99mTechnetium- or Cy7-Labeled Fab(Tocilizumab) as Potential Multiple Myeloma Imaging Agents

Title:99mTechnetium- or Cy7-Labeled Fab(Tocilizumab) as Potential Multiple Myeloma Imaging Agents

Volume: 21 Issue: 14

Author(s): Ximena Camacho*, Carolina Perroni, Camila L. Machado, Camila de Godoi Carneiro, Mara de Souza Junqueira, Daniele Faria, María F. García, Marcelo Fernández, Natalia Oddone, Juan Benech, Carlos A. Buchpiguel, Hugo Cerecetto, Roger Chammas, Eloisa Riva, Pablo Cabral and Juan P. Gambini

Affiliation:

• Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica, Montevideo,Uruguay

Keywords: Fab(Tocilizumab), molecular imaging, IL-6R, multiple myeloma, ^99mTechnetium- or Cy7-lableled Fab(Tocilizumab).

Abstract:

Background: Multiple Myeloma (MM) is a malignant hematologic disorder and the second most common blood cancer. Interleukin-6 (IL-6) has been identified as a crucial factor for the proliferation and survival of MM cells and the overexpression of IL-6 receptor is being studied as a molecular target for therapeutic and diagnostic use in myelomas and other comorbidities. Tocilizumab is a humanized monoclonal antibody that binds IL-6R.

Objective: We aim to label and evaluate Fab(Tocilizumab) with ^99mTechnetium or Cy7 as potential MM imaging agents.

Methods: IL-6R distribution was analyzed by Laser Confocal Microscopy (LCM) in MM cell lines. Fab(Tocilizumab) was produced by the digestion of Tocilizumab with papain for 24h at 37°C, derivatized with NHS-HYNIC-Tfa and radiolabeled with ^99mTc. Radiochemical stability and in vitro cell assays were evaluated. Biodistribution and SPECT/CT were performed. Also, Fab(Tocilizumab) was labeled with Cy7 for in vivo fluorescence imaging up to 72h.

Results: LCM analysis demonstrates IL-6R distribution on MM cell lines. Incubation with papain resulted in complete digestion of Tocilizumab and exhibited a good purity and homogeneity. Radiolabeling with 99mTc via NHS-HYNIC-Tfa was found to be fast, easy, reproducible and stable, revealing high radiochemical purity and without interfering with IL-6R recognition. Biodistribution and SPECT/CT studies showed a quick blood clearance and significant kidney and MM engrafted tumor uptake. Cy7-Fab(Tocilizumab) fluorescent imaging allowed MM1S tumor identification up to 72h p.i.

Conclusion: These new molecular imaging agents could potentially be used in the clinical setting for staging and follow-up of MM through radioactive whole-body IL-6R expression visualization in vivo. The fluorescent version could be used for tissue sample evaluation and to guide surgical excision, if necessary.

Cite this article as:

Camacho Ximena *, Perroni Carolina , Machado L. Camila , de Godoi Carneiro Camila , de Souza Junqueira Mara , Faria Daniele , García F. María , Fernández Marcelo , Oddone Natalia , Benech Juan , Buchpiguel A. Carlos , Cerecetto Hugo , Chammas Roger , Riva Eloisa , Cabral Pablo and Gambini P. Juan , 99mTechnetium- or Cy7-Labeled Fab(Tocilizumab) as Potential Multiple Myeloma Imaging Agents, Anti-Cancer Agents in Medicinal Chemistry 2021; 21 (14) . https://dx.doi.org/10.2174/1871520621999210104181238