Antengene and Calithera Biosciences Enter into Worldwide Exclusive License Agreement to Develop and Commercialize CD73 Inhibitor CB-708 (ATG-037)

SHANGHAI and SOUTH SAN FRANCISCO,Calif.,May 17,2021 -- Antengene Corporation Limited ("Antengene",SEHK: 6996.HK),a leading innovative biopharmaceutical company dedicated to discovering,developing and commercializing global first-in-class and/or best-in-class therapeutics in hematology and oncology,and Calithera Biosciences,Inc. ("Calithera",Nasdaq: CALA),a clinical-stage biotechnology company focused on discovering and developing novel small molecule drugs for the treatment of cancer and other life-threatening diseases,todayannounced an exclusive,worldwide license agreement for the development and commercialization of CB-708 (ATG-037),Calithera's small molecule inhibitor of CD73.

Under the terms of the license agreement,Calithera will receive an upfront payment and potential development,regulatory and sales milestones,and is eligible to receive tiered royalties on sales of the licensed product withinthe range ofsingle to low double-digits.

CD73 generates adenosine that is highly immunosuppressive. It enhances the proliferation of cancer cells through downregulation of IFN-γ,NK cells,and CD8+ T cells. Tumors harness multiple CD73 mediated pathways to avoid an immune response. Therefore,effective blockade of this target represents an ideal opportunity to restore immune competence in cancer patients,with strong potential to synergize with conventional therapies and other checkpoint inhibitors. CB-708 is a highly potent,selective,orally-bioavailable inhibitor of CD73 that has great potential as either a monotherapy or in combination against a range of tumor types.

Preclinical data presented at the 2019 American Association for Cancer Research (AACR) Annual Meeting and the 2019 Society for Immunotherapy of Cancer (SITC) Annual Meeting demonstrated that CB-708 has immune-mediated,single agent activity in syngeneic mouse tumor models. In preclinical studies,CB-708was well-tolerated and showed enhanced anti-tumor activity when combined with either an anti-PD-L1 immunotherapy or with chemotherapeutic agents,such as oxaliplatin or doxorubicin. CB-708has completed GLP toxicology studies and is poised to advance into clinical development.

"We are excited to continue the advancement of CB-708 through our deep experience in global clinical development and extensive track record in commercialization in major markets around the world," said Dr. Jay Mei,Founder and Chief Executive Officer of Antengene."CB-708is a highly differentiated oral small molecule CD73 inhibitor with best-in-class potential due to its oral-bioavailability and high potency. It overcomes the 'hook-effect'of clinical anti-CD73 antibodies and could completely block CD73 activity in vitro. Antengene will continue to complete the GMP manufacturing of CB-708and advance it into clinical trials for the treatment of multiple cancers including solid tumors and hematologic malignancies. This agreement brings a great addition to our portfolio of 12 assets with synergistic potential,is a testament to our abilities in accelerating global development,and represents another step in realizing our mission of treating patients beyond borders."

"This agreement validates the capabilities of our drug discovery engine and represents a significant milestone for our CD73 program," said Susan Molineaux,PhD,president and chief executive officer of Calithera. "Antengene brings significant enthusiasm and proven global capabilities to the development and future commercialization of CB-708,a potential best-in-class oral small molecule CD73 inhibitor. This licensing agreement enables the continued advancement of this promising program,while allowing Calithera to focus our resources on our more advanced clinical programs evaluating telaglenastat in non-small cell lung cancer and CB-280 in cystic fibrosis."

About Antengene

Antengene Corporation Limited ("Antengene",SEHK: 6996.HK) is a leading clinical-stage R&D driven biopharmaceutical company focused on innovative medicines for oncology and other life-threatening diseases. Antengene aims to provide the most advanced anti-cancer drugs to patients in the Asia Pacific Region and around the world. Since its establishment in 2017,Antengene has built a broad and expanding pipeline of clinical and pre-clinical stage assets through partnerships as well as in-house drug discovery,and obtained 15 investigational new drug (IND) approvals and submitted 5 new drug applications (NDA) in multiple markets in Asia Pacific. Antengene's vision is to "Treat Patients Beyond Borders". Antengene is focused on and committed to addressing significant unmet medical needs by discovering,developing and commercializing first-in-class/best-in-class therapeutics. For more information,please visit: www.antengene.com.

About Calithera Biosciences

Calithera Biosciences is a clinical-stage biopharmaceutical company pioneering the discovery and development of targeted therapies that disrupt cellular metabolic pathways to preferentially starve tumor cells and enhance immune-cell activity. Driven by a commitment to rigorous science and a passion for improving the lives of people impacted by cancer and other life-threatening diseases,Calithera is advancing a pipeline of first-in-clinic,oral therapeutics to meaningfully expand treatment options available to patients. Calithera is headquartered in South San Francisco,California. For more information about Calithera,please visit www.calithera.com.

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