Towards a vaccine against bronchiolitis

La bronchiolite est due au très contagieux « virus respiratoire syncytial » (VRS), qui crée chaque année une épidémie hivernale. Chez les plus de 65 ans, sa mortalité est en ligne avec celle de la grippe, et le VRS est la deuxième cause de mortalité infantile. Il touche 90 % des bébés avant leurs 24 mois.

Posted Sep 7, 2022, 7:15 AMUpdated on Sep 7, 2022 at 7:29 am

A vaccine against bronchiolitis, this respiratory virus common in babies and the elderly, is an old dream that is coming true. Vaccine candidates from several major pharmaceutical companies are launched in the last sprint. The first to touch the finish line could well be French, because at this stage, the injectable product of Sanofi is the most advanced.

According to our information, its evaluation by Europe could take place very quickly, possibly as early as September. If it gives a favorable opinion, the marketing authorization of such a product would be a major medical advance, because the needs are massive.

90% of babies affected

Bronchiolitis is caused by the very contagious “respiratory syncytial virus” (RSV), which creates an annual winter epidemic and pulmonary complications (pneumonia, etc.) in very young or fragile people. Thus, among those over 65, its mortality is in line with that of the flu, recalled in August the scientific journal “The Lancet”. RSV also affects 90% of babies within the first two years of life and is the second leading cause of infant death.

For premature babies, with an immature pulmonary system, there is indeed a monoclonal antibody (Synagis, from AstraZeneca), but it is very expensive and requires five injections during the epidemic season with very limited effectiveness.

33 candidates

Only a more effective, simpler treatment (for example an injection protecting the entire viral season) and less expensive would allow general vaccination. In the past, laboratories had tried to develop such a vaccine. But research came to a halt in the 1960s when babies died in clinical trials.

For ten years, scientific advances have relaunched developments. Today, research abounds. “The Lancet” lists 33 vaccine candidates in various stages of clinical development around the world, including 9 in phase three tests. Called “vaccines” for simplicity, they do not all cause the body to produce antibodies that fight the virus (this is the definition of a vaccine). Some are injections of “monoclonal antibodies”, that is to say antibodies directly, the body does not manufacture them itself. Which makes sense for babies, because their immune system is not yet capable of it.

Test on 2,300 babies

To develop a vaccine, it remains to choose its target, between babies and the elderly. For Sanofi, it’s babies. In 2017, it joined forces with AstraZeneca, which is developing and manufacturing it in the United States. The French will market it, the two sharing equally costs and profits, in the event of success. Their product, Nirsevimab, is an ambitious monoclonal antibody: a single injection to protect throughout the viral season during the first year of life in healthy infants, premature or full term.

Tested on 2,350 infants, Nirsevimab shows an efficacy of 79.5% against infections requiring medical treatment, compared to a placebo. What unclog hospitals in winter and reduce the consumption of antibiotics, if its cost makes possible a general vaccination. It is ambition.

In 2017, worldwide, for babies, “medical expenses directly related to RSV – including hospitalizations, outpatient consultations and follow-up care – were estimated at 4.82 billion euros”, recalled Sanofi in 2020 to investors. The application for marketing authorization for this potential blockbuster is scheduled for the second half of the year in the United States and has already been made in Europe. Hence the hope of an opinion given in mid-September.

Of the world behind

Sanofi, if successful, will not be alone for long. It jostles on his heels. Another giant is also targeting the infant niche with a monoclonal antibody: the American Merck MSD. But its phase three clinical trials only recently started. A possible marketing in case of success will not be before 2023 at best.

What about seniors? Infant products cannot work for them. A monoclonal antibody delivers the amount of antibody needed to neutralize the virus, it depends on the weight of the patient. For an adult, it would take such a quantity that an injection would be impossible (it would take an infusion!) and the cost unthinkable.

Reserved for adults

But others are targeting this market of seniors and immunocompromised people, where analysts estimate potential sales at at least ten billion dollars a year. Again, it’s coming soon. In June, Britain’s GSK announced successful phase 3 testing of its vaccine candidate, followed by US rival Pfizer on August 25. The latter shows a protection of 66.7% of over sixty years against an RSV infection manifested by two symptoms (86% for three symptoms).

Both submit their dossier this semester to the regulatory authorities for marketing. And the next generation advance. American biotech Moderna has a messenger RNA vaccine candidate in phase 3 testing and dreams of combining it with the one it is developing against influenza and its existing Covid vaccine, Spikevax, for a 3-in-1 respiratory vaccine. eighteen months here.

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