Improved Therapy of B-Cell Non-Hodgkin Lymphoma by Obinutuzumab-Dianthin Conjugates in Combination with the Endosomal Escape Enhancer SO1861

Abstract

Immunotoxins do not only bind to cancer-specific receptors to mediate the elimination of tumor cells through the innate immune system, but also increase target cytotoxicity by the intrinsic toxin activity. The plant glycoside SO1861 was previously reported to enhance the endolysosomal escape of antibody-toxin conjugates in non-hematopoietic cells, thus increasing their cytotoxicity manifold. Here we tested this technology for the first time in a lymphoma in vivo model. First, the therapeutic CD20 antibody obinutuzumab was chemically conjugated to the ribosome-inactivating protein dianthin. The cytotoxicity of obinutuzumab-dianthin (ObiDi) was evaluated on human B-lymphocyte Burkitt’s lymphoma Raji cells and compared to human T-cell leukemia off-target Jurkat cells. When tested in combination with SO1861, the cytotoxicity for target cells was 131-fold greater than for off-target cells. In vivo imaging in a xenograft model of B-cell lymphoma in mice revealed that ObiDi/SO1861 efficiently prevents tumor growth (51.4% response rate) compared to the monotherapy with ObiDi (25.9%) and non-conjugated obinutuzumab (20.7%). The reduction of tumor volume and overall survival was also improved. Taken together, our results substantially contribute to the development of a combination therapy with SO1861 as a platform technology to enhance the efficacy of therapeutic antibody-toxin conjugates in lymphoma and leukemia.

Saponin Fraction CIL1 from Lysimachia ciliata L. Enhances the Effect of a Targeted Toxin on Cancer Cells

“…One other alternative interesting solution is the use of saponins, which themselves do not have the ability to reach target cells but can enhance the uptake of targeted toxins [ 8 ]. To date, studies using both saponin fractions and isolated compounds have been successfully tested in vitro or in vivo [ 30 , 31 , 32 , 33 , 34 ].…”

Synergistic Cytotoxicity of a Toxin Targeting the Epidermal Growth Factor Receptor and the Glycosylated Triterpenoid SO1861 in Prostate Cancer

“…For enhanced efficacy we decided to combine our targeted toxin with SO1861, which was shown to enhance the endosomal escape of other targeted toxins containing ribosome inactivating proteins, like dianthin or saporin [35][36][37], but not that of EGF-ETA' (targeted toxin with a toxin domain (aa 276-638) of PE), which was attributed to different intracellular trafficking [38]. In a first step, we therefore deleted the C-terminal KDEL-like sequence to generate EGF-PE24mutΔREDLK.…”

Enhanced cytotoxicity of a Pseudomonas Exotoxin A based immunotoxin against prostate cancer by addition of the endosomal escape enhancer SO1861

“…Overall survival was examined by Kaplan Meier survival analysis and log-rank test using GraphPad Prism. Tumor regression to growth ratio as the sum of tumor mass loss and tumor mass gain over all tumors within each treatment group was calculated as described ( Panjideh et al, 2022 ). If one tumor completely disappears during treatment and another one with the same volume doubles in size, then the ratio for these two tumors is 1.0.…”

“…It is thought that the glycosylated triterpenoids can associate with proteins that were internalized into endolysosomal compartments and mediate their release through the membrane into the cytosol ( Fuchs et al, 2017 ). They were successfully used for the endosomal release of antibody drug conjugates, targeted toxins or immunotoxins containing the plant toxins dianthin and saporin, which resulted in enhanced cytotoxicity by several orders of magnitudes and enhanced antitumor activity in vivo ( Holmes et al, 2015 ; von Mallinckrodt et al, 2014 ; Gilabert-Oriol et al, 2015 ; Gilabert-Oriol et al, 2016 ; Bhargava et al, 2017 ; Panjideh et al, 2022 ). For yet unknown reasons, glycosylated triterpenoids do not generally lead to a decisive increased cytosolic uptake of internalized proteins.…”