280Bio Provides Update on the KRAS Inhibitor TEB-17231 at the 2023 AACR Annual Meeting

A broadly acting KRAS Inhibitor,TEB-17231,robustly blocks tumor growth and overcomes KRASG12C inhibitor mediated resistance

SHANGHAI,March 21,2023 -- 280Bio,Inc. a clinical stage biotechnology company,focused on the development of precision oncology medicines,today announced a presentation featuring the Company's lead development candidate TEB-17231 at the AACR Annual Meeting in Orlando,Florida to be held April 14-19,2023. 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 presentation describes preclinical findings on a lead series of small molecule inhibitors directed against multiple KRAS-mutation-altered tumor cell lines. The lead candidate TEB-17231 showed robust tumor growth inhibition,against KRASG12V,KRASG12C,KRASG12D and other RAS mutant tumor cell lines. TEB-17231 was also shown to be active in blocking tumor growth in KRASG12C-resistant cell lines bearing different secondary mutations in KRAS. With its excellent pharmacologic properties,TEB-17231 oral dosing demonstrates strong inhibition of in vivo KRAS mutant xenograft tumor growth.

The presentation details at 2023 AACR are as follows:

The small molecule KRAS inhibitor,blocks tumor progression and overcome KRASG12C inhibitor mediated resistance

Session Category: Molecular/Cellular Biology and Genetic; Session Title: Ras-related Signaling; Monday April 17,2023 1.30PM to 5.00PM EST

Location Section 11,Poster Board 11 abstract # 2627

280Bio is advancingTEB-17231 through IND enabling studies in preparation for Phase1 studies for the treatment of KRAS-mutated cancer patients.

Reflecting on the importance of the discovery and early research being presented at AACR 2023,Michael Hui,MBA,CEO & President of 280Bio,stated,"We are actively developing TEB-17231 given its demonstrated abilities to effectively inhibit different KRAS mutant tumor cells through its actions in KRAS signaling. We are excited that TEB-17231 is emerging from the company's KRAS target hub discovery platform,exemplifying the utility of our strong medicinal chemistry capabilities at 280Bio. The strategic collaboration with the MD Anderson Cancer Center (MDACC),Houston,TX,further contributes to our understanding of this interesting drug class and KRAS signaling mechanisms,and will accelerate development of TEB-17231 and other KRAS target hub agents toward the clinic."

"The scientific presentation at the AACR meeting of our KRAS lead candidate TEB-17231 highlights the progress we made to move the drug candidate this year into the clinic",said Dr. Xu Zusheng,General Manager and Head of Research and Development of Yingli Pharma,"Novel agents that interfere with KRAS signaling are highly desirable,particularly in cancers where KRAS is dysregulated. Precision oncology approaches offer the advantage of identifying the KRAS mutated cancers that may be most susceptible to these novel targeted agents. The TEB-17231 drug candidate potentially brings an additional treatment option to address a high unmet need for many patients with cancer."

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. The company's strong medicinal chemistry and pharmacology capabilities are the foundation for 280Bio's oncology portfolio targeting KRAS,PIK3CA,P53 and PARG (genomic instability),with several drug candidates entering IND-enabling development in 2023. The company has a strategic collaboration with MD Anderson Cancer Center to advance several oncology agents into clinical development in the U.S./E.U.,including the Yingli Pharma inhibitors,linpersilib (PI3Kδ inhibitor) in a T-cell lymphoma Phase 2 trial and YL-13027 (TGFβR1 inhibitor) currently in a Phase 1 dose escalation study.

Media Contact:

Michael Hui,MBA

President & CEO 280Bio

Hui@280Bio.com