CStone Pharmaceuticals announced that the National Medical Products Administration (NMPA) of China has approved the anti-PD-L1 antibody sugemalimab (Cejemly®) for the treatment of relapsed or refractory extranodal NK/T-cell lymphoma (R/R ENKTL). Sugemalimab becomes the world's first anti-PD-1/PD-L1 monoclonal antibody approved specifically for R/R ENKTL. The approval of sugemalimab for R/R ENKTL is supported by the GEMSTONE-201 study, which was designed to evaluate the efficacy and safety of sugemalimab as monotherapy for the treatment of adult patients with R/R ENKTL.

The results showed that sugemalimab significantly improved the objective response rate (ORR) compared to historical controls. In 78 evaluable patients, ORR assessed by Independent Radiology Review Committee (IRRC) was 44.9% with a complete response (CR) rate of 35.9%. The investigator-assessed ORR was highly consistent with IRRC's evaluation.

Subgroup analyses also indicated that sugemalimab is likely to be efficacious across a broad range of patients with ENKTL, including those who were heavily pretreated, regardless of objective response to prior therapies. Sugemalimab also demonstrated a well-tolerated safety profile in patients with R/R ENKTL, and no new safety signals were observed. The primary results from GEMSTONE-201 were presented as an oral presentation at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting and published by the internationally renowned oncology journal, the Journal of Clinical Oncology (JCO), in March 2023.

The anti-PD-L1 monoclonal antibody sugemalimab was discovered by CStone using the 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. The NMPA of China has approved three indications for sugemalimab for the treatment of patients with unresectable Stage III NSCLC whose disease has not progressed following concurrent or sequential platinum-based chemoradiotherapy and in combination with chemotherapy for the first-line treatment of patients with metastatic squamous and non-squamous NSCLC, and for the treatment of patients with R/R ENKTL.

The supplemental biologics license applications for sugemalimab in combination with chemotherapy for first-line treatment of locally advanced or metastatic gastric or gastroesophageal junction (G/GEJ) adenocarcinoma, and in combination with chemotherapy for first-line treatment of unresectable locally advanced, recurrent, or metastatic esophageal squamous cell carcinoma have been accepted by the NMPA of China and are currently under review. In addition, the European Medicines Agency (EMA) and the Medicines and Healthcare products Regulatory Agency (MHRA) in the United Kingdom have both accepted the marketing authorization applications (MAAs) for sugemalimab in combination with chemotherapy as a first-line treatment for metastatic NSCLC, and the two MAAs are currently under review. CStone formed a strategic collaboration agreement with Pfizer that includes the development and commercialization of sugemalimab in mainland China, and a framework to bring additional Oncology medicines to the Greater China market.

The GEMSTONE-201 study is a single-arm, multicenter, Phase 2 pivotal study designed to evaluate the efficacy and safety of sugemalimab as monotherapy for the treatment of adult patients with R/R ENKTL. Based on the encouraging preliminary efficacy results, sugemalimab has been granted Orphan Drug Designation and BTD by the U.S. FDA for the treatment of T-cell lymphoma and adults with R/R ENKTL respectively. It has also been granted BTD by the NMPA of China.

In January 2022, the GEMSTONE-201 study, as assessed by the Independent Radiology Review Committee, met its pre-specified primary endpoint. In June 2022, the full results of the GEMSTONE-201 study were reported in an oral presentation at the American Society of Clinical Oncology (ASCO) Annual Meeting. In March 2023, the prestigious international oncology journal, the Journal of Clinical Oncology (JCO), published the results of the registrational trial for sugemalimab in the treatment of R/R ENKTL (GEMSTONE-201).

Extranodal natural killer/T-cell lymphoma (ENKTL) is a subtype of mature T cell and NK cell lymphoma. In 2012, a multicenter pathological classification survey of 10,002 lymphoma patients from China showed that ENKTL accounted for approximately 6% of all lymphomas and 28% of mature T-cell and NK-cell lymphomas. There is no existing approved effective salvage treatment for patients with R/R ENKTL whose disease has progressed on a L-asparaginase-based standard regimen.

Patients also typically respond poorly to conventional treatments. Clinicians often have limited treatment options for such patients due to rapid disease progression and poor survival outcomes with a one-year survival rate of less than 20%. In China, the currently available targeted monotherapy for these patients has a complete response (CR) rate of approximately 6%.

Thus, there are significant unmet medical needs in patients who do not respond to first-line treatment. In addition, research shows broad similarity in the clinical presentation and treatment outcomes in the Western and Asian populations for ENKTL, although ENKTL is more prevalent in East Asia and Latin America.