73MO - Longitudinal probing of combinatorial immunotherapy (anti-VEGF/anti-PD1) response in advanced nasopharyngeal carcinoma, at single cell resolution

Background

In this study, we aimed to identify mechanisms and prognostic biomarkers associated with the influence of anti-angiogenic therapy to response against immune checkpoint inhibitors (ICI) in advanced Nasopharyngeal cancer (NPC). We generated a longitudinal, single-cell, spatial transcriptomic atlas of NPC patients treated with Bevacizumab (anti-VEGF) and Pembrolizumab (anti-PD1) to define “cell-state alterations” within the tumor ecosystem of responders versus non-responders.

Methods

We performed single-cell RNA-sequencing (scRNA-seq) and spatial transcriptomics, to analyze longitudinal samples from patients treated with either monotherapy (5 weeks of Pembro) (Arm A); or combinatorial therapy (1 week of Bev + 4 weeks of Bev+Pembro) (Arm B).

Results

Clinical outcome data obtained from the phase II open-labelled randomized study suggested that patients in Arm B had higher ORR (50.0% vs 12.5%, p=0.003), and longer median PFS (18.5 vs. 1.6 months, p<0.001) than Arm A. Our scRNA-seq data revealed remarkable alterations in the tumor microenvironment (TME) of Arm B-responders with 1-week of Bev treatment, defined by i) endothelial normalization/remodelling; ii) enhanced pro-inflammatory signatures in tumor-associated endothelial cells and in cancer-associated fibroblasts (iCAFs), and iii) increase innate immune response (NK cells and neutrophils), iv) reduced exhausted T cells, immune-suppressive Tregs, and pro-remodelling macrophages. Notable clonal expansion of T and B cell receptors (TCR/BCR) suggested their role in the anti-tumor response. Spatial transcriptomics validated these findings, which importantly also revealed spatial neighbourhoods associated with these emergent cell-states, revealing potential cross-regulatory cell-cell interactions, which could modulate response to combinatorial therapy.

Conclusions

We suggest that anti-VEGF reverses endothelial anergy and remodels the NPC-TME from an immune tolerant to an immune-active state to enhance the efficacy against immune checkpoint inhibitors.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

A*STAR Singapore.

Funding

National Medical Research Council Singapore.

Disclosure

All authors have declared no conflicts of interest.