Moderna guides 2 mRNA assets through early clinical tests

Moderna manufacturing site
Moderna is already planning a pivotal phase 3 trial of the cytomegalovirus vaccine candidate. (Moderna)

Moderna has shared data from two phase 1 trials of mRNA candidates, providing early evidence that its mission to equip the body to make its own drugs could succeed. The trials tested cytomegalovirus (CMV) vaccine mRNA-1647 and chikungunya virus candidate mRNA-1944.

CMV represents the bigger opportunity for Moderna. The CMV candidate vaccine features six mRNAs that encode for two antigens found on the surface of the virus. By instructing a patient’s own cells to make the antigens in vivo, Moderna thinks the vaccine candidate can equip the immune system to take out the virus, thereby preventing the thousands of annual birth defects linked to infections. 

To test that idea, Moderna randomized 169 healthy adult volunteers to receive either placebo or one of four doses of mRNA-1647. Subjects who received mRNA-1647 experienced dose-dependent increases in levels of neutralizing antibodies, suggesting the candidate works as hoped.

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Moderna saw one grade 4 adverse event—elevated partial thromboplastin time—and a clutch of lesser safety and tolerability signals. None of the serious adverse events were classed as related to the vaccine, leading Moderna to conclude that the candidate can advance.

The next step is to run a dose-confirmation phase 2. In parallel, Moderna is already planning a pivotal phase 3 trial of the vaccine candidate, putting mRNA-1647 at the forefront of its efforts to bring a product to market.

Moderna published details of the CMV study alongside results from a phase 1 trial of its chikungunya candidate. The chikungunya program, which is supported by the Defense Advanced Research Projects Agency, is targeting a small commercial opportunity but could serve as a valuable proof of concept for a key part of Moderna’s pipeline.

The chikungunya candidate encodes for an antibody against the virus. Candidates that work along similar lines are central to Moderna’s long-term plans, but the biotech had never previously shown it could cause the human body to produce secreted proteins. The chikungunya data change that.

Participants in the small trial experienced dose-dependent increases in the antibody, providing an early clinical sign that Moderna’s technology can trigger production of secreted proteins. Moderna thinks subjects produced therapeutic levels of the antibody.

The trial also picked up some safety signals. Notably, one of the four subjects to receive the highest dose of mRNA-1944 suffered a grade 3 elevated heart rate that resolved spontaneously. Moderna only treated four subjects with the high dose. All other arms of the trial featured six subjects. 

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