Moderna Inc. (MRNA  ) is developing mRNA-1769 as a mpox vaccine for use in adults.

Currently, a Phase 1/2 trial evaluating the safety, tolerability, and immunogenicity of mRNA-1769 in Healthy Participants is underway. The 351-subject trial was started in 2023, and data is anticipated in 2025.

In a paper released in Cell, Moderna's mRNA-1769 had been more effective than the Bavarian Nordic A/S (BVNRY  ) Jynneos vaccine in preventing severe disease and reducing virus levels in monkeys.

Jynneos is based on modified vaccinia Ankara (MVA).

MVA immunization reduced lesions in challenged non-human primates (NHPs), but most MVA-immunized animals were still classified as experiencing "grave" disease (over 250 lesions) based on WHO lesion number classification. By contrast, none of the mRNA-immunized animals reached the criteria for "severe" disease (over 100 lesions) during the infection period.

While MVA and mRNA-1769 conferred complete protection following lethal mpox infection challenge, mRNA-immunized animals experienced 10-fold fewer lesions, reduced disease duration, and substantial mitigation of circulating and mucosal viremia in the mRNA cohort.

The paper highlights that despite the effectiveness of the Jynneos vaccine against mpox, issues in supply, unfavorable reactogenicity, incomplete immunity, and uncertainty of cross-protection to more virulent strains provide critical motivation for the development of a potential new vaccine modality for improved vaccines to cover these gaps.

BioNTech SE (BNTX  ) is also developing an mRNA vaccine for mpox, BNT166a, which is also in Phase 1/2 study, with data readout expected in May 2025.

Price Action: MRNA stock is down 1.39% at $72.42 at the last check on Friday.