Abstract B146: Design and preclinical evaluation of CPL976-MMAE - novel, potent AXL-PD-L1 bispecific antibody conjugated with MMAE in targeted anticancer therapy

Abstract

Abstract Background: Antibody-drug conjugates (ADCs) combine the specificity of antibodies with the potency of highly cytotoxic agents, reducing the off-target effects and improve effectiveness with more precising delivery of the payload to the tumor site. Strong correlation has been established between AXL and PD-L1 expression levels in many types of cancer. Therefore, targeting both proteins simultaneously ensure high cancer specificity in delivering the toxic payload. We have developed a bispecific antibody, that strongly induces receptor internalization. Our bispecific ADC combines anti-AXL and anti-PD-L1 construct with toxic MMAE (Monomethyl auristatin E, a potent tubulin inhibitor toxin), for better targeting to solid tumor cells and greatly reducing off-target effects. Materials and Methods: CPL976-MMAE was prepared with site-specific conjugation technology using Fc glycan remodeling and click-chemistry. Briefly, after enzymatic trimming of the N-linked glycans in the Fc pocket of antibody, the terminal GlcNAc was extended with 6-N3-GalNAc using GalNAc-transferase, allowing metal-free click conjugation of the MMAE payload. Bispecific antibodies chosen for conjugation were first characterized in vitro for the interaction with the extracellular domain of human AXL and PD-L1 using surface plasmon resonance and flow cytometry. After the conjugation with MMAE, ADCs cytotoxicity, and selectivity were evaluated in the human breast cancer model (MDA-MB-231) with high expression of both targets, AXL and PD-L1, using SytoX and Hoechst. The human embryonic kidney cell line (HEK-293) with minimal expression of targets, was used as a negative control. The efficacy of conjugates were evaluated in xenograft mouse model. Results: Analytical characterization by RP-HPLC confirmed efficient conjugation and homogeneity of the conjugates. Conjugates showed improved cellular uptake, selectivity, and anticancer activity, compared to unconjugated MMAE in the AXL/PD-L1 overexpressing cancer cell lines. Additionally, HEK-293 cells were not affected by conjugates in concentrations applied in the assay with use of the breast cancer cell lines. This implies enhanced safety by reducing off-target side effects compared to free auristatin. The efficacy of the compound was confirmed in xenograft mouse model. Conclusions: We have designed a new, potentially first-in-class anti-AXL/PD-L1 bispecific antibody conjugated with MMAE, which showed robust and selective antitumor effects in human cancer models. Citation Format: Delfina Popiel, Krzysztof Lacek, Anna Jabłońska, Aleksandra Sowińska, Agnieszka Bojko - Matuszek, Damian Kołakowski, Filip Mituła, Sebastian Kwiatkowski, Magdalena Bojko, Tomasz Kornatowski, Beata Kliszcz, Tomasz Banach, Michał Górka, Jerzy Pieczykolan, Maciej Wieczorek, Olga Abramczyk. Design and preclinical evaluation of CPL976-MMAE - novel, potent AXL-PD-L1 bispecific antibody conjugated with MMAE in targeted anticancer therapy [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 B146.