Abstract CT264: Improved clinical outcomes in patients received treatment beyond tumor progression with AdAPT-001 +/- a checkpoint inhibitor

Abstract Background AdAPT-001 is an oncolytic adenovirus with a TGF-β trap. Pseudoprogression (PsP) or transient tumor enlargement from intense T cell infiltration was commonly observed with AdAPT-001 in immune competent mouse models. We evaluated progression-free survival (PFS) and overall survival (OS) in 36 treatment-resistant patients (pts) that received AdAPT +/- an ICI on a Phase 2 clinical trial. Methods RECIST1.1 assessment was performed every 8 weeks. PsP was defined as progressive disease (PD) on RECIST 1.1 with subsequent tumor regression during TBP. The decision to TBP was based on investigator-assessed clinical benefit and the potential for late responses with minimal adverse events. Log rank tests were applied to compare PFS between pts with and without PsP and to compare OS between pts with and without TBP. Results Median (m) PFS was longer in pts with PsP and TBP (3.7, 95% CI: 1.6 - ) than without it (2.0, 95% CI: 1.8 - 3.7, log-rank test p = 0.97). mOS months was significantly longer in pts with TBP (median not reached) vs. no TBP (7.8, 95% CI: 6.1 - log-rank test p = 0.053). Conclusion A high frequency of PsP occurred on this Phase 2 study likely from infiltration of treatment-activated immune cells. AdAPT-001 mediated PsP and TBP may serve as markers of prolonged clinical benefit. Further validation in larger numbers of future patients is warranted. Citation Format: Anthony P. Conley, Tony Reid, Chris Larson, Bryan Oronsky, Scott Caroen, Meaghan Stirn, Erica Burbano, Nacer Abrouk, Christina L. Roland, Jeannie Williams, Lucy B. Kennedy. Improved clinical outcomes in patients received treatment beyond tumor progression with AdAPT-001 +/- a checkpoint inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT264.