A robust pipeline targeting multiple respiratory diseases

We are advancing VLP vaccine candidates that have the potential to induce high neutralizing antibody (nAb) titers for more effective protection. These vaccines are intended to help protect the most vulnerable populations, including older adults, against severe disease.

Progressing multiple assets in the clinic

*Icosavax does not plan to pursue the IVX-121 RSV monovalent candidate as a standalone candidate for RSV in older adults, and plans to transition development to the IVX-A12 bivalent RSV/hMPV candidate following Phase 1.

Icosavax has worldwide nonexclusive rights with exception of South Korea (which is not included in the licensed territory), which will convert to exclusive rights in North America and Europe (including Switzerland and United Kingdom) starting in 2025, with non-exclusivity maintained elsewhere.

All of our development programs target areas where there are important unmet needs. There are no approved vaccines for RSV or hMPV, and there are opportunities to improve protection from flu vaccines. In addition, COVID-19 vaccine options are needed, even as we evolve from pandemic to endemic status.

Top 5 pathogens detected in adults hospitalized with community-acquired pneumonia (EPIC study; pre-COVID-19)1

IVX-A12 RSV/hMPV bivalent program

Our first combination vaccine candidate, IVX-A12, targets BOTH RSV and hMPV, two of the top five causes of pneumonia in adults1

Icosavax announced the initiation of Phase 1 for IVX-A12 for the prevention of RSV and hMPV in October of 2022. This follows on the heels of positive topline data for the RSV component of the vaccine, IVX-121, reported in June of 2022. There are currently no approved vaccines for RSV or hMPV, and we are differentiated as the only company pursuing RSV and hMPV with the VLP modality and the only company with a combination RSV/hMPV candidate in the clinic.

RSV and hMPV are related Pneumoviridae that have overlapping seasonal circulation. Both viruses are common, with high re-infection rates. RSV is estimated to cause ~177,000 hospitalizations/year and ~14,000 deaths/year in US adults 65+. The economic burden in the US is estimated at $1.5–3B in direct medical costs for ages 60+. For hMPV, data support similar morbidity and mortality to that seen with RSV or flu.2-5

In our RSV/hMPV development program, we have focused on developing and advancing VLPs that stimulate high nAb titers. Every log2 improvement in nAb titers is believed to lead to a clinically relevant improvement in disease outcome.

Consistent with the evolution of the field, we are utilizing prefusion stabilized F antigens for display on our VLPs

Both our RSV and hMPV VLPs employ the F protein responsible for viral cell entry. F proteins undergo conformational changes upon fusing to the cell membrane; utilizing prefusion F protein may lead to higher nAb titers.

IVX-121 for RSV: Prefusion RSV-F protein may lead to higher nAb titers

Data support prefusion F antigens including DS-Cav1 for targeting RSV6, and IVX-121—the RSV component of IVX-A12—is a VLP with multivalent display of stabilized prefusion F proteins.

IVX-241 for hMPV:
Prefusion stabilized F
hMPV/A antigen selected

In hMPV, prefusion F protein has been shown in the mouse model to have ~6X nAb titers compared to postfusion F antigen.8,9

Clinical development is progressing following positive topline results in RSV

A Phase 1/1b trial involving the RSV component of the combination vaccine, IVX-121, was initiated in September of 2021. Positive topline interim results were reported in June of 2022 and are summarized below.

IVX-121 for RSV: Ph 1/1b trial initiated September 2021

Allows comparison to NIH DS-Cav1 Phase 1 data in YA, as representative of stablized prefusion F-based vaccines

Assessment of safety and immonogenicity in OA and potential to counter immunosenescence

Assessment of long-term safety and durability and response to additional dose of IVX-121 in OA

Positive IVX-121 (RSV VLP) Phase 1/1b topline interim results10

Briefly, data show:

  • High RSV-A and RSV-B neutralizing antibody titers seen from the lowest dose tested
  • Similarly robust responses in older vs. younger adults
  • Favorable tolerability
  • Suitability for combination (tolerability profile at maximum dose tested in Phase 1 [250 µg] and immunogenicity down to 25 µg gives room for multivalent combinations)

Topline immunogenicity data: RSV-A nAb geometric mean titers (in IU/mL)
of unadjuvanted IVX-121 are comparable in young and older adults

GMT expressed in IU/mL – Viroclinics Live nAb Assay. GMT: geometric mean titer; LLoQ = 9.9; GMFR: geometric mean fold rise (Day 28) from baseline. Assays conducted by Viroclinics.

