Lipid Nanoparticle-encapsulated mRNA-2752 Encoding Human OX40L, IL-23, and IL-36γ Plus Durvalumab Induces an Immunostimulatory Effect Within the Tumor Microenvironment in Patients with Advanced Solid Tumors

PURPOSE: mRNA-2752, a lipid nanoparticle (LNP)‒encapsulated, mRNA-based therapeutic encoding OX40L, IL-36γ, and IL-23, has demonstrated modulation of the tumor microenvironment (TME) and antitumor efficacy in combination with immune checkpoint inhibitors (CPI) in CPI-resistant models. PATIENTS AND METHODS: In this phase 1 study (NCT03739931) of intratumoral mRNA-2752 monotherapy (Arm A) or mRNA-2752 plus durvalumab (Arm B) in advanced solid tumors, the primary objectives were safety, tolerability, determination of maximum tolerated dose (MTD), and objective response rate (ORR) per RECIST v1.1 in CPI‒resistant melanoma (Arm B only). RESULTS: Among 134 patients (Arm A, n=19; Arm B, n=115), the MTD was not reached; a recommended dose for expansion of ≤8 mg was selected. Dose-limiting toxicities included two grade 2 cytokine-release syndrome events in Arm B. Treatment-related adverse events were mostly grade 1/2; grade 3 mRNA-2752-related adverse events occurred in 1 patient (5.3%) in Arm A and 29 patients (25.2%) in Arm B. In the CPI-resistant melanoma cohort (n=28), across doses, the confirmed ORR was 17.9% (95% CI, 6.1%‒36.9%) and disease control rate was 42.9% (95% CI, 24.5%‒62.8%). Increased peripheral cytokine levels and sustained inflammatory responses in the TME were observed, particularly in patients with an objective response. CONCLUSIONS: mRNA-2752 monotherapy or in combination with durvalumab demonstrated antitumor activity with manageable safety in patients with heavily pretreated, relapsed, or resistant solid tumors, particularly in patients with CPI-resistant melanoma. In addition, biomarker analyses demonstrated a sustained inflammatory response within the TME. Together, these findings support investigation of mRNA-based therapeutics for patients with advanced cancer.