Arcturus Therapeutics Holdings Inc.

Item 1. Legal Proceedings.

From time to time, we may be involved in various legal proceedings and subject to claims that arise in the ordinary course of business, and the results of litigation and claims are inherently unpredictable and uncertain. Other than as set forth below, we are not currently a party to any material legal proceedings.

On September 23, 2025, we filed a lawsuit against AbbVie Inc., Capstan Therapeutics, Inc. and other defendants in the United States District Court for the Southern District of California, asserting claims for trade secret misappropriation and breach of contract. The defendants filed a motion to discuss the complaint in December 2025, and we filed an opposition to that motion in January 2026. On March 30, 2026, the Court denied in part and granted in part the motion to dismiss. The Court gave us leave to amend on the points where it granted the motion. We filed an Amended Complaint on April 13, 2026, against the same defendants and asserting the same claims.

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. On March 27, 2026, we submitted our Statement of Claim. The arbitration is ongoing with a hearing scheduled to occur in the third quarter of 2026.