• Sugemalimab is the world’s first PD-L1 monoclonal antibody to show the statistically significant and clinically meaningful overall survival improvement in combination with chemotherapy for patients with treatment-naïve stage IV non-small cell lung cancer across both squamous and non-squamous histology
• The pre-specified interim overall survival analysis showed that sugemalimab in combination with chemotherapy significantly prolonged the median overall survival by 8.5 months over placebo in combination with chemotherapy and lowered the risk of death by 35%. Survival benefits were observed across all subgroups regardless of tumor pathology types or PD-L1 expression levels
• The formal overall survival analysis data may support regulatory discussions for sugemalimab in multiple countries and regions outside of Greater China

Suzhou, China, June 7, 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 a poster presentation of the pre-specified overall survival (OS) results from the registrational GEMSTONE-302 study of sugemalimab for the first-line stage IV non-small cell lung cancer (NSCLC) at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting. The results showed that sugemalimab in combination with chemotherapy statistically significant and clinically meaningful improved patients’ OS. Clinical benefits were observed in all subgroups. Sugemalimab showed a well-tolerated safety profile and no new safety signals were observed.

Professor Caicun Zhou, Principal Investigator of the GEMSTONE-302 registrational study of sugemalimab and Director of the Department of Oncology, Shanghai Pulmonary Hospital, Tongji University, said, “The goal of first-line treatment for advanced lung cancer is to maximally improve outcome of our patients. Sugemalimab in combination with chemotherapy demonstrated durable clinical benefits,significant overall survival improvement, a well-tolerated safety profile in patients with advanced lung cancer. The Chinese Society of Clinical Oncology (CSCO) Clinical Guidelines for the Diagnosis and Treatment of NSCLC have granted Grade I recommendation to sugemalimab plus chemotherapy as preferred first-line treatment of patients with stage IV non-squamous/squamous NSCLC without driver alterations. We hope that sugemalimab will benefit more Chinese NSCLC patients and help them achieve long-term survival.”

Dr. Jason Yang, Chief Medical Officer of CStone, said, “The overall survival represents a gold standard efficacy endpoint in the clinical trials of advanced cancer. When we designed the study, we predictably set the OS as a pre-specified endpoint. The updated data further demonstrated the important value of sugemalimab in the first-line treatment of metastatic NSCLC. While significantly prolonging the OS, sugemalimab also continued to show a well-tolerated safety profile. We are advancing registrational studies of sugemalimab in gastric cancer, esophageal squamous cell carcinoma, and lymphoma, so as to enable sugemalimab to benefit a broader population of cancer patients.”

The GEMSTONE-302 study is designed to evaluate the efficacy and safety of sugemalimab in combination with chemotherapy in first-line treatment-naïve patients with stage IV NSCLC as compared to placebo in combination with chemotherapy. The primary endpoint of the study was investigator-assessed progression-free survival (PFS). Secondary endpoints included OS, Blinded Independent Central Review (BICR) -assessed PFS, investigator-assessed PFS in patients with PD-L1 expression ≥1%, objective response rate (ORR), duration of response (DoR) and safety.

Data cut-off date was 22 November 2021 at interim OS analysis

^*Data cut-off date was 15 March 2021 at final PFS analysis, available at Zhou, C., Wang, Z., Sun, Y., Cao, L., Ma, Z., Wu, R., ... & Yang, J. (2022). Sugemalimab versus placebo, in combination with platinum-based chemotherapy, as first-line treatment of metastatic non-small-cell lung cancer (GEMSTONE-302): interim and final analyses of a double-blind, randomised, phase 3 clinical trial. The Lancet Oncology.

About Sugemalimab

The anti-PD-L1 monoclonal antibody sugemalimab was developed by CStone using OmniRat^® transgenic animal platform, which allows creation of fully human antibodies in one step. Sugemalimab is a fully human, full-length anti-PD-L1 immunoglobulin G4 (IgG4) monoclonal antibody, which may allow a reduced the risk of immunogenicity and toxicity for patients, a unique advantage over similar drugs.

Currently, the NMPA of China has approved sugemalimab (Cejemly^®)

• In combination with pemetrexed and carboplatin as first-line treatment of patients with metastatic non-squamous NSCLC, lacking EGFR and ALK genomic tumor aberrations; and in combination with paclitaxel and carboplatin as first-line treatment of patients with metastatic squamous NSCLC
• For the treatment of patients with unresectable stage III non-small cell lung cancer whose disease has not progressed following concurrent or sequential platinum-based chemoradiotherapy

With its proven therapeutic advantages, sugemalimab is set to be recommended by the 2022 Chinese Society of Clinical Oncology (CSCO) clinical guidelines for the diagnosis and treatment of NSCLC, in combination with chemotherapy as the first-line treatment of patients with stage IV non-squamous/squamous NSCLC without driver alterations; or as a consolidation therapy in patients with stage III NSCLC following concurrent or sequential platinum-based chemoradiotherapy.

CStone formed a strategic collaboration agreement with EQRx, under which EQRx licensed the exclusive rights to sugemalimab for development and commercialization outside of Greater China.

About GEMSTONE-302 study

The GEMSTONE-302 study is a randomized, double-blind Phase 3 study, designed to evaluate the efficacy and safety of sugemalimab in combination with chemotherapy as a first-line treatment for patients with stage IV NSCLC as compared to placebo in combination with chemotherapy. The primary endpoint of the study was investigator-assessed PFS. Secondary endpoints included OS, BICR-assessed PFS, investigator-assessed PFS in patients with PD-L1 expression ≥1%, ORR, DoR and safety.

In August 2020, the GEMSTONE-302 study met its primary endpoint of significantly prolonged progression-free survival, with a favorable safety profile and no new safety signals, as compared to placebo combined with chemotherapy, as assessed by the independent data monitoring committee at the planned interim analysis. PFS data were presented in a Proffered Paper Oral Presentation (Late-Breaking Abstract) at ESMO Asia 2020.

In July 2021, the final analysis of PFS from the GEMSTONE-302 study showed that sugemalimab in combination with chemotherapy demonstrated continuous improvement in PFS, with the risk of disease progression or death reduced by 52%, together with a trend toward improved OS. Data were presented in a Mini Oral Presentation (Late-Breaking Abstract) at the IASLC 2021 World Conference on Lung Cancer. The results of the GEMSTONE-302 study were published in The Lancet Oncology in January 2022.

In January 2022, the GEMSTONE-302 study met the overall survival endpoint.

About CStone

CStone Pharmaceuticals (HKEX: 2616) is a biopharmaceutical company focused on researching, developing, and commercializing 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 eight drug 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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