Tebentafusp-tebn With LDT in Metastatic UM

PART 1: TEBENTAFUSP AND IE Part 1A, Phase I/II: This is a single-arm study of 18 patients treated with combination therapy (tebentafusp-tebn with hepatic IE with GM-CSF), with the first cohort of six patients being enrolled in a safety lead in. The SKCC DSMC will monitor and approve the cohort expansion. The preliminary clinical efficacy endpoint is defined as a target 6-month liver-specific PFS rate of 60%. All patients will receive a 4-week induction course of tebentafusp-tebn alone (Cycle 1) using the approved step-up dosing regimen. Should the 4th dose be tolerated well as an outpatient, patients will receive their first IE treatment on Cycle 2 week 1 followed by continued weekly tebentafusp-tebn on weeks 2, 3, and 4 of Cycle 2. Patients will not receive tebentafusp-tebn concurrently with their first IE treatment during Week 1 of Cycle 2. Should Cycle 2 be well tolerated, patients may receive both tebentafusp-tebn and IE on Week 1 of subsequent cycles, with tebentafusp administered alone on weeks 2-4 of subsequent cycles. Patients may skip 1 week of tebentafusp in order to travel to TJU for IE without this being a protocol deviation. Part 1B, Phase II: If the safety and preliminary efficacy in Part 1A are met, the study will then proceed with a randomized phase II trial. 52 patients will be randomized in a 2:1 ratio to receive tebentafusp-tebn in combination with hepatic IE or tebentafusp-tebn alone, with PFS as the primary endpoint. Secondary endpoints will include ORR, duration of response, systemic PFS, and OS. Patients randomized to tebentafusp-tebn + IE arm will be treated as above (See Figure 1). Patients randomized to tebentafusp-tebn alone will receive weekly treatment using the approved step-up dosing regimen. Tumor biopsies will be optional for all patients on this portion of the study; however, peripheral blood and ctDNA will be collected as above. PART 2: TEBENTAFUSP AND TACE The trial will conduct a single-arm, two-stage phase II trial of sequential TACE with BCNU followed by tebentafusp-tebn in 39 patients with higher liver tumor burden (greatest tumor size \>5 cm and/or ≥50% liver involvement on imaging). Patients with unilobar disease will first receive at least two treatments of TACE with 300mg BCNU; patients with bilobar disease will receive at least 4 treatments. Following completion of the TACE course, patients will receive tebentafusp-tebn on a weekly basis at the standard-care step-up dosing regimen. Patients will undergo imaging studies at baseline, after completion of every two TACE treatments, and every 8 weeks thereafter while on tebentafusp-tebn alone. Tumor biopsies will be performed at baseline, following TACE, and after 4 weeks of treatment with tebentafusp-tebn. Peripheral blood will be collected for serum cytokine and PBMC analysis after completion of each TACE treatment and every 4 weeks thereafter. ctDNA will be collected at the time of each interval scan. Correlative studies will be performed as above in Part 1. Following the initial TACE treatments and subsequent tebentafusp induction, patients may receive additional TACE treatments at the discretion of the investigator. These will only be offered once a patient is through tebentafusp induction and has transitioned outpatient. Patients who proceed with additional TACE will hold tebentafusp the week of treatment and be followed with weekly labs to ensure return to baseline before proceeding with next scheduled tebentafusp at the discretion of the investigator. Participants will continue treatment until confirmed disease progression, or for as long as the patient is deriving clinical benefit in the opinion of the treating investigator with approval of the study PI. The treating investigator may provide rationale and request approval for treatment beyond progression via email to the Study PI.