Abstract 6406: Clinical and translational results of the academic ARIANES Phase 2 basket study: Longitudinal single-cell analysis of patient tumors identifies biological correlates of response to PARP inhibitors and anti-PD-L1 therapy

Abstract Background: Poly (ADP-ribose) polymerase inhibitors (PARPi) have immunomodulatory properties that may potentiate anti-PD-L1 therapy. To explore this, we developed the academic ARIANES phase 2 basket trial, which evaluated the PARPi rucaparib (R) and the anti-PD-L1 atezolizumab (A) in selected patients (pts). We performed single-cell RNA + T cell receptor sequencing (scRNA+TCR-seq) on 3 sequential tumor biopsies in a pts subset. Methods: ARIANES comprised 4 molecularly-selected DNA damage response deficient (DDRd), 3 platinum-sensitive, and 2 unselected cohorts of pts with non-small cell lung (NSCLC), prostate (CRPC), and other non-breast non-ovarian cancers. R was administered for 3 weeks, followed by R+A. Primary endpoint was overall response rate (ORR) at 12 weeks per cohort. scRNA+TCR-seq was performed on fresh biopsies collected at baseline, on R, and on R + A in the same lesion, with concomitant plasma collection. We tracked the evolution over time of tumor and microenvironment cells, differentially expressed genes and signatures within each cell population, and TCR clonal dynamics. Results: ARIANES enrolled 130 pts, including 27 DDRd CRPC and 3 DDRd NSCLC pts, on which we focus here. Best ORR by RECIST v1.1 was 22% (6/27) in CRPC pts, and mPFS: 7.9 months (95% CI 4 - 11.1) at data cut-off. ORR was 0% in NSCLC pts. We successfully profiled 3 sequential fresh biopsies in 2 BRCA2-mutant CRPC, 1 ATM-mutant, and 1 RAD54L-mutant NSCLC pts. Tumor, T and B lymphoid, myeloid, plasma, dendritic, NK, endothelial, and stromal cells were identified in all samples. Differential expression testing unveiled PARP1 upregulation in tumor cells on R. One CRPC pt with prolonged partial response displayed activation of innate immune sensing pathways (including cGAS-STING and IFN signaling) in tumor and immune cells, as well as JAK/STAT and CCL5, all increasing gradually on R and R + A; scTCR-seq revealed the expansion of specific T cell clonotypes on R + A. One ATM-mutant NSCLC pt with 6-month stable disease displayed increased cGAS/STING, JAK/STAT and CCL5 activation on R in NK cells only, and no TCR expansion. None of the above was observed in the 2 pts who progressed. Complete clinical and translational study results will be presented at the congress. Conclusion: Sequential scRNA+TCR-seq enables the dynamic assessment of tumor and immune cells on therapy. Our data confirms the potential of R to activate innate immune pathways in pt tumors, and R + A to induce T cell activation and clonal expansion. To our knowledge, this is the first study providing a longitudinal single-cell resolution analysis of the clonal evolution of tumor and immune cells in pts on PARPi + anti-PD-L1. We identify potential biological correlates of therapy response, including the activation of innate immune pathways and TCR expansion. Citation Format: Julien Vibert, Clémence Hénon, Lambros Tselikas, Baptiste Bonnet, Arnaud Pagès, Alice Bernard-Tessier, Léo Colmet-Daage, Roman Chabanon, Nicolas Dorvault, Clémence Astier, Anas Gazzah, Aurore Jeanson, Aurélien Parpaleix, Ronan Flippot, Natacha Naoun, Anna Patrikidou, Pernelle Lavaud, Giulia Baciarello, Emeline Colomba, Alina Fuerea, Laurence Albiges, Christophe Massard, Santiago Ponce, Yohann Loriot, Stéphane Champiat, Capucine Baldini, Fanny Bouquet, Nathalie Droin, Karim Fizazi, Damien Vasseur, Patricia Martin-Romano, Etienne Rouleau, Kaïssa Ouali, Sophie Postel-Vinay. Clinical and translational results of the academic ARIANES Phase 2 basket study: Longitudinal single-cell analysis of patient tumors identifies biological correlates of response to PARP inhibitors and anti-PD-L1 therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6406.