Arcturus Therapeutics Holdings Inc.

Item 5. Other Information.

Rule 10b5-1 Trading Arrangements

During the three months ended June 30, 2026, none of our directors or officers, as defined in Rule 16a-1(f) of the Exchange Act, adopted orterminated a “Rule 10b5-1 trading arrangement” (as defined in Item 408 of Regulation S-K of the Exchange Act) intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act, other than as set forth below:

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Lance Kurata, our Chief Legal Officer, adopted a Rule 10b5-1 trading arrangement as of May 15, 2026. Mr. Kurata's trading arrangement provides for the exercise of options to purchase up to 30,000 shares of common stock and the subsequent sale of up to an aggregate of 30,000 shares of common stock, beginning on August 14, 2026 and ending on March 31, 2027.

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Dr. Padmanabh Chivukula, Chief Scientific Officer and Chief Operating Officer, adopted a Rule 10b5-1 trading arrangement on May 14, 2026. Dr. Chivukula’s trading arrangement provides for the sale of up to an aggregate of 60,000 shares of common stock, beginning on August 14, 2026 and ending on December 31, 2027.

Termination of Vaccine Collaboration with CSL Seqirus

On August 3, 2026, we entered into the Termination Agreement with CSL Seqirus pursuant to which we mutually terminated the CSL Collaboration Agreement, effective as of such date. Under the Termination Agreement, we received a one-time cash payment of $12.0 million from CSL Seqirus. In addition, we were released from a liability and from repayment of an R&D credit with an aggregate value of approximately $16 million.

As a result of the termination, we regained strategic control of our vaccine portfolio, including KOSTAIVE® and our vaccine programs for seasonal influenza, pandemic influenza, RSV and EBV, subject to ongoing arrangements with Meiji Seika Pharma (“Meiji”) for the Northern Hemisphere 2026-2027 season, which is expected to end on or around June 30, 2027. Beginning with the Northern Hemisphere 2027–2028 season, we expect to work directly with Meiji for KOSTAIVE® activities in Japan.

We are obligated to pay CSL Seqirus single-digit royalties and revenue-sharing payments on our future commercialization of vaccine products formerly licensed under the CSL Collaboration Agreement and successor products, where certain CSL Seqirus intellectual property is incorporated into such products, subject to agreed terms and conditions and applicable time limitations. With respect to certain of the vaccine products, we are obligated to pay a percentage of upfront payments received from future licensees up to pre-agreed amounts.

As a result of the termination, we expect deferred revenue from CSL Seqirus of approximately $5.2 million associated with remaining performance obligations under the CSL Collaboration Agreement to be recognized during the third quarter of 2026.

In connection with the termination, the parties agreed to dismiss the arbitration and exchanged mutual releases of claims. See “Part II – Other Information – Item 1. Legal Proceedings” for more information.

The foregoing description of the Termination Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Termination Agreement, a copy of which the Company intends to file with the Commission as an exhibit to the Company’s Quarterly Report on Form 10-Q for the quarter ending September 30, 2026.