Introduction: Multiple Myeloma (MM) is a haematological malignancy in which Interleukin-6 (IL-6) plays a crucial role in its growth and spread. The monoclonal antibody Tocilizumab binds strongly to IL-6 receptors, inhibiting their function. Our aim is to evaluate the potential of 177LuLu-labeled Toclilzumab as a theranostic agent for MM. Methods: Tocilizumab was derivatised with DOTA-NHS ester and radiolabeled with 177LuLu. The stability of the radiochemical compound was evaluated, and in vitro binding and immunoreactive fraction assays were performed. Biodistribution was assessed at 24 and 48 h post-injection (n = 5) in normal and MM-bearing BALB/c nude mice. Results: 177LuLu-DOTA-Tocilizumab remained stable in all tested solutions. Epitope recognition was confirmed by cell-binding studies, and an immunoreactive fraction of 83.7% was observed. In vivo biodistribution studies revealed high tumor uptake over time, with tumor-to-muscle ratios of 11.66 ± 3.81 and 9.54 ± 1.75 at 24 and 48 h, respectively. Discussion: This study focused on the synthesis and characterisation of a new radiolabeled theranostic agent against IL6R, 177LuLu-DOTA-Tocilizumab. This agent demonstrated high radiochemical stability and strong binding to IL-6R in the MM cell line. Biodistribution studies indicated selective retention of the agent in tumor tissue, highlighting its potential for targeted imaging and therapy in IL-6R-positive cancers and paving the way for future research into its application in related diseases. Conclusions: 177LuLu-DOTA-Tocilizumab represents a potential theranostic agent for MM. Therefore, we expect this agent to open the way to new diagnostic and therapeutic strategies for this devastating disease.
Camacho et al. (Tue,) studied this question.