CStone announces first patient enrollment in the U.S. in the Phase 1 clinical trial of CS5001, a potential global best-in-class ROR1-targeting ADC

Commencement of the first-in-human clinical trial of CS5001 marks another key milestone for CStone's Pipeline 2.0

Global development of CS5001 is conducted in the form of a multi-regional clinical trial,with sites initiated in the US and Australia,and an IND application accepted by the NMPA in China

As one of the most advanced ROR1 ADCs in clinical development,CS5001 has demonstrated therapeutic potential in multiple hematological and solid malignancies

SUZHOU,China,March 31,2022 -- CStone Pharmaceuticals ("CStone",HKEX: 2616),a leading biopharmaceutical company focused on the research,development,and commercialization of innovative immuno-oncology therapies and precision medicines,today announced that the first patient has been enrolled in the U.S. in the Phase 1 clinical trial for CS5001. This is a remarkable milestone for CStone's Pipeline 2.0 strategy.

CS5001 is a potential global best-in-class antibody-drug conjugate (ADC),targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1). As one of the three most advanced ROR1 ADCs worldwide,CS5001 has been approved for the initiation of a multi-regionalclinical trial in the US and Australia. The China National Medical Products Administration (NMPA) has accepted the investigational new drug (IND) application of CS 5001. This first-in-human Phase 1 study aims to evaluate the safety,tolerability,pharmacokinetics,and preliminary anti-tumor activity of CS5001 in advanced B cell lymphomas and solid tumors.

ROR1 is an oncofetal protein with low or no expression in adult tissues but high expression in a variety of cancers including various forms of leukemia and non-Hodgkin lymphoma,breast,lung,and ovarian cancers,making it an ideal ADC target. Results from pre-clinical studies showed that CS5001 exhibited potent and selective cytotoxicity to a variety of ROR1-expressing cancer cell lines and demonstrated remarkable in vivo antitumor activity in both hematological and solid tumor xenograft models. The preclinical data were presented as a late-breaking abstract at the 33rd AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics 2021.

Dr. Archie Tse,Chief Scientific Officer of CStone,said: "We are very glad to have the first patient enrolled in the first-in-human study of CS5001. This potentially best-in-class ROR1 ADC contains a number of differentiated features which may translate into a wider therapeutic window against a variety of cancer types -- a fully human antibody backbone,proprietary site-specific conjugation,and tumor-cleavable linker and prodrug technology. Results from the preclinical studies of CS5001 already showed its therapeutic potential in ROR1-expressing hematological and solid malignancies. We will swiftly execute the global development program of CS5001,starting with this Phase 1 study to characterize its safety and preliminary efficacy in the treatment of advanced B-cell lymphoma and selected solid tumors."

About CS5001（ROR1 ADC）

CS5001 is a clinical-stage antibody-drug conjugate (ADC) targeting ROR1 (receptor tyrosine kinase-like orphan receptor 1). CS5001 has uniquely designed and LCB's proprietary tumor-cleavable linker and pyrrolobenzodiazepine (PBD) prodrug. Only after reaching the tumor,the linker and prodrug are cleaved to release the PBD toxin,resulting in lethal DNA cross-links in cancer cells. The use of the linker plus PBD prodrug effectively helps addressing the toxicity problem associated with traditional PBD payloads,leading to a better safety profile. Additionally,CS5001 utilizes site-specific conjugation for a precise drug antibody ratio of 2 which enables homogeneous production and large-scale manufacturing.

In October 2020,CStone signed a licensing agreement with LegoChem Biosciences,Inc. (LCB) for the development and commercialization of CS5001 which was originally generated by collaboration of LCB and ABL Bio,both South Korea-based leading biotech companies. Under the agreement,CStone obtains the exclusive global right to lead development and commercialization of CS5001 outside the Republic of Korea.

About CStone

CStone Pharmaceuticals (HKEX: 2616) is a biopharmaceutical company focused on research,and commercialization of innovative immuno-oncology and precision medicines to address the unmet medical needs of cancer patients in China and worldwide. Established in 2015,CStone has assembled a world-class management team with extensive experience in innovative drug development,clinical research,and commercialization. The company has built an oncology-focused pipeline of 15 drug candidates with a strategic emphasis on immuno-oncology combination therapies. Currently,CStone has received seven NDA approvals for four drugs. CStone's vision is to become globally recognized as a world-renowned biopharmaceutical company by bringing innovative oncology therapies to cancer patients worldwide.

For more information about CStone,please visit: www.cstonepharma.com.

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