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Session: Radiobiological Modeling and Biologically Guided RT [Return to Session]

Targeted MR Contrast Nanoparticles for Programmed Death Ligand-1 Expression

N Brown1,2*, G Bort3,4, P Rocchi3,4, L Carmes3,4, M Iyer1,2, T Doussineau3, F Lux3,4, J Schoenfeld2, M Dougan5, O Tillement3,4,6, R Berbeco2, (1) Northeastern University, Department of Physics Boston, MA, (2) Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Department of Radiation Oncology, Boston, MA,(3) NHTherAguix, Lyon, France, (4) Universite Claude Bernard, Lyon, France, (5) Division of Gastroenterology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA,(6) Institut Lumie`re-Matie`re, UMR 5306, Universite Lyon1-CNRS, Universite de Lyon, Villeurbanne Cedex, France


SU-K-206-7 (Sunday, 7/10/2022) 5:00 PM - 6:00 PM [Eastern Time (GMT-4)]

Room 206

Purpose: Programmed death ligand-1 (PDL1) expression has been linked to tumor resistance and upregulated by tumor cells following radiation therapy to avoid immune clearance. Anti-PDL1 immunotherapy has proven successful in multiple cancers, however within similar tumors heterogenous outcomes are seen among patients necessitating the need for PDL1 expression monitoring prior, during, and post-treatment. To this end, we have developed an MR contrast agent using polysiloxane gadolinium nanoparticles (AGuIX) surface modified with a highly specific single-domain antibody (VHH-A12) against PDL1. AGuIX are currently in clinical trials as novel theranostic nanoparticles for MR tumor contrast and radiation dose amplification.

Methods: Two separate chemistries were developed to attach a novel single-domain PDL1 nanobody (VHH-A12) to the surface of AGuIX. A sortase-catalyzed litigation was developed with a heptamutant sortase followed by purification via Ni-NTA beads and a vivaspin collector. A second azide-DBCO click chemistry was developed in a two-step process: 1) AGuIX were first surface modified with DBCO-(PEG)-NHS and A12 nanobody was modified with NHS-(PEG)-azide 2) followed by a click reaction between DBCO-azide. Final product purity and conjugation success were characterized via HPLC-UV. Binding of the conjugate was verified via competition ELISA comparing free A12 against AGuIX-A12 and AGuIX.

Results: The sortagging chemistry reaction yielded a final product of 186 Gd/VHH while the DBCO-azide-click chemistry yielded a final product of 8.5 Gd/VHH, confirming a higher ratio of VHH to AGuIX with the latter. ELISA binding to PDL1 revealed a strong binding affinity of 16nM AGuIX-A12 compared to 5.957 nM free A12. No binding affinity was able to be determined for non-targeted AGuIX.

Conclusion: A novel MR diagnostic tool for PDL1 expression has been developed using a single-domain antibody with high specificity for PDL1 in conjugation with theranostic AGuIX nanoparticles.

Funding Support, Disclosures, and Conflict of Interest: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Viewray, Inc. Some authors are employed by NH Theraguix.


Contrast, MRI, Radioimmunotherapy


TH- Small Animal RT: Development (new technology and techniques)

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