Targeting of immune checkpoint regulator V-domain Ig suppressor of T-cell activation (VISTA) with Zr-labelled CI-8993.

Background: CI-8993 is a fully human IgG1κ monoclonal antibody (mAb) that binds specifically to immune checkpoint molecule VISTA (V-domain Ig suppressor of T-cell activation). Phase I safety has been established in patients with advanced cancer (NCT02671955). To determine the pharmacokinetics and biodistribution of CI-8993 in patients, we aimed to develop Zr-labelled CI-8993 and validate PET imaging and quantitation in preclinical models prior to a planned human bioimaging trial.

Radiolabelling and preclinical characterisation of [Zr]Zr-Df-ATG-101 bispecific to PD-L1/4-1BB.

Purpose: ATG-101, a bispecific antibody that simultaneously targets the immune checkpoint PD-L1 and the costimulatory receptor 4-1BB, activates exhausted T cells upon PD-L1 crosslinking. Previous studies demonstrated promising anti-tumour efficacy of ATG-101 in preclinical models. Here, we labelled ATG-101 with Zr to confirm its tumour targeting effect and tissue biodistribution in a preclinical model.

Preclinical radiolabeling, in vivo biodistribution and positron emission tomography of a novel pyrrolobenzodiazepine (PBD)-based antibody drug conjugate targeting ASCT2.

Introduction: Anti-ASCT2 antibody drug conjugate (ADC) MEDI7247 has been under development as a potential anti-cancer therapy for patients with selected relapsed/refractory hematological malignancies and advanced solid tumors by MedImmune. Although promising efficacy was observed in the clinic, pharmacokinetic (PK) analyses observed low exposure of MEDI7247 in phase I hematological patients. To investigate the biodistribution properties of MEDI7247, MEDI7247 and control antibodies were radiolabeled with zirconium-89 and in vitro and in vivo properties characterized.

Radiolabelling and preclinical characterization of Zr-Df-radiolabelled bispecific anti-PD-L1/TGF-βRII fusion protein bintrafusp alfa.

Purpose: Τhis study aimed to optimize the Zr-radiolabelling of bintrafusp alfa investigational drug product and controls, and perform the in vitro and in vivo characterization of Zr-Df-bintrafusp alfa and Zr-Df-control radioconjugates.

Methods: Bintrafusp alfa (anti-PD-L1 human IgG1 antibody fused to TGF-β receptor II (TGF-βRII), avelumab (anti-PD-L1 human IgG1 control antibody), isotype control (mutated inactive anti-PD-L1 IgG1 control antibody), and trap control (mutated inactive anti-PD-L1 human IgG1 fused to active TGF-βRII) were chelated with p-isothiocyanatobenzyl-desferrioxamine (Df). After radiolabelling with zirconium-89 (Zr), radioconjugates were assessed for radiochemical purity, immunoreactivity, antigen binding affinity, and serum stability in vitro.

Molecular imaging of T cell co-regulator factor B7-H3 with Zr-DS-5573a.

B7-H3 is a transmembrane protein widely expressed in a variety of cancers and has been shown to play a role in anti-tumor immunity. This study aims to develop a molecular imaging probe to identify B7-H3 expression in tumors and to develop Zr-DS-5573a as a theranostic that could aid patient selection in clinical Phase I studies. The anti-B7-H3 humanised monoclonal antibody DS-5573a was labeled with zirconium-89 (Zr-), and assessed for radiochemical purity, immunoreactivity (Lindmo analysis), antigen binding affinity (Scatchard analysis), and serum stability .