Here we report safety and interim efficacy of the first clinical trial of rigosertib in combination with the immune checkpoint inhibitor (ICI) nivolumab, in advanced KRAS mutated NSCLC patients who progressed on first line ICI-containing treatment….Of 13 patients evaluable for treatment response, 1 achieved a complete response (CR; KRAS G12V), 2 experienced partial response (PR; KRAS G12C and G12D) and 1 had stable disease (KRAS G12V), for a total disease control rate of 31%. The durability of response for the CR and 2 PRs were 7, 8 and 6 months, respectively, with the latter PR continuing to respond on treatment....Combination of Rigosertib and Nivolumab is safe, well tolerated and has shown early efficacy for the treatment of KRAS mutated NSCLC patients with prior progression on ICI.