Targeting of immune checkpoint regulator V-domain Ig suppressor of T-cell activation (VISTA) with 89Zr-labelled CI-8993

Burvenich, Ingrid; Wichmann, Christian; McDonald, Alexander; Guo, Nancy; Rigopoulos, Angela; Huynh, Nhi; Vail, Mary; Allen, Stacey; O'Keefe, Graeme Joseph; Scott, Fiona; Soikes, Raul; Angelides, Steven; von Roemeling, Reinhard; Scott, Andrew

doi:10.1007/s00259-024-06854-z

Targeting of immune checkpoint regulator V-domain Ig suppressor of T-cell activation (VISTA) with 89Zr-labelled CI-8993

journal contribution

posted on 2024-11-06, 01:44 authored by Ingrid BurvenichIngrid Burvenich, Christian WichmannChristian Wichmann, Alexander McDonaldAlexander McDonald, Nancy Guo, Angela RigopoulosAngela Rigopoulos, Nhi HuynhNhi Huynh, Mary VailMary Vail, Stacey Allen, Graeme Joseph O'Keefe, Fiona ScottFiona Scott, Raul Soikes, Steven AngelidesSteven Angelides, Reinhard von Roemeling, Andrew ScottAndrew Scott

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 89Zr-labelled CI-8993 and validate PET imaging and quantitation in preclinical models prior to a planned human bioimaging trial. Methods: CI-8993 and human isotype IgG1 control were conjugated to the metal ion chelator p-isothiocyanatobenzyl-desferrioxamine (Df). Quality of conjugates were assessed by SE-HPLC, SDS-PAGE, and FACS. After radiolabelling with zirconium-89 (89Zr), radioconjugates were assessed for radiochemical purity, immunoreactivity, antigen binding affinity, and serum stability in vitro. [89Zr]Zr-Df-CI-8993 alone (1 mg/kg, 4.6 MBq) or in combination with 30 mg/kg unlabelled CI-8993, as well as isotype control [89Zr]Zr-Df-IgG1 (1 mg/kg, 4.6 MBq) were assessed in human VISTA knock-in female (C57BL/6 N-Vsirtm1.1(VSIR)Geno, huVISTA KI) or control C57BL/6 mice bearing syngeneic MB49 bladder cancer tumours; and in BALB/c nu/nu mice bearing pancreatic Capan-2 tumours. Results: Stable constructs with an average chelator-to-antibody ratio of 1.81 were achieved. SDS-PAGE and SE-HPLC showed integrity of CI-8993 was maintained after conjugation; and ELISA indicated no impact of conjugation and radiolabelling on binding to human VISTA. PET imaging and biodistribution in MB49 tumour-bearing huVISTA KI female mice showed specific localisation of [89Zr]Zr-Df-CI-8993 to VISTA in spleen and tumour tissues expressing human VISTA. Specific tumour uptake was also demonstrated in Capan-2 xenografted BALB/c nu/nu mice. Conclusions: We radiolabelled and validated [89Zr]Zr-Df-CI-8993 for specific binding to huVISTA in vivo. Our results demonstrate that 89Zr-labelled CI-8993 is now suitable for targeting and imaging VISTA expression in human trials.

Funding

This work was supported by funding from Curis Inc. We acknowledge the Australian Cancer Research Foundation for providing funds to purchase the nanoPET/MR imaging equipment and the Operational Infrastructure Support program of the Victorian State Government. This research was also undertaken using the Solid Target Laboratory, an ANSTO-Austin-LICR Partnership, also supported by the National Imaging Facility and the Victorian Government. The authors acknowledge the scientific and technical assistance of the National Imaging Facility, a National Collaborative Research Infrastructure Strategy (NCRIS) capability, at the La Trobe-ONJC

History

Publication Date

2024-11-01

Journal

European Journal of Nuclear Medicine and Molecular Imaging

Volume

51

Issue

13

Pagination

11p. (p. 3863-3873)

Publisher

Springer Nature

ISSN

1619-7070

Rights Statement

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