406MO - Unique molecular features of Epstein Barr virus-specific cytotoxic T lymphocyte (EBV-CTL) as biomarkers for advanced nasopharyngeal cancer (NPC) patients who received chemotherapy and EBV-CTL

Background

We previously reported the efficacy of gemcitabine and carboplatin (GC) chemotherapy followed by 6 cycles of EBV-CTL therapy in a Phase II trial involving 35 subjects with locally recurrent/metastatic NPC (NCT00690872). Subsequently, an international multi-centre randomized Phase 3 trial comparing this regimen with chemotherapy was completed (NCT02578641). No biomarkers of efficacy have been identified of polyclonally expanded T cells in any solid tumour. Therefore, our aim is to analyse the samples collected from the completed Phase II trial for biomarker discovery.

Methods

The EBV-CTL infusion products were immunophenotyped by 37-marker cytometry by time of flight analysis. Polyfunctionality of infusion products were evaluated using single-cell (sc) functional proteomics platform in selected patients. Then, TCR repertoire analyses of the EBV-CTL and longitudinal peripheral blood (PB) samples were carried out. Recurrent cervical lymph node metastatic NPC tissue taken upon relapse at 9 years post EBV-CTL treatment of a very long-term survivor (after he had achieved complete remission) was studied using spatial transcriptomics and multiplex immunofluorescence staining.

Results

Multivariance analysis showed balanced clinical parameters, e.g. EBV titers, response to GC, between long-term survivors (LS) and short-term survivors (SS) using 2-year OS as the cutoff accordingly. We then identified that EBV-CTL of LS consisting of more CD27+ T cells and higher number of CD4+ cells, demonstrated much higher polyfunctionality upon stimulation. TCR repertoire analysis revealed higher degree of polyclonal expansion and more pre-existing/persistent clonotypes in LS. Spatial analyses revealed loss of HLA-A and new immune checkpoint expression in the recurrent tumour of a very LS > 9 years to relapse after complete metabolic remission.

Conclusions

We report unique characteristics of the EBV-CTL infusion products associated with improved survival. These findings in the EBV CTL and PB could be applied to translational analyses in the above-mentioned completed Phase 3 randomised trial and to establish potential biomarkers.

Clinical trial identification

NCT00690872.

Editorial acknowledgement

Legal entity responsible for the study

National Cancer Centre Singapore.

Funding

National Medical Research Council (NMRC).

Disclosure

All authors have declared no conflicts of interest.