High response rates for T-VEC in early metastatic melanoma (stage IIIB/C-IVM1a)

Talimogene laherparepvec (T-VEC) is a modified herpes simplex virus, type 1 (HSV-1), which can be administered intralesionally in patients with stage IIIB/C-IVM1a unresectable melanoma (EMA label). The phase 3 OPTiM registration study showed an overall response rate (ORR) of 26%. Since December 2016, 48 eligible patients started treatment at the Netherlands Cancer Institute. We included 26 patients in this study with a follow up time ≥6 months, reporting Overall Response Rate (ORR), Disease Control Rate (DCR), Adverse Events (AE), prior treatment for melanoma and baseline characteristics, documented in a prospectively maintained database. In house developed treatment protocol consists of clinical evaluation, periodic PET-CT and histological biopsies for response evaluation. Median follow-up was 12.5 months. Of 26 patients, 16 (61.5%) had a Complete Response (CR) as their best response. Seven (26.9%) patients had a Partial Response (PR) as their best response, 1 (3.8%) patient Stable Disease (SD) and 2 (7.7%) patients Progressive Disease (PD). Best ORR was 88.5%. DCR was 92.3%. Grade 1-2 AEs occurred in all patients. Mostly, these consisted of fatigue, influenza-like symptoms and injection site erythema. All patients underwent prior treatment. Prior treatment did not influence response or toxicity of T-VEC. Best ORR for T-VEC monotherapy at our institute was 88.5% with 61.5% achieving a CR. This prospective study for T-VEC in early metastatic (stage IIIB/C-IVM1a) melanoma demonstrated superior results to the phase 3 OPTiM study and confirms the role of oncolytic immunotherapy for melanoma.