Development of contrast and molecular ultrasound methods to guide immune checkpoint cancer therapy

Immune checkpoint inhibitor (ICI) is only effective in 20–50% of cancer patients. Tumor endothelial cells (ECs) and blood vessels contribute to immune evasion. The objective of this work was to develop and investigate the utility of contrat and molecular ultrasound (CMUS) to guide or predict ICI treatment response through longitudinal imaging of tumor ECs and blood vessels. We first validated, using commercially available targeted and non-targeted microbubbles (MBs), that these can be used to predict ICI therapy response. A total of 33 wild-type mice (immuno-competent with varying treatment response) implanted with CT26 colon cancer were used. Animals were imaged longitduinally during an ICI treatment regiment (10mg/kg anti-PD-L1). Quantification was with standard perfusion (blood flow/volume) and molecular (differential targeted enhancement, dTE) parameters. We also developed and validated human-translatable anti-PDL1 targeted MBs based on aptamers and click chemistry and validated those in 12 animals. Results indicate that both perfusion parameters and the dTE could differentiate between responders and non-responders with signficance (p < 0.05), with potentially complementary inight. Translatable MBs were also capable of providing adequate quantification of PD-L1 expression on ECs. Take together, our results suggest that ultrasound-based contrast and molecular ultrasound could ptorvide a real-time dynamic tool for bedside guidance of ICI therapies in cancer patients.