Abstract 2651: A novel CD19 targeting antibody-drug conjugate, huB4-DGN462, shows promising in vitro and in vivo activity in CD19-positive lymphoma models

Background. CD19 is a cell surface membrane protein expressed in most mature and immature B cell neoplasms, making it a promising target for antibody-drug conjugate (ADC) therapy for B cell malignancies. Here we describe the preclinical activity of a novel CD19-targeting ADC, based on the potent indolinobenzodiazepine DNA-alkylating payload DGN462. Methods. The humanized anti-CD19 antibody, huB4, was conjugated to DGN462 via a cleavable disulfide linker, sulfo-SPDB. In vitro activity of the huB4-DGN462 ADC or the unconjugated DGN462 toxin was evaluated in 54 lymphoma cell lines [27 diffuse large B cell lymphomas (DLBCL); 10 mantle cell lymphomas; 6 marginal zone lymphomas; 5 anaplastic large T-cell lymphomas; 6 others]. Cell proliferation/viability after 72h of exposure was measured using a MTT assay. Apoptosis activation was defined by at least 1.5-fold increase in caspase 3/7 signal activation in respect to controls using the Promega ApoTox-Glo Triplex Assay. Gene expression profiling (GEP) was performed with the Illumina HumanHT-12 Expression BeadChips on untreated cell lines followed by GSEA (NES > |2|, P |1.2|; P Results. huB4-DGN462 was cytotoxic against a broad panel of 48 B cell lymphoma cell lines (median IC50 100 pM; 95%CI, 38-214). The cytotoxic activity was not limited by P53, BCL2, MYC or CDKN2A status, or associated with DLBCL cell of origin. Consistent with overall lower CD19 expression, huB4-DGN462 was significantly (p-value=0.007) less active in eight T cell-derived lymphomas (median IC50 of 1.75 nM (95%CI, 0.5-5.75)) than in B cell lymphomas. huB4-DGN462 induced caspase 3/7 activation in 48/54 cell lines (89%) consistent with an apoptotic mechanism of action. huB4-DGN462 demonstrated compelling anti-tumor activity after a single intravenous dose in two diffuse large B-cell lymphoma cell line xenograft models: DoHH2 (a subcutaneous model) and Farage (a disseminated model). In the DoHH2 model, huB4-DGN462 resulted in a significant, dose-dependent tumor growth delay and survival benefit at 1.7 mg Ab/kg compared to a non-targeted control DGN462 ADC. In the disseminated Farage model, a significant dose-dependent increase in survival was observed in mice treated with as low as 0.17 mg Ab/kg of huB4-DGN462. At 1.7 mg Ab/kg, the life span was increased >400% compared to untreated mice. Conclusions. The novel ADC huB4-DGN462 presented strong preclinical anti-lymphoma activity, which provides evidence for further study. Citation Format: Eugenio Gaudio, Chiara Tarantelli, Alberto J. Arribas, Roberta Pittau Bordone, Andrea Rinaldi, Georg Stussi, Emanuele Zucca, Davide Rossi, Anastasios Stathis, Min Li, Alan Wilhem, Kate Lai, Qifeng Qiu, Stuart Hicks, Callum Sloss, Francesco Bertoni. A novel CD19 targeting antibody-drug conjugate, huB4-DGN462, shows promising in vitro and in vivo activity in CD19-positive lymphoma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2651. doi:10.1158/1538-7445.AM2017-2651