NeoACTIVATE Arm C: Phase II trial of neoadjuvant atezolizumab and tiragolumab for high-risk operable Stage III melanoma

PURPOSE: Neoadjuvant ± adjuvant immunotherapy improves event-free survival (EFS) versus adjuvant immunotherapy alone for high-risk resectable Stage III melanoma. However, the optimal regimen balancing efficacy and tolerability is unknown. T-cell immunoglobulin and ITIM domain (TIGIT) is a promising immune checkpoint whose therapeutic potential in Stage III melanoma is underexplored. METHODS: In this phase II trial, patients with resectable, macroscopic Stage III melanoma received four 21-day neoadjuvant cycles of 1200 mg IV atezolizumab (anti-PD-L1) + 600 mg IV tiragolumab (anti-TIGIT), therapeutic lymph node dissection (TLND) and eight adjuvant cycles of atezolizumab. Primary endpoints were pathologic response and recurrence-free survival (RFS) after TLND in patients receiving adjuvant therapy; secondary and exploratory endpoints included adverse events (AEs), EFS and distant metastasis-free survival (DMFS). RESULTS: Thirty-four patients initiated neoadjuvant atezolizumab/tiragolumab and were evaluable for AEs, pathologic response and EFS. 76.5 % had > 1 metastatic lymph node at baseline and 73.5 % were Stage IIIC. Thirty patients had per protocol TLND. Major pathologic responses (MPR, ≤10 % viable tumor) were observed in 16/34 patients (47.1 %). With 19.9 months median follow-up, 12-month EFS was 72.0 % (95 %CI 57.9-89.5 %), 12-month RFS was 73.3 % (95 %CI 56.9-94.5 %), and 12-month DMFS 86.0 % (95 %CI 72.2-100 %). 12-month RFS and DMFS for patients with an MPR were both 91.7 % (95 %CI: 77.3-100 %). Grade 3 + AEs at least possibly neoadjuvant treatment-related occurred in 2 patients (5.9 %). CONCLUSION: Among patients with high-risk resectable Stage III melanoma, neoadjuvant atezolizumab/tiragolumab was a promising regimen with a favorable safety profile and warrants further study. A strategy to personalize neoadjuvant regimen selection is needed.