Single-center phase 1 trial of intratumoral injection of mRNA-2752 and pembrolizumab for high-risk ductal carcinoma in situ

Intratumoral immunotherapy that leverages the biological characteristics of high-risk ductal carcinoma in situ (DCIS) may be able to reduce the extent of surgical treatment. A phase 1 nonrandomized trial at the University of California San Francisco evaluated intratumoral injection of pembrolizumab plus messenger RNA-2752 for high-risk DCIS. The treatment was associated with flulike symptoms and grade 1 or 2 local reactions with no serious systemic toxic effects, and resulted in an 80% overall response rate. All patients with HER2-positive of HR-negative DCIS experienced at least a partial response, with one-third experiencing complete resolution of the tumor, and high baseline immune cells were associated with response. The authors conclude that intratumoral immunotherapy for high-risk DCIS appeared safe and showed a promising efficacy signal.