AZ agrees $1.1bn deal to buy RSV jab developer Icosavax

Not content with taking on the respiratory syncytial virus (RSV) prevention market with its antibody-based therapy Beyfortus, AstraZeneca has agreed to buy US biotech Icosavax and its phase 3-ready vaccine candidate.

The $15-per-share deal is a 43% premium to Icosavax’s closing share price yesterday and values the company at around $1.1 billion, of which $800 million is payable near-term, with the remainder tied to certain future achievements. It is due to close in the first quarter of 2024, subject to financial regulatory reviews.

Icosavax’s pipeline of respiratory disease vaccines is headed by IVX-A12, a virus-like particle (VLP) shot that targets both RSV and human metapneumovirus (hMPV), two major causes of serious respiratory tract infections, particularly in older people.

There are currently no approved vaccines targeting hMPV, so, AZ is hoping to fill that need with the combination jab whilst also leapfrogging GSK and Pfizer, which earlier this year brought the first RSV vaccines for the over-60s age group to market. Icosavax’s shot already has a fast-track designation from the FDA.

AZ said in a statement on the deal this morning that IVX-A12 is furthest along in development among vaccines targeting RSV and hMPV and also offers a “differentiated profile” compared to GSK’s Arexvy and Pfizer’s Abrysvo, which have been predicted to drive a global market that could eventually be worth between $5 billion and $10 billion a year.

Recently reported phase 2 data with the candidates showed strong antibody responses against both viruses one month after immunisation, and layering in protection against hMPV could be a key differentiator for IVX-A12.

RSV is known to be a massive problem, causing around 177,000 hospitalisations in the over-60s in the US each year and approximately 29,000 deaths. Numbers for hMPV are hard to gauge because testing is rare, but it has been estimated to affect millions of people in the US every year.

Most cases are mild, but in the very young, older adults, and people with underlying health conditions – just like RSV – it is known to cause more severe disease requiring hospitalisation.

One meta-analysis of other studies published earlier this year estimated a 10% mortality rate among older adult patients admitted to hospital, which would put it in roughly the same ballpark as both RSV and influenza.

AZ has a strong heritage in the RSV category with Sanofi-partnered preventive antibody Beyfortus (nirsevimab) for the prevention of RSV in newborns and infants, which was approved in Europe in 2022 and in the US earlier this year, as well as its forerunner Synagis (palivizumab), which is now sold by Sobi. It competes with Abrysvo, which is approved as a maternal vaccine.

That makes AZ a strong partner for the IVX-A12, according to Icosavax's chief executive, Adam Simpson, who said AZ’s involvement “offers the opportunity to accelerate, and expand access to, our potential first-in-class combination vaccine.”

AZ said the VLP technology used in the vaccine could lead to “a stronger immune response, greater breadth of protection, greater durability requiring fewer boosters and, compared to the current adjuvanted RSV vaccine, a lower incidence of side effects.”