Arcturus Therapeutics Holdings Inc.

Item 1. Legal Proceedings.

On May 30, 2025, we initiated an arbitration against CSL Seqirus before the International Chamber of Commerce, seeking payment of a milestone under the CSL Collaboration Agreement based on the European Commission’s grant of marketing authorization for a presentation of KOSTAIVE® in the European Union. On July 25, 2025, CSL Seqirus submitted an Answer in the arbitration contending that it does not have a current obligation to pay the milestone. The arbitration is ongoing, and the parties remain committed to the ongoing success of the collaboration.

From time to time, we may be involved in various legal proceedings and subject to claims that arise in the ordinary course of business, including those related to governmental inquiries, intellectual property and commercial relationships. The subject matter of any such legal proceedings or claims are or will be highly complex and subject to substantial uncertainties. The outcome of any such proceedings or claims, regardless of the merits, are and will be inherently uncertain; therefore, assessing the likelihood of loss and any estimated damages is difficult and subject to considerable judgment.