RAPT Therapeutics, Inc. announced safety and efficacy data from its Phase 2 trial of FLX475 (tivumecirnon) in patients with advanced non-small cell lung cancer (NSCLC) who had no prior checkpoint inhibitor therapy. The trial evaluated FLX475, an oral small molecule CCR4 antagonist designed to block the migration of regulatory T cells, in combination with the checkpoint inhibitor pembrolizumab. In this cohort of NSCLC patients, 36 patients were evaluable for efficacy, of which 20 were PD-L1 positive.

In these PD-L1 positive patients, the combination of FLX475 and pembrolizumab showed a 40% (8/20) confirmed ORR and a median PFS of 6.3 months as of the data cut off date, with seven patients continuing on study. For comparison, historical pembrolizumab monotherapy activity in checkpoint inhibitor-naive and previously-treated NSCLC patients showed a confirmed ORR of 18% and a median PFS of 4.0 months. The confirmed ORR for the combination of FLX475 & pembrolizumab in PD-L1 low and high subsets were 38% (6/16) and 50% (2/4), respectively.

For comparison, the ORR for pembrolizumab Monotherapy in the PD-L1 low and High subsets has been previously reported as 10% and 30%, respectively. The data were presented in a poster at the Society for Immunotherapy of Cancer (SITC) 38th Annual Meeting being held in San Diego. The presenting author was Julie Brahmer, M.D., Co-director of the Upper Aerodigestive Department and Professor of Oncology, Johns Hopkins University.