Study to Investigate Lifileucel Regimen Plus Pembrolizumab Compared With Pembrolizumab Alone in Participants With Untreated Advanced Melanoma.

This is a Phase 3, multicenter, open-label, randomized, parallel group, treatment study to assess the efficacy and safety of lifileucel in combination with pembrolizumab compared with pembrolizumab alone in participants with untreated, unresectable or metastatic melanoma. Participants randomized to the pembrolizumab monotherapy arm who subsequently have a blinded independent central review- verified confirmed progressive disease (PD) will be offered lifileucel monotherapy in an optional crossover period.