⁸⁹Zr-Imuno-PET/¹¹¹In-Imuno- SPECT: desenvolvimento radiofarmacêutico de agentes de imagem molecular para receptores EGF

Abstract

BENEDETTO, Raquel. 89 Zr immuno-PET/ 111 In imuno-SPECT: Radiopharmaceutical development of molecular imaging agents for EGF receptors. 200 p. Thesis (Doutorado em Tecnologia Nuclear) Instituto de Pesquisas Energéticas e Nucleares-IPEN-CNEN/SP. São Paulo: 2017. The low selectivity of conventional methods for cancer diagnosis and therapy, as well as the fact that these methods could not achieve the desired therapeutic success, constitute difficulties for the oncological practice. In this regard, radiolabeled monoclonal antibodies (mAbs) applied in diagnostic techniques have been highlighted, since they allow the selective delivery of the radiation to the specific target. The radioimmunodiagnosis methodology (RID), using radiolabeled anti-EGFR mAbs, enables previous screening, evaluating resistance to treatment and stratifying patients who may present benefits to cetuximab immunotherapy. In addition, it allows monitoring the progression of the therapy, aiming for a more effective and directed treatment, leading the personalized medicine approach. A radioimmunoconjugate is not yet available for diagnosis and management of cancer in Brazil. In this context, this research was carried out to develop a pharmaceutical formulation to standardize a routine production of radiopharmaceuticals for diagnosis and monitoring head and neck cancer and colorectal carcinoma: 111 In-DTPA-cetuximab and 89 Zr-DFO-cetuximab. In addition, corroborate in the elucidation of the tumor cells resistance mechanisms to EGFR-targeted therapy, through in vitro and in vivo radioimmunoconjugate binding studies to cellular receptors. Regarding to the radiopharmaceuticals studied, cetuximab was conjugated to DTPA chelator at 1:20 molar ratio and to DFO at 1: 5, and these processes were successful and optimized, showing good reproducibility. Immunoconjugates showed preservation of immunoreactivity and high stability when stored at-20 o C for up to 6 months. These immunoconjugates when radiolabeled with 111 In and 89 Zr have exhibited radiochemical purity above 95%, without any post-labeling purification, and the radioimmunoconjugates have demonstrated stability for a time that allows them to be transported to clinics far from the producer center. 111 In-DTPA-cetuximab in vitro analyzes in FaDu-C10 cells (resistant cell line) has presented an inexpressive percentage of binding and internalization of the radioimmunoconjugate, ensuring the resistance model conferred to this cell line. The MicroPET/CT imaging study has revealed a reduction in uptake profile for "Blocking" group, with an excess of unlabeling cetuximab, and an intense 89 Zr-DFOcetuximab uptake in squamous cell tumor for "Non-blocking" group, that evidenced the in vivo radioimmunoconjugate specificity. The biodistribution studies of the radiopharmaceuticals were well-matched with those described in the literature and they validated the results obtained through the MicroSPECT/CT and MicroPET/ CT images. In addition, these studies in vivo have displayed a substantial tumor uptake, according wi...

89Zr-DFO-Cetuximab as a Molecular Imaging Agent to Identify Cetuximab Resistance in Head and Neck Squamous Cell Carcinoma

“…Similar to in vitro results, a correlation was observed between EGFR expression and tumor uptake of 89 Zr-DFO-cetuximab by small animal PET/CT imaging as shown in Figure 5. Benedetto 59 previously performed the blocking study, and the small animal PET/CT images have revealed a reduction in uptake profile for ''blocking'' group (with an excess of unlabeling cetuximab) and an intense 89 Zr-DFO-cetuximab uptake in FCS for ''non-blocking'' group, that illustrated the in vivo radioimmunoconjugate specificity. A higher level of radiotracer accumulation was observed in the FCS compared with FCR tumors.…”