Javier Narbona

Immunotoxins are chimeric molecules with high potential as therapeutic candidates that combine antibody specificity to recognize and bind tumor-associated antigens and the cytotoxic potency of the enzymatic activity of a toxin, leading to the selective death of target cells. The use of immunotoxins as therapeutic tools remains limited by various issues, such as selecting the appropriate tumor-associated antigen (TAA), penetration difficulties in solid tumors, low renal clearance, and low toxic payload. For this purpose, in this work we have designed a novel trimeric immunotoxin (IMTXTriA33αS) against colorectal cancer, combining the scFv against GPA33 as a targeting domain and the fungal ribotoxin α-sarcin (αS) as the toxic fragment, linked by a trimerization domain (TIE^XVIII). Our results demonstrate that IMTXTriA33αS has greater avidity and toxic load, showing a very significant increase in its in vitro and in vivo antitumor efficacy, due to its trimeric structure.

Allergies constitute one of the major health problems worldwide, increasing their prevalence in developed countries. To overcome this multifactorial disease, immunotherapy and the use of immune molecules, such as immunotoxins, have arisen as promising therapeutic tools. We have designed, produced, and characterized a new immunotoxin called IL-33αS, encompassing the murine IL-33 (mIL-33) as the target domain and the ribotoxin α-sarcin as the toxic domain. IL-33 is a widely described alarmin that binds to the ST2 receptor of a variety of immune cells, including ILC2s, leading to Th2-derived inflammatory response, as occurs in allergic reactions. Both IL-33αS and mIL-33 were successfully produced in the methylotrophic yeast Pichia pastoris and purified to homogeneity through affinity chromatography for their characterization. Both IL-33αS and mIL-33 were able to specifically bind to ST2⁺ Raw 264.7 cells, and IL-33αS kept the ribonucleolytic activity of α-sarcin, allowing IL-33αS to exhibit cytotoxic effects against ST2⁺-targeted cells. In addition, IL-33αS induced significantly less secretion of the Th2-linked cytokine IL-13 in comparison to mIL-33, suggesting steric interference produced by the presence of the α-sarcin. These results assess the potential therapeutic effect of this new immunotoxin against allergies, causing ST2-targeted cytotoxicity while avoiding the Th2 cytokine secretion.

Immunotherapy has revolutionized cancer treatment landscape, boosting strong antitumoral responses in patients with advanced tumors. However, the success of immunotherapy in solid tumors has been m...

Immunotoxins (ITXs) are chimeric molecules that combine the specificity of a targeting domain, usually derived from an antibody, and the cytotoxic potency of a toxin, leading to the selective death of tumor cells. However, several issues must be addressed and optimized in order to use ITXs as therapeutic tools, such as the selection of a suitable tumor-associated antigen (TAA), high tumor penetration and retention, low kidney elimination, or low immunogenicity of foreign proteins. To this end, we produced and characterized several ITX designs, using a nanobody against EGFR (V_HH 7D12) as the targeting domain. First, we generated a nanoITX, combining V_HH 7D12 and the fungal ribotoxin α-sarcin (αS) as the toxic moiety (V_HHEGFRαS). Then, we incorporated a trimerization domain (TIE^XVIII) into the construct, obtaining a trimeric nanoITX (TriV_HHEGFRαS). Finally, we designed and characterized a bispecific ITX, combining the V_HH 7D12 and the scFv against GPA33 as targeting domains, and a deimmunized (DI) variant of α-sarcin (BsITXαSDI). The results confirm the therapeutic potential of α-sarcin-based nanoITXs. The incorporation of nanobodies as target domains improves their therapeutic use due to their lower molecular size and binding features. The enhanced avidity and toxic load in the trimeric nanoITX and the combination of two different target domains in the bispecific nanoITX allow for increased antitumor effectiveness.

Due to its incidence and mortality, cancer remains one of the main risks to human health and lifespans. In order to overcome this worldwide disease, immunotherapy and the therapeutic use of immunotoxins have arisen as promising approaches. However, the immunogenicity of foreign proteins limits the dose of immunotoxins administered, thereby leading to a decrease in its therapeutic benefit. In this study, we designed two different variants of non-immunogenic immunotoxins (IMTXA33αSDI and IMTXA33furαSDI) based on a deimmunized variant of the ribotoxin α-sarcin. The inclusion of a furin cleavage site in IMTXA33furαSDI would allow a more efficient release of the toxic domain to the cytosol. Both immunotoxins were produced and purified in the yeast Pichia pastoris and later functionally characterized (both in vitro and in vivo), and immunogenicity assays were carried out. The results showed that both immunotoxins were functionally active and less immunogenic than the wild-type immunotoxin. In addition, IMTXA33furαSDI showed a more efficient antitumor effect (both in vitro and in vivo) due to the inclusion of the furin linker. These results constituted a step forward in the optimization of immunotoxins with low immunogenicity and enhanced antitumor activity, which can lead to potential better outcomes in cancer treatment.