Abstract 7173: Mechanistic studies of fibroblast activation protein activated prodrug AVA6000 in pancreatic and liposarcoma models

Abstract Background: This study shows single agent and combinatorial activity of AVA6000 (Faridoxorubicin, FAP-Dox), in pancreatic cancer and liposarcoma, cancer associated fibroblast co-culture models. Fibroblast activation protein (FAP) is a transmembrane serine protease and present in cancer associated fibroblasts and some cancer cells. AVA6000 is a FAP cleavable peptide drug conjugate comprised of doxorubicin and a dipeptide that is selectively cleaved by FAP to release active doxorubicin within the tumour microenvironment. We aimed to study a) FAP-specific release of doxorubicin b) combinatorial activity of AVA6000 with DNA damage repair inhibitors, in preclinical models. Methods: Cancer cells, labelled with GFP, were co-cultured with pancreatic stellate cells (PSCs) showing features of myofibroblastic cancer associated fibroblasts (such as alpha smooth muscle antigen expression) which expressed FAP. Cancer cell growth was quantified by counting the number of GFP labelled cancer cells per well, with cancer cells alone (i.e. no CAFs) used as controls. In addition, we studied the effects of the FAP inhibitor Talabostat (PT100) in reversing the effects of AVA6000 in co-culture conditions. Further, we tested the effects of the combination of an ATR inhibitor BAY1895344 in combination with AVA6000 in the coculture system. Results: The GI50 of AVA6000 in two pancreatic cancer cell lines ASPC-1 and Mia-Paca-2 in the co-culture system with PSCs was 58±21.4nM, (Stdev,n=3) and 66.5±16.3nM (Stdev, n=3). No GI50 was obtained in both cell lines at the highest concentration of AVA6000 studied in both cell lines (100nM n=3) if PSCs were not included in the culture. In addition, we demonstrated that the FAP inhibitor talabostat at 100µM reversed any growth inhibition by AVA6000 (highest concentration of AVA6000 tested 100nM) confirming AVA6000 activation was FAP dependent. We further studied the growth inhibition of AVA6000 in the liposarcoma cell line SW872-GFP in co-culture with FAP expressing fibroblasts GI50 30.6±6.7 nM (StdevD, n=4). The GI50 of AVA6000 was not achieved in the absence of fibroblasts at 100nM and the FAP inhibitor talabostat reverses this growth inhibitor effect in the co-culture system. The combination of AVA6000 and BAY1895344 in the co-culture yielded a 2 fold shift in GI50. Conclusions: AVA6000, is selectively activated by FAP expressing PSCs and is active in pancreatic and liposarcoma co-culture models. It also exhibits synergistic growth inhibition activity with ATR inhibitors in liposarcoma co-culture models. Clinical trials of AVA6000 are ongoing (NCT04969835). Citation Format: Lisa Pickard, Ekta Paranjape, Brian Cunningham, Udai Banerji. Mechanistic studies of fibroblast activation protein activated prodrug AVA6000 in pancreatic and liposarcoma models abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7173.