Abstract 5086: Functional profiling in lung tumor explants show contributions of the tumor microenvironment to response of Dato-DXdex vivo

Abstract Background: Antibody drug conjugates (ADCs) have demonstrated significant antitumor activity against multiple treatment refractory cancers. While Trastuzumab deruxtecan, a HER2 directed ADC, has shown impressive clinical activity in HER2-expressing cancers, the ability to predict responses of ADCs by IHC has been limited. Dato-DXd is a TROP2 directed ADC that is currently being studied in a number of registrational phase 3 trial incld. TROPION-Lung01. In the phase 1b TROPION-Pan tumor 01 trial (TP01) response to Dato-DXd did not correlate to TROP2 IHC expression. Here we investigate molecular determinants of sensitivity to Dato-DXd using short-term microfluidic culture of patient derived organotypic tumor spheroids (PDOTS). Methods: Surgical NSCLC cases collected from Brigham and Women’s Hospital and St. Elizabeth’s Medical Center under an IRB approved protocol were studied. PDOTS were generated as previously described. Ex vivo response was assessed by live/dead imaging, TROP2 antigen density on EPCAM+ cells by flow cytometry (FCM) and by immunofluorescence (IF). T cell and myeloid cell populations were analyzed by FCM of CD45+ cells isolated during tumor preparation. For a subset of samples single cell RNA sequencing (scRNAseq) was performed. Results: Eleven NSCLC explants were studied. Two specimens were excluded due to excess of fibrotic material. Response to Dato-DXd was measured by change in raw live cell area compared to control samples. Median response to Dato-DXd was -48. 5% (ranging from +33. 9% to -77. 8%). Using a cut-off of -40%, four cases were characterized as non-responders (NR) and 5 as responders (R). Tumor TROP2 expression by IF ranged from 0 to 3+ with no relationship between TROP2 expression and response being observed. TROP2 staining positivity by IF didn’t correlate to Dato-DXd sensitivity ex vivo. TROP2 FCM, on the other hand discriminated between responsive and non-responsive models in 100% of the cases, using a cutoff of MFI 13000. Furthermore, we observed an increase of tumor CD8 abundance in Dato-DXd R compared to NR (median %CD8 in R 10. 3% (range 5. 1%-62. 5%) ; median %CD8 of live cells in NR 2. 3% (range 1. 2%-3. 7%) p-value 0. 029). Conversely, we also observed a trend of higher granulocytic myeloid-derived suppressor cells abundance in NR compared to R (NR median %gMDSC of CD15+ cells 84. 1% (range 73. 4%-90. 2%) ; R median %gMDSC 61. 7% (range 54. 3%-90. 6%) ; p-value 0. 069). In 2 cases with high and low TROP2 MFI available scRNAseq data showed TROP2 expression exclusively in tumor cells, with further analysis ongoing. Conclusion: By functionally profiling NSCLC PDOTS that retain immune cells, we correlated multiple parameters with ex vivo response to Dato-DXd. Our results have important implications for precision deployment of ADCs and suggest that target tumor antigen density in conjunction with addition immune cell features may refine patient selection strategy. Citation Format: Satoru Yasuda, Elena Ivanova, Ha V. Vo, Sophie Kivlehan, Iliana Gjeci, Minh Ha, Patrick Lizotte, Raphael Bueno, David A. Barbie, Cloud P. Paweletz. Functional profiling in lung tumor explants show contributions of the tumor microenvironment to response of Dato-DXdex vivo 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 (6Suppl): Abstract nr 5086.