— Sugemalimab becomes the first Chinese anti-PD-L1 antibody to receive Breakthrough Therapy Designation from the U.S. FDA

Suzhou, China, October 22nd, 2020 - CStone Pharmaceuticals (Suzhou) Co., Ltd. (“CStone,” HKXE: 2616) today announced that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation (BTD)to anti-PD-L1 antibody sugemalimab for the treatment of adult patients with relapsed or refractory extranodal natural killer/T-cell lymphoma (R/R ENKTL). This represents another major breakthrough for CStone after the U.S. FDA granted Orphan Drug Designation (ODD) to its anti-PD-L1 antibody sugemalimab to treat T-cell lymphoma in October 2020.

Breakthrough Therapy Designation (BTD) is a process designed to expedite the development and review of drugs that are intended to treat a serious condition and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over available therapy on a clinically significant endpoint(s).Receiving the Breakthrough Therapy Designation will greatly accelerate the development and commercialization of sugemalimab in the U.S.

ENKTL is a subtype of mature T cell and NK cell lymphoma¹. R/R ENKTL is highly malignant and aggressive with a poor prognosis. There is a lack of effective salvage treatments for patients with R/R ENKTL if standard L-asparaginase-based regimens fail. Patients also respond poorly to conventional treatments. Clinicians often have limited treatment options for such patients, as the disease progresses rapidly, and the survival period is extremely short with a 1-year survival rate of less than 20%². In China, the current approved targeted monotherapy for these patients has a complete response (CR) rate of approximately 6%^3,4. Thus, there are significant unmet medical needs in this patient population in which first-line treatment has failed. An oral presentation of data from the CS1001-201 study, in which sugemalimab monotherapy was evaluated in adult patients with R/R ENKTL, was presented by the leading Principle Investigator Professor Huiqiang HUANG of Sun Yat-sen University Cancer Center at the 2020 annual meeting of the Chinese Society of Clinical Oncology (CSCO).According to the data presented, the objective response rate (ORR) of 38 evaluable patients was 44.7%, with a CR rate of 31.6%; the median duration of response (mDoR) was 16.8 months. Median overall survival (mOS) of the 43 patients who received study drug treatment was 19.7 months, and the 1-year OS rate was 55.5%. Sugemalimab is expected to become a new treatment option for these patients.

Dr. Jason Yang, Chief Medical Officer of CStone, said, “We have seen significant unmet needs for treatment among R/R ENKTL patients. Compared with data from other existing drugs, the efficacy data for sugemalimab represents a remarkable breakthrough. The Breakthrough Therapy Designation granted by the U.S. FDA recognizes the clinical value of sugemalimab. We are committed to advancing the development of sugemalimab, including by working closely with the U.S. FDA and the National Medical Products Administration (NMPA) of China, and will bring sugemalimab to patients across the globe as soon as possible.”

CS1001-201 Study

CS1001-201 is a single-arm, multicenter, Phase II pivotal study designed to evaluate the efficacy and safety of sugemalimab as monotherapy for the treatment of adult patients with R/R ENKTL. The primary endpoint of this study is ORR as assessed by the Independent Radiology Review Committee (IRRC). On August 31st, 2020, it has received clearance from the U.S. FDA for the Investigational New Drug (IND) application, and a Study May Proceed (SMP) letter.

About Sugemalimab（CS1001）

Sugemalimab is an investigational anti-PD-L1 monoclonal antibody discovered by CStone. Authorized by a company based in the U.S., Ligand Pharmaceuticals Inc. (NASDAQ: LGND), sugemalimab is developed using the OmniRat^® transgenic animal platform, which can generate fully human antibodies in one stop. As a fully human, full-length anti-PD-L1 monoclonal antibody, sugemalimab mirrors the natural G-type immunoglobulin 4 (“IgG4”) human antibody, which may reduce the risk of immunogenicity and toxicities in patients, a potentially unique advantage over similar drugs.

Sugemalimab has completed a Phase I dose-escalation study in China. During Phase 1a and 1b stages of the study, sugemalimab showed antitumor activity in multiple tumor types and was well-tolerated.

Currently, sugemalimab is being investigated in a number of ongoing clinical trials. In addition to a Phase I bridging study in the U.S., the clinical programs in China include one multi-arm Phase Ib study for several tumor types, one Phase II registrational study for lymphoma, and four Phase III registrational studies, respectively, for stage III/IV non-small cell lung cancer, gastric cancer, and esophageal cancer. The phase III clinical trial of sugemalimab in patients with stage IV non-small cell lung cancer has reached its primary endpoint. CStone plans to submit a new drug application (NDA) to the National Medical Products Administration (NMPA) of China soon.

About CStone

CStone is a biopharmaceutical company focused on developing and commercializing innovative immuno-oncology and precision medicines to address the unmet medical needs of cancer patients in China and worldwide. Established at the end of 2015, CStone has assembled a world-class management team with extensive experience in innovative drug development, clinical research, and commercialization. With a strategic emphasis on immuno-oncology combination therapies, the Company has built an oncology-focused pipeline of 15 drug candidates, including five late-stage candidates at pivotal trials or registration stages. With an experienced team, a rich pipeline, a robust clinical development-driven business model and substantial funding, CStone’s vision is to become globally recognized as a leading Chinese biopharmaceutical company by bringing innovative oncology therapies to cancer patients worldwide.

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