A Phase II Trial of Tebentafusp in HLA-A*02:01 Positive Patients With Advanced Clear Cell Sarcoma

This will be a multi-center, open label, phase II study of tebentafusp in patients with unresectable or metastatic CCS. Patients who screen positive for HLA-A\*02:01 and meet the eligibility requirements will be treated with weekly tebentafusp. Radiographic assessment via CT or MR (where CT is not feasible or per the investigator's discretion) will occur at baseline and every subsequent 6 weeks through 48 weeks, and then every 9 weeks thereafter. Patients will be treated until progression of disease or unacceptable toxicity. All patients treated with tebentafusp will undergo mandatory research biopsies at baseline and on-treatment (week 6), if it is safe and feasible to do so. Serial peripheral blood samples for correlative analysis will be collected at baseline and at various time points on treatment. Patients who are HLA-A\*02:01-negative and ineligible to receive tebentafusp will be prospectively enrolled onto a separate study arm and treated with physicians' choice of treatment. They will also be radiographically assessed at the same schedule as patients treated with tebentafusp, if feasible, and kept on this treatment arm until progression of disease or unacceptable toxicity on the physicians' choice regimen.