Specific KRAS-Mutant Cancers Are Sensitive to Inhibition of V-type ATPases

Mutations in the Ras family of proteins, particularly KRAS, are critical in numerous types of cancer. However, clinically approved drugs targeting most mutations of KRAS are still needed. One strategy currently in development to target KRAS-mutant tumors focuses on their need for high levels of basal autophagy and constitutive activation of macropinocytosis (MP), which both provide nutrients by degradation of macromolecules produced by vacuolar H⁺ ATPases (V-ATPases). Exploitation of this dependence on V-ATPases has been attempted through use of inhibitors such as Bafilomycin A1, but toxicity prevents their use in the clinic. Recently, Tolani and colleagues synthesized dihydro-pyrazole-5-carboxamide molecules to target a developmental pathway and evaluated their ability to target growth of Ras- and Raf-mutant cells, identifying 249C as the lead compound. This small molecule also blocked autophagy and MP, and investigation into its cellular target using a CRISPR screen, chemoproteomic screens, and comparative profiling indicated its ability to bind and inhibit V-ATPase. Moreover, 249C was selective for Ras-mutant cells and demonstrated the highest potency in mouse embryonic fibroblasts with KRASG12V and G13D mutations. Evaluation of 249C as a single agent in vivo using a xenograft SW48 colon cancer model with genetically matched stable derivatives introducing different KRAS mutations indicated that treatment reduced tumor volume, with KRASG13D tumors demonstrating the greatest effects followed by G12V mutations. Additionally, there were no significant changes to mouse body weight during treatment, and alterations to the human ether-à-go-go-related gene, which is known to be affected using previous autophagy and MP inhibitors, were also not observed, suggesting reduced risk for adverse events during 249C treatment. This was further confirmed using the BioMAP Phenotypic Safety and Toxicology profiling screen in which 249C showed no adverse events among 100 biomarker readouts. In summary, this study described the discovery, target identification, and mechanism of action of 249C, indicating its functionality in KRASG13D/KRASG12V-mutant cancers and supporting its potential therapeutic relevance and use in ongoing phase Ia/b clinical trials in lung, colon, and pancreatic cancers.

Tolani B, Celli A, Yao Y, Tan YZ, Fetter R, Liem CR, et al. Ras-mutant cancers are sensitive to small molecule inhibition of V-type ATPases in mice. Nat Biotechnol 2022 Jul 25 [Epub ahead of print].

Note:Research Watch is written by Cancer Discovery editorial staff. Readers are encouraged to consult the original articles for full details. For more Research Watch, visit Cancer Discovery online at http://cancerdiscovery.aacrjournals.org/CDNews.