Sosei Confirms New Data Demonstrating AZD4635, a Novel A2A Receptor Antagonist, Induces Anti-Tumor Immunity Alone and in Combination With Anti-PD-L1 in Preclinical Models

Sosei Group Corporation ("Sosei” or the "Company”; TSE Mothers Index: 4565), the world leader in GPCR medicine design and development, announces that new preclinical data for AZD4635 was presented by AstraZeneca in a poster (abstract 3751) yesterday at the American Association of Cancer Research Annual Meeting, 17 April 2018; Chicago, IL, USA.

AZD4635 is a potent and selective, orally available, small molecule adenosine A_2A receptor (A_2AR) antagonist. It was discovered by Sosei’s wholly-owned subsidiary Heptares Therapeutics and AstraZeneca licensed exclusive global rights to the molecule in 2015.

The poster is entitled "Inhibition of A_2AR by AZD4635 induces anti-tumor immunity alone and in combination with anti-PD-L1 in preclinical models,” and highlighted the following results:

• Adenosine signalling through the A_2AR results in a range of immunosuppressive effects which can promote tumour growth
• AZD4635 is an oral, specific A_2AR antagonist that is demonstrated to reverse adenosine mediated T cell suppression.
• Treatment with AZD4635 alone and in combination with an anti-PD-L1 antibody led to a significant reduction in tumour growth in syngeneic tumour models exhibiting both high and low levels of adenosine
• These effects were absent in immune-deficient animals confirming the immune-mediated mechanism of action. Further exploration of target engagement by AZD4635 is ongoing.
• These data suggest that AZD4635 has the potential to restore immune responsiveness resulting in anti-tumour benefits alone and in combination with other cancer immunotherapies irrespective of the background tumour adenosine levels

AZD4635 is currently in a Phase 1 clinical trial as a single agent and in combination with AstraZeneca’s anti-PD-L1 antibody IMFINZI® (durvalumab) in patients with solid malignancies (NCT02740985).

Notes to Editors

About AZD4635

AZD4635 is a potent and selective, orally available, small molecule adenosine A_2A receptor (A_2AR) antagonist discovered by Sosei subsidiary Heptares Therapeutics and licensed to AstraZeneca in 2015. High levels of adenosine are found in tumour microenvironments and benefit the progression of cancer. By activating the adenosine A_2A receptor increased adenosine levels impair T-cell function and result in suppression of the host immune response. AZD4635 specifically blocks adenosine signalling via the A_2A receptor signalling resulting in increased immune responsiveness and potential to destroy cancer cells and decrease tumour burden, A_2A receptor antagonism can therefore promote the anti-cancer response of T-cells within the tumour microenvironment, offering a novel mechanism of action as a mono- or combination therapy.

About Sosei

Sosei is an international biopharmaceutical company focused on the design and development of new medicines originating from its proprietary GPCR-targeted StaR® technology and structure-based drug design platform capabilities. The Company is advancing a broad and deep pipeline of partnered and wholly owned product candidates in multiple therapeutic areas, including CNS, cancer, metabolic diseases and other rare/specialty indications. The Company’s leading clinical programs include a proprietary Phase 2 candidate for dementia with Lewy bodies (DLB) in Japan, together with partnered candidates aimed at the symptomatic treatment of Alzheimer’s disease (with Allergan) and immuno-oncology approaches to treat cancer (with AstraZeneca). Sosei’s additional partners and collaborators include Novartis, Pfizer, Daiichi-Sankyo, PeptiDream, Kymab and MorphoSys. The Company is headquartered in Japan with R&D facilities in the UK.

Sosei is listed on the Mothers Index of the Tokyo Stock Exchange (ticker: 4565). For more information, please visit http://www.sosei.com/en/.

Forward-looking statements

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