Development and preclinical evaluation of theranostic agents targeting muc16/ca125 and nectin-4 expression in breast, ovarian and pancreatic cancers
Year: 2023
Type: dissertation
Abstract: Small protein domain-based affinity reagents and full-length antibodies that recognize cancer biomarkers can be used as vehicles to deliver contrast agents (imaging) or cytotoxic payloads (therapy) to the site of tumours. The development of theranostic agents allows for both therapy as well as monitoring the progression of cancer. Ovarian, pancreatic and Triple-negative breast cancers (TNBC) are associated with poor prognosis and worse survival rates, where effective ‘theranostic’ probes are much needed. MUC16 is over-expressed in 90% of epithelial ovarian cancer (EOC) and 65% of pancreatic ductal adenocarcinomas (PDAC), and nectin-4 is over-expressed in 60% of TNBC. This thesis aims to develop fully human small protein-based affinity reagents and antibodies against cancer biomarkers MUC16 and nectin-4 and evaluate them as potential theranostic agents for the immuno-PET imaging and radioimmunotherapy of these cancers. We developed fully human monoclonal antibodies, M16Ab and anti-N4 antibodies against MUC16 and nectin-4, respectively, using phage display. In addition, we developed small protein-based affinity reagents against MUC16 and nectin-4 from a human protein scaffold using phage display. The small protein binders were conjugated with p-SCN-Bn-DFO and radiolabeled with 89Zr. The binding affinity and specificity of the 89Zr radiolabeled small protein binders were evaluated by saturation radioligand binding assay, and the results showed increased non-specific binding. It was concluded that the conjugation and the radiolabeling processes affected the fold and stability of the small protein binders, and for that, we did not proceed further with them. M16Ab and anti-N4 antibodies were conjugated with p-SCN-Bn-DFO and radiolabeled with 89Zr. DFO-M16Ab and DFO-anti-N4 were then evaluated for binding specificity and affinity on cells using flow cytometry. In vivo, evaluation of 89Zr-M16Ab and 89Zr-anti-N4 radioimmunoconjugates (RIC) was studied at 24-120 h using PET/CT imaging and biodistribution in mice bearing MUC16 and nectin-4 positive or negative xenografts. M16Ab and anti-N4 antibodies were conjugated with macropa and radiolabeled with the alpha particle 225Ac. Dosimetry and biodistribution of 225Ac-M16Ab and 225Ac-anti-N4 RICs were studied in healthy mice, and the in vivo efficacy was evaluated in mice bearing MUC16 expressing SW1990 pancreatic cancer xenografts and TNBC MDA-MB-468 xenograft. Mice were treated with two doses of 350 nCi or 500 nCi administered 10 days apart. Tumor growth was monitored using a digital calliper. For M16Ab, Macropa and DFO conjugation did not affect the binding affinity or specificity of M16Ab. MicroPET/CT imaging and biodistribution studies of 89Zr-M16Ab showed high and specific tumor uptake in mice bearing MUC16 expressing SW1990 xenograft and not in MUC16 negative SKOV3 xenografts. All mice treated with low and high doses showed a remarkable decrease in tumor growth following the administration of only two doses of 225Ac-M16Ab. For anti-N4 antibody, Macropa and DFO conjugated anti-N4 showed low nM affinity (3 nM) to nectin-4, which was not significantly different compared to the radiolabeled antibody (10 nM). MicroPET/CT imaging and biodistribution of the MDA-MB-468 xenograft injected with 89Zr-anti-N4 antibody showed high and specific tumor uptake of (14.14 ± 5.1 %IA/g) and (13.2 ± 1.12 %IA/g) injected dose per gram (%IA/g) at 24 h and 120 h post-injection (p.i.), respectively. All mice treated with 225Ac–anti-N4 (350 nCi or 500 nCi) had complete tumor remission by day 20.
Author: Babeker, Hanan
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W6990369893