Icosavax raises $100M to take RSV, COVID-19 vaccines into clinic

Icosavax has raised $100 million to study viruslike particle (VLP) vaccines against diseases including respiratory syncytial virus (RSV) and COVID-19. The series B round equips Icosavax to take two assets into clinical trials this year.

Seattle-based Icosavax is built on a computationally designed VLP technology. Using the platform, the biotech is working to overcome the at-scale manufacturing challenges that have held back VLP vaccines so far. The platform supports the design of proteins that self-assemble into VLPs, potentially resulting in vaccines that provide strong, durable protection without causing safety issues.

RA Capital Management has stepped up to back Icosavax’s ambitions, leading a $100 million round that also attracted the support of investors including Janus Henderson Investors, Perceptive Advisors and Sanofi Ventures.

Icosavax will use the money to move a vaccine against RSV into the clinic this year. The candidate builds on work by the National Institutes of Health (NIH) on RSV candidate DS-Cav1. Icosavax licensed DS-Cav1, which the NIH put through phase 1, and incorporated it into its VLP vaccine IVX-121.

Preclinical work suggests IVX-121 induces higher and more durable antibody responses than DS-Cav1 alone. Icosavax expects to enter the clinic this year. The first-in-human assessment of VLP display of DS-Cav1 will inform the transition to a bivalent vaccine that protects against RSV and human metapneumovirus (hMPV), another viral cause of pneumonia with a similar seasonal epidemiology to RSV. 

The RSV-hMPV vaccine will demonstrate whether the multivalent antigen display capabilities of Icosavax’s VLPs result in vaccines that protect against multiple pathogens. If successful, Icosavax could protect elderly people from the life-threatening viruses.

Icosavax will use another piece of the funding to take a COVID-19 vaccine into human testing. The VLP vaccine displays the SARS-CoV-2 Spike protein receptor binding domain to stimulate immune responses against the coronavirus. When paired with an adjuvant, the candidate provided durable protection in nonhuman primates, encouraging Icosavax to plan to move into the clinic this year. 

The timeline puts Icosavax well behind the leaders in the COVID-19 vaccine space. Icosavax is yet to commit to a strategy for the candidate beyond the phase 1, explaining that data from the clinical trial will “inform potential development paths in the rapidly evolving COVID vaccine landscape.”