397P Early decreases in KRAS mutant allele frequency (MAF) predicts clinical benefit to the PLK1 inhibitor onvansertib in combination with FOLFIRI/bev in 2L treatment of metastatic colorectal carcinoma (mCRC)

Abstract

Patients (pts) with mCRC have few treatment options and poor outcome, particularly those with KRAS mutation (mKRAS). After failure of 1L treatment, the ORR for FOLFIRI/bev is 5-13%, with PFS 4-6 mos, and OS 10-12 mos. Onvansertib (Onv), is a highly specific PLK1 inhibitor, currently being investigated in combination with FOLFIRI/bev in 2L treatment of mKRAS mCRC (NCT03829410). Preliminary results indicate that Onv+ FOLFIRI/bev is well tolerated and efficacious (Lenz et al, JCO 2022). We investigated the utility of measuring early changes of KRAS MAF, using liquid biopsies, to predict clinical benefit to Onv+FOLFIRI/bev.