Background Antibody-therapeutics, including immune-checkpoint inhibitors, have transformed cancer patients’ lives. Despite these advances, nearly 90% of oncology drugs fail in phase III clinical trials due to a lack of therapeutic efficacy. One major challenge is the lack of technologies that can measure in vivo drug delivery and activity at cellular resolution in the intact human tumor microenvironment (TME). Thus, it remains unclear how therapeutic drugs interact with various cell types and extracellular matrix (ECM) in the complex TME ecosystem of human patients.

Methods To address this challenge, we developed a single-cell spatial pharmacology apporach to image drug, drug target, and cellular and ECM components of the intact human TME at the (sub)cellular resolution. We conducted first-in-human clinical trials across multiple solid tumors by intravenous infusion of a near-infrared fluorescent antibody.^1–3 We conjugated and validated a DNA-barcoded CODEX antibody panel with over 50 protein markers for deep spatial profiling of human immune cells, cancer-associated fibroblasts, and ECM proteins. We measured drug-target-microenvironment interactions in situ in tumor surgical specimens by integrating high-resolution imaging of therapeutic antibodies, CODEX for highly multiplexed proteomics imaging of cells and ECM, and spatial transcriptomics.

Results The integrative single-cell spatial pharmacology technique, for the first time, enabled the identification of specific cell types that a therapeutic antibody binds, and the quantification of antibody-target engagement and penetration depth into tumors in situ at single-cell resolution in human tumors. Furthermore, this method measured drug-target-microenvironment interactions in situ at unprecedented resolution in the intact human TME, and identified the cellular and ECM barriers to antibody delivery into clinical tumors, which has important therapeutic implications.

Conclusions In summary, we have established a novel single-cell spatial pharmacology framework to decipher in vivo drug-target-microenironment interactions. This is a generalizable framework that can be broadly applicable to antibody therapeutics such as immune checkpoint inhibitors. This technique holds great promise to uncover drug mechanisms of action, identify optimal doses, and seek new biomarkers for patient stratification for the current and next-generation immuno-oncology drugs.

Acknowledgements This work is funded by the Stanford Translational Research and Applied Medicine grant and by the National Cancer Institute of the National Institutes of Health under Award Number K99CA267171.

References

1. Lu G, Fakurnejad S, Martin BA, van den Berg NS, van Keulen S, Nishio N, Zhu AJ, Chirita SU, Zhou Q, Gao RW, Kong CS, Fischbein N, Penta M, Colevas AD, Rosenthal EL. ‘Predicting Therapeutic Antibody Delivery into Human Head and Neck Cancers’. Clin Cancer Res. 2020 Jun 1;26(11):2582–2594.

2. Lu G, Nishio N, van den Berg NS, Martin BA, Fakurnejad S, van Keulen S, Colevas AD, Thurber GM, Rosenthal EL. ‘Co-administered antibody improves penetration of antibody-dye conjugate into human cancers with implications for antibody-drug conjugates’. Nat Commun. 2020 Nov 9;11(1):5667.

3. Lu G, van den Berg NS, Martin BA, Nishio N, Hart ZP, van Keulen S, Fakurnejad S, Chirita SU, Raymundo RC, Yi G, Zhou Q, Fisher GA, Rosenthal EL, Poultsides GA. ‘Tumour-specific fluorescence-guided surgery for pancreatic cancer using panitumumab-IRDye800CW: a phase 1 single-centre, open-label, single-arm, dose-escalation study’. Lancet Gastroenterol Hepatol. 2020 Aug;5(8):753–764.

Ethics Approval The use of patient tissue samples and data was approved by the Stanford’s Institutional Review Board. Written informed consent was obtained from all patients