280 Bio receives IND approval from the FDA for YL-17231

---The Company announces to initiate Phase 1 Clinical Trial with the KRAS inhibitor YL-17231 in US--

SHANGHAI and SOUTH SAN FRANCISCO,Calif.,July 7,2023 -- 280Bio,Inc. a clinical stage biotechnology company focused on the development of precision oncology medicines,today announced that the U.S. Food and Drug Administration (FDA) has granted the company's Investigational New Drug (IND) application for the investigational drug YL-17231,a small molecule inhibitor of RAS signaling. The approval enables the initiation of the Phase 1 clinical study for YL-17231 in the US. KRAS,NRAS and HRAS genes are frequently mutated in many tumor indications with the oncogenic mutations leading to tumor cell growth. YL-17231 demonstrated in pre-clinical research to potently inhibit tumor cell proliferation in vitro and invivo,exhibiting activity with a variety of RAS mutations,including tumors that have become resistant to KRAS G12C inhibitors. 280Bio will initiate a Phase 1 study for the treatment of advanced cancer patients with RAS mutations in their tumors.

"The IND approval by the FDA enables 280Bio to initiate the Phase 1 clinical trial of our novel KRAS inhibitor marking a major milestone for the company's clinical development program." said Michael Hui,Chief Executive Officer of 280Bio Inc.,"We are excited to explore the therapeutic potential of YL-17231 targeting a broad patient population with RAS mutations to potentially create a transformative therapy option."

280Bio will advance YL-17231 into a U.S.-based Phase 1 clinical study at multiple clinical cancer research centers in the U.S including the MD Anderson Cancer Center,Houston,Texas. The Company plans to start enrollment of patients in the dose escalation part of Phase1 in the fourth quarter of 2023.

Reflecting on the high unmet need for newly developed cancer agents,Dr. Zusheng Xu,General Manager and Head of Research and Development of Yingli Pharma,said "We are excited that YL-17231 has emerged from the company's discovery platform,exemplifying the utility of our strong medicinal chemistry capabilities. YL-17231 has a broader activity than many current KRAS inhibitors and demonstrated strong inhibition of in vivo KRAS mutant xenograft tumor growth in our preclinical investigations. With its excellent pharmacologic properties,we are hopeful that YL-17231 will demonstrate to be safe and efficacious during continuous oral dosing in patients."

YL-17231 has been co-developed by 280Bio and Yingli Pharma and emerges from the strategic collaboration of 280Bio with The University of Texas MD Anderson Cancer Center,where further preclinical research of the investigational drug is continuing.

About 280Bio

280Bio,headquartered in the San Francisco Bay Area,is developing innovative precision small molecule inhibitors for the treatment of cancer. 280Bio is a clinical-stage biotechnology company and a wholly owned subsidiary of Shanghai Yingli Pharmaceutical Co.,Ltd.,Shanghai,China (Yingli Pharma). The 280Bio pipeline is focused on novel oral oncology drug candidates directed at frequently mutated genetic changes in signaling pathways and the known genetic instability features of many cancers. The company's strong medicinal chemistry and pharmacology capabilities are the foundation for 280Bio's oncology portfolio. In addition to YL-17231,the strategic collaboration with MD Anderson Cancer Center is currently advancing several oncology agents into clinical development in the U.S./E.U.,including the Yingli Pharma linpersilib (PI3Kδ inhibitor approved in China in 2022) in a T-cell lymphoma Phase 2 trial and YL-13027 (TGFβR1 inhibitor) currently in a Phase 1 dose escalation study.

280Bio Contact:

Michael Hui,MBA

President & CEO 280Bio

Hui@280Bio.com