In August 2024, the World Health Organization (WHO) declared mpox a public health emergency of international concern (PHEIC), two years after the agency previously declared an emergency for an outbreak of the virus with the epicentre in Europe.
The organisation has called on companies and governments to rally together to help countries in Africa by providing vaccines where possible, however, due to there being just one approved vaccine available, there is an urgent need for more development.
Clinical research on mpox has been relatively neglected. As a result, there are several unmet needs in the treatment space.
A recent trial of antiviral medication tecovirimat showed it was not better than placebo other than in subgroups, meaning there remains a significant unmet need for treatment. As a result, it is more important than ever to work in the prevention space to try and avoid any further outbreaks where possible. These vaccines must be made accessible and available to populations most at risk, many of whom come from deprived countries which do not have the infrastructure available.
There are several ongoing vaccine trials for mpox, including mRNA candidates and investigations into possible vaccines for the paediatric population.
Two pipeline mRNA vaccines in clinical trials
Two mRNA vaccines are coming to the end of Phase I/II trials that will help shape the trial design for pivotal studies.
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By GlobalDataModerna is trialling its mRNA mpox vaccine in a Phase I/II trial (NCT05995275) assessing the safety, tolerability, and immunogenicity of mRNA-1769 in healthy adults. mRNA-1769 is an mRNA vaccine being trialled for the prevention of mpox and smallpox. The trial is taking place at sites across the UK and Moderna said the data will help to shape a pivotal trial of the vaccine. The trial is due to conclude in June 2025.
Moderna is known for mRNA therapeutics and is the leading player in the mRNA vaccines space.
Anaelle Tannen, infectious disease analyst at GlobalData said that Moderna’s trial design should show the real benefits of the vaccine candidate, acknowledging that the sponsor’s knowledge of these kinds of drugs will have helped while they were designing the study.
“The use of mRNA technology will likely become more widespread, with trials occurring across various other disease indications. Whilst interim results are yet to be published, the design of the trial, as an RCT is good. Furthermore, the trial is occurring over 22 months and involves 351 participants across 12 sites which increases the power and validity of the study,” says Tannen.
Dr David Schwartz, a medical epidemiologist and board-certified pathologist in infectious disease pathology, including in pregnancy, says he has high hopes for Moderna’s candidate following preclinical data announced earlier this month.
“Moderna’s mRNA proved to be a very effective product in the preclinical study. All subjects in the investigative arm survived compared to non-immunised controls and these subjects also had fewer mpox lesions. We’ve already learned about mRNA vaccines during the Covid-19 pandemic and they’re incredibly safe. They may not be very long-lasting in terms of their protective effects, but they’re incredibly safe overall,” says Schwartz.
BioNTech SE is also trialling an mRNA vaccine candidate, BNT-166A. The Phase I/II trial (NCT05988203) aims to evaluate the safety, tolerability, reactogenicity and immunogenicity of BNT166a for active immunisation against mpox in adults aged between 18 and 65. Sites included are in the US and UK and the study is due to complete in May 2025.
“BioNTech also has experience with mRNA technology and has marketed several Covid-19 mRNA vaccines. The trial is taking place over a shorter period, only 12 months, compared to Moderna’s drug candidate, and includes only 64 participants across nine sites. While this study design is sufficient, the Moderna trial is definitely stronger,” Tannen adds.
Dr Itzchak Levy, director of the HIV/AIDS centre and expert in infectious diseases at Israel’s Sheba Hospital, said that he has high hopes for both mRNA candidates.
“Of course, the first great success was in Covid-19 so I think that it’s so obvious that it will also be quite effective in mpox. Unfortunately, because it has historically been a virus only prevalent in Africa, not many people have investigated it much until about two years ago. I think that it’s important to develop more vaccines and I believe these will be mRNA.”
Bavarian Nordic’s Jynneos being investigated in paediatric patients
Bavarian Nordic’s Jynneos vaccine is now being investigated in paediatric patients in the Democratic Republic of Congo.
Jynneos is a traditional live attenuated vaccine and is already approved for the prevention of mpox and smallpox in adults aged 18 years and older who are at an increased risk of infection.
The Phase II trial (NCT06549530) will include 460 patients and is evaluating the immunogenicity and safety of the Jynneos in children from two years to less than 12 years of age compared to adults aged 18-50 years of age for the prevention of smallpox, mpox and related orthopoxvirus infections. The trial is due to be completed in June 2025.
Both Tannen and Schwartz are optimistic about the trial, mostly because it is targeting key populations who are currently more at risk of contracting the virus, which neither Moderna’s or BioNTech’s candidates are yet targeting.
“What we’ve seen with a mpox during this particular outbreak is that it tends to be infecting younger people and so children are especially at risk. I think that study will therefore provide valuable information, and we also need studies on pregnant women,” says Schwartz.
“The trial is planned to occur over seven months in the Democratic Republic of Congo, where the current outbreak is. There is a great need for more vaccines as well as vaccines that are effective across all age groups as the outbreak continues to grow,” says Tannen.
Levy is happy to see a trial involving paediatric patients but has some concerns about this vaccine.
“Current vaccines are still using the active virus which can trigger adverse events, especially in patient populations who are immunocompromised. This will not be as prevalent with mRNA because it is proteins rather than the active virus,” adds Levy.
