• Sugemalimab in combination with chemotherapy as first-line treatment of advanced gastric adenocarcinoma/gastroesophageal junction adenocarcinoma with PD-L1 expression ≥5% demonstrated statistically significant and clinically meaningful improvement in progression-free survival. The risk of disease progression or death was reduced by 34%. An encouraging trend in overall survival was also observed. Clinical benefit was demonstrated across all pre-specified subgroups.
• Sugemalimab became the world’s first anti-PD-L1 monoclonal antibody to achieve positive results in a phase 3 study in gastric adenocarcinoma/gastro-esophageal junction adenocarcinoma.
• Sugemalimab has achieved positive results in four registrational studies.

Suzhou, China, November 11^th, 2022 - CStone Pharmaceuticals (“CStone”, HKEX: 2616), a leading biopharmaceutical company focused on research, development, and commercialization of innovative immuno-oncology therapies and precision medicines, today announced that the GEMSTONE-303 study, in which sugemalimab in combination with chemotherapy is used as a first-line treatment of unresectable locally advanced or metastatic gastric adenocarcinoma/gastro-esophageal junction (GEJ) adenocarcinoma with PD-L1 expression ≥5%, has met one of its primary endpoints, progression-free survival (PFS). Sugemalimab in combination with chemotherapy demonstrated statistically significant and clinically meaningful improvement in investigator-assessed PFS, compared with placebo plus chemotherapy, HR=0.66 (95% CI: 0.54, 0.81), p-value <0.0001. Median PFS in the sugemalimab arm was 7.6 months v.s. 6.1 months in the placebo arm. Data also showed a clear trend toward benefit for overall survival (OS) with HR=0.75 (95% CI: 0.59, 0.96). Median OS was 14.6 months in the sugemalimab arm v.s. 12.5 months in the placebo arm. The safety profile was consistent with previous findings across the studies for sugemalimab, and no new safety signals were observed.

The GEMSTONE-303 study is a multi-center, randomized placebo-controlled phase 3 registrational clinical trial designed to evaluate the efficacy and safety of sugemalimab plus capecitabine and oxaliplatin (CAPOX) as the first-line treatment in patients with unresectable locally advanced or metastatic gastric adenocarcinoma or GEJ adenocarcinoma with PD-L1 expression ≥5%. The primary endpoints are investigator-assessed PFS and OS. Secondary endpoints include blinded independent central review (BICR)-assessed PFS, investigator-assessed objective response rate (ORR) and duration of response (DoR).

Professor Lin Shen, the lead Principal Investigator of the GEMSTONE-303 study and vice president of Peking University Cancer Hospital, said, “Gastric cancer is a common cancer in China, and gastric adenocarcinoma accounted for over 90% of gastric malignancies. Most patients with gastric adenocarcinoma were diagnosed at an advanced stage, and those with unresectable or metastatic gastric cancer had poor prognosis, so they urgently need new solutions. Today, we are excited about the PFS positive results of the GEMSTONE-303 study in patients with gastric adenocarcinoma/gastro-esophageal junction adenocarcinoma and very confident for the OS result. We have high expectations that the drug will provide an optimized treatment option for this patient population.”

Dr. Jason Yang, Chief Executive Officer of CStone, said, “We are pleased that the registrational study of sugemalimab for the treatment of gastric cancer achieved positive results after it previously demonstrated robust efficacy in patients with non-small cell lung cancer and extranodal NK/T cell lymphoma. We expect to hold regulatory discussions in China to enable this potential new treatment to benefit gastric cancer patients. CStone is committed to addressing unmet clinical needs, and we will strive to bolster oncology research and bring forward more first-in-class or best-in-class therapies.”

About gastric cancer

Gastric cancer is one of the most common cancers globally. According to the GLOBOCAN 2020 data, there were more than 1 million new cases of gastric cancer worldwide and 769,000 deaths in 2020. The incidence and mortality of gastric cancer ranked 5th and 4th respectively among all common cancers worldwide. With the highest burden on gastric cancer, China accounts for nearly half of the world’s new cases and deaths of gastric cancer every year. Gastric adenocarcinoma accounted for more than 90% of all gastric malignancies, and the incidence of gastro-esophageal junction adenocarcinoma has also shown a rising trend in recent years.

About Sugemalimab

The anti-PD-L1 monoclonal antibody sugemalimab was discovered 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 reduce the risk of immunogenicity and toxicity for patients, a unique advantage over similar drugs.

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

Non-small cell lung cancer (NSCLC):

1. Combination Therapy

• In combination with pemetrexed and carboplatin as first-line treatment of patients with metastatic non-squamous non-small cell lung cancer (NSCLC), with no known EGFR and ALK genomic tumor aberrations.
• In combination with paclitaxel and carboplatin as first-line treatment of patients with metastatic squamous non-small cell lung cancer (NSCLC).

2. Monotherapy

• For the treatment of patients with unresectable stage III non-small cell lung cancer (NSCLC) whose disease has not progressed following platinum-based concurrent or sequential chemoradiotherapy.

With its proven therapeutic advantages, sugemalimab is 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.

In addition, the NMPA of China has accepted and granted priority review to the supplemental new drug application (sNDA) for sugemalimab in the treatment of patients with relapsed or refractory extranodal natural killer/T-cell lymphoma (R/R ENKTL).

About CStone

CStone (HKEX: 2616) is a biopharmaceutical company focused on research, development, 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 nine NDA approvals for its four drugs. Multiple late-stage drug candidates are now under pivotal clinical trials or registration. 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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