Identification of the nucleotide-free state as a therapeutic vulnerability for inhibition of selected oncogenic RAS...

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• RAS guanosine triphosphatases (GTPases) are frequently mutated in human cancers, presenting a significant therapeutic challenge.
• The nucleotide-free (apo) state of RAS has been identified as a critical regulator of cell signaling.
• Targeting specific RAS states offers a promising strategy for selective cancer therapy.

Purpose of the Study:

• To develop a novel therapeutic approach targeting the apo RAS state.
• To identify and characterize a molecule that selectively binds and inhibits apo RAS.
• To evaluate the efficacy of targeting apo RAS in preclinical cancer models.

Main Methods:

• Development of the R15 monobody designed to bind exclusively to the apo state of all RAS isoforms.
• In vitro and cellular assays to assess R15 binding and RAS capture in the apo state.
• Evaluation of R15's inhibitory effects on RAS signaling and transforming activity in cancer cell lines and patient-derived xenografts (PDXs).

Main Results:

• The R15 monobody selectively binds the apo state of all three RAS isoforms, irrespective of mutation status.
• R15 effectively captures RAS in the apo state within cells.
• R15 demonstrated inhibition of signaling and transforming activity in RAS mutants with fast intrinsic nucleotide exchange rates.
• Intracellular R15 expression reduced tumor formation in KRAS(G12D)-mutant PDXs and other select RAS-driven cancers.

Conclusions:

• Targeting the apo RAS state with the R15 monobody provides a selective approach to inhibit oncogenic RAS.
• This strategy is effective against a subset of RAS mutants, particularly those with fast exchange rates.
• The R15 monobody represents a potential drug-like molecule for treating cancers driven by specific RAS mutations.