KRAS-driven cancers are notoriously difficult to treat due to poor pharmacodynamics of downstream inhibitors and resistance to anti-EGFR drugs. IMP-1 is a post-transcriptional regulator of KRAS mRNA. As a novel therapeutic approach, the targeting of the IMP-1-KRAS mRNA complex with a spiropyrrolizidine derivative (UNBC152), was studied. LC-MS analysis of UNBC152 indicated presence of impurities. The purpose of this study was to synthesize UNBC152 and determine the responsible bioactive molecule within the impurities. LC-MS and TLC suggested the presence of a bioactive [3+3] cycloaddition side product (SPOPP) in UNBC152. SPOPP suppressed KRAS expression in human colorectal cancer cells. Fluorescence polarization determined that SPOPP did not impact the IMP-1-KRAS mRNA interaction. SPOPP induced G2/M cell cycle arrest as shown by flow cytometry. MTT assay confirmed the SPOPP-induced growth inhibition in SW480 (IC50 = 4.17 μM) and HT29 (IC50 = 6.76 μM). These findings represent a first reporting on the bioactivity of SPOPP.
