Spatial Single‑Cell Platform Reveals Barriers to Antibody Delivery in Solid Tumors

Targeting solid tumors remains one of oncology’s most persistent challenges. Even when a therapeutic antibody is well‑designed, and its molecular target is clear, the drug often struggles to reach its destination inside the dense, heterogeneous architecture of human tumors. Understanding why these agents fail in patients has been a longstanding blind spot in cancer pharmacology.

A new study from Vanderbilt University Medical Center and Stanford University begins to close that gap. In work published in Nature Biotechnology, researchers developed a single-cell spatial pharmacology (SSP) platform, an experimental and analytical system that visualizes drug–tumor interactions directly in human solid tumors. The approach provides a high‑resolution view of drug delivery, target engagement, and the physical barriers that shape therapeutic response.

Eben Rosenthal, MD, the Barry and Amy Baker professor and chair of otolaryngology–head and neck surgery at Vanderbilt Health, is senior author of the paper, titled “Single‑cell spatial pharmacobiology identifies conserved stromal barriers to therapeutic antibody delivery in human solid tumors.” Rosenthal and co‑author Guolan Lu, PhD, of Stanford University School of Medicine, developed SSP to quantify how antibody‑based therapies behave once they enter the tumor microenvironment.

“Identifying the reason drugs fail in so many cancer patients is a high priority, and SSP can help,” Rosenthal said. “Current pharmacology tools and imaging methodologies do not provide the answers we need to understand which drugs fail due to poor delivery and which ones fail due to insufficient activity upon entering the tumor.”

Using SSP, the team found pronounced spatial heterogeneity in both drug delivery and target engagement across head and neck, pancreatic, and other solid tumor types. The data point to a consistent culprit: the stromal architecture, known as the dense, noncancerous tissue surrounding tumors, which acts as a physical barrier that limits antibody penetration.

“This approach allows us to examine how the drug distributes within the tumor, the cell types with which it interacts, how strongly it engages its molecular target, and how the architecture of the tumor microenvironment shapes its delivery and activity,” Rosenthal said.

The study included analysis of panitumumab‑IRDye800CW, an antibody used in Phase I trials and which is under investigation for fluorescence‑guided surgery. Rosenthal’s group has long been at the forefront of integrating fluorescence imaging into cancer research and surgical oncology.

“By directly measuring drug delivery at the site of targeted antibody therapy, SSP can distinguish tumor regions that are biologically unresponsive from those that are simply underexposed to the agent. We hope additional study in larger sample sizes of patients can help further validate the application of SSP to identify barriers to drug efficacy,” Rosenthal added.

By exposing the physical and biological barriers that shape drug performance in human tissue, the platform offers a path toward designing tools that account for the true complexity of the tumor microenvironment.

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