First-in-human phase I/II, open-label study of mRNA-2416 alone or combined with durvalumab in patients with advanced solid tumors and ovarian cancer.

Background: mRNA-2416 is a novel lipid nanoparticle-encapsulated messenger RNA (mRNA) encoding human OX40 ligand (OX40L) for intratumoral (Itu) injection. OX40L plus immune checkpoint inhibitor (ICI) increased preclinical antitumor activity, thus mRNA-2416 plus ICI may potentiate antitumor activity.

Methods: This first-in-human, phase I/II, open-label, multicenter study examined the safety, tolerability, and efficacy of mRNA-2416 alone (arm A) or with durvalumab (arm B) in patients with advanced solid tumors or lymphoma (NCT03323398). Phase I primary objectives included assessment of safety/tolerability and maximum tolerated dose (MTD)/recommended dose for expansion; phase II arm B dose expansion assessed objective response rate in ovarian cancers. Secondary objectives included pharmacokinetics, disease control rate, duration of response, and progression-free survival (PFS). Assessments of immunologic response to treatment were exploratory.

Results: From August 2017 to August 2021, 79 patients were enrolled; 61 received treatment (arm A: 39, arm B: 22), including 16 in the expansion cohort. MTD was not reached. Treatment-related emergent adverse events were primarily grade 1/2, with 8 grade 3 and no grade 4/5 events. On-treatment tumor biopsies demonstrated increased OX40L protein expression, elevated PD-L1, and proinflammatory responses. Tumor shrinkage occurred in injected and surrounding non-injected tumors. Median (95% CI) PFS was 60.0 (50.0 to 108.0) and 50.0 (38.0 to 55.0) days for arms A and B, respectively.

Conclusions: mRNA-2416 alone or with durvalumab was well tolerated. Pharmacodynamic analyses support Itu mRNA proof-of-concept. Predefined primary efficacy endpoints were not met in an exploratory cohort of ovarian cancer. Additional research is warranted to further inform this therapeutic approach.