Efficacy analysis of MASTERKEY-265 phase 1b study of talimogene laherparepvec (T-VEC) and pembrolizumab (pembro) for unresectable stage IIIB-IV melanoma.

9568Background: T-VEC is a herpes simplex virus (HSV)-1 -based oncolytic immunotherapy designed to selectively replicate in tumors, produce GM-CSF and stimulate antitumor immune responses in melanoma. T-VEC significantly improved durable response rate vs GM-CSF in stage IIIB-IV melanoma patients (pts) with injectable tumors. Pembro inhibits programmed cell death protein 1 and improves survival in advanced melanoma. The combination may further improve clinical benefit. Here we report phase 1b efficacy, safety and biomarker data from a phase 1b/3 study of T-VEC+pembro in unresectable stage IIIB-IV melanoma (NCT02263508) with all pts having started on T-VEC+pembro ≥ 6 mo prior. Methods: Key inclusion criteria: unresectable stage IIIB-IV melanoma, injectable lesions; no prior systemic tx; and ECOG PS 0-1. T-VEC: ≤ 4 mL in (sub)cutaneous/nodal lesions, 106 PFU/mL d1, 108PFU/mL d22 then Q2W; pembro: IV, 200 mg d36 then Q2W. Tx until first occurrence of: complete response (CR); no injectable tumors (for T-VEC); ...