CStone Pharmaceuticals announced that the company presented the final progression-free survival (PFS) analysis and data results from GEMSTONE-302 study, a registrational clinical study of sugemalimab for the first-line treatment of patients with stage IV NSCLC, in a late-breaking oral presentation at the IASLC 2021 World Conference on Lung Cancer (IASLC 2021 WCLC) hosted by the International Association for the Study of Lung Cancer. GEMSTONE-302 is the first randomized, double-blind, Phase 3 study of an anti-PD-L1 monoclonal antibody plus chemotherapy as first-line treatment for stage IV squamous and non-squamous NSCLC. It is designed to evaluate the efficacy and safety of sugemalimab or placebo in combination with chemotherapy as first-line treatment in patients with stage IV NSCLC. As of March 15, 2021, among the 479 patients enrolled, 79 (24.7%) versus 12 (7.5%) were still on treatment in the sugemalimab plus chemotherapy and placebo plus chemotherapy groups, respectively. In patients with both squamous and non-squamous NSCLC, the results of sugemalimab plus chemotherapy versus placebo plus chemotherapy were as follows: The investigator-assessed PFS was 9.0 months vs 4.9 months, HR=0.48 The median OS was 22.8 months vs 17.7 months, HR=0.67, although the OS events (accounted for 55% of the pre-defined number of events at OS final analysis) have not yet met the pre-defined interim analysis plan The 12-month PFS rate was 36.4% vs 14.8%, and 24-month OS rate was 47.1% vs 38.1% The objective response rate (ORR) was 63.4% vs 40.3%, and the duration of response (DoR) was 9.8 months vs 4.4 months PFS benefits observed in different pathologic types: Squamous: The median PFS was 8.3 months vs 4.8 months, HR=0.3 Non-squamous: The median PFS was 9.6 months vs 5.9 months, HR=0.59 PFS benefits observed in all PD-L1 expression levels: PD-L1<1%: The median PFS was 7.4 months vs 4.9 months, HR=0.55 PD-L1 1-49%: The median PFS was 8.8 months vs 4.8 months, HR=0.53 PD-L1=50%: The median PFS was 12.9 months vs 5.1 months, HR=0.41 Sugemalimab plus chemotherapy had a well-tolerated safety profile, and no new safety signals were observed. The incidences of Grade=3 treatment emergent adverse events (TEAEs) were reported in 64.1% and 61.6% of patients in the two groups, respectively, The incidences of Grade=3 immune-related adverse events (irAEs) were reported in 4.1% and 0% of patients in the two groups, respectively. Sugemalimab is an investigational anti-PD-L1 monoclonal antibody discovered by CStone. Authorized by the U.S.-based Ligand Corporation, sugemalimab is developed by 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 reduces the risk of immunogenicity and potential toxicities in patients, a unique advantage over similar drugs. Currently, sugemalimab is being investigated in a number of ongoing clinical trials, including one Phase 2 registration study for lymphoma (CS1001-201) and four Phase 3 registrational studies in stage III NSCLC, stage IV NSCLC, gastric cancer, and esophageal cancer, respectively.