Medicenna Announces the Launch of a Marketed Public Offering of Securities

NOT FOR DISSEMINATION INTO THE UNITED STATES OR FOR DISTRIBUTION TO U.S. NEWSWIRE SERVICES

TORONTO and HOUSTON, May 13, 2026 — Medicenna Therapeutics Corp. (“Medicenna” or the “Company”) (TSX: MDNA), a clinical-stage immunotherapy company focused on the development of Superkines targeting cancer and autoimmune diseases, announced today the launch of a marketed public offering (the “Offering”) of securities of the Company (the “Securities”).

The type of Securities to be issued, the price of each Security, the size of the Offering and the final terms of the Offering will be determined by negotiation between the Company and Bloom Burton Securities Inc. (“Bloom Burton”) in the context of the market with the final terms to be determined at the time of pricing. Bloom Burton will act as the sole agent for the Offering and be conducted on a best efforts agency basis.

The Company plans to use the net proceeds from the Offering primarily to advance the clinical and regulatory development of the Company’s lead programs (including MDNA11 and MDNA113), to fund working capital and for general corporate purposes.

The Offering will be made pursuant to a prospectus supplement (the “Prospectus Supplement”) to the Company’s existing short form base shelf prospectus dated June 4, 2025 (the “Base Shelf Prospectus”) to be filed in British Columbia, Alberta and Ontario. The Securities may also be offered in certain other jurisdictions outside of Canada, provided that a placement therein does not give rise to any prospectus, registration or continuous disclosure obligations on the part of the Company**.**

The Base Shelf Prospectus is available under the Company’s profile on SEDAR+ at www.sedarplus.ca and, upon determination of the final terms of the Offering, and the signing of an agency agreement between the Company and Bloom Burton, the Prospectus Supplement will be filed and available on SEDAR+ at www.sedarplus.ca.

The closing of the Offering will be subject to customary closing conditions, including the receipt of all necessary regulatory and stock exchange approvals.

The Securities issuable in connection with the Offering will not be registered under the United States Securities Act of 1933, as amended (the “1933 Act”), or any U.S. state securities laws and may not be offered or sold in the “United States” (as such term is defined in Regulation S under the 1933 Act) except pursuant to an effective registration statement under the 1933 Act and applicable U.S. state securities laws or an available exemption from the registration requirements of the 1933 Act and applicable U.S. state securities laws.

This news release does not constitute an offer to sell or the solicitation of an offer to buy any of the securities described herein, nor will there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state or jurisdiction.

About Medicenna Therapeutics

Medicenna is a clinical-stage immunotherapy company focused on developing novel, highly selective versions of IL-2, IL-4 and IL-13 Superkines and first-in-class Empowered Superkines. Medicenna’s long-acting IL-2 Superkine, MDNA11, is a nextgeneration IL-2 with superior affinity toward CD122 (IL-2 receptor beta) and no CD25 (IL-2 receptor alpha) binding, thereby preferentially stimulating cancer-killing effector T cells and NK cells. Medicenna’s first-in-class targeted PD-1 x IL-2 bifunctional, MDNA113, is in development for solid tumors and was designed using the Company’s proprietary BiSKITs™ (Bifunctional SuperKine ImmunoTherapies) and T-MASK™ (Targeted Metalloprotease Activated SuperKine) platforms. Medicenna’s IL-4 Empowered Superkine, bizaxofusp (formerly MDNA55), has been studied in 5 clinical trials enrolling over 130 patients, including a Phase 2b trial for recurrent GBM, the most common and uniformly fatal form of brain cancer. Bizaxofusp has obtained FastTrack and Orphan Drug status from the FDA and FDA/EMA, respectively.

For more information, please visit www.medicenna.com.

Investor/Media Contact

Shushu Feng Investor Relations, Medicenna Therapeutics (416) 964-5442 [email protected]