A Study of Lifileucel (Tumor-infiltrating Lymphocytes) in Adults With Advanced Melanoma

Inclusion Criteria: * Participant has a histologically or pathologically confirmed diagnosis of Stage IIIC, IIID, or IV unresectable or metastatic melanoma. * The participant has an ECOG performance status of 0 or 1 and an estimated life expectancy of \> 6 months. * The participant must have experienced radiographic disease progression on: 1 prior line of an anti-PD-(L)1 treatment (as a monotherapy or as part of a combination) for advanced melanoma and/or during or within ≤ 12 weeks after adjuvant anti-PD-(L)1 treatment (as a monotherapy or as part of a combination). Participants who have BRAF V600 mutation positive melanoma may have received 1 additional prior line of treatment with a BRAF inhibitor ± a MEK inhibitor. * Participant is assessed as having at least one resectable lesion (or aggregate lesions) for lifileucel generation. * Participant must have at least one measurable disease as defined by RECIST 1.1 following tumor resection. * Participants who are \> 70 years of age may be allowed to enroll after the investigator discusses with the medical monitor. * Participants of childbearing potential or those with partners of childbearing potential must be willing to practice an approved method of highly effective birth control. * Participants must have adequate organ function. * Participant is willing to receive optimal supportive care, including intensive care, from enrollment until the first post-treatment tumor assessment. Exclusion Criteria: * Participant has melanoma of uveal/ocular origin. * Participant has symptomatic untreated brain metastases. * Participant has active uveitis that requires active treatment. * Participant has an active medical illness(es) that, in the opinion of the investigator, would pose increased risks for study participation, such as systemic infections; seizure disorders; coagulation disorders; or other active major medical illnesses of the cardiovascular, respiratory, or immune systems. * Participant has any form of primary or acquired immunodeficiency (eg, SCID or AIDS). * Participant had another primary malignancy within the previous 3 years (except for those that do not require treatment or were curatively treated \>1 year ago, and in the judgment of the investigator do not pose a significant risk of recurrence.) * Participant has a history of allogeneic cell or organ transplant. * Concurrent enrollment in another clinical study, unless it is an observational (non-interventional) clinical study or during the follow-up period of an interventional study. Other protocol defined inclusion/exclusion criteria could apply.