therapeutic potential of tyrosine kinase inhibitors in chemo-immunotherapy of B-cell acute lymphoblastic leukemia involving rituximab [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 3324.