Abstract A006: 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 demonstrates 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 the 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 protein levels. 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, which inhibits KRAS G12V, TEAD1-4 and downstream signaling, including MYC. 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 designs, EFTX-G12V-pTEAD is conjugated to an EGFR linear ligand that enables high tumor-to-normal tissue payload delivery and limits systemic exposure. 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 are largely cleared through the proximal tubules; therefore, we anticipate the potential for less kidney toxicity and a wider therapeutic window using this therapeutic modality. Using the H727 lung cancer model, compared with control siRNA delivery, although EFTX-G12V resulted in significant tumor growth inhibition, we observed that dual KRAS G12V and pan-TEAD targeting with EFTX-G12V-pTEAD resulted in significantly improved tumor growth inhibition, deeper tumor responses, and more durable disease control. 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 McLarnon, Kristina Whately, Snehasudha Sahoo, Lori O'Brien, Chad Pecot. Synergistic co-targeting of KRAS G12V and pan-TEAD by an EGFR-directed, inverted chimeric RNAi molecule [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RAS Oncogenesis and Therapeutics; 2026 Mar 5-8; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(5_Suppl_1):Abstract nr A006.