Mutant KRAS (mut-KRAS) is the prototypical undruggable cancer target. It is found in 25% of patient tumors across many cancer types and an estimated 320,000 individuals/yr who will be diagnosed with mut-KRAS in the US most of who will die of their disease. KRAS has been the single most studied human oncogene for over 30 years and yet there is no effective treatment. Mut-KRAS plays a critical role in driving tumor growth and resistance to therapy, and its effects are so powerful that it overrides the activity of many of the new molecularly targeted signaling drugs being developed for cancer today such that they cannot be used in patients with mut-KRAS. Thus, finding new agents that inhibit mut-KRAS is arguably the most important unmet medical need in cancer today. We have identified CNKSR1 as a surrogate target whose inhibition will block the growth of mut-KRAS cancer cells without affecting wild type-KRAS (wt-KRAS) cell growth. CNKSR1 is a protein associated with KRAS in the membrane signaling nanocluster that regulates cancer cell growth and invasion. CNKSR1 has a pleckstrin homology (PH) domain that binds to membrane phosphatidylinositols and we have shown this PH-domain is critical for mut-KRAS activity. Using a homology model for the PH-domain of CNKSR1, molecular docking and drug design, followed by synthetic chemistry we have identified compounds that bind with high affinity to the PH domain of CNKSR1, inhibit KRAS signaling inhibit cancer cell growth and have in vivo antitumor activity.. Thus, our hypothesis is: "While there is currently no effective therapy for mut-KRAS tumors, targeting the PH-domain of CNKSR1 a protein necessary for mut-KRAS but not wt-KRAS cell growth, offers a window of opportunity for developing small molecules inhibitors as agents to treat mut-KRAS tumors" The objectives of our study are: 1) to synthesize and evaluate in vitro the small molecules as CNKSR1 PH-domain inhibitors with drug-like properties;and 2) to investigate the pharmacokinetics and antitumor activity to provide a drug candidate for late pre-clinical development.

Public Health Relevance

RAS is the single most studied human oncogene and yet despite extensive efforts extending over 30 years since its discovery it remains the prototypical undruggable cancer target. New approaches to identifying agents to inhibit mutant KRAS is a pressing medical need as an estimated 320,000 patients/yr in the US with mutant KRAS will die of their disease. We have found that CNKSR1, a protein associated with KRAS in the membrane signaling nanocluster that regulates cancer cell growth and invasion, is essential for mutated but not non-mutated KRAS cell growth. CNKSR1 has a druggable pleckstrin homology domain for which we have experience developing inhibitors. We have used computational modeling and design and synthesis to identify a series of novel optimized chemical compounds. We will evaluate the optimized compounds for inhibition of mutant KRAS cancer cell growth and anticancer activity as leads for late preclinical development as cancer drugs.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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Zhao, Ming
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Phusis Therapeutics, Inc.
United States
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