University of North Carolina Lineberger Comprehensive Cancer Center researchers and colleagues have demonstrated that a uniquely engineered RNA drug that utilizes a tumor-specific targeting molecule to zero in on a mutated gene called KRAS G12V could potentially stop KRAS-dependent cancers in their tracks. The drug is also novel in that it uses a process known as RNA interference (RNAi) that can selectively turn off—or silence—mutated genes such as KRAS.
The preclinical findings were published in Cancer Cell on June 19.
“The only two approved KRAS inhibitors, both of which target the KRAS G12C form of the gene, were approved in 2021 and 2022. Unfortunately, G12C mutations represent only about 11% of all KRAS mutations, meaning that the vast majority of KRAS-mutant tumors still do not have clinically approved inhibitors,” said Chad V. Pecot, MD, corresponding author of the article and professor of medicine at UNC School of Medicine. “We chose to go after KRAS G12V because it is the second most common KRAS mutation, it is a particularly challenging mutation to drug, and there is a clear need for more mutation-specific inhibitors that can target mutations other than KRAS G12C.”
KRAS mutations are present in nearly 25% of all human cancers, and they frequently occur in some of the most prevalent tumor types, such as lung (35%), colorectal (50%) and pancreatic cancers (92%). Some KRAS mutations occur at a higher frequency in certain cancer subtypes: the G12V mutation is a common KRAS mutation amongst lung (22%), colon (22%) and pancreatic (30%) cancers.
Starting in the lab, the researchers set out to identify a promising cell surface receptor that could selectively deliver their RNA molecules into the tumor cells. They found that the Epidermal Growth Factor Receptor (EGFR), which is overexpressed in many cancers, was one of the most attractive cancer-specific targets identified through single-cell RNA-sequencing.
“Our technology takes advantage of EGFR being highly expressed on tumor cells compared to normal tissues,” said Pecot, co-leader of the UNC Lineberger Molecular Therapeutics Research Program and director of the UNC RNA Discovery Center. “The experimental drug we developed, EFTX-G12V, is highly unique in two ways. First, it uses a tumor-specific targeting binding molecule as a ‘homing device.’ Second, we developed a chemically stabilized RNA molecule that is mutation selective, which is a significant advance in the RNAi field and represents a promising future for treating cancer with newer technologies.”
After numerous lab studies, the researchers evaluated EFTX-G12V for its effectiveness in various mouse models of lung, colon and pancreatic cancers. In all of the models, they observed EFTX-G12V resulted in highly significant tumor growth inhibition, including some complete and durable responses.
Interestingly, they found mutation-selective inhibition outperformed a pan-KRAS targeting approach, suggesting the non-mutated form of KRAS (called KRAS wild type) may have anti-tumor roles. Mechanistically, the mutation-selective silencing was more effective at inhibiting many tumor hallmarks than pan-KRAS targeting, including the growth of new blood vessels to feed tumors.
These findings suggest that sparing non-mutated KRAS silencing (or blockade) could have advantageous effects and therefore have important implications in the field. Also, in preliminary studies using mice with intact immune systems, the scientists did not observe evidence of toxicity, even when the experimental therapy was given at up to 10 times the effective dose, meaning it is potentially safe to administer.
According to Pecot, the findings in mice are sufficient to merit moving the technology forward. The next step is to complete the required safety and toxicology studies. If the results from those studies show that the drug is safe, the researchers will file an Investigational New Drug application with the FDA and begin a Phase 1 clinical trial in people.
“What’s so exciting about our technology to me is that it is highly modular, meaning that we can swap out one RNA-silencing component for another, targeting virtually any cancer gene,” Pecot said. “We have several other targets that we are now evaluating, and we’re excited to explore these through our own lab and developing collaborations.”
Pecot added that their technology makes it possible to create multi-targeting molecules, called inverted chimeras, that connect two RNA-silencers that target different genes, and use the chimera molecules to target a KRAS mutation while simultaneously targeting a second gene that is involved in driving resistance to KRAS therapies.
“These two-in-one chimeric molecules can enable us to tackle the problem of drug resistance and enhance the durability of response of our KRAS drugs” Pecot said.
Authors and disclosures
Pecot was supported part by the National Institutes of Health, a University Cancer Research Fund Innovator Award, Kickstarter Venture Services Commercialization awards, Lung Cancer Initiative of North Carolina Innovation and Alumni Awards, and a North Carolina Biotechnology Translation Research Grant.
Pecot holds intellectual property interests on this work, and he is a founder of, and holds equity in, EnFuego Therapeutics, Inc.
A complete listing of authors, funding sources and disclosures is available in the published paper.