Theranostic Potential of [177Lu]Lu-DOTA-Tocilizumab in Multiple Myeloma: A Preclinical Evaluation

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 [177Lu]Lu-labeled Toclilzumab as a theranostic agent for MM.

Methods: Tocilizumab was derivatised with DOTA-NHS ester and radiolabeled with [177Lu]Lu. 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: [177Lu]Lu-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, [177Lu]Lu-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: [177Lu]Lu-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.