Synthesis and Biochemical Characterization of Investigational Pyrazolopyrimidine-Based Allosteric KRAS Modulators

We describe the synthesis and biochemical characterization of a series of compounds derived from a previously reported pyrazolopyrimidine-based KRAS inhibitor [ACS Omega2019, 4 (2), 2921-2930]. Dozens of derivatives were made primarily by modifying the substituents of the pyrazolo-pyrimidine core with the goal of increasing binding affinity to KRAS and improving inhibitory activities against wild-type and oncogenic mutants of KRAS using biophysical measurements and cell proliferation assays. We show that while many of the new compounds exhibited a dramatic increase in binding affinity to KRAS, in many cases, that did not translate into improved potency in inhibiting cell growth. Considering the high binding affinities (up to single-digit nanomolar) and low micromolar inhibitory activities across multiple KRAS mutant cancer cells, we propose that these new derivatives will serve as useful investigational agents for KRAS studies or as starting points for further derivatization and structure-activity relationship studies.