Liquid biopsy as promising source of plasma extracellular vesicle biomarkers of response to cabozantinib (CABO) plus durvalumab (DURVA) in patients with advanced urothelial carcinoma (UC) or non-UC variant histologies (VH) after platinum chemotherapy: The phase 2 ARCADIA trial.
Authors: Mereu Alessandro , Salsetta Jeannette , Lalli Luca , Squarcina Paola , Banfi Cristina , Sgambelluri Francesco , Mortarini Roberta , Huber Veronica , Stellato Marco , Raggi Daniele , Guadalupi Valentina , Claps Melanie , Bottiglieri Achille , Walter Ferrari Bravo , Calareso Giuseppina , Alessi Alessandra , Procopio Giuseppe , Necchi Andrea , Rivoltini Licia , Giannatempo Patrizia 
Published: January 2024

687 Background: As components of the liquid biopsy, Extracellular Vesicles (EVs) have gained major interest as biomarkers of diagnosis, prognosis and prediction of response/resistance to cancer therapies. Here we investigated if plasma EV immune profile, size and concentration in concert with plasma proteomics might discriminate responding from non-responding patients affected by advanced urothelial carcinoma (UC) or non-UC variant histologies (VH) undergoing cabozantinib (CABO) plus Durvalumab (DURVA) combination therapy after platinum chemotherapy (NCT03824691). Methods: We evaluated 40 patients for their plasma EV profile at baseline and at the first reassessment after 2-4 months of therapy. Baseline samples of 50 patients (40 plus additional 10 patients) were evaluated for their predictive potential. EVs were profiled using modified MACSplex technology (Miltenyi Biotec) coupled with flow cytometry and nanoparticle tracking analysis (NTA). Whole plasma was also searched for further indicators of response/resistance by proteomics (92 analytes, Immune-oncology panel, Olink). Results: Preliminary analysis of the single EV markers measuredin baseline samples evidenced no major association with response, although patients with VH histology showed a significant enrichment of CD1c and CD14 expressing EVs. Upon inclusion in the analysis of the on-therapy time point we were able to detect in the whole case set an increase of immune markers, including CD14, CD1c, CD2, CD20, CD8 and CD69; EV markers CD9, CD63 and CD81; platelet markers CD29, CD31 and CD326. This was also reflected by the global distribution of EV markers, which evidenced unexpectedly high levels of EVs exposing CD81 EV marker and CD8 already at baseline, with a further increase after therapy initiation. Finally, the dichotomization by response highlighted that a statistically significant increase of immune EVs was detectable almost exclusively in responding patients. NTA and plasma proteomics are currently ongoing. Conclusions: Our preliminary results suggest that the early dynamics in plasma EVs may inform on the clinical outcome to DURVA plus CABO. The significant increase of EVs expressing immune markers measured at first reassessment in responding patients may derive from the activation of the immune system induced by therapy. The comprehensive analysis of EV profiles, size and concentration together with plasma proteomics could give rise to predictive/prognostic biomarkers of response in this clinical setting, especially in patients with non-UC variant histologies. Acknowledgements. AIRC IG-25078 to VH, NET-2016-02361632 from Italian Health Ministry to A. Anichini. Clinical trial information: NCT03824691 .