For patients with advanced melanoma who have exhausted standard immune checkpoint inhibitor options, the prospect of meaningful, durable remissions has historically been slim. A comprehensive review published in Cancer now maps the expanding clinical landscape of intratumoral therapies — a field that directly challenges the assumption that systemic treatment must always precede or dominate local intervention.
The review traces the evolution from talimogene laherparepvec (T-VEC), the first FDA-approved oncolytic viral therapy for a solid tumor, which established proof-of-concept by encoding granulocyte-macrophage colony-stimulating factor within a modified herpes simplex virus type 1. Clinical trials across more than a decade — spanning monotherapy and combination regimens with checkpoint inhibitors — have documented improved objective response rates and durable remissions even among patients whose tumors had already developed resistance to checkpoint blockade. Critically, next-generation agents now incorporate fusogenic proteins and additional immunostimulatory transgenes designed to amplify both local cytotoxicity and systemic immune priming, extending the reach of what was once a purely locoregional strategy. Emerging protocols include image-guided injection into visceral lesions, broadening eligibility well beyond superficial or accessible tumors.
This review arrives at a pivotal moment. The combination of intratumoral agents with anti-PD-1 or anti-CTLA-4 therapies appears to exploit a synergistic mechanism: local tumor destruction releases neoantigens that prime systemic T-cell responses, potentially converting immunologically 'cold' tumors into 'hot' ones. That mechanistic logic makes intratumoral therapy particularly compelling as a salvage strategy rather than merely an adjunct. Limitations worth noting include the heterogeneity across trials in patient selection, endpoints, and injection techniques, making cross-study comparisons difficult. Most data remain from single-arm or early-phase trials, and head-to-head comparisons with systemic salvage regimens are sparse. Still, for a disease where checkpoint-resistant progression carries a grim prognosis, the trajectory here — from a single approved agent to a diversified pipeline with evolving delivery technology — represents genuinely significant clinical progress, not incremental refinement.