FDA Grants Fast Track Status to ARCT-2304 for H5N1 Influenza Protection

The FDA has granted Fast Track Designation to ARCT-2304, Arcturus Therapeutics’ investigational self-amplifying mRNA (sa-mRNA) vaccine developed to protect against pandemic influenza A (H5N1). ARCT-2304, also known as LUNAR-H5N1, is part of the company’s proprietary STARR mRNA platform and aims to support rapid, scalable immunization during global influenza threats.¹

The Fast Track designation is designed to expedite the development and regulatory review of treatments that address serious or unmet medical needs. For ARCT-2304, this status allows for more frequent FDA communication, rolling data submissions, and potential eligibility for Priority Review.¹

ARCT-2304 entered Phase 1 clinical trials in November 2024, enrolling 200 healthy adults across multiple US sites. The study evaluates different dosing and vaccination schedules in participants ages 18 to 80, measuring immune responses through standard assays like hemagglutination inhibition and virus neutralization. Interim data are expected in the second half of 2025.²

The sa-mRNA platform enables in vivo amplification of mRNA, meaning smaller doses are needed to trigger immune responses, a potential advantage over conventional mRNA, egg-based, or cell-based vaccine technologies. Additionally, the vaccine is lyophilized and refrigerator-stable, simplifying logistics and storage for widespread distribution.²

We spoke with Arcturus Therapeutics in January 2025 after the Phase 1 trial began. In an exclusive interview, Neda Safarzadeh, vice president and head of investor relations, public relations, and marketing, discussed the significance of ARCT-2304. She said, “LUNAR-H5N1’s self-amplifying mRNA platform enhances immune response and offers better liver durability, providing a more robust and lasting defense compared to conventional vaccines.”²

According to the CDC, there is no currently approved or recommended vaccine for the general public against avian influenza, including H5N1. While seasonal flu vaccines do not offer protection against these viruses, the CDC has developed H5 candidate vaccine viruses (CVVs) that could quickly produce vaccines if needed. These CVVs are expected to offer strong protection.³

This highlights the significance of the FDA expediting the development and review of ARCT-2304, addressing an unmet medical need. The Fast Track designation aligns with national preparedness efforts and reflects the urgent need for vaccine solutions against potential pandemic strains.

References

1. Arcturus Therapeutics. Arcturus Therapeutics receives U.S. FDA Fast Track Designation for the STARR® mRNA vaccine candidate ARCT-2304 for pandemic influenza A virus. Arcturus Therapeutics. April 10, 2025. Accessed April 10, 2025. https://www.businesswire.com/news/home/20250410338815/en/Arcturus-Therapeutics-Receives-U.S.-FDA-Fast-Track-Designation-for-the-STARR-mRNA-Vaccine-Candidate-ARCT-2304-for-Pandemic-Influenza-A-Virus-H5N1

2. Arcturus Therapeutics Announces Initiation of Phase 1 H5N1 Flu Vaccine Trial. Businesswire. Published January 10, 2024. Accessed April 10, 2025. https://www.businesswire.com/news/home/20250110432449/en/Arcturus-Therapeutics-Announces-Initiation-of-Phase-1-H5N1-Flu-Vaccine-Trial

3. Centers for Disease Control and Prevention. Avian Influenza (Bird Flu): About Bird Flu. Updated December 30, 2024. Accessed April 10, 2025. https://www.cdc.gov/bird-flu/about/index.html#:~:text=Viruses%20in%20People-,Vaccines,against%20avian%20influenza%20A%20viruses