Icosavax has initiated a Phase II clinical trial of IVX-A12, a bivalent vaccine candidate, for the treatment of older adults with respiratory syncytial virus (RSV) and human metapneumovirus (hMPV).

IVX-A12 consists of two virus-like particle (VLP) vaccine candidates including IVX-121 and IVX-241.

The multi-centre, placebo-controlled, observer-blinded, randomised study intends to enrol nearly 250 healthy older adults aged 60 years and above to assess the immunogenicity and safety of a single dose of IVX-A12 with and without CSL Seqirus’ adjuvant MF59.

A single dose of IVX-A12 includes 150µg of IVX-121 (RSV) and 150µg of IVX-241 (hMPV) that correspond to antigen content of 84µg RSV and 82µg hMPV, respectively.

Topline interim results from the trial are anticipated in the first quarter of next year.

Icosavax CEO Adam Simpson said: “The initiation of this Phase II trial for IVX-A12 marks another important milestone for Icosavax, as we advance this potential first-in-class combination vaccine candidate into mid-stage development.

“We are highly encouraged by the recent findings from the Phase I study of IVX-A12 and believe that it has the potential to address an unmet need as the first bivalent vaccine candidate against both RSV and hMPV, two of the leading causes of pneumonia in adults.”

Icosavax plans to explore the potential of IVX-121 protecting against hMPV infection in a nonclinical passive transfer model using the clinical samples from the Phase II study.

A Phase IIb proof-of-concept trial to assess the efficacy (hMPV human challenge) of IVX-121, along with the durability and longer-term safety of immune response, will also be initiated based on the selection of the formulation from the Phase II study.