• Pathologically confirmed and documented cutaneous melanoma- CM patients (including acral melanoma) with unresectable or metastatic disease

• HLA-A\*02:01 positive

• Adequate selected organ function per protocol

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

• Disease progression (resistance, toxicity) on or after at least one PD-1 inhibitor, applied either as monotherapy or in combination with other therapies as treatment for unresectable or metastatic cutaneous melanoma

• Patients with BRAF mutation should have been treated with one prior line of BRAF-directed therapy (with or without a MEK inhibitor) prior to initial eligibility assessment, unless deemed not clinically indicated at Investigator's discretion due to concurrent medical condition, prior toxicity, or if declined by the patient

• Life expectancy more than 6 months

• Measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST 1.1)

• Female patient of childbearing potential must use adequate contraception from randomization until 12 months after the infusion of IMA203 or in line with the instructions provided for investigator's choice treatment (in the control arm)

• Male patient must agree to use effective contraception or be abstinent while on study and for 6 months after the infusion of IMA203 or in line with the instructions provided for investigator's choice treatment (in the control arm)

• The patient must have recovered from any side effects of prior therapy to Grade 1 or lower prior to randomization.