Durability out to 12 months for IVX-121, the RSV portion of IVX-A12, will continue to be assessed in a Phase 1b extension.

Based on this positive data, we have moved into development of our IVX-A12 RSV/hMPV combination vaccine. We announced initiation of our Phase 1 trial in October of 2022. The Phase 1 and 2 studies for IVX-A12 will help us to optimize our bivalent formulation and inform clinical endpoints for a potential POC Phase 2b efficacy study.

IVX-A12 Phase 1 and 2 trials will assess safety and immunologic non-interference

COVID-19 program

Better vaccines for COVID-19 are needed

We believe there will be a need for better vaccines and value beyond the pandemic in COVID-19, and this is an area of interest to the company for its optionality as a potential component of our combination vaccines vision.

COVID-19 has taken a particularly large toll on the older adult population. Through March of 2022, there have been ~2.5 million hospitalizations among those age 60+ and ~712,000 deaths among adults 65+ in the US alone. The economic burden is also severe, with an estimated ~$28B in preventable COVID-19 hospitalizations costs among unvaccinated adults (18+).*11,12

Although COVID-19 vaccines are available, the emergence of variant strains, reactogenicity, and limited durability of current approaches have created gaps and thus a need for additional vaccine modalities. It is likely that COVID-19 boosters will continue to be needed, and options with lower reactogenicity and longer duration—potential benefits of our VLP approach—are likely to be preferred. Combination vaccines are also likely to be the preferred choice, and combinability is an expected benefit of VLP technology.

Preclinical COVID-19 candidate development is in process, and we are currently focusing on a bivalent strategy for a COVID-19 candidate displaying computationally engineered receptor binding domain (RBD) antigens.

*Extrapolated from six months data to an annualized figure.

Flu program

Flu is an important part of our vision

A VLP-based vaccine targeting influenza—potentially deployed as part of a combination vaccine—is being pursued. In relation to this initiative, we also have plans to build a rapid production system capable of supporting seasonal flu, which we expect to also enhance our pandemic response capabilities.

There is an unmet need for a flu vaccine with improved efficacy, particularly in the older adult population. Even though numerous marketed vaccines are available, flu still causes ~380K hospitalizations and ~20K deaths/year in the US—the majority in people over 65.13 In addition, despite their commercial success, existing flu vaccines have historically had sub-par efficacy (~20%–50% over the last 10 years) and need to be updated every season.13

US flu disease burden, 2019–2020 flu season13

Sub-par efficacy is seen with currently available flu vaccines13

*2020-2021 flu vaccine effectiveness was not estimated due to low flu virus circulation during the 2020-2021 flu season.
Interim vaccine effectiveness estimates, as of June 2022.

Preclinical candidate development is in process.

1. CDC, EPIC study. 2. CDC, RSV Trends and Surveillance. 3. CDC Health Alert Network, alert CDCHAN-00443. 4. Sieling WD et al. Influenza Other Respir Viruses. 2021;15(5):670-677. 5. Herring WL et al. Vaccine. 2022;40(3):483-493. 6. Ruckwardt TJ et al. Lancet Respir Med. 2021;9(10):1111-1120. 7. Mas V et al. PLoS Pathog. 2016;12(9):e1005859. 8. Battles MB et al. Nat Commun. 2017;8(1):1528. 9. Hsieh C-L et al. Nat Commun. 2022;13(1):1299. 10. Data on file. Icosavax, Inc. 11. CDC, COVID data tracker for hospitalizations and deaths. 12. Peterson-KFF Health System Tracker. 13. CDC, flu seasonal burden and seasonal flu vaccine effectiveness studies.