Abstract 5084: A first-in-class bispecific antibody CPL976 with a dual PD-L1/AXL mechanism of action that promotes common biological antitumor effects in in vitro and in vivo models
Authors: Popiel Delfina , Kołakowski Damian , Bojko-Matuszek Agnieszka , Lacek Krzysztof , Jabłońska Anna , Sowińska Aleksandra , Mituła Filip , Bojko Magdalena , Wiernicki Bartosz , Mikołajczyk Agata , Kornatowski Tomasz , Flis Krzysztof , Skupińska Monika , Hucz-Kalitowska Joanna , Mróz Emilia , Choroś Małgorzata , Wieczorek Maciej , Pieczykolan Jerzy , Abramczyk Olga 
Published: March 2024

Abstract
Background: Bispecific antibodies emerged as a leading drug class for cancer therapy and are becoming increasingly interesting for the therapeutic applications. The Gas6/Axl signaling pathway contributes to the immunosuppressive tumor microenvironment by increasing the expression of PD-L1 and tumor-derived chemokines. This results in increased infiltration of macrophages, monocytes, and myeloid-derived suppressor cells, but decreased infiltration of CD4+ and CD8+ T cells and dendritic cells in the tumor bed. The PD-1/PD-L1-mediated signaling pathway is a well-known mechanism responsible for T-cell inhibition, consequently disrupting their ability to eliminate tumor cells. In addition, AXL and PD-L1 are concurrently highly expressed in many tumors. Therefore, bispecific antibody that inhibits both axes seems like a promising therapeutic strategy engaging anti-proliferative effect by AXL inhibition, and cytotoxic properties of effector T cells by breaking the PD-1/PD-L1 axis.
Materials and Methods: Bispecific antibody CPL976 was designed as a VHH-Fc-VHH format, with two VHHs raised against PD-L1 and two against AXL. Activity, selectivity, and potential for internalization and degradation of targets were studied on cancer cell lines with different expression levels of the targets. In addition, CPL976 efficacy was verified in syngeneic mouse models, when antibodies were administered intravenously at different doses for 3 weeks.
Results: We confirmed the CPL976’s innovative mechanism of action based on the strong and simultaneous engagement of both therapeutic targets, and potential internalization and degradation of target proteins in cancer cell lines with different expression levels of AXL and PD-L1 (MDA-MB 231, A375, A549, H1299). Potent and dose-dependent in vivo antitumor activity was observed in the syngeneic mouse model, where at a dose of 15mg/kg remission of the tumor was observed in 5/8 compared to 0/8 in the control group.
Conclusions: CPL976 is the bispecific antibody that combines the effects of cancer inhibition by interacting with AXL and immunotherapy by disrupting the PD-1/PD-L1 axis. The use of the bispecific antibodies simultaneously targeting PD-L1 and AXL provokes internalization of the targets to maximize the biological effect of the inhibition of the receptor/ligand complexes (AXL/cGAS6, PD-1/PD-L1) formation. Simultaneous action on both therapeutic targets may help achieve an enhanced immune response against cancer cells and lead to tumor eradication and overcoming the primary and secondary resistance to PD-1/PD-L1 targeted therapies.
Citation Format: Delfina Popiel, Damian Kołakowski, Agnieszka Bojko-Matuszek, Krzysztof Lacek, Anna Jabłońska, Aleksandra Sowińska, Filip Mituła, Magdalena Bojko, Bartosz Wiernicki, Agata Mikołajczyk, Tomasz Kornatowski, Krzysztof Flis, Monika Skupińska, Joanna Hucz-Kalitowska, Emilia Mróz, Małgorzata Choroś, Maciej Wieczorek, Jerzy Pieczykolan, Olga Abramczyk. A first-in-class bispecific antibody CPL976 with a dual PD-L1/AXL mechanism of action that promotes common biological antitumor effects in in vitro and in vivo models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5084.