Medicenna Selects its Lead Immuno-Oncology Clinical Candidate, MDNA19, from its IL-2 Superkine Platform

MDNA19 demonstrates robust efficacy and safety with or without checkpoint inhibitors in preclinical models; Clinical studies expected to commence in 2020

TORONTO and HOUSTON, July 31, 2019 /PRNewswire/ - Medicenna Therapeutics Corp.  ("Medicenna" or "the Company") (TSX: MDNA, OTCQB: MDNAF), a clinical stage immunotherapy company developing first-in-class Superkines and Empowered Cytokines, today announced the selection of MDNA19 (formerly, MDNA109-LA1) as its second immuno-oncology clinical candidate for the treatment of cancer. MDNA19 is a best-in-class long-acting IL-2 developed from Medicenna's Superkine platform that has shown unique ability to selectively stimulate cancer killing immune cells without the limitations seen with other long-acting IL-2 programs. Medicenna expects to begin clinical trials with MDNA19 in 2020.

"We are excited to announce MDNA19 as our lead clinical candidate for the treatment of solid tumors which marks a major milestone for Medicenna and our Superkine platform," said Dr. Fahar Merchant, President and CEO of Medicenna. "Unlike competing IL-2 programs which are unable to meaningfully stimulate cancer killing immune cells, MDNA19 is designed to dramatically boost the population of immune cells to attack cancer instead of immune cells that protect cancer while maintaining a superior safety profile. We strongly believe that MDNA19 could deliver increased benefits to the patient, expand partnering opportunities and become a core driver of the Company's short and long term success."

As recently presented at the 2019 Immuno-Oncology Pharma Congress in Boston, MDNA19 showed disabled binding to the CD25 subunit of the IL-2 receptor and enhanced selectivity towards CD122, resulting in much higher activation of effector T cells relative to Tregs without the toxicity associated with Proleukin®. In addition, MDNA19 inhibited tumor growth with minimal dosing (once weekly for 2 weeks) in mice with pre-established tumors.

Long range studies with the precursor MDNA109-LA and immune checkpoint inhibitors (ICIs) have shown potent tumor control, with the majority of mice remaining tumor free for over 150 days. These mice were also highly resistant to multiple tumor re-challenges without further treatment, indicating development of long-term memory response.

"Following extensive screening and testing of dozens of potential candidates we are excited to select MDNA19 as our lead clinical candidate based on exceptional pre-clinical safety and efficacy results," said Dr. Moutih Rafei, Associate Professor in the Department of Pharmacology and Physiology at the Université de Montreal and Head of Discovery at Medicenna. "The ability of the MDNA109 platform to reverse tumor growth in aggressive mouse tumor models and retain long-term cure rates despite multiple re-challenges without further treatment is impressive, particularly when combined with immune checkpoint therapy. Variants of MDNA19 can be genetically fused to targeted antibodies to create Immunocytokines or used to arm oncolytic viruses and CAR-T cells without the toxicities associated with Proleukin®."

With IND-enabling studies expected to be completed next year, Medicenna expects to enter clinical studies with MDNA19 in 2020.

About MDNA109
Developed by scientists at Stanford University, MDNA109 is an engineered version of IL-2 that binds up to 200 times more effectively to IL-2Rβ (CD122), thus greatly increasing its ability to activate and proliferate the immune cells needed to fight cancer. MDNA109 is an IL-2 Superkine that preferentially drives the expansion and responses of effector T cells and Natural Killer (NK) cells over Treg cells. It is the only IL-2 in development with a distinct mechanism by virtue of its high affinity towards CD122 allowing it to effectively combat NK cell anergy (exhaustion) which occurs frequently after cancer immunotherapy.

About Medicenna Therapeutics Corp.
Medicenna is a clinical stage immunotherapy company focused on oncology and the development and commercialization of novel, highly selective versions of IL-2, IL-4 and IL-13 Superkines and first in class Empowered Cytokines™ (ECs) for the treatment of a broad range of cancers. Supported by a US$14.1M non-dilutive grant from CPRIT (Cancer Prevention and Research Institute of Texas), Medicenna's lead IL4-EC, MDNA55, has completed enrolling patients in a Phase 2b clinical trial for rGBM, the most common and uniformly fatal form of brain cancer, at top-ranked brain cancer centres in the US. MDNA55 has been studied in five clinical trials involving 132 patients, including 112 adults with rGBM. MDNA55 has demonstrated compelling efficacy and has obtained Fast-Track and Orphan Drug status from the FDA and FDA/EMA respectively. For more information, please visit www.medicenna.com.

This news release contains forward-looking statements relating to the future operations of the Company and other statements that are not historical facts. Forward-looking statements are often identified by terms such as "will", "may", "should", "anticipate", "expects" and similar expressions. All statements other than statements of historical fact, included in this release, including, without limitation, statements that MDNA19 is a best in class long-acting IL-2 and that has shown unique ability to selectively stimulate cancer killing immune cells without the limitations seen with other long-acting IL-2 programs, that competing IL-2 programs cannot meaningfully stimulate cancer killing immune cells, that MDNA19 will deliver increased benefits to patients, expand partnering opportunities for Medicenna and also be a core driver of the Company's continued success, that IND-enabling studies will be completed next year and MDNA19 is expected to enter clinical studies in 2020, and statements related to the future plans and objectives of the Company, are forward-looking statements that involve risks and uncertainties. There can be no assurance that such statements will prove to be accurate and actual results and future events could differ materially from those anticipated in such statements. Important factors that could cause actual results to differ materially from the Company's expectations include the risks detailed in the annual information form of the Company dated June 24, 2019 and in other filings made by the Company with the applicable securities regulators from time to time.

The reader is cautioned that assumptions used in the preparation of any forward-looking information may prove to be incorrect. Events or circumstances may cause actual results to differ materially from those predicted, as a result of numerous known and unknown risks, uncertainties, and other factors, many of which are beyond the control of the Company. The reader is cautioned not to place undue reliance on any forward-looking information. Such information, although considered reasonable by management at the time of preparation, may prove to be incorrect and actual results may differ materially from those anticipated. Forward-looking statements contained in this news release are expressly qualified by this cautionary statement. The forward-looking statements contained in this news release are made as of the date of this news release and the Company will update or revise publicly any of the included forward-looking statements only as expressly required by Canadian securities law.

SOURCE Medicenna Therapeutics Corp.

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