• Males and females age ≥ 18 years Enrollment of patients ≥ 70 years of age may be allowed at principal investigator discretion.

• Eastern Cooperative Oncology Group (ECOG) performance status 0 - 1

• At least one measurable target lesion, as defined by Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1

‣ Lesions in previously irradiated areas (or other local therapy) should not be selected as target lesions, unless treatment was ≥ 3 months prior to Screening, and there has been demonstrated disease progression in that lesion

• Women of childbearing potential must have a negative serum pregnancy test 48 hours prior to initiating treatment

• Patients with unresectable or metastatic melanoma (stage IIIc or stage IV)

• Patients must have progressed following 1-3 prior systemic therapy including a programmed cell death protein-1 (PD-1) blocking antibody; and if proto-oncogene B-Raf (BRAF) V600 mutation positive, a BRAF inhibitor or BRAF inhibitor in combination mitogen-activated extracellular signal-regulated kinase (MEK) inhibitor

• At least one resectable lesion (or aggregate of lesions resected) of a minimum 1.5 cm in diameter post-resection to generate TIL; surgical removal with minimal morbidity (defined as any procedure for which expected hospitalization is ≤ 3 days)

• Adequate hematologic and organ function

• Patients must have recovered from all prior therapy-related adverse events (AEs) to ≤ grade 1 (per Common Terminology Criteria for Adverse Events \[CTCAE\] version \[v\] 5.0), except for alopecia or vitiligo, prior to enrollment (tumor resection)

‣ Patients with documented ≥ grade 2 diarrhea or colitis because of previous treatment with immune checkpoint inhibitor(s) must have been asymptomatic for at least 6 months and/or had a normal colonoscopy post-immune checkpoint inhibitor treatment, by visual assessment, prior to tumor resection

• Patients with immunotherapy-related endocrinopathies stable for at least 6 weeks (eg, hypothyroidism), and controlled with hormonal replacement (non-corticosteroids), are allowed

• Patients must have a washout period of ≥ 28 days from prior anticancer therapy(ies) to the start of the planned reduced dose lymphodepletion (RDL) preconditioning regimen:

‣ Targeted therapy: MEK/BRAF or other targeted agents

⁃ Chemotherapy

⁃ Immunotherapy: anti-CTLA-4/anti-PD-1, other monoclonal antibodies (mAb), or vaccine

⁃ Palliative radiation therapy is permitted so long as it does not involve lesions being selected for TIL, or as target or non-target lesions. Washout is not required if all related toxicities have resolved to ≤ grade 1 as per CTCAE v 5.0

• Women of child-bearing potential and men with partners of child-bearing potential must agree to practice sexual abstinence or to use the forms of contraception listed in Child-Bearing Potential/Pregnancy section for the duration of study participation and for 12 months following the last dose of IL-2 or until the first dose of the next anti-cancer therapy, whichever occurs first