Immuno-PET Imaging of ⁸⁹Zr Labeled Anti-PD-L1 Domain Antibody

Abstract

Recently, various immuno-PET tracers based on monoclonal antibodies (mAbs), engineered scaffold proteins, and peptides were developed to target either programmed cell death protein 1 (PD-1) or programmed cell death ligand 1 (PD-L1), showing promise in assessment of immune checkpoints. We sought to develop an immunotherapeutic agent based PET probe that enables real-time assessment of PD-L1 expression and evaluation of antibody drug biodistribution to select eligible candidates for anti-PD-1/PD-L1 immunotherapies. KN035, a 79.6 kDa size anti-PD-L1 domain antibody under analysis in clinical trials, was used to develop the immuno-PET probe, Zr-Df-KN035. Immuno-PET studies were performed to monitor PD-L1 levels in nude mice bearing LN229 xenografts with positive expression for PD-L1, and to evaluate the whole-body biodistribution in healthy non-human primates (NHPs). LN229 xenografts were markedly visualized from 24 h after injection ofZr-Df-KN035, with elevated accumulation persisting for up to 120 h. Tumor radioactivity was notably reduced in the presence of excess KN035. Mouse ex vivo biodistribution studies performed at 24 and 120 h revealed tumor-to-muscle ratios as high as 5.64 ± 0.65 and 7.70 ± 1.37, respectively. In the NHP model, PET imaging demonstrated low background. The liver and kidney showed moderate accumulation with the highest SUV value of 1.15 ± 0.15 and 2.13 ± 0.10 at 72 h, respectively. The spleen, lymph nodes, and salivary glands were also slightly visualized. In conclusion, Zr-Df-KN035, a novel anti-PD-L1 domain antibody-based probe, shows the feasibility of noninvasive in vivo evaluation of PD-L1 expression. This work further provides a template for immunotherapeutic agent based imaging to evaluate human PD-L1 expression and to augment our understanding of therapeutic agent biodistribution, leading to better therapeutic strategies in the future.

PET Imaging of Tumor PD-L1 Expression with a Highly Specific Nonblocking Single-Domain Antibody

“…For a competitive binding assay, the tumor cell (A375-hPD-L1) uptake of 68 Ga-NOTA-Nb109 was studied with and without pretreatment with a 1,000-fold molar excess of unlabeled Nb109 or KN035. The PD-L1 antibody KN035 has been approved as an investigational new drug for the treatment of advanced or metastatic solid tumors (NCT02827968, NCT03101488, and NCT03248843) (4,26).…”

Tracers for non-invasive radionuclide imaging of immune checkpoint expression in cancer

“…A 89 Zr-labeled mAb against mouse PD-L1 was used to show increased tracer uptake in a syngeneic head and neck tumor model after fractionated radiotherapy (Kikuchi et al 2017). Other research teams have also successfully employed mAbs for imaging of PD-L1 using different radionuclides, including 89 Zr, 111 In, 64 Cu and 131 I (Hettich et al 2016;Chatterjee et al 2016;Josefsson et al 2016;Nedrow et al 2017aNedrow et al , 2017bLesniak et al 2016;Li et al 2018;Moroz et al 2018;Truillet et al 2018;Pang et al 2018).…”

Nanobodies: Next Generation of Cancer Diagnostics and Therapeutics

“…Imaging tumor angiogenesis has been explored through targeting vascular cell adhesion molecule-1 (VCAM-1), a marker associated with metastasis and immune evasion, and anti-VCAM-1 nanobody-microbubbles have been used for ultrasound imaging of murine carcinomas ( 12 ). Nanobody probes targeting immune checkpoints (ICP) CTLA-4 and programmed death ligand 1 (PD-L1) ( 34 – 38 ) have been implemented in nuclear imaging with high T/B ratios ( 39 , 40 ), and a phase I clinical study of the 99m Tc–PD-L1 nanobody was recently completed ( 35 ). Notably, Lecocq et al ( 41 ) developed the first anti-LAG-3 nanobodies for SPECT/CT imaging, demonstrating potential applications for detecting tumor-infiltrating immune cells.…”