San Diego-based Arcturus Therapeutics (Nasdaq: ARCT) has terminated its self-amplifying mRNA collaboration with CSL Seqirus through a settlement agreement, recovering global rights to KOSTAIVE (ARCT-154), the world's first approved sa-mRNA vaccine, along with seasonal influenza, pandemic influenza, RSV, and EBV vaccine programs. The move unwinds a deal that originally carried a headline value of approximately USD 4.3 billion.
Under the settlement, CSL Seqirus will pay Arcturus a one-time USD 12 million cash payment, and Arcturus will be released from approximately USD 16 million in R&D credit liabilities, bringing the effective settlement value to roughly USD 28 million. The agreement also resolves an arbitration dispute over a European regulatory approval milestone payment — a dispute Arcturus had initiated in May 2025 after the European Commission approved KOSTAIVE as the first sa-mRNA COVID-19 vaccine in February 2025. Japan rights for the 2026–2027 season remain subject to existing arrangements with Meiji Seika Pharma as a transitional carve-out.
The original December 2022 collaboration had granted CSL Seqirus an exclusive global license to Arcturus's STARR sa-mRNA and LUNAR lipid nanoparticle delivery platforms across at least six vaccine targets, with USD 200 million paid upfront, and up to USD 4.3 billion in milestone commitments.
Arcturus said it intends to evaluate development, commercialization, and partnering opportunities for the recovered portfolio. The company's stated strategic focus has shifted toward rare disease programs, with the Thermo Fisher Scientific collaboration announced in July 2026 to support Phase III development of ARCT-032, an inhaled mRNA therapy for cystic fibrosis, cited as the primary execution priority.