Icosavax Initiates Phase 1 Trial of IVX-A12 Against RSV & hMPV in Older Adults

Icosavax, Inc. recently announced the initiation of a Phase 1 clinical trial of IVX-A12, a combination bivalent RSV and hMPV VLP vaccine candidate, in older adults.

IVX-A12 is comprised of IVX-121, Icosavax’s RSV prefusion F protein VLP vaccine candidate, and IVX-241, Icosavax’s hMPV prefusion F protein VLP vaccine candidate. The company previously announced positive topline interim Phase 1/1b results for IVX-121 in June 2022.

With this trial initiation, IVX-A12 becomes the first combination bivalent vaccine candidate against both respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) to enter the clinic, and the first candidate from Icosavax’s novel VLP platform to receive IND authorization in the US.

“The initiation of a Phase 1 trial for IVX-A12 is an important step toward our vision for creating pan-respiratory vaccines, and I am pleased with the execution by our team. Not only is IVX-A12 Icosavax’s first combination bivalent VLP vaccine candidate, it is also the most advanced vaccine candidate against both RSV and hMPV in older adults, and the only clinical stage VLP in this space,” said Adam Simpson, Chief Executive Officer of Icosavax. “The inclusion of a proprietary prefusion hMPV-F component in a combination RSV/hMPV vaccine candidate is differentiating from the current RSV candidates in Phase 3 development, and is intended to address two leading causes of pneumonia in one shot. In older adults, RSV is estimated to cause approximately 177,000 hospitalizations and 14,000 deaths each year in the US alone, and data support similar morbidity and mortality for hMPV. As such, we look forward to sharing topline results from this first trial of a combined RSV and hMPV vaccine candidate in mid-2023, and thereafter plan to initiate a Phase 2 trial of IVX-A12 in 2H 2023.”

The Phase 1 clinical trial of IVX-A12 is a randomized, observer-blinded, placebo-controlled, multi-center study designed to evaluate the safety and immunogenicity of multiple dosage levels of IVX-A12, with and without CSL Seqirus’ proprietary adjuvant MF59.

The company anticipates enrolling up to 120 healthy older adults aged 60 to 75 years. Subjects will be administered a single shot of IVX-A12, at one of three combination dosage levels below, or placebo:

• 75 µg of IVX-121 and 75 µg of IVX-241, with or without MF59
• 75 µg of IVX-121 and 150 µg of IVX-241, with or without MF59
• 75 µg of IVX-121 and 225 µg of IVX-241, without MF59

The objective of the Phase 1 study of IVX-A12 is to evaluate safety, and immunogenicity against both RSV and hMPV, as well as to assess immunologic non-interference. Icosavax anticipates announcing topline interim results from this Phase 1 trial in mid-2023, with subjects thereafter followed through 12 months after vaccination. Contingent upon a positive outcome from this trial, the company then expects to initiate a Phase 2 trial for IVX-A12 in 2H 2023.

The IVX-121 (RSV) component of IVX-A12 (RSV/hMPV) demonstrated robust immunogenicity and favorable tolerability in a prior Phase 1/1b study, and a subset of these Phase 1b older adult subjects continue to be followed, with six-month immunogenicity data expected by early-2023 and 12-month immunogenicity data in mid-2023.

Icosavax is a biopharmaceutical company leveraging its innovative VLP platform technology to develop vaccines against infectious diseases, with an initial focus on life-threatening respiratory diseases and a vision for combination and pan-respiratory vaccines. Icosavax’s VLP platform technology is designed to enable multivalent, particle-based display of complex viral antigens, which it believes will induce broad, robust, and durable protection against the specific viruses targeted. Icosavax’s pipeline includes vaccine candidates targeting respiratory syncytial virus (RSV) and human metapneumovirus (hMPV), as well as programs in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza. Icosavax was formed in 2017 to advance the breakthrough VLP technology from the Institute for Protein Design at the University of Washington with the goal to discover, develop, and commercialize vaccines against infectious diseases. Icosavax is located in Seattle. For more information, visit www.icosavax.com.