Combination synergy of spliceosome modulator ADC with a K-Ras inhibitor in <i>K-Ras</i> –mutated pancreatic cancers.

Abstract

e16427 Background: AKTX-101 is a TROP2 ADC containing the spliceosome modulator payload, PH1(1). PH1 can target oncogenic driver splice variants such as AR-v7 and WT Androgen Receptor in prostate cancer. Alternative splicing of K-Ras results in two isoforms, 4A and 4B. When K-Ras WT carcinoma cells were treated with PH1, exon skipping of KRAS RNA was altered in a region common to both isoforms (2). AKTX-101 exhibited single digit nM potency in NCI-H441 lung cancer model with a K-Ras G12V driver mutation. Methods: To investigate the potential efficacy of AKTX-101 in pancreatic cancer, in vitro cytotoxicity assays were performed using 4 cell lines with oncogenic K-Ras G12C or G12D mutations. Here we tested AKTX-101 vs 3 TROP2 ADCs bearing topoisomerase I-payloads, alone, and in combination with adagrasib. In the combination experiments, ADCs were fixed at their IC50 concentrations, or at 20nM if IC50 was not reached, and adagrasib was varied from a top concentration of 100µM with nine 4-fold serial dilutions. The mean for the Bliss Independence scores was used to determine combination index: Bliss scores of &gt; 5 indicated synergy and &lt; -5 reflected antagonism. Results: In KRAS G12C and G12D mutant pancreatic cancer cell lines, the combination of AKTX-101 and adagrasib exhibited synergistic cell killing not seen with the other TROP2 ADC/adagrasib combinations. Mean Bliss scores were &gt; 10 for the AKTX-101+ adagrasib combination, vs. primarily negative Bliss scores for the competitor TROP2 ADCs/adagrasib combinations, suggesting synergy may be due to novel biology of PH1 targeting splicing. Conclusions: The TROP2 ADC, AKTX-101 exhibited synergistic efficacy with adagrasib in K-Ras G12C and G12D mutated pancreatic cancer cell lines. This synergy may be linked to PH1-specific effects on K-Ras splicing and may have contributed to improved adagrasib efficacy in G12D-mutated pancreatic cancer, where currently adagrasib is not approved. References Mitra SK, Monteith W, Do M, Tuffy G, Savage S, Kang J, Abuhay M, Losic T, Ghone S, Haskins WE, Jammalamadaka V, Satyal S. Cancer Res. 2023;83(7_Supplement):6297. Mitra SK, Jammalamadaka V, Kang J, Losic T, Tuffy G, Liang TW, Tipton K, Lopez A, Savage S, Monteith W, Haskins WE, Jurica MS, Satyal S, Do M. Development of a splicing modulator-based ADC payload class with immune stimulatory properties for cancer therapy. Cancer Res . 2021;81(13_Supplement):1832. In vitro combinations of Trop2 ADCs with adagrasib. K-Ras mutation Cell line AKTX-101 IC50 (nM) Adagrasib (Ada) IC50 (nM) Bliss Mean AKTX-101 + Ada Bliss Mean SG + Ada Bliss Mean Dato-DXd + Ada Bliss Mean Sac-TMT + Ada G12C PA1266 &gt;20.0 2288.5 15.95 -6.18 -3.87 -5.22 G12D HPAF-II &gt;20.0 3346.7 17.55 -13.73 -11.63 -12.16 G12D Panc 10.05 &gt;20.0 4387.7 17.51 -5.87 8.23 -3.29 G12D SW-1990 &gt;20.0 2529.5 6.78 -5.20 -4.74 -7.66 Where SG= Sacituzumab govetican, Dato-DXd= Datopotamab deruxtecan, Sac-TMT= Sacituzumab tirumotecan.