AstraZeneca Strengthens Respiratory Illness Pipeline With Acquisition of Icosavax

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The deal includes Icosavax’s lead investigational candidate, IVX-A12, a potential first-in-class vaccine being developed for both respiratory syncytial virus and human metapneumovirus.

AstraZeneca has announced an agreement to acquire Icosavax, Inc, in a deal that could reach $1.1 billion. The acquisition of Icosavax, a clinical-stage biopharmaceutical company focused on vaccine development, is expected to bolster AstraZeneca’s Vaccines & Immune Therapies late-stage pipeline with Icosavax’s protein virus-like particle (VLP) platform.1

Icosavax’s lead investigational candidate, IVX-A12, is a potential first-in-class, Phase III-ready, combination protein VLP vaccine being developed for both respiratory syncytial virus (RSV) and human metapneumovirus (hMPV).

“This virus-like particle vaccine technology has the potential to transform prevention against severe infectious diseases, including RSV and hMPV,” Iskra Reic, executive vice president, Vaccines & Immune Therapies, AstraZeneca, said in a press release. “With the addition of Icosavax’s Phase III-ready lead asset to our late-stage pipeline, we will have a differentiated, advanced investigational vaccine, and a platform for further development of combination vaccines against respiratory viruses. This aligns with our strategy to deliver a portfolio of therapies to address high unmet needs in infectious diseases, and our ambition to protect the most vulnerable patients who have high risk of severe outcomes.”1

Under the terms of the deal, AstraZeneca will acquire all of Icosavax’s outstanding shares for $15 per share in cash at closing, as well as a non-tradable contingent value right for up to $5 per share in cash if specific milestones are achieved. AstraZeneca’s upfront payment represents a premium of approximately 43% of Icosavax’s closing market price on December 11, 2023. If all milestones are achieved, the upfront and maximum potential contingent value payments are approximately $1.1 billion.

The acquisition of the novel vaccine holds significance because there are currently no treatments or preventative therapies available for hMPV and no approved combination vaccines for RSV. IVX-A12 is the most advanced investigational vaccine targeting both RSV and hMPV and has a differentiated profile compared with RSV vaccines currently on the market, according to AstraZeneca. The liquid, refrigerator-stable formulation is comprised of IVX-121, an RSV prefusion F protein VLP vaccine candidate, and IVX-241, an hMPV prefusion F protein VLP vaccine candidate.

An ongoing, randomized, observer-blinded, placebo-controlled, multi-center Phase II trial is analyzing the safety and immunogenicity of a single dose of IVX-A12, with and without CSL Seqirus’ proprietary adjuvant MF59. Researchers enrolled 264 adults aged 60 to 85 years, of whom 241 were evaluable for immunogenicity.

Participants were administered a single dose of either IVX-A12 at the 300 µg combination dosage level (150 µg of RSV VLP (IVX-121) and 150 µg of hMPV VLP (IVX-241), with or without MF59, or placebo. The trial found that IVX-A12 produced robust immune responses against both RSV and hMPV at day 28 across both formulations with and without adjuvant.2 The FDA has awarded the novel vaccine with Fast Track Designation.

“We’re delighted to announce positive topline interim data from our Phase 2 trial of IVX-A12, our potential first-in-class combination vaccine candidate against RSV and hMPV,” Icosavax Chief Executive Officer Adam Simpson said in a press release.2 “We believe that IVX-A12 has the potential to address a significant unmet need and, as the furthest advanced RSV and hMPV combination vaccine in the clinic, to build on an emerging, large market opportunity.”

Icosavax’s pipeline also includes novel candidates as potential components for future combination and pan-respiratory vaccines, including influenza and SARS-CoV-2.1 AstraZeneca stated that the acquisition is expected to close in the first quarter of 2024.

“We are pleased to announce the proposed acquisition of Icosavax by AstraZeneca as we believe it offers the opportunity to accelerate, and expand access to, our potential first-in-class combination vaccine for older adults at risk of RSV and hMPV,” Simpson said in the release.1 “We look forward to combining our skills and expertise in advancing the development of IVX-A12 with AstraZeneca’s decades of experience in RSV, resources, and capabilities in late-stage development.”


1. AstraZeneca to acquire Icosavax, including potential first-in-class RSV and hMPV combination vaccine with positive Phase II data. AstraZeneca. News release. December 12, 2023. Accessed December 12, 2023.

2. Icosavax Announces Positive Topline Interim Phase 2 Results for Combination VLP Vaccine Candidate IVX-A12 Against RSV and hMPV in Older Adults. Icosavax. News release. December 12, 2023. Accessed December 12, 2023.

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