Transcript: RAS inhibitors: A new era of clinical success

Alex: Welcome to another episode of ResearchPod. Today, we're looking at a significant shift in cancer research. For decades, a family of proteins called RAS was considered impossible to target with drugs.

Sam: That's right. RAS proteins act like molecular switches that tell cells when to grow. When these switches get stuck in the "on" position due to mutations, they drive uncontrolled tumor growth. For forty years, scientists couldn't find a way to bind to these proteins and stop them — leading many to label them "undruggable."

Alex: So this paper is documenting the end of that era? And the core problem was that these proteins were just too slippery to target?

Sam: Exactly. The challenge was that RAS proteins didn't have the right physical pockets or grooves for a drug molecule to latch onto — like trying to grip a perfectly smooth ball. We've moved past that barrier, but now a new challenge has emerged: cancer cells are very good at finding ways to survive even when we do attack them.

Alex: Right, so it's not just about finding a drug that works once — it's about preventing the cancer from evolving around it. How are researchers actually getting these drugs to stick now?

Sam: The first approach was to target the protein when it's in its inactive, "off" shape. Think of it like trying to handcuff someone while they're asleep. It works for a while, but the cancer eventually changes its shape slightly to escape the cuff.

Alex: So if you only target the inactive shape, the cancer just stays in the active shape to avoid the drug. What's the alternative?

Sam: The newer approach uses what researchers call "molecular glues." Imagine a specialized fastener that works even when someone is actively moving around. These glue-like compounds lock the RAS protein to another protein inside the cell — a kind of chaperone — effectively disabling it even while it's active.

Alex: So the glue forces the protein into a position where it can't send its "grow" signals anymore, regardless of what the cancer tries to do?

Sam: Precisely. By targeting the active "on" state, we stop the protein regardless of the specific mutation it carries. That's a meaningful improvement, because it prevents the tumor from simply switching to a slightly different version of the protein to survive.

Alex: So you've moved from catching the protein when it's asleep to locking it down while it's awake. But even then, the cancer finds another way around?

Sam: It often does. Even with these glues working, cancer cells will try to find escape routes — activating different internal signaling pathways to keep growing, as if taking a detour around a roadblock.

RAS inhibitors: A new era of clinical success

Matthias Drosten, Mariano Barbacid

Oct 29, 2025·5:27·pmc·Original Paper

RAS inhibitorsDrug resistanceKRAS mutationsCombination therapiesMolecular glues

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5 min

Briefing

The Shift in RAS Targeting

For decades, RAS proteins were considered 'undruggable' due to their high affinity for GTP and the lack of suitable binding pockets for small molecules. This paradigm shifted with the discovery of allosteric pockets that allow for the inhibition of specific mutant isoforms, most notably KRASG12C. The subsequent clinical approval of inhibitors like sotorasib and adagrasib marked the beginning of a new era in precision oncology for patients with RAS-mutant cancers.

Evolution of Inhibitor Classes

The field has rapidly expanded beyond first-generation KRASG12C inhibitors. Current strategies include:

Allele-specific inhibitors: Targeting specific mutations like KRASG12D, though these have faced challenges with pharmacological properties and the emergence of secondary mutations.
PanKRAS and PanRAS inhibitors: Designed to target a broader range of mutations and paralogs, these drugs aim to overcome the limitations of allele-specific approaches. Notably, panRAS inhibitors like daraxonrasib have demonstrated significant clinical activity, even in difficult-to-treat cancers like pancreatic ductal adenocarcinoma (PDAC).
Molecular Glues and PROTACs: Novel modalities that either sterically hinder effector binding or target the oncoprotein for degradation, offering potential advantages over traditional inhibitors.

The Challenge of Resistance

Despite initial clinical successes, patient responses are often transient. Resistance typically emerges through genetic mechanisms—such as new mutations in RAS paralogs or upstream signaling receptors—and non-genetic mechanisms like transcriptional adaptation. The authors emphasize that monotherapy is unlikely to provide durable cures. Instead, the future of RAS-targeted therapy lies in rational combination strategies, such as pairing RAS inhibitors with immune checkpoint inhibitors or agents that target downstream signaling nodes (e.g., EGFR or STAT3) to prevent tumor escape.

Key Terms and Definitions

KRASG12C: A specific mutant isoform of the KRAS protein where glycine at position 12 is replaced by cysteine, making it a primary target for early covalent inhibitors.
OFF-state Inhibitors: Drugs that bind to RAS proteins only when they are in the GDP-bound, inactive conformation.
PanRAS Inhibitors: Therapeutic agents capable of inhibiting multiple RAS isoforms (KRAS, NRAS, and HRAS) regardless of the specific mutation, offering a broader spectrum of activity.
Molecular Glue: A type of drug that facilitates a physical interaction between a target protein (like RAS) and another protein (like a chaperone), resulting in the inhibition of the target's function.
PROTACs: Proteolysis Targeting Chimeras that recruit E3 ubiquitin ligases to a target protein, marking it for degradation by the cell's proteasome.

Abstract

RAS oncoproteins have been considered undruggable for decades. However, recent advances have led to the development of a large variety of RAS inhibitors. While a multitude of drugs is currently under clinical evaluation, some of them have already been approved in specific contexts, leading to a continuous improvement of available therapeutic options for patients with RAS-mutant cancers. In this Viewpoint, we discuss different classes of RAS inhibitors, with emphasis on those that are currently tested in the clinic including allele-specific KRAS, panKRAS, and panRAS inhibitors. We also address determinants of response to RAS inhibition such as the tumor context or potential resistance mechanisms. Finally, we provide an outlook on the future of RAS targeting, which is likely to involve combination therapies. The rapid approval of several RAS inhibitors reflects the urgency to develop novel therapeutic strategies to treat RAS-mutant cancers.

RAS inhibitors: A new era of clinical success | Matthias Drosten, Mariano Barbacid | ResearchPod

RAS inhibitors: A new era of clinical success: Research Paper Podcast