Metronomic chemotherapy is defined as frequent low-dose administration without prolonged drug-free breaks. Combining immune-checkpoint inhibitors and metronomic chemotherapy is a new approach to improve responses and delay onset of resistance to immune-checkpoint inhibitors. This multicenter, Phase II, open-label, single-arm study was designed to assess the safety and efficacy of metronomic oral vinorelbine in combination with immune-checkpoint inhibitors in advanced non-small-cell lung cancers progressing after first-line platinum-based chemotherapy. The recommended metronomic oral vinorelbine dose will be determined during a safety run-in period including 12 patients; the main study will include 59 additional patients. The primary outcome is progression-free survival at 4 months. Secondary outcomes are safety of the combination, median overall survival, objective response rate, disease-control rate at 4 months and quality of life (NCT03801304).