Open-Label, Phase II Study of Talimogene Laherparepvec Plus Pembrolizumab for the Treatment of Advanced Melanoma That Progressed on Prior Anti–PD-1 Therapy: MASTERKEY-115,

Background Treatment options for immunotherapy-refractory melanoma are an unmet need. MASTERKEY-115 phase II, open-label, multicenter trial evaluated talimogene laherparepvec (T-VEC) plus pembrolizumab in advanced melanoma that progressed on prior programmed cell death protein-1 (PD-1) inhibitors. Methods Cohorts 1 and 2 comprised patients (unresectable/metastatic melanoma) who had primary or acquired resistance, respectively, and disease progression within 12 weeks of their last anti–PD-1 dose. Cohorts 3 and 4 comprised patients (resectable disease) who underwent complete surgery, received adjuvant anti–PD-1, and experienced recurrence. Cohort 3 were disease-free for < 6 months and Cohort 4 for ≥ 6 months after starting the adjuvant anti–PD-1 therapy and before confirmed recurrence. The primary endpoint was objective response rate (ORR) per RECIST v1.1. Secondary endpoints included complete response rate (CRR), disease control rate (DCR) and progression-free survival (PFS) per RECIST v1.1 and irRC-RECIST, and safety. Results Of 72 enrolled patients, 71 were treated. The ORR (95% CI) was 0%, 6.7% (0.2–32.0), 40.0% (16.3–67.7), and 46.7% (21.3–73.4) in cohorts 1–4, respectively; iORR was 3.8% (0.1–19.6), 6.7% (0.2–32.0), 53.3% (26.6–78.7), and 46.7% (21.3–73.4). iCRR was 0%, 0%, 13.3%, and 13.3%. Median iPFS (months) was 5.5, 8.2, not estimable [NE], and NE for cohorts 1–4, respectively; iDCR was 50.0%, 40.0%, 73.3%, and 86.7%. Treatment-related adverse events (TRAEs), grade ≥ 3 TRAEs, serious, and fatal AEs occurred in 54 (76.1%), 9 (12.7%), 24 (33.8%), and 10 (14.1%) patients, respectively. Conclusion T-VEC-pembrolizumab demonstrated antitumor activity and tolerability in PD-1-refractory melanoma, specifically in patients with disease recurrence on or after adjuvant anti–PD-1. Trial registration ClinicalTrials.gov identifier - NCT04068181