Abstract 1755: IKS03, a CD19-targeted antibody drug conjugate with enhanced efficacy and tolerability for treatment of B-cell lymphomas
Authors: Thirlway Jenny , Lodge Adam , Williamson Daniel J. , Mysliwy Justyna , Deckert Jutta , Chauchet Xavier , Cons Laura , Park Yun-Hee , Ryu Hyun-Min , Han Na Ra , Song Ho Young , Chung Chul-Woong , Lutz Robert J. 
Published: June 2022

Abstract
Background: Lymphoma is the most common hematological malignancy with non-Hodgkin B-cell lymphomas (NHL), including those with high unmet clinical need such as relapsed/refractory Diffuse Large B Cell Lymphoma (DLBCL), and Mantle-Cell Lymphoma (MCL), representing 90% of all lymphoma cases. CD19 is an attractive target for antibody-directed lymphoma therapies as it is expressed in most B cell malignancies, with normal tissue expression limited to B-cells thus reducing any on-target toxicity concerns. Antibody Drug Conjugates (ADCs) are the focus of intense interest as a means to provide selective tumor killing with increased efficacy and less toxicity than standard of care chemotherapies. IKS03 is an ADC comprised of an anti-CD19 antibody conjugated to a proprietary DNA-crosslinking PBD prodrug and includes a tumor-selective glucuronide-trigger technology for payload release and activation. ADC activity requires processing by beta-glucuronidase, a lysosomal enzyme often upregulated in tumor cells, while normal tissues with low levels of the enzyme are less able to process the ADC and are differentially spared.
Methods: IKS03 was generated via chemo-enzymatic bioconjugation at defined sites on the antibody yielding an ADC with a drug to antibody ratio of 2. In vivo efficacy was evaluated in CD19-expressing cell line-derived xenograft models in mice including Farage (DLBCL, Germinal Centre B-cell subtype), OCI-LY10 (DLBCL, Activated B-Cell subtype), Granta-519 (MCL) and Ramos (Burkitt’s lymphoma). Activity was compared to benchmark ADCs known to have demonstrated clinical efficacy. Efficacy was also assessed in low passage DLBCL patient-derived xenograft models of known genomic profile. Toxicology studies were conducted in cynomolgus monkeys with immunophenotyping by flow cytometry included to quantify the level of normal B-cells following IKS03 administration.
Results: IKS03 is highly effective in causing tumor regressions in DLBCL models at doses that are well tolerated. Complete regressions were observed with a single dose of 0.1 mg/kg in the Farage xenograft model. IKS03 is also highly active in the Granta-519 MCL model, with complete regressions observed with a single dose of 0.1 mg/kg. Tumor regression was observed in a high-grade triple-hit lymphoma PDX model with a single 0.3 mg/kg dose. IKS03 was tolerated in monkeys at the highest dose tested of 1.5 mg/kg (single dose). IKS03 cross reacts with monkey CD19 and reduced B-cell depletion was observed in relation to comparator agents, even at doses much greater (1.5 mg/kg) than that needed for complete responses in B-cell lymphoma mouse models (0.1 mg/kg).
Conclusion: Preclinical data demonstrates that IKS03’s advanced ADC design results in an increased therapeutic margin compared to traditional ADCs with DNA-crosslinking payloads, with increased efficacy and decreased toxicity.
Citation Format: Jenny Thirlway, Adam Lodge, Daniel J. Williamson, Justyna Mysliwy, Jutta Deckert, Xavier Chauchet, Laura Cons, Yun-Hee Park, Hyun-Min Ryu, Na Ra Han, Ho Young Song, Chul-Woong Chung, Robert J. Lutz. IKS03, a CD19-targeted antibody drug conjugate with enhanced efficacy and tolerability for treatment of B-cell lymphomas [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 1755.