Moderna's experimental mpox vaccine reduces severity of disease, early study finds

By Eleanor Laise

Messenger RNA technology may help improve on currently available mpox vaccines, researchers say

Amid mounting concerns about the spread of mpox, an experimental vaccine from Moderna Inc. may be poised to offer additional protection beyond currently available vaccines, research published Wednesday shows.

Moderna's investigational shot mRNA-1769 more effectively limited mpox symptoms and disease duration in primates, compared with a modified vaccinia Ankara (MVA) injection-a type of vaccine that is currently used to combat mpox, according to the new study published in the journal Cell. The study, led by researchers at Moderna and the U.S. Army Medical Research Institute of Infectious Diseases, involved groups of macaques who were given the mRNA vaccine, the MVA vaccine, or no vaccine at all and then exposed to a lethal strain of mpox.

The animals vaccinated with the mRNA vaccine lost less weight, had fewer lesions, and had a shorter disease duration than those who received the MVA vaccine, the researchers found. All of the vaccinated animals survived the mpox infection, according to the study, while five of the six unvaccinated animals died of the disease. Compared with the MVA vaccine, the mRNA vaccine also resulted in lower viral loads in the blood and throat swabs, the researchers found, suggesting that it might more effectively reduce transmission.

The MVA vaccine contains a weakened version of a whole virus, whereas mRNA technology allows for a more selective approach. "With the mRNA vaccine, we're able to pick pieces of the virus that can give the most potent and most effective immune response," Galit Alter, a virologist and immunologist at Moderna and senior author of the study, said in a statement. "By doing that instead of being distracted by an entire virus, you're able to narrow down on the pieces of the virus that give you protection."

Mpox, an infectious disease that can cause fever, a painful rash, muscle aches and other symptoms, is sparking public health concerns globally as cases surge in parts of Africa. The World Health Organization last month declared the mpox outbreak a public health emergency of international concern, with potential to spread further across Africa and beyond. The rapid spread of a new mpox strain, clade 1b, is particularly concerning, the WHO said.

Bavarian Nordic's MVA vaccine, Jynneos, is already approved for the prevention of mpox and has been the main vaccine used in the U.S. during a clade 2 mpox outbreak that started in 2022, according to the Centers for Disease Control and Prevention. The vaccine maker's American depositary receipts (BVNRY) surged last month as the company said it would ramp up manufacturing to ensure ongoing equitable access to the mpox vaccine.

Shares of Emergent BioSolutions Inc. (EBS) also got an mpox boost last week after the Food and Drug Administration approved an expansion of the label for its ACAM2000 vaccine, which was originally approved for prevention of smallpox, to include prevention of mpox in people at high risk for infection. That vaccine, however, has more known side effects and limitations on its use, according to the CDC.

The new research on Moderna's vaccine opens the door to improving on those immunization options. "With the mRNA technology, we're able to produce a vaccine that gives quite potent responses with a very tolerable safety profile," Jay Hooper, a virologist at the U.S. Army's infectious-disease institute and senior author of the study, said in a statement. "We've been trying to get a vaccine that will prevent spread like ACAM2000 but without the safety issues. This is showing that mRNA technology might be able to fill that niche."

Moderna is studying mRNA-1769 in an early-stage clinical trial that has enrolled about 350 participants across several sites in the United Kingdom. That trial is expected to be completed next year, the company said in a statement.

BioNTech (BNTX) also said late last year that it was launching an early-stage trial of an experimental mRNA-based mpox vaccine, BNT166.

Moderna's stock (MRNA) has dropped 27% in the year to date, while the S&P 500 SPX is up 16.3%.

-Eleanor Laise

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09-04-24 1100ET

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