Abstract 1875: Synergistic co-targeting of KRAS G12V and pan-TEAD by an EGFR-directed, inverted chimeric RNAi molecule.

Abstract While KRAS has long been considered an “undruggable” oncoprotein, advancements in structural and chemical biology have resulted in KRAS G12C, G12D, pan-KRAS and pan-RAS small molecule inhibitors. Although several have shown clinical promise, therapeutic resistance remains a significant problem. Recently, YAP/TAZ activation has emerged as a common resistance mechanism to KRAS inhibition. YAP and TAZ act as transcription coactivators with the TEAD1-4 transcription factors as part of the Hippo signaling pathway. Several groups have already shown that pan-TEAD (pTEAD) inhibition synergizes with KRAS inhibition, and YAP and KRAS exhibit pathway crosstalk in cancer. Previously, we developed EFTX-G12V, a first-in-class EGFR-directed KRAS G12V selective siRNA that displays excellent single agent efficacy in lung, colon and pancreatic cancers. Further, we developed a novel inverted chimeric siRNA design that incorporates two oncogene-targeting siRNAs linked by an endo-nucleolytic DNA bridge. The chimeric siRNA design ensures equivalent molar targeting of both gene transcripts in the same cell with enhanced metabolic stability and tumor accumulation. Here, we describe the development of chemically modified pTEAD targeting siRNAs and subsequent development of a KRAS G12V, pTEAD targeting chimeric siRNA. We used a structure-activity relationship screening approach to identify a highly potent fully chemically modified siRNA that inhibits TEAD1-4 at both the mRNA and the protein level. This pTEAD siRNA inhibited cancer cell growth in vitro and showed no concerning off-target effects. Using this siRNA and EFTX-G12V we developed EFTX-G12V-pTEAD, that inhibits KRAS G12V, TEAD1-4 and downstream signaling at both the mRNA and the protein level. Importantly, EFTX-G12V-pTEAD showed improved inhibition of downstream targets when compared to each single agent siRNA highlighting the value of the chimeric siRNA. Similar to our previously described siRNAs, EFTX-G12V-pTEAD is conjugated to an EGFR linear ligand that enables high tumor-to-normal tissue payload delivery and limits systemic exposure. In vivo evaluation of EFTX-G12V-pTEAD in comparison to single agent EFTX-G12V in both xenograft and immunocompetent cancer models are planned to evaluate durability, efficacy and safety. Importantly, small molecule pTEAD inhibitors cause kidney toxicity including podocyte effacement, proteinuria and albuminuria, which has limited their clinical utility. Using spatial profiling in the kidney, we found that our siRNA molecules do not enter podocytes and largely clear through the proximal tubules, therefore we anticipate the potential for less kidney toxicity and a wider therapeutic window using this therapeutic modality. Together our findings represent a technological advance in multi-oncogene targeting using RNAi and a therapeutic modality capable of addressing resistance to KRAS inhibitors. Citation Format: Lyla Stanland, Alessandro Porrello, Sarah R. McLarnon, Lori L. O'Brien, Chad V. Pecot. Synergistic co-targeting of KRAS G12V and pan-TEAD by an EGFR-directed, inverted chimeric RNAi molecule 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 1875.