Because complete inhibition of mutant KRAS is challenging, we evaluated if dual KRAS blockade with EFTX-G12V (RNAi) and allosteric inhibition (RMC-7977) could improve MAPK inhibition. We found an additive or synergistic effect in several KRAS mutant lines and near complete pERK inhibition.

(10/11)

Using a syngeneic model from Mariano Barbacid’s lab, we observed EFTX-G12V phenocopies anti-tumor effects of tamoxifen-inducible KRAS G12V flox. Consistent w KRAS small molecule inhibitors, we observed highly significant and rapid increases of CD8+ T-cells and many granzyme B+ lymphocytes.

(9/11)

In a KRAS G12V colon model, we observed that prolonged EFTX-G12V treatment led to pEGFR feedback activation, which was largely mitigated by the addition of an anti-EGFR antibody. This indicates the GE11-mediated receptor uptake mechanism for siRNA delivery is compatible with an EGFR Ab.

(8/11)

We found less pEGFR reactivation in colon cancer models with EFTX-G12V, whereas pan-KRAS targeting had robust pEGFR reactivation + increases in tEGFR. We observed decreased pYAP S127 with EFTX-G12V, consistent with YAP-TEAD activation as a likely resistance pathway that emerges.

(7/11)

RNAseq demonstrated mutant-selective silencing results in deep suppression of many cancer hallmarks, and tumor angiogenesis as uniquely suppressed by mutant selective Rx. We observed significant inhibition of microvessel density with EFTX-G12V, and inconsistent effects with pan-KRAS Rx.

(6/11)

EFTX-G12V had significant anti-tumor activity in lung, colon + pancreatic cancer models.

Compared with a more potent pan-KRAS siRNA molecule based on in vitro activity, EFTX-G12V unexpectedly outperformed pan-KRAS inhibition in vivo, prompting us to investigate whether differences exist.

(5/11)

The GE11C-targeting EFTX-G12V siRNA = EFTX-G12V, an EGFR-directed KRAS G12V selective RNAi molecule

Pharmacodynamics demonstrated a single dose of EFTX-G12V resulted in ~80-90% KRAS mRNA + protein silencing in the tumor. We observed minimal to no KRAS WT silencing in those tissues.

(4/11)

For delivery, recent scRNAseq profiling suggested EGFR is a very differentially expressed cancer receptor. GE11 peptide, a EGFR binding peptide without mitogenic activity, covalently linked to siRs could result in receptor-mediated endocytosis and a high efficiency of cancer cell delivery.

(3/11)

To create a KRAS G12V mutant selective siRNA, we utilized sequence optimization and leveraged steric properties of 2OMe modifications to create EFTX-G12V V4 Hi2OMe. Thermodynamics, Ago2 modeling, RNAseq + using isogenic lines confirmed mutant selective KRAS G12V inhibitor + spares KRAS WT.

(2/11)

Now in @Cancer_Cell our group reports the development of a first-in-class EGFR-directed KRAS G12V selective inhibitor.

We address two major challenges with RNAi therapeutics in cancer:
1) Delivery, delivery, delivery
2) Achieving mutant selectivity

www.cell.com/cancer-cell/...

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