Real-world outcomes with T-VEC in patients with anti-PD-1 resistant in-transit disease from melanoma and Merkel cell carcinoma

<h2>Abstract</h2><h3>Background and Objectives</h3> Talimogene laherparepvec (T-VEC) is an intralesional cancer immunotherapy in patients with unresectable stage IIIB-IV melanoma and Merkel cell carcinoma (MCC). This study assesses T-VEC outcomes in patients with in-transit melanoma and MCC refractory to anti-PD-1 blockade. <h3>Methods</h3> All patients with advanced melanoma or MCC with ≥ 1 measurable lesion(s) were retrospectively evaluated from 2019 to 2023. Only those who received ICI therapy for ≥ 3 months with progression of regional metastasis prior to receiving T-VEC were included. Clinicopathologic and treatment data were reviewed. <h3>Results</h3> Seventeen patients underwent T-VEC therapy, consisting of thirteen melanoma and four MCC cases. Median age was 75.9 and 79.6 for melanoma and MCC cases respectively. Eleven melanoma (84 %) and three MCC (75 %) cases received extremity injections. Median number of in-transit metastatic sites for melanoma and MCC were 4 and 10; respectively, and the median number of treatment cycles per patient was five in both groups. Ten total patients responded with 8 complete responses and 2 partial responses, while five (4 melanoma; 1 MCC) had disease progression. Of seventeen patients, two discontinued T-VEC due to grade 3 + adverse events. <h3>Conclusion</h3> T-VEC following or in conjunction with immunotherapy exhibits tolerability and potential benefit in patients with advanced MCC and melanoma